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{{Short description|Extinct order of heavily armoured reptiles}}
{{Use dmy dates|date=December 2023}}
{{Automatic taxobox
| name = Aetosaurs
| fossil_range = [[Late Triassic]], {{Fossil range|231.4|201.4}}
| image = HMNS Desmatosuchus cropped.jpg
| image_upright = 1.2
| image_caption = Skeletal mount of ''[[Desmatosuchus]]''
| taxon = Aetosauria
| authority = Lydekker, 1887
| subdivision_ranks = Subgroups
| subdivision = * {{extinct}}''[[Aetosauroides]]''
* {{extinct}}'''Stagonolepididae''' <small> Lydekker, 1887 ''sensu'' Heckert & Lucas, 2000</small>
** {{extinct}}'''[[Aetosaurinae]]'''
** {{extinct}}'''Stagonolepidoidea / Desmatosuchia''' <small> Case, 1920 ''sensu'' Parker, 2016</small>
*** {{extinct}}'''[[Desmatosuchinae]]'''
*** {{extinct}}'''Stagonolepidinae''' <small> Lydekker, 1887 ''sensu'' Heckert & Lucas, 2000</small>
**** {{extinct}}''[[Calyptosuchus]]''?
**** {{extinct}}''[[Polesinesuchus]]''
**** {{extinct}}''[[Stagonolepis]]''
}}

'''Aetosaurs''' ({{IPAc-en|eɪ|ˌ|ɛ|t|oʊ|ˈ|s|ɔr}}) are heavily armored reptiles belonging to the [[extinct]] [[order (biology)|order]] '''Aetosauria''' ({{IPAc-en|eɪ|ˌ|ɛ|t|oʊ|ˈ|s|ɔr|i|ə}}; from [[Ancient Greek|Greek]], {{lang|grc|[[wikt:ἀετός|ἀετός]]}} (aetos, "eagle") and {{lang|grc|[[wikt:σαυρος|σαυρος]]}} ({{lang|grc-Latn|sauros}}, "lizard")). They were medium- to large-sized [[Omnivore|omnivorous]] or [[Herbivore|herbivorous]] [[Pseudosuchia|pseudosuchians]], part of the branch of [[archosaur]]s more closely related to [[crocodilia]]ns than to [[bird]]s and other [[dinosaur]]s. All known aetosaurs are restricted to the [[Late Triassic]], and in some strata from this time they are among the most abundant fossil [[vertebrate]]s. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like [[Osteoderm|osteoderms]] (bony [[scute]]s). Aetosaur fossil remains are known from [[Europe]], [[North America|North]] and [[South America]], parts of [[Africa]], and [[India]]. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic [[tetrapod]] [[index fossil]]s. Many aetosaurs had wide geographic ranges, but their [[Stratigraphy|stratigraphic]] ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.<ref name="HL02">{{cite journal |last=Heckert |first=A. B. |author2=Lucas, S. G. |year=2002 |title=South American occurrences of the Adamanian (Late Triassic: Latest Carnian) index taxon ''Stagonolepis'' (Archosauria: Aetosauria) and their biochronological significance |journal=Journal of Paleontology |volume=76 |issue=5 |pages=852–863 |doi=10.1666/0022-3360(2002)076<0852:SAOOTA>2.0.CO;2 |s2cid=128610620 |url=http://www.24hourscholar.com/p/articles/mi_qa3790/is_200209/ai_n9124079?pi=scl |issn=0022-3360 |author2-link=Spencer G. Lucas }}{{Dead link|date=October 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref name="LSG98a">{{cite journal |last=Lucas |first=S. G. |year=1998 |title=Global Triassic tetrapod biostratigraphy and biochronology |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=143 |pages=347–384 |doi=10.1016/S0031-0182(98)00117-5 |issue=4|bibcode=1998PPP...143..347L |citeseerx=10.1.1.572.872 }}</ref><ref name="Detal13" />

Nearly all aetosaurs (except for the genus ''[[Aetosauroides]]'') belong to the [[family (biology)|family]] '''Stagonolepididae'''. Over 20 [[genera]] of aetosaurs have been described, and recently there has been controversy regarding the description of some of these genera. Two distinct subdivisions of aetosaurs are currently recognized, Desmatosuchia and [[Aetosaurinae]], based primarily on broad differences in skull [[Morphology (biology)|morphology]].<ref name=":0" /> Osteoderms structure is generally one of the most useful traits for inferring aetosaur relations more precisely. Among other archosaurs, aetosaurs are most closely related to ''[[Revueltosaurus]]'', a small reptile originally known from teeth mistakenly referred to herbivorous dinosaurs.<ref name="Detal13" />

Aetosaur remains were first discovered in the early 19th century, although the first remains that were described were mistaken for fish [[Scale (anatomy)|scales]]. Aetosaurs were later recognized as [[crocodile]] relatives, at which point they were interpreted as semiaquatic scavengers closely related to [[phytosaur]]s. Subsequent work has established that aetosaurs were entirely terrestrial animals, and were likely herbivorous to some extent. Some forms have characteristics that may have been adaptations to digging for food. Supposed nesting structures have also been referred to aetosaurs, but this connection is considered ambiguous.<ref name="Detal13" />

==Description==

=== Skull anatomy ===
[[File:Aetosaur skull diagrams.png|left|thumb|272x272px|Aetosaur skull reconstructions: (A) ''[[Aetosaurus ferratus]]'', (B) ''[[Paratypothorax andressorum]]'', (C) ''[[Stagonolepis robertsoni]]'', (D) ''[[Desmatosuchus smalli]]'', (E) ''[[Aetosauroides scagliai]]'']]
The skull of aetosaurs is relatively small compared to the body, and is quite distinctive in shape. Teeth are absent from both the front of the [[premaxilla]] (the bone forming the tip of the snout) and the front of the [[dentary]] (the toothed bone of the lower jaw).<ref name="NSJ11">{{cite journal|last=Nesbitt|first=S.J.|year=2011|title=The early evolution of archosaurs: relationships and the origin of major clades|journal=Bulletin of the American Museum of Natural History|volume=352|pages=1–292|doi=10.1206/352.1|hdl=2246/6112|s2cid=83493714|doi-access=free}}</ref><ref name=":0" /> The teeth which are present are usually small and bulbous, ranging from basic conical forms to leaf-like shapes with large serrations. These are probably indicative of an [[omnivorous]] or [[herbivorous]] diet, and similar adaptations are seen in other archosaurs with less reliance on meat in their diet.<ref name="RLC88">{{cite book |last=Carroll |first=Robert L. |title=Vertebrate Paleontology and Evolution |url=https://archive.org/details/vertebratepaleon0000carr |url-access=registration |year=1988 |publisher=W.H. Freeman and Company |isbn=978-0-7167-1822-2 |author-link=Robert L. Carroll }}</ref><ref name="Detal13" /> A few aetosaurs have teeth with a ziphodont shape, meaning that the teeth are recurved, serrated, and flattened from the side. This shape, which is predominant in ''[[Aetosauroides]]'' and a small specimen tentatively referred to ''[[Coahomasuchus]]'',<ref name=":0" /> is typical of [[carnivorous]] archosaurs.<ref name=":1">{{Cite journal|last1=Brust|first1=Ana Carolina Biacchi|last2=Desojo|first2=Julia Brenda|last3=Schultz|first3=Cesar Leandro|last4=Paes-Neto|first4=Voltaire Dutra|last5=Da-Rosa|first5=Átila Augusto Stock|date=15 August 2018|title=Osteology of the first skull of Aetosauroides scagliai Casamiquela 1960 (Archosauria: Aetosauria) from the Upper Triassic of southern Brazil (Hyperodapedon Assemblage Zone) and its phylogenetic importance|journal=PLOS ONE|language=en|volume=13|issue=8|pages=e0201450|doi=10.1371/journal.pone.0201450|issn=1932-6203|pmc=6093665|pmid=30110362|bibcode=2018PLoSO..1301450B|doi-access=free}}</ref>

In some aetosaurs (particular members of the group Desmatosuchia), the tip of the snout is expanded sideways into a flattened 'shovel' shape, akin to the snout of a [[pig]]. The [[Nares|external nares]] (nostril holes) are elongated, much larger than the [[Antorbital fenestra|antorbital fenestrae]] (a hole on the side of the skull). Many aetosaurs have a small knob on the premaxilla which projects into the nares from below. In all aetosaurs except ''Aetosauroides'', the rear edge of the naris receives a contribution from the concave front edge of the [[Maxilla|maxilla bone]]. At the rear upper part of the skull, a hole known as the [[supratemporal fenestra]] is positioned and exposed on the side, unlike most other archosaurs where it is mostly visible when viewing the skull from above.<ref name="PWG07" /><ref name="NSJ11" /><ref name=":0" /> The [[braincase]] is fairly standard by pseudosuchian standards, though the opening for the [[Abducens nerve|''abducens'' nerve]] passes through the [[Parabasisphenoid|parabasisphenoid bone]] (at the lower front part of the braincase), rather than the [[Prootic|prootic bone]] (at the upper front part). This trait is otherwise only seen in ''Revueltosaurus'' and [[crocodylomorpha|crocodylomorphs]] among archosaurs.<ref name="GW02">{{cite journal |last=Gower |first=D. J. |author2=Walker A. D. |year=2002 |title=New data on the braincase of the aetosaurian archosaur (Reptilia: Diapsida) ''Stagonolepis robertsoni'' Agassiz |doi=10.1046/j.1096-3642.2002.00023.x|journal=[[Zoological Journal of the Linnean Society]] |volume=136 |issue=1 |pages=7–23|doi-access=free }}Archosaurian Anatomy and Palaeontology: Essays in Memory of Alick D. Walker, DB Norman & DJ Gower (eds.)</ref><ref name="NSJ11" /><ref>{{Cite journal|last1=Parker|first1=William G.|last2=Nesbitt|first2=Sterling J.|last3=Irmis|first3=Randall B.|last4=Martz|first4=Jeffrey W.|last5=Marsh|first5=Adam D.|last6=Brown|first6=Matthew A.|last7=Stocker|first7=Michelle R.|last8=Werning|first8=Sarah|title=Osteology and relationships of ''Revueltosaurus callenderi'' (Archosauria: Suchia) from the Upper Triassic (Norian) Chinle Formation of Petrified Forest National Park, Arizona, United States|journal=The Anatomical Record|year=2022 |volume=305 |issue=10 |pages=2353–2414 |language=en|doi=10.1002/ar.24757|pmid=34585850|pmc=9544919 |s2cid=238216840|issn=1932-8494}}</ref> The mandible (lower jaw) is described as 'slipper'-shaped in many aetosaurs. This is due to a combination of features: the front of the dentary strongly tapers to a point, while the underside of the dentary sometimes flexes into a 'chin' (downwards projection) which may expose the [[Splenial|splenial bone]] as well. The jaw joint is set at a low position, and the [[Articular bone|articular]] (the bone of the lower jaw which connects to the cranium) often has a tall projection right behind the jaw joint.<ref name="PWG07" /><ref name=":0" /><ref name=":1" />

=== Postcranial anatomy ===
[[File:Desmatosuchus spurensis.jpg|thumb|320x320px|Life restoration and size diagram of ''[[Desmatosuchus spurensis]]'']]
In most respects apart from their skull and armor, the skeletal anatomy of aetosaurs was fairly standard among other large Triassic pseudosuchians. The hindlimbs developed a "pillar-erect" limb posture similar to that seen in "[[Rauisuchia|rauisuchians]]", a related [[Evolutionary grade|grade]] of carnivorous Triassic pseudosuchians ancestral to crocodylomorphs.<ref name=HL02/> A pillar-erect limb posture is one where the [[femur]] [[joint|articulates]] vertically with the [[acetabulum]] of the hip, which is angled downward, so that the leg is positioned beneath the body and acts as a weight-bearing pillar. Nevertheless, there was likely significant variation in the hip structure of aetosaurs, and the forelimbs may have had a semi-sprawling 'hybrid' stance. While the hindlimb posture is similar to rauisuchians, other traits are more [[plesiomorphic]] (typical to ancestral pseudosuchians), such as the stout [[pelvis]] and broad, five-toed feet.<ref name=RLC88/> The forelimbs were smaller than the hind limbs, and the [[Radius (bone)|radius]] in particular was much shorter than the [[humerus]]. Nevertheless, their low and heavy body shape requires that all aetosaurs were [[quadrupeds]]. They had multiple adaptations to strengthen the body in response to their heavy armor: the [[Iliofibularis|''iliofibularis'' muscle]] attached to a lower position on the [[fibula]], the [[fourth trochanter]] of the [[femur]] was enlarged, the [[transverse processes]] (rib attachments) developed into long massive pedestals, and the largest species even acquired [[Hyposphene-hypantrum articulation|hyposphene-hypantrum]] reinforcements between their vertebrae.<ref name="Detal13" /><ref name=":0" />

Although aetosaurs were generally wide-bodied reptiles, there is some variation in the degree of this trend. The [[Typothoracinae|typothoracines]], exemplified by ''[[Typothorax]]'' and ''[[Paratypothorax]],'' had a very broad, disc-shaped carapace, edged by small spines or keels and transitioning to a narrow tail. The largest species of typothoracines may have been around 3 meters (9.8 feet) in length and 110 kg (243 lbs) in weight. The [[Desmatosuchini|desmatosuchines]] ([[Desmatosuchinae]] ''[[sensu stricto]]''), such as ''[[Desmatosuchus]]'' and ''[[Longosuchus]]'', had moderately narrower bodies and no belly armor. However, they also acquired spinier back armor, especially in the cervical (neck) region.<ref name="PSI08">{{cite journal|last=Parker|first=W. G.|author2=Stocker, M. R.|author3=Irmis, R. B.|year=2008|title=A new desmatosuchine aetosaur (Archosauria; Suchia) from the Upper Triassic Tecovas Formation (Dockum Group) of Texas|journal=Journal of Vertebrate Paleontology|volume=28|issue=2|pages=692–701|doi=10.1671/0272-4634(2008)28[692:ANDAAS]2.0.CO;2|s2cid=84455880 |issn=0272-4634}}</ref> ''Desmatosuchus'' was likely one of the largest known aetosaurs, at {{cvt|4|-|6|m}} in length and {{cvt|280|kg|lb}} in weight.<ref name="PWG05">{{cite journal |last=Parker |first=W.G. |year=2005 |title=A new species of the Late Triassic aetosaur ''Desmatosuchus'' (Archosauria: Pseudosuchia) |journal=Comptes Rendus Palevol |volume=4 |issue=4 |pages=327–340 |doi=10.1016/j.crpv.2005.03.002|bibcode=2005CRPal...4..327P }}</ref><ref name="Detal13" /><ref>von Baczko, M. B., Desojo, J. B., Gower, D. J., Ridgely, R., Bona, P., &
Witmer, L. M. (2021). [https://www.researchgate.net/publication/355407927_New_digital_braincase_endocasts_of_two_species_of_Desmatosuchus_and_neurocranial_diversity_within_Aetosauria_Archosauria_Pseudosuchia New digital braincase endocasts of two species of Desmatosuchus and neurocranial diversity within Aetosauria (Archosauria: Pseudosuchia)]. The Anatomical Record, 1–20. https://doi.org/10.1002/ar.24798</ref> Aetosaurs which do not fit into these two categories, such as ''[[Stagonolepis]]'' and ''[[Neoaetosauroides]]'', generally had narrow forms, slender limbs, and a restriction in the carapace above the hip.<ref name="Detal13" /> This body type is plesiomorphic (ancestral) to the other two shapes, with some narrow-bodied aetosaurs more closely related to typothoracines and others closer to desmatosuchines.<ref name=":0" /> Some plesiomorphic genera, like the widespread [[Norian]] genus ''[[Aetosaurus]]'' and the [[Carnian]] ''[[Coahomasuchus]]'', tended to be small, about a metre (3.2 ft) in length.<ref name="HL99">{{cite journal |doi=10.1080/02724634.1999.10011122 |last=Heckert |first=A. B. |author2=Lucas S. G. |year=1999 |title= A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs |journal=Journal of Vertebrate Paleontology |volume=19 |issue=1 |pages=50–68|bibcode=1999JVPal..19...50H |citeseerx=10.1.1.563.9516 }}</ref> Others were larger, such as the [[Basal (phylogenetics)|basal]]-most aetosaur ''Aetosauroides'' and the early desmatosuchine ''[[Calyptosuchus]]''.<ref name="Detal13" />

==== Armor ====
[[File:Martz Stagonolepis skeletal terminology.jpg|thumb|302x302px|Skeletal diagram of ''[[Stagonolepis|Stagonolepis robertsoni]]'', showing osteoderm terminology|left]]
Aetosaurs were very heavily armored, with rows of large, interlocking bony plates, known as [[osteoderms]], protecting the back, sides, belly, and tail.<ref name="RLC88" /> These osteoderms generally have a [[wikt:quadrangular|quadrangular]] (four-sided) shape, and were most certainly used as a defense against predators. Most osteoderms are heavily pitted on their upper surfaces and smooth on their undersides. They have a heterogenous internal structure: the inner portion of each osteoderm is made of [[Cancellous bone|cancellous]] or spongy bone (also called [[diploë]]) and their outer portions are made up of compact bone.<ref name="Detal13">{{Cite journal|last1=Desojo|first1=J. B.|last2=Heckert|first2=A. B.|last3=Martz|first3=J. W.|last4=Parker|first4=W. G.|last5=Schoch|first5=R. R.|last6=Small|first6=B. J.|last7=Sulej|first7=T.|year=2013|title=Aetosauria: A clade of armoured pseudosuchians from the Upper Triassic continental beds|url=https://www.researchgate.net/publication/251249384|journal=Geological Society, London, Special Publications|volume=379|issue=1|pages=203–239|bibcode=2013GSLSP.379..203D|doi=10.1144/SP379.17|s2cid=129267515}}</ref> In life, these plates were probably covered in a keratinous (horn) covering, like modern crocodilian [[Scute|scutes]], which are another example of pseudosuchian osteoderms.<ref name=EHC69>{{cite book |last=Colbert |first=E. H. |year=1969 |title=Evolution of the Vertebrates |url=https://archive.org/details/evolutionofverte00colb |url-access=registration |edition=2nd |publisher=John Wiley & Sons |isbn=978-0-471-38461-8 |author-link=Edwin H. Colbert}}</ref> Osteoderms are useful in diagnosing aetosaur taxa, and aetosaur species can often be identified from individual scutes based on their shape, structure, or ornamentation pattern.<ref name=LB85>{{cite journal |last=Long |first=R. A. |author2=Ballew K. L. |year=1985 |title=Aetosaur dermal armor from the late Triassic of southwestern North America, with special reference to material from the Chinle Formation of Petrified Forest National Park |journal=Museum of Northern Arizona Bulletin |volume=47 |pages=45–68}}</ref><ref name=Chinleana2>{{cite web |url=http://chinleana.blogspot.com/2009/02/aetosaur-paper-that-changed-everything.html |title=The Aetosaur Paper that Changed Everything |first=Bill |last=Parker |date=13 February 2009 |work=Chinleana |publisher=Blogspot |access-date=8 January 2010}}</ref><ref name="Detal13" />

Aetosaurs have four rows of osteoderms running along their [[Dorsal (anatomy)|dorsal]] (back) side, forming a continuous plate often called the [[carapace]]. The inner two rows, which flank the midline of the spinal column, are known as paramedian osteoderms. These tend to be wider than long and strongly ornamented with radiating pits or grooves. Nearly all aetosaurs possess a small boss or raised surface, known as a dorsal eminence, on the upper surface of each plate. The dorsal eminence is often set posteriorly (backwards) or medially (inwards) on their respective paramedian osteoderm, though there are many exceptions within the group. The paramedian osteoderms almost always have raised or depressed anterior edges, where the plates are overlapped by the ones in front of them. If the anterior edge is raised, the area is called an anterior bar, while if it is depressed, the area is called an anterior lamina. Although two paramedian osteoderm rows are common in early archosauriforms, few reptiles approach aetosaurs in the complexity of their osteoderms. The osteoderms of [[Doswelliidae|doswelliids]], [[Erpetosuchidae|erpetosuchids]], and certain [[Crocodylomorpha|crocodylomorphs]] are occasionally confused or compared with those of aetosaurs. Both an anterior bar and dorsal eminence occur in ''[[Acaenasuchus]]'', a close relative of aetosaurs originally misidentified as a juvenile desmatosuchine.<ref name="PWG07" /><ref name="Detal13" /><ref name=":0" /><ref>{{Cite journal|last1=Marsh|first1=Adam D.|last2=Smith|first2=Matthew E.|last3=Parker|first3=William G.|last4=Irmis|first4=Randall B.|last5=Kligman|first5=Ben T.|date=2020|title=Skeletal Anatomy of ''Acaenasuchus geoffreyi'' Long and Murry, 1995 (Archosauria: Pseudosuchia) and its Implications for the Origin of the Aetosaurian Carapace|journal=Journal of Vertebrate Paleontology|volume=40|issue=4|pages=e1794885|doi=10.1080/02724634.2020.1794885|bibcode=2020JVPal..40E4885M |s2cid=225136804|issn=0272-4634|doi-access=free|hdl=10919/102375|hdl-access=free}}</ref>
[[File:Typothorax coccinarum cropped.jpg|thumb|322x322px|Life restoration of ''[[Typothorax coccinarum]]'']]
The outer two rows of osteoderms, which lie beside the paramedians, are known as lateral osteoderms. They parallel the paramedians over nearly the entire backside, though the first two paramedians behind the head (known as nuchal osteoderms) are solitary. Lateral plates generally are separated into two surfaces, or flanges, flexed between their dorsal eminence. The upper, or dorsal flange lies in the same plane as the paramedian osteoderms. The lower/outer, or lateral flange wraps down onto the side of the body. The dorsal eminence between these flanges often has the form of a low blade, knob, or spike. In the cervical lateral osteoderms, which are positioned on the neck, the dorsal eminence tends to manifest as a prominent spike.<ref name="Chinleana1">Bill Parker (12 August 2009). "[http://chinleana.blogspot.com/2009/08/aetosaurs-101-osteoderm-nomenclature.html Aetosaurs 101: Osteoderm Nomenclature]." ''Chinleana''. Accessed 8 January 2010.</ref> This is taken to an extreme in desmatosuchines such as ''[[Longosuchus]]'' and ''[[Desmatosuchus]]'', where the spike is enlarged into a sharply curved horn.<ref name="PWG07">{{cite journal|last=Parker|first=W. G.|year=2007|title=Reassessment of the aetosaur ''Desmatosuchus chamaensis'' with a reanalysis of the phylogeny of the Aetosauria (Archosauria:Pseudosuchia)|url=http://www.miketaylor.org.uk/dino/nm/Parker2007-Heliocanthus.pdf|journal=Journal of Systematic Palaeontology|volume=5|issue=1 |pages=41–68|doi=10.1017/S1477201906001994|bibcode=2007JSPal...5...41P |s2cid=85826683}}</ref>

In most aetosaurs (a major exception being [[Desmatosuchini|desmatosuchines]]), the underside of the animal is also protected by osteoderms. These ventral (belly) osteoderms are generally smaller and flatter than the dorsal series, and are arranged into a larger number of rows (usually 5 - 14 rows), at least in the torso. Ventral osteoderms rows usually curve outwards and separate under the hip, leaving a wide gap for the [[Cloaca|cloacal]] opening. Large, hooked spines occur around this opening in ''Typothorax'', one of the few exceptions to a general rule of smooth ventral osteoderms. Ventral rows break up into a shagreen of small plates on the neck, and a small number of wide rows under the tail. A dense assortment of small, non-overlapping plates, known as appendicular osteoderms, covered the front and hindlimbs.<ref name="Detal13" /><ref>{{Cite journal|last1=Heckert|first1=Andrew B.|last2=Martínez|first2=Ricardo N.|last3=Celeskey|first3=Matthew D.|date=2021|title=Anatomical Details of Aetosauria (Archosauria: Pseudosuchia) as Revealed by an Articulated Posterior Skeleton from the Upper Triassic Ischigualasto Formation, San Juan Province, Argentina|url=https://bioone.org/journals/ameghiniana/volume-58/issue-6/AMGH.05.09.2021.3426/Anatomical-Details-of-Aetosauria-Archosauria--Pseudosuchia-as-Revealed-by/10.5710/AMGH.05.09.2021.3426.full|journal=Ameghiniana|volume=58|issue=6|pages=464–484|doi=10.5710/AMGH.05.09.2021.3426|s2cid=239751891|issn=0002-7014}}</ref>

==History==

=== Early European finds ===
Aetosaur material was first described by [[Swiss people|Swiss]] paleontologist [[Louis Agassiz]] in 1844. He named the genus ''[[Stagonolepis]]'' from the [[Lossiemouth Sandstone]] in [[Elgin, Moray|Elgin]], [[Scotland]], but considered the fossil to be a [[Devonian]] fish rather than a Triassic reptile. This may be because he considered the strata to be part of the [[Old Red Sandstone]], and thus [[Paleozoic]] in age. Agassiz mistook the osteoderms for large rhomboidal scales, which he thought were arranged in a similar pattern to those of [[gar]]s. He also thought that these supposed scales were very similar to those of the [[lobe-finned fish]] ''[[Megalichthys]]'' due to their large size.<ref name="AL44">{{cite book |last=Agassiz |first=L. |year=1844 |title=Monographie des poisons fossils du Vieux Grés Rouge ou Systéme Dévonien (Old Red Sandstone) des Iles Britanniques ed de Russie |url=https://www.biodiversitylibrary.org/item/26658#7 |publisher=Jent et Gassman |location=Neuchâtel |pages=171}}</ref>

[[English people|English]] biologist [[Thomas Henry Huxley]] reconsidered the fish scales described by Agassiz and considered them to belong to a crocodilian. He first proposed this to the [[Geological Society of London]] in 1858, and went into more detail in an 1875 paper in the society's quarterly journal. By this time, new material had been uncovered from Elgin that indicated that ''Stagonolepis'' was not a fish, but a reptile. However, ''Stagonolepis'' was still known primarily by scutes and imprints of scutes, many of which were not well preserved.<ref name=HTH75>{{cite journal |last=Huxley |first=T.H. |year=1875 |title=On ''Stagonolepis Robertsoni'', and on the evolution of the Crocodilia |journal=Quarterly Journal of the Geological Society |volume=31 |issue=1–4 |pages=423–438 |doi=10.1144/GSL.JGS.1875.031.01-04.29|hdl=2027/hvd.32044107172884 |s2cid=130033385 |hdl-access=free }}</ref>

[[File:Aetosaurus ferratus.JPG|thumb|left|The articulated skeletons of 22 ''Aetosaurus'', discovered near [[Stuttgart]], [[Germany]] and first described by [[Oskar Fraas]] in 1877. The skeletons are now in the [[State Museum of Natural History Stuttgart]].]]
More complete aetosaur remains were found from the [[Lower Stubensandtein]] of [[Germany]] in the 1870s. Among them were complete articulated skeletons of 22 aetosaurs. These specimens were found in a large sandstone [[outcrop]] near [[Stuttgart]] and were preserved together in an area less than 2 square metres in size. The animals were probably buried under lake sediment soon after they died, with the flow of water repositioning their bodies on the lake bed and putting them in close proximity to one another. In 1877, German paleontologist [[Oscar Fraas]] assigned these specimens to the newly erected genus ''[[Aetosaurus]]''. Fraas named the genus after the skull's resemblance to the head of an eagle, with a narrow, elongate skull and a pointed snout.<ref name=FO77>{{cite journal |last=Fraas |first=O. |year=1877 |title=''Aetosaurus ferratus'' Fr. Die gepanzerte Vogel-Echse aus dem Stubensandstein bei Stuttgar |journal=Festschrift zur Feier des 400jährigen Jubiläums der Eberhard-Karls-Universät zu Tübingen, Wurttembergische Naturwissenschaftliche Jahreshefte |volume=33 |issue=3 |pages=1–22}}</ref>

=== First American aetosaurs ===
The first aetosaurs from North America were also being described in the 1870s. American paleontologist [[Edward Drinker Cope]] named ''[[Typothorax]]'' in 1875 and ''Episcoposaurus'' in 1877, both of which were from [[New Mexico]]. However, Cope considered these genera to be [[Phytosaur|phytosaurs]], crocodile-like aquatic archosaurs that were also common in the Late Triassic. While new material referable to ''Typothorax'' has been found in recent years throughout the American southwest, ''Episcoposaurus'' is no longer considered valid. Cope, along with later paleontologists such as [[Friedrich von Huene]], recognized that remains of the [[type species]] ''E. horridus'' actually belonged to ''Typothorax''. At the time, Cope considered Aetosauria to belong to [[Rhynchocephalia]], an order of reptiles that includes the living [[tuatara]]. He also thought that the tightly fitting osteoderms, which were thought to be fused to the ribs, indicated that aetosaurs were transitional between rhynchocephalians and [[turtle]]s.<ref name="NL89" /> Another species, ''E. haplocerus'', was reassigned to ''Desmatosuchus'' in 1953.<ref name="GJT53">{{cite journal|last=Gregory |first=J.T. |year=1953 |title=''Typothorax'' and ''Desmatosuchus'' |journal=Postilla, Peabody Museum of Natural History Bulletin |issue=16 |pages=1–27 |url=http://www.peabody.yale.edu/scipubs/bulletins_postillas/ypmP016_1953.pdf |url-status=dead |archive-url=https://web.archive.org/web/20100627062541/http://www.peabody.yale.edu/scipubs/bulletins_postillas/ypmP016_1953.pdf |archive-date=27 June 2010 }}</ref>

[[File:Stegomus arcuatus Marsh.JPG|thumb|right|Photograph of the carapace of ''[[Stegomus]]'', described by Marsh in 1896]]
A third North American genus called ''Stegomus'' was named by [[Othniel Charles Marsh]] in 1896.<ref name="MOC96">{{cite journal |doi=10.2475/ajs.s4-2.7.59 |last=Marsh |first=O.C. |year=1896 |title=A new belodont reptile (''Stegomus'') from the Connecticut River Sandstone |journal=American Journal of Science |volume=2 |pages=59–62 |issue=7|bibcode=1896AmJS....2...59M |url=https://zenodo.org/record/1450162 }}</ref> Marsh had a long-time rivalry with Cope that was made famous in the [[Bone Wars]] of the late 19th century, in which the two tried to out-compete one another in the field and in scientific literature. Unlike Cope's aetosaurs, ''Stegomus'' was found from the eastern United States in [[Connecticut]]. Marsh also recognized ''Stegomus'' as an aetosaur rather than a phytosaur in his initial description of the genus. Like Cope, many paleontologists tended to consider aetosaur scutes to belong to phytosaurs during this time period.<ref name="Chinleana2" /> Marsh considered aetosaurs to be closely related to dinosaurs based on their elongated [[Metatarsal bones|metatarsals]] (foot bones).<ref name="NL89" />

As a distinct group, Aetosauria was named in 1889 by English [[naturalist]] [[Richard Lydekker]] and [[zoologist]] [[Henry Alleyne Nicholson]].<ref name="NL89">{{cite book |last=Nicholson |first=H.A. |author2=Lydekker, R. |year=1889 |chapter=Order Crocodilia |title=A manual of palaeontology for the use of students, with a general introduction on the principles of palaeontology |chapter-url=https://books.google.com/books?id=bMBDAAAAIAAJ |volume=II |publisher=Nature |pages=1180–1196}}</ref> They considered Aetosauria to be one of three [[suborder]]s of the order Crocodilia, the other two being [[Parasuchia]] (a group including phytosaurs and other Triassic forms) and [[Eusuchia]] (a group including all post-Triassic crocodylomorphs). Nicholson and Lydekker placed a single family within the suborder, Aëtosauridæ. They considered aetosaurs to be similar to living crocodilians despite their longer metatarsals.<ref name="NL89" />

=== 20th century updates ===
Aetosaur material continued to be described into the early 20th century, with notable paleontologists such as [[Barnum Brown]] and [[Charles Camp]] collecting specimens.<ref name=Chinleana3>{{cite web |url=http://chinleana.blogspot.com/2009/08/who-has-worked-on-aetosaurs.html |title=Who Has Worked on Aetosaurs? |first=Bill |last=Parker |date=9 August 2009 |work=Chinleana |publisher=Blogspot |access-date=24 July 2010}}</ref> Better remains of American aetosaurs helped to establish anatomical info for some common species, such as ''Desmatosuchus spurensis'' (described in detail by [[E.C. Case]] in 1922) and ''"Typothorax" meadei'' (now ''[[Longosuchus]]'', described by [[H.J. Sawin]] in 1947).<ref name=SHJ47>{{cite journal |last=Sawin |first=H.J. |year=1947 |title=The pseudosuchian reptile ''Typothorax meadei'' |journal=Journal of Paleontology |volume=21 |issue=3 |pages=201–238}}</ref> However, aetosaur remains were still being confused with those of phytosaurs, and they were still considered to be predominantly carnivorous and semiaquatic "parasuchians" . [[Alick Walker|A.D. Walker]]'s 1961 redescription of ''Stagonolepis robertsoni'' helped to divert these notions and established a more modern view of aetosaurian anatomy and ecology.<ref>{{Cite journal|last=Walker|first=A. D.|date=31 August 1961|title=Triassic reptiles from the elgin area: Stagonolepis, Dasygnathus and their allies|url=https://royalsocietypublishing.org/doi/10.1098/rstb.1961.0007|journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences|volume=244|issue=709|pages=103–204|doi=10.1098/rstb.1961.0007|bibcode=1961RSPTB.244..103W|s2cid=83730309}}</ref>

==Distribution==
[[File:Aetosaur distribution map.svg|thumb|right|400px|Aetosaur [[body fossil]]s have been found in North America, South America, Europe, and parts of Asia and Africa.]]
Aetosaur fossils have been found on all continents except [[Australia]] and [[Antarctica]], giving them a nearly worldwide distribution during the Late Triassic. Aetosaur remains are most abundant in northern ([[Laurasia|Laurasian]]) continents, and fossils are particularly common in the [[Chinle Formation]] and [[Dockum Group]] of the southwestern [[United States]]. Most fossils have been found in [[Arizona]], [[New Mexico]], and [[Texas]].<ref name=Hetal07b>{{cite book |last=Heckert |first=A.B. |author2=Spielmann, J.A. |author3=Lucas, S.G. |author4=Hunt, A.P. |year=2007 |chapter=Biostratigraphic utility of the Upper Triassic aetosaur ''Tecovasuchus'' (Archosauria:Stagonolepididae), an index taxon of St. Johnsian (Adamanian:Late Carnian) time |chapter-url=http://paleo.cortland.edu/globaltriassic/Bull41/16-Heckert%20et%20al%20(Aeto%20redux).pdf |title=The Global Triassic |editor=Lucas, S.G. |editor2=Spielmann, J.A. |series=New Mexico Museum of Natural History and Science Bulletin |volume=41 |pages=51–57 |access-date=17 July 2010 |archive-date=27 September 2011 |archive-url=https://web.archive.org/web/20110927060146/http://paleo.cortland.edu/globaltriassic/Bull41/16-Heckert%20et%20al%20(Aeto%20redux).pdf |url-status=dead }}</ref> Some remains have also been found in [[Wyoming]], [[Colorado]], and [[Utah]], particularly in [[Canyonlands National Park]] and [[Zion National Park]].<ref name=SK10>{{cite book |last=Santucci |first=V.L. |author2=Kirkland, J.I. |year=2010 |chapter=An overview of National Park Service paleontological resources from the parks and monuments in Utah |chapter-url=https://ugs.academia.edu/documents/0101/8766/Santucci___Kirkland_2010_UGA28ed3-p.589-623_Paleo_Resources_Utah_Parks_and_Monuments.pdf |title=Geology of Utah's Parks and Monuments |editor=Sprinkel, D.A. |editor2=Chidsey, T.C. Jr. |editor3=Anderson, P.B. |series=2010 Utah Geological Association Publication 28 |edition=3rd |pages=589–623 }}{{Dead link|date=February 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Aetosaurs are also known from the [[Newark Supergroup]] along the East Coast of the United States, in states such as [[Connecticut]] and [[North Carolina]].<ref name=LHH1998>{{cite journal|last=Lucas |first=S.G. |author2=Heckert, A.B. |author3=Huber, P. |year=1998 |title=''Aetosaurus'' (Archosauromorpha) from the Upper Triassic of the Newark Supergroup, eastern United States, and its biochronological significance |journal=Palaeontology |volume=41 |issue=6 |pages=1215–1230 |url=http://palaeontology.palass-pubs.org/pdf/Vol%2041/Pages%201215-1230.pdf |url-status=dead |archive-url=https://web.archive.org/web/20120309062222/http://palaeontology.palass-pubs.org/pdf/Vol%2041/Pages%201215-1230.pdf |archive-date=9 March 2012 }}</ref> ''Aetosaurus'' and ''Paratypothorax'' have been recovered from the [[Fleming Fjord Formation]] of [[Jameson Land]], on the east coast of [[Greenland]].<ref name="Jetal94">{{cite journal|last=Jenkins |first=F.A. |author2=Shubin, N.H.|author3= Amaral, W.W. |author4=Gatesy, S.M. |author5=Schaff, C.R. |author6=Clemmensen, L.B. |author7=Downs, W.R. |author8=Davidson, A.R. |author9=Bonde, N. |author10=Osbaeck, F.F. |year=1994 |title=Late Triassic continental vertebrates and depositional environments of the Fleming Fjord Formation, Jameson Land, East Greenland |journal=Meddelelser om Grønland, Geoscience |volume=32 |pages=1–25|doi=10.7146/moggeosci.v32i.140904 |doi-access=free }}</ref> These two genera were originally named from the [[Stubensandstein|Lower Stubensandstein]] of Germany. [[Scotland]], [[Poland]], and [[Italy]] have also produced aetosaur fossils. A few aetosaurs are known from northern Africa, with scutes having been found from the late Carnian [[Timesgadiouine Formation]] in Morocco.<ref name="LSG98b">{{cite journal |last=Lucas |first=S.G. |year=1998 |title=The aetosaur ''Longosuchus'' from the Triassic of Morocco and its biochronological significance |journal=Comptes Rendus de l'Académie des Sciences, Série IIA |volume=326 |issue=8 |pages=589–594 |doi=10.1016/S1251-8050(98)80211-5|bibcode=1998CRASE.326..589L }}</ref><ref>{{Cite journal|last1=Parker|first1=William G.|last2=Martz|first2=Jeffrey W.|date=14 July 2010|title=Using positional homology in aetosaur (Archosauria: Pseudosuchia) osteoderms to evaluate the taxonomic status of ''Lucasuchus hunti''|url=https://www.researchgate.net/publication/249023832|journal=Journal of Vertebrate Paleontology|volume=30|issue=4|pages=1100–1108|doi=10.1080/02724634.2010.483536|bibcode=2010JVPal..30.1100P |s2cid=83713904|issn=0272-4634}}</ref> During the Late Triassic, Morocco would have been in close proximity with the Newark Supergroup of North America in the [[supercontinent]] of [[Pangaea]]. It is also possible that ''Desmatosuchus'' was present in Africa, as fossils from the [[Zarzaitine Series]] in [[Algeria]] have been referred to the genus.<ref name=HL99/>

[[File:Brachychirotherium.svg|thumb|left|200px|''[[Brachychirotherium]]'' [[Ichnite|footprints]] and [[trackway]]s.]]Aetosaurs are also found in areas corresponding to [[Gondwana]] (southern Pangaea), though they are considerably less common or diverse than in Northern continents. South American aetosaurs are known from [[Argentina]], [[Brazil]], and [[Chile]]. In Argentina, ''[[Aetosauroides]]'' and ''[[Neoaetosauroides]]'' hail from the Carnian [[Ischigualasto Formation]] and Norian [[Los Colorados Formation]], respectively.<ref name="SCS07">{{cite journal|last=Silva |first=R.C. Da |author2=Carvalho, I. De S. |author3=Schwanke, C. |year=2007 |title=Vertebrate dinoturbation from the Caturrita Formation (Late Triassic, Paraná Basin), Rio Grande do Sul State, Brazil |journal=Gondwana Research |volume=11 |issue=2007 |pages=303–310 |doi=10.1016/j.gr.2006.05.011 |bibcode=2007GondR..11..303C |url=http://acd.ufrj.br/ismar/3/3_18.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110706163103/http://acd.ufrj.br/ismar/3/3_18.pdf |archive-date=6 July 2011 }}</ref><ref name="HL02" /> In Brazil, fossils have been found in the [[Santa Maria Formation|Santa Maria]] and [[Caturrita Formation]]s in [[Rio Grande do Sul]] (Paleorrota).<ref name="HL99" /><ref name="SCS07" /> Chilean aetosaurs are represented by one fragmentary genus, ''[[Chilenosuchus]]'', from the [[Antofagasta Region]].<ref name=DJB01>{{cite journal |last=Desojo |first=J.B. |year=2001 |title=Redescripcion del aetosaurio Chilenosuchus forttae Casamiqueal (Diapsida: Arcosauria): presencia de Triasico continental en el norte de Chile |journal=Revista Geológica de Chile |volume=30 |issue=1 |pages=53–63 |url=http://www.paleoglot.org/files/Desojo%2003.pdf |doi=10.4067/s0716-02082003000100004|doi-access=free }}</ref> Aetosaurs have also been found in [[India]], which, along with South America, was part of [[Gondwana]] during the Late Triassic. Early accounts of Indian aetosaurs were based on material from the [[Lower Maleri Formation|Maleri Formation]] in south-central India, although most of these remains were too inadequate to assign specimens to any particular genus. Based on published descriptions, the Indian aetosaur fossils most closely resemble ''Longosuchus'' and ''Paratypothorax,'' which are considerably more specialized than most described Gondwanan aetosaurs.<ref name=Hetal-07>{{cite book |last=Heckert |first=A.B. |author2=Lucas, S.G. |author3=Hunt, A.P. |author4=Spielmann, J.A. |year=2007 |chapter=Late Triassic aetosaur biochronology revisited |chapter-url=http://paleo.cortland.edu/globaltriassic/Bull41/16-Heckert%20et%20al%20(Aeto%20redux).pdf |title=The Global Triassic |editor=Lucas, S.G. |editor2=Spielmann, J.A. |series=New Mexico Museum of Natural History and Science Bulletin |volume=41 |pages=49–50 |access-date=17 July 2010 |archive-date=27 September 2011 |archive-url=https://web.archive.org/web/20110927060146/http://paleo.cortland.edu/globaltriassic/Bull41/16-Heckert%20et%20al%20(Aeto%20redux).pdf |url-status=dead }}</ref> In 2023 a new aetosaur was named from the [[Lower Dharmaram Formation]] of India as ''[[Venkatasuchus|Venkatasuchus armatus]]'', a [[Typothoracinae|typothoracine]] aetosaur.<ref name="HRB23" />  Reports of aetosaurs from Madagascar<ref name=LH02>{{cite journal |last=Lucas |first=S.G. |author2=Heckert, A.P. |year=2002 |title=The ''Hyperodapedon'' biochron, Late Triassic of Pangea |journal=Albertiana |volume=27 |pages=30–38 |url=http://www.uu.nl/EN/faculties/science/organisation/depts/biology/research/chairs/Palaeoecology/projects/ALBERTIANA/downloads/Documents/e-albertiana27.pdf#page=30}}</ref><ref name="B06">{{Cite journal|last1=Burmeister|first1=Kurtis C.|last2=Flynn|first2=John J.|last3=Parrish|first3=J. Michael|last4=Wyss|first4=Andre R.|date=2006|title=Paleogeographic and biostratigraphic implications of new early Mesozoic vertebrates from Poamay, central Morondava Basin, Madagascar|url=https://books.google.com/books?id=ulvmCQAAQBAJ&pg=PA457|journal=New Mexico Museum of Natural History & Science Bulletin|volume=37|pages=457–475}}</ref> are based on probable [[crocodylomorpha|crocodylomorph]] scutes.<ref name=Pa08>{{cite journal |last=Parker |first=William G. |year=2008 |title=Description of new material of the aetosaur ''Desmatosuchus spurensis'' (Archosauria: Suchia) from the Chinle Formation of Arizona and a revision of the genus ''Desmatosuchus'' |journal=PaleoBios |volume=28 |pages=1–40}}</ref> Supposed aetosaurian footprints and skeletal material from [[South Africa]] are also unsubstantiated.<ref>{{Cite journal|last=Knoll|first=Fabien|date=1 January 2004|title=Review of the tetrapod fauna of the "Lower Stormberg Group" of the main Karoo Basin (southern Africa) : implication for the age of the Lower Elliot Formation|url=https://doi.org/10.2113/175.1.73|journal=Bulletin de la Société Géologique de France|volume=175|issue=1|pages=73–83|doi=10.2113/175.1.73|issn=0037-9409}}</ref>

[[Ichnite|Footprints]] belonging to the [[ichnogenus]] ''[[Brachychirotherium]]'' are often associated with aetosaurs.<ref name=HLL93>{{cite book |last=Hunt |first=A.P. |author2=Lockley, M.G.|author3= Lucas, S.G. |year=1993 |chapter=Vertebrate and invertebrate tracks and trackways from Upper Triassic Strata of the Tucumcari Basin, East-Central New Mexico, U.S.A. |title=The Nonmarine Triassic |editor=Lucas, S.G. |editor2=Morales, M. |series=New Mexico Museum of Natural History and Science Bulletin |volume=3 |pages=199–201}}</ref><ref name=Hetal10>{{cite journal |last=Heckert |first=A.B. |author2=Lucas, S.G.|author3= Rinehart, L.F.|author4= Celesky, M.D.|author5= Spielmann, J.A.|author6= Hunt, A.P. |year=2010 |title=Articulated skeletons of the aetosaur ''Typothorax coccinarum'' Cope (Archosauria: Stagonolepididae) from the Upper Triassic Bull Canyon Formation (Revueltian: early-mid Norian), eastern New Mexico, USA |journal=Journal of Vertebrate Paleontology |volume=30 |issue=3 |pages=619–642 |doi=10.1080/02724631003763524 |bibcode=2010JVPal..30..619H |s2cid=140536594 |url=http://pdfserve.informaworld.com/852191__922419027.pdf}}</ref> ''Brachychirotherium'' are known from [[Rio Grande do Sul]] in Paleorrota, [[Brazil]]<ref name=SCS07/> as well as [[Italy]],<ref name=AM00>{{cite journal |last=Avanzini |first=M. |year=2000 |title=''Synaptichnium'' tracks with skin impressions from the Anisian (middle Triassic) of the Southern alps (val di non - Italy) |journal=Ichnos |volume=7 |issue=4 |pages=243–251 |doi=10.1080/10420940009380164|bibcode=2000Ichno...7..243A |s2cid=129651942 }}</ref> [[Germany]],<ref name=HH83>{{cite journal |last=Haubold |first=H. |year=1983 |title=Archosaur evidence in the Buntsandstein (Lower Triassic) |journal=Acta Palaeontologica Polonica |volume=28 |issue=1–2 |pages=123–132 |url=http://www.app.pan.pl/archive/published/app28/app28-123.pdf}}</ref> the eastern United States,<ref name=OB88>{{cite book |last=Olsen |first=P.E. |author2=Baird, D. |year=1988 |chapter=The ichnogenus ''Atriepus'' and its significance for Triassic biostratigraphy |title=The Beginning of the Age of Dinosaurs: Faunal Change Across the Triassic-Jurassic Boundary |editor=Padian, K. |publisher=Cambridge University Press |location=Cambridge |pages=61–88 |isbn=978-0-521-36779-0}}</ref> and many other aetosaur-bearing locales. They are also common in the southwestern United States, having been found in Canyonlands National Park and [[Dinosaur National Monument]].<ref name=SK10/> Many of these tracks have a narrow gauge (meaning the left and right prints are placed closely together) and nearly overstep each other. A 2011 functional analysis of the skeleton of ''[[Typothorax|Typothorax coccinarum]]'' indicated that it had the range of movement necessary to produce the tracks.<ref name=LH11>{{cite journal |last=Lucas |first=S.G. |author2=Heckert, A.B. |year=2011 |title=Late Triassic aetosaurs as the trackmaker of the tetrapod footprint ichnotaxon ''Brachychirotherium'' |journal=Ichnos |volume=18 |issue=4 |pages=197–208 |doi=10.1080/10420940.2011.632456|bibcode=2011Ichno..18..197L |s2cid=128893544 }}</ref>

== Classification ==

===Taxonomy===
Aetosaurs belong to [[Pseudosuchia]], a clade of archosaurs that includes living crocodilians and is characterized by the distinctive structure of the [[Tarsus (skeleton)|ankle bones]].{{Dubious|date=July 2018}} Aetosaurs were traditionally referred to a (now obsolete) group called the [[Thecodontia|thecodonts]], which included all "[[basal (phylogenetics)|primitive]]" crocodilian relatives that lived in the Triassic. With the rise of [[phylogenetics]], aetosaurs were later placed in a group called [[Suchia]], which included many Triassic crurotarsans as well as later crurotarsans, including crocodilians.<ref name=Betal10>{{cite journal |last=Brusatte |first=S.L. |author2=Benton, M.J.|author3= Desojo, J.B.|author4= Langer, M.C. |year=2010 |title=The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida) |journal=Journal of Systematic Palaeontology |volume=8 |issue=1 |pages=3–47 |doi=10.1080/14772010903537732 |bibcode=2010JSPal...8....3B |url=https://www.pure.ed.ac.uk/ws/files/8232155/PDF_Brusatteetal2010ArchosaurPhylogeny.pdf |hdl=20.500.11820/24322ff3-e80e-45f2-8d53-d35fd104195c |s2cid=59148006 |hdl-access=free }}</ref>

Originally, all aetosaurs were considered members of the family Stagonolepididae. Early [[phylogenetics|phylogenetic analyses]] split aetosaurs into two subfamilies, Aetosaurinae and Desmatosuchinae. Aetosaurines are characterized by projections called eminences on the dorsal paramedian osteoderms that are close to the midline of the back. Desmatosuchines have a few more distinguishing characteristics, including grooves on the dorsal paramedians that help them lock to the lateral plates in a tight articulation. Many desmatosuchines have long spikes projecting from the lateral plates. These spikes are especially prominent in ''Desmatosuchus''. Aetosaurines, on the other hand, tend to have less spikes. Many aetosaurines, such as ''Aetosaurus'' and ''Neoaetosauroides'', have smooth carapaces and lack spikes altogether.<ref name=PWG07/> More recent studies (see [[Aetosaur#Phylogeny|below]]) have favored a third group, Typothoracinae, which like Desmatosuchinae has long spikes, but differs in having more sharply angled joints between osteoderms. Moreover, the genus ''[[Aetosauroides]]'' is now often classified outside Stagonolepididae as a non-stagonolepidid aetosaur, making the names Aetosauria and Stagonolepididae no longer synonymous.<ref name=Aetobarbakinoides>{{cite journal |author1=Julia B. Desojo |author2=Martin D. Ezcurra |author3=Edio E. Kischlat |year=2012 |title=A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late Triassic of southern Brazil |journal=Zootaxa |volume=3166 |pages=1–33 |issn=1175-5334 |url=http://www.mapress.com/zootaxa/2012/f/z03166p033f.pdf |doi=10.11646/zootaxa.3166.1.1 }}</ref>

====List of genera====
{| class="wikitable sortable" align="center" width="100%"
|- 
! Genus
! Status
! Age
! Location
! Geological unit
! class="unsortable" | Notes
! class="unsortable" | Images
|-
| 
''[[Acaenasuchus]]'' 
| Non-aetosaurian
| middle [[Norian]] (Adamanian)
|
{{flag|USA}} (Arizona)
|
[[Chinle Formation]] ([[Blue Mesa Member]], [[Sonsela Member]])
| A valid species of non-aetosaur [[Aetosauriformes|aetosauriform]], previously considered a valid aetosaur or juvenile specimens of ''Desmatosuchus spurensis.''
|
|-
| 
''[[Acompsosaurus]]''
| ''[[Nomen dubium]]'' 
| [[Late Triassic]] (Adamanian)
|
{{flag|USA}} (New Mexico)
|
[[Chinle Formation|Chinle Group]] ([[Bluewater Creek Formation]])
| A dubious aetosaur based on a [[pelvis]] which is now lost. Possibly a junior synonym of ''Stagonolepis'' or ''Calyptosuchus''.
| [[File:Acompsosaurus pelvis.jpg|150px]]
|-
| 
''[[Adamanasuchus]]''
| Valid 
| early - middle [[Norian]] (Adamanian)
|
{{flag|USA}} (Arizona)
|
[[Chinle Formation]] ([[Blue Mesa Member]])
| A large desmatosuchian, closely related to ''Calyptosuchus'' and ''Scutarx.''
|
|-
| 
''[[Aetobarbakinoides]]''
| Valid
| late [[Carnian]] - early [[Norian]]
|
{{flag|Brazil}}
|
[[Santa Maria Formation]]
|
An aetosaur with aetosaurine-like osteoderms and desmatosuchine-like vertebrae.
|
|-
| 
''[[Aetosauroides]]''
| Valid
| [[Carnian]] - [[Norian]]
|
{{flag|Argentina}},<br/>
{{flag|Brazil}}
|
[[Ischigualasto Formation]],<br/>
[[Santa Maria Formation]]
| Currently considered the most basal aetosaur, as well as the most well-studied member of the group from Gondwana. It may have had a more carnivorous diet than most other aetosaurs.
| [[File:Aetosauroides scagliai life restoration.jpg|150px]]
|-
| 
''[[Aetosaurus]]''
| Valid 
|
middle [[Norian]] - early [[Rhaetian]]? (Revueltian)
|
{{flag|Germany}},<br/>
{{flag|Italy}},<br/>
{{flag|Greenland}}<br/>
|
[[Stubensandtein|Lower Stubensandtein]],<br/>
[[Zorzino Limestone|Calcare di Zorzino Formation]],<br/>
[[Fleming Fjord Formation]]
| A small (1.5 m, 5&nbsp;ft long) [[Aetosaurinae|aetosaurine]] aetosaur with a wide geographic distribution in Europe.
| [[File:Aetosaurus_many_specimens.jpg|150px]]
|-
|
''[[Apachesuchus]]''
| Valid
| late [[Norian]] - [[Rhaetian]] (Apachean)
|
{{flag|USA}}
|
[[Redonda Formation]]
| A large, late-surviving probable typothoracine known solely from smooth osteoderms.
|
|-
| 
''[[Argentinosuchus]]''
| ''[[Nomen dubium]]''
| [[Carnian]] - [[Norian]]
|
{{flag|Argentina}}
|
[[Ischigualasto Formation]]
| An indeterminate aetosaur similar to ''Aetosauroides'' and ''Stagonolepis''
|
|-
| 
''[[Calyptosuchus]]'' 
| Valid
| early - middle [[Norian]] (Adamanian)
|
{{flag|USA}} (Arizona, Texas)
|
[[Chinle Formation]] ([[Blue Mesa Member]]), [[Tecovas Formation]]
|A desmatosuchian similar to ''Stagonolepis'', which it was formerly considered to be a species of.
|
|-
| 
''[[Chilenosuchus]]''
| Valid 
| [[Late Triassic]]
|
{{flag|Chile}}
|[[El Bordo Formation]]
|
A poorly-known aetosaur similar to ''Typothorax''. It was found in strata that were originally thought to be [[Carboniferous]] or [[Permian]] in age, rather than Triassic.
|
|-
| 
''[[Coahomasuchus]]''
| Valid 
| [[Carnian]]? (Otischalkian)
|
{{flag|USA}} (Texas, North Carolina)
|
[[Colorado City Formation]],<br/>
[[Pekin Formation]]
| A small but wide-bodied aetosaur closely related to typothoracines.
|
|-
| 
''[[Desmatosuchus]]''
| Valid 
| early - middle [[Norian]] (Adamanian - earliest Revueltian?)
|
{{flag|USA}} (Texas, Arizona, New Mexico)<br/>
|
[[Cooper Canyon Formation]],<br/>
[[Tecovas Formation]],<br/>
[[Santa Rosa Formation, New Mexico|Santa Rosa Formation]],<br/>
[[Chinle Formation]] ([[Blue Mesa Member]], [[Sonsela Member]])
|Namesake of the desmatosuchines, one of the largest, most common, and most impressively-armored aetosaurs.
| [[File:Desmatosuchus Exhibit Museum of Natural History 02.JPG|150px]]
|-
| 
''[[Garzapelta]]'' 
| Valid 
| [[Norian]]? (Adamanian - Revueltian)
|
{{flag|USA}} (Texas)
| 
[[Cooper Canyon Formation]]
| A possible paratypothoracine that possessed lateral osteoderms that converged with those of desmatosuchines
|
|-
| 
''[[Gorgetosuchus]]'' 
| Valid 
| [[Carnian]]? (Otischalkian)
|
{{flag|USA}} (North Carolina)
| 
[[Pekin Formation]]
| A possible desmatosuchin characterized by cervical osteoderms that almost encircle the neck
|
|-
|
''[[Heliocanthus]]'' 
| Junior synonym 
|
|
| 
| Junior synonym of ''[[Rioarribasuchus]]''
|
|-
|''[[Kocurypelta]]''
|Valid
|[[Late Triassic]]
|{{flag|Poland}}
|[[Grabowa Formation]]
|A paratypothoracin diagnosed from skull fragments
|
|-
|''[[Kryphioparma]]''
|Valid
|early - middle [[Norian]] (Adamanian)
|{{flag|USA}} (Arizona)
|[[Chinle Formation]] ([[Blue Mesa Member]])
|A typhothoracine based on fossils previously referred to ''Tecovasuchus''
|
|-
| 
''[[Longosuchus]]'' 
| Valid 
| [[Carnian]]? (Otischalkian)
|
{{flag|USA}} (Texas)

|
[[Colorado City Formation]]<br/>
|A well-described desmatosuchin, the subject of major studies on aetosaur anatomy in the mid-20th century.
| [[File:Longosuchus BW.jpg|150px]]
|-
| 
''[[Lucasuchus]]''
| Valid 
| [[Norian|Carnian]]? (Otischalkian)
|
{{flag|USA}} (Texas, North Carolina)
|
[[Colorado City Formation]],<br/>
[[Pekin Formation]]
|A desmatosuchin often conflated with ''Longosuchus'', which it coexisted with.
|
|-
| 
''[[Neoaetosauroides]]'' 
| Valid 
| middle [[Norian]] (Revueltian)
|
{{flag|Argentina}}
| 
[[Los Colorados Formation]] 
|A late-surviving basal desmatosuchian with apparent adaptations for a more carnivorous diet than most other aetosaurs.
| [[File:Neoaetosauroides.jpg|150px]]
|-
| 
''[[Paratypothorax]]'' 
| Valid 
| [[Norian]]
(Adamanian - Revueltian)
|
{{flag|Germany}},<br/>
{{flag|USA}} (Arizona, New Mexico, Texas),<br/>
{{flag|Greenland}}<br/>
|
[[Lower Stubensandstein]],<br/>
[[Chinle Formation]],<br/>
[[Dockum Group]],<br/>
[[Fleming Fjord Formation]]
| The widespread and well-known namesake of the clade Paratypothoracini. Some authors have suggested that it represents an adult form of ''Aetosaurus''. 
| [[File:Paratypothorax andressorum.JPG|150px]]
|-
|''[[Polesinesuchus]]''
|Valid?
|late [[Carnian]] - early [[Norian]]
|{{flag|Brazil}}
|[[Santa Maria Formation]]
|A small aetosaur based on an immature specimen, which may be referrable to ''Aetosauroides''.
|
|-
|
''[[Redondasuchus]]''
| Valid 
| late [[Norian]] - Rhaetian (Apachean)
|
{{flag|USA}} (New Mexico)
|
[[Redonda Formation]]
|A large typothoracinae often considered a close relative or species of ''Typothorax.''
|
|-
|
''[[Rioarribasuchus]]''
| Valid
| middle - late [[Norian]] (Revueltian)
|
{{flag|USA}} (New Mexico, Arizona)
|
[[Chinle Formation]] ([[Petrified Forest Member]], [[Sonsela Member]]),<br/>
[[Bull Canyon Formation]]
| A narrow-bodied paratypothoracin with elongated spines on paramedian osteoderms above the hip.
|
|-
|
''[[Scutarx]]''
| Valid
| middle [[Norian]] (Adamanian)
|
{{flag|USA}} (Arizona, Texas)
|
[[Chinle Formation]] ([[Sonsela Member]]), <br/>
[[Cooper Canyon Formation]]
|A strongly-armored desmatosuchian closely related to ''Calyptosuchus''.
| [[File:Scutarx-deltatylus_1.jpg|150px]]
|-
|
''[[Sierritasuchus]]''
| Valid 
| early - middle [[Norian]] (Adamanian)
|
{{flag|USA}} (Texas)
|
[[Tecovas Formation]]
|
A desmatosuchin known from an immature specimen originally assigned to ''Desmatosuchus.''
|
|-
|
''[[Stagonolepis]]''
| Valid 
| [[Carnian]]
|
{{flag|Scotland}},<br/>
{{flag|Poland}}
|
[[Lossiemouth Sandstone]],<br/>
[[Krasiejów]] deposits
| The first aetosaur to be described, previously used as a [[wastebasket taxon]] for other narrow-bodied basal aetosaurs.
| [[File:Stagonolepis Warsaw.jpg|150px]]
|-
|
''[[Stegomus]]''
| Junior synonym or Nomen dubium
| [[Norian]] (Revueltian)
|{{flag|USA}} (Connecticut, New Jersey, North Carolina)
|[[New Haven Arkose]],<br/>
[[Passaic Formation]],<br/>
[[Sanford Formation]]
| A small aetosaur only known from interior molds of a dorsal carapace. Often interpreted as a dubious genus or a junior synonym of ''[[Aetosaurus]]''<ref name="LHH1998" />
|
|-
|
''[[Stenomyti]]''
| Valid 
| late [[Norian]] (Revueltian)
|
{{flag|USA}} (Colorado)
|
[[Chinle Formation]] ([[red siltstone member]])
|
A small basal aetosaurine originally assigned to ''Aetosaurus,'' a close relative.
|
|-
|''[[Tecovasuchus]]''
|Valid
|early - middle [[Norian]] (Adamanian)
|{{flag|USA}} (Texas, New Mexico, Arizona?)
|[[Tecovas Formation]],<br/>
[[Chinle Formation|Chinle Group]] ([[Bluewater Creek Formation]], [[Blue Mesa Member]]?)
|A typical wide-bodied paratypothoracin
|
|-
|
''[[Typothorax]]''
|
Valid 
|
middle - late [[Norian]] (latest Adamanian - Revueltian)
|
{{flag|USA}} (Arizona, Texas, New Mexico)
|
[[Chinle Formation]] ([[Sonsela Member]], [[Petrified Forest Member]]),<br/>
[[Cooper Canyon Formation]],<br/>
[[Bull Canyon Formation]],
| An abundant wide-bodied typothoracine, known from multiple articulated skeletons.
| [[File:Typothorax coccinarum skeleton.jpg|150px]]
|-
|
''[[Venkatasuchus]]''<ref name=HRB23>{{Cite journal |last1=Haldar |first1=A. |last2=Ray |first2=S. |last3=Bandyopadhyay |first3=S. |year=2023 |title=A new typothoracine aetosaur (Archosauria, Pseudosuchia) from the Upper Triassic of India with insights on biostratigraphy, diversification, and paleobiogeography |journal=Journal of Vertebrate Paleontology |at=e2253292 |doi=10.1080/02724634.2023.2253292 |s2cid=265506966 }}</ref>
|
Valid 
|
middle [[Norian]] to [[Rhaetian]]
|
{{flag|India}} 
|
[[Lower Dharmaram Formation]]
| A wide-bodied typothoracine, known from a series of associated paramedian and lateral osteoderms as well as an isolated paramedian osteoderm.
|
|-
|}

===Phylogeny===
{|style="margin-left: 1em;; margin-bottom: 0.5em; width: 300px; border: #99B3FF solid 1px; background-color: #FFFFFF; color: #000000; float: right; "
|
{{center|1=<u>'''[[Cladogram]] from Parrish (1994)'''<ref name=PJM94/></u>}}
<br/>
{{clade| style=font-size:75%;line-height:85%
|label1=Rauisuchiformes&nbsp;
|1={{clade
   |1=[[Prestosuchidae]]
   |label2=&nbsp;'''Aetosauria'''&nbsp;
   |2={{clade
      |1=''Aetosaurus''
      |2={{clade
         |1={{clade
            |1=''Aetosauroides''
            |2=''Stagonolepis''}}
         |2={{clade
            |1=''Longosuchus''
            |2=''Desmatosuchus''
            |3={{clade
               |1=''Typothorax''
               |2=''Paratypothorax''}} }}
         |3=''Neoaetosauroides''
}} }} }} }}
|}

Aetosaur [[phylogeny]] was first investigated in 1994 by [[paleontologist]] [[J. Michael Parrish]]. ''Aetosauroides'', ''Aetosaurus'', ''Desmatosuchus'', ''Longosuchus'', ''Neoaetosauroides'', ''Stagonolepis'', and ''Typothorax'' were included in the phylogenetic analysis. Aetosaurs were found to form a [[clade]] with rauisuchians, which Parrish termed Rauisuchiformes. Rauisuchiformes also included the superorder [[Crocodylomorpha]], to which living [[crocodilia]]ns belong. Parrish found Aetosauria to be a [[monophyletic]] group and thus a true clade consisting of a common aetosaur ancestor and all of its descendants. To phylogenetically define Aetosauria, Parrish identified five [[synapomorphies]], or shared characteristics. The first synapomorphy concerned the jaw, with the [[premaxilla]] at its tip being edentulous (toothless), upturned, and wide to form a "shovel". Moreover, the [[dentary bone]] in the lower jaw is also toothless, upturned, and broad. The reduced size and simple conical shape of the teeth was considered another synapomorphy. Two more synapomorphies of aetosaurs are shared with crocodylomorphs, but were not considered to be an indication of a close phylogenetic relationship; the body is covered in dorsal and ventral armor to form a complete carapace, and the paramedian osteoderms are much wider than they are long, with distinctive pitting. A final synapomorphy was found in the structure of the limb bones. In all aetosaurs, the limbs are very robust, with large muscle attachments such as the deltopectoral crest of the [[humerus]], the [[fourth trochanter]] of the [[femur]], the intracondylar ridge of the [[tibia]], and the iliofibularis trochanter of the [[fibula]].<ref name=PJM94>{{cite journal |doi=10.1080/02724634.1994.10011552 |last=Parrish |first=J.M. |year=1994 |title=Cranial osteology of ''Longosuchus meadei'' and the phylogeny and distribution of the Aetosauria |journal=Journal of Vertebrate Paleontology |volume=14 |issue=2 |pages=196–209|bibcode=1994JVPal..14..196P }}</ref>

In Parrish's phylogenetic analysis, ''Aetosaurus'' was found to be the most [[basal (phylogenetics)|basal]] member of the clade, the earliest to diverge after the [[most recent common ancestor]]. After ''Aetosaurus'', there is a [[polytomy]] of three smaller clades in which it is unknown which clade diverged first from the group. Within this polytomy there was ''Neoaetosauroides'', a clade containing ''Aetosauroides'' and ''Stagonolepis'', and another polytomy that included ''Longosuchus'', ''Desmatosuchus'', and a clade containing ''Paratypothorax'' and ''Typothorax''.

A later study by paleontologists [[Andrew B. Heckert]] and [[Spencer G. Lucas]] in 1999 expanded the number of synapomorphies that diagnose Aetosauria to 18. New synapomorphies included [[temporal fenestra]]e, or holes, that opened on the side of the skull rather than the top, lateral osteoderms articulating with the paramedians, and osteoderms covering the limbs. ''Aetosaurus'' was still found to be the most basal member, but the phylogeny of more [[Synapomorphy|derived]] aetosaurs differed in that ''Typothorax'' and ''Paratypothorax'' were split into two different clades with their [[sister taxa]] being ''Desmatosuchus'' and ''Longosuchus'', respectively. More importantly, a new aetosaur called ''Coahomasuchus'' was included in the analysis. ''Coahomasuchus'' was found to be a basal aetosaur closely related to ''Stagonolepis'', and also appeared early in the fossil record of aetosaurs. Previously, basal members were only known from later times, occurring after more advanced aetosaurs.<ref name=HL99/>

In 2003, paleontologists [[Simon R. Harris]], [[David J. Gower]], and [[Mark Wilkinson (paleontologist)|Mark Wilkinson]] examined previous phylogenetic studies of aetosaurs and criticized the way in which they used certain characters to produce cladograms. They concluded that only three hypotheses of aetosaur relationships from previous studies were still true: that ''Aetosaurus'' is the most basal aetosaur, that ''Aetosauroides'' is the sister taxon of ''Stagonolepis robertsoni'', and that ''Longosuchus'' and ''Desmatosuchus'' are more closely related to each other than either is to ''Neoaetosauroides''. They also went on to correct the trees from all previous analyses.<ref name=HGW03>{{cite journal |last=Harris |first=S.R. |author2=Gower, D.J.|author3= Wilkinson, M. |year=2002 |title=Intraorganismal homology, character construction, and the phylogeny of aetosaurian archosaurs (Reptilia, Diapsida) |journal=Systematic Biology |pmid=12746149 |volume=52 |issue=2 |pages=239–52 |doi= 10.1080/10635150309341|url=http://www.bmnh.org/PDFs/SH_03_homology.pdf|doi-access=free }}</ref>

More recently, a 2007 analysis by paleontologist [[William G. Parker]] resulted in a larger tree of aetosaur phylogenetics with the inclusion of ''Heliocanthus''. Based on the tree, Parker defined the clades [[Typothoracisinae]] and [[Paratypothoracisini]], both within Aetosaurinae. Parker also gave a revised phylogenetic definition of Aetosauria, mentioning that the previous definition, made by Heckert and Lucas in 2000, was somewhat ambiguous.<ref name=PWG07/> Heckert & Lucas (2000) defined Aetosauria as a [[stem-based taxon]], claiming that Aetosauria included all crurotarsans that were more closely related to ''Desmatosuchus'' than to the immediate sister group of Aetosauria.<ref name=HL00>{{cite journal |last=Heckert |first=A. B. |author2= Lucas S. G. |year=2000 |title=Taxonomy, phylogeny, biostratigraphy, biochronology, paleobiogeography, and evolution of the Late Triassic Aetosauria (Archosauria: Crurotarsi) |journal=Zentralblatt für Geologie und Paläontologie, Teil I |volume=11-12 |pages=1539–1587}}</ref> Because the immediate sister group of Aetosauria was uncertain, Parker offered a new definition with several non-aetosaur crurotarsan genera rather than one sister group. According to Parker, Aetosauria included all taxa more closely related to ''Aetosaurus'' and ''Desmatosuchus'' than to ''[[Leptosuchus]]'', ''[[Postosuchus]]'', ''[[Prestosuchus]]'', ''[[Poposaurus]]'', ''[[Sphenosuchus]]'', ''[[Alligator]]'', ''[[Gracilisuchus]]'', and ''[[Revueltosaurus]]''.<ref name=PWG07/>

A new genus of aetosaur, ''[[Aetobarbakinoides]]'', was named in 2012. The phylogenetic analysis in that study found Aetosaurinae to be a [[paraphyletic]] grouping. As a paraphyletic group, aetosaurines would share a [[most recent common ancestor]] that is also the ancestor of other non-aetosaurine aetosaurs, and thus could not form their own [[clade]].<ref name=Aetobarbakinoides/> Parker's 2007 analysis accepted this definition. In 2002, Heckert and Lucas defined Aetosaurinae as "a [[stem-based taxon]] containing all taxa more closely related to ''Aetosaurus'' than to the last common ancestor of ''Aetosaurus'' and ''Desmatosuchus''".<ref name=PWG07/> The 2012 study placed ''Aetosaurus'' at the base of the stagonolepidid clade, with traditional aetosaurine taxa placed in successively more [[Synapomorphy|derived]] positions. In the analysis, these taxa are actually more closely related to ''Desmatosuchus'' than to ''Aetosaurus''. Thus, under Heckert and Lucas's definition Aetosaurinae might be restricted to only ''Aetosaurus'' itself.

Another finding of this study was that ''Aetosauroides'' lies outside Stagonolepididae. If this phylogeny is correct, Stagonolepididae and Aetosauria would not be equivalent groupings, and ''Aetosauroides'' would be the first non-stagonolepidid aetosaur. The following [[cladogram]] simplified after an analysis presented by Devin K. Hoffman, Andrew B. Heckert, and Lindsay E. Zanno.<ref>{{Cite journal|last1=Hoffman|first1=Devin K.|last2=Heckert|first2=Andrew B.|last3=Zanno|first3=Lindsay E.|date=13 February 2018|title=Under the armor: X-ray computed tomographic reconstruction of the internal skeleton of Coahomasuchus chathamensis (Archosauria: Aetosauria) from the Upper Triassic of North Carolina, USA, and a phylogenetic analysis of Aetosauria|journal=PeerJ|language=en|volume=6|pages=e4368|doi=10.7717/peerj.4368|pmid=29456892|pmc=5815331|issn=2167-8359|doi-access=free}}</ref>

{{Clade|{{clade
 |1=''[[Aetosauroides]]''
 |label2=[[Stagonolepididae]]
 |2={{clade
  |label1=[[Aetosaurinae]]
  |1={{clade
   |1=''[[Coahomasuchus]]''
   |2=''[[Aetosaurus]]''
   |label3=[[Typothoracisinae]]
   |3={{clade
    |1={{clade
     |1=''[[Gorgetosuchus]]''
     |2=''[[Redondasuchus]]''
     |3=''[[Typothorax]]'' }}
    |2={{clade
     |1=''[[Tecovasuchus]]''
     |2={{clade
      |1=''[[Rioarribasuchus]]''
      |2={{clade
       |1=''Paratypothorax'' 19003
       |2=''[[Paratypothorax]]'' type }} }} }} }} }}
  |2={{clade
   |label1=Stagonolepidinae
   |1={{clade
    |1=''[[Calyptosuchus wellesi]]''
    |2=''[[Stagonolepis robertsoni]]'' }}
   |label2=[[Desmatosuchinae]]
   |2={{clade
    |1=''[[Neoaetosauroides]]''
    |2={{clade
     |1={{clade
      |1=''[[Polesinesuchus]]''
      |2=''[[Aetobarbakinoides]]'' }}
     |2={{clade
      |1=''[[Longosuchus]]''
      |2={{clade
       |1=''[[Sierritasuchus]]''
       |2=''[[Acaenasuchus]]''
       |3={{clade
        |1=''[[Desmatosuchus smalli]]''
        |2=''[[Desmatosuchus spurensis]]'' }} }} }} }} }} }} }} }}|label1='''Aetosauria'''}}

In 2016, William Parker conducted a new phylogenetic analysis of the Aetosauria, proposing an alternative hypothesis of aetosaur relationships. Below is the cladogram:<ref name=":0">{{Cite journal|last=Parker|first=William G.|date=21 January 2016|title=Revised phylogenetic analysis of the Aetosauria (Archosauria: Pseudosuchia); assessing the effects of incongruent morphological character sets|journal=PeerJ|language=en|volume=4|pages=e1583|doi=10.7717/peerj.1583|pmid=26819845|pmc=4727975|issn=2167-8359|doi-access=free}}</ref>

{{clade| style=font-size:90%;line-height:85%
|label1=&nbsp;'''Aetosauria'''&nbsp;
|1={{clade
   |1=''[[Aetosauroides scagliai]]''
   |label2=&nbsp;[[Stagonolepididae]]&nbsp;
   |2={{clade
      |label1=&nbsp;[[Aetosaurinae]]&nbsp;
      |1={{clade
         |1=''[[Stenomyti huangae]]''
         |2={{clade
            |1=''[[Aetosaurus ferratus]]''
            |2=''[[Coahomasuchus kahleorum]]''
            |label3=&nbsp;[[Typothoracinae]]&nbsp;
            |3={{clade
               |1=''[[Apachesuchus heckerti]]''
               |2={{clade
                  |1={{clade
                     |1=''[[Typothorax coccinarum]]''
                     |2=''[[Redondasuchus rineharti]]'' }}
                  |label2=&nbsp;[[Paratypothoracisini]]&nbsp;
                  |2={{clade
                     |1=''[[Rioarribasuchus chamaensis]]''
                     |2={{clade
                        |1=SMSN 19003
                        |2={{clade
                           |1=''[[Tecovasuchus chatterjeei]]''
                           |2={{clade
                              |1=''[[Paratypothorax]] sp.''
                              |2=''[[Paratypothorax andressorum]]'' }} }} }} }} }} }} }} }}
      |label2=&nbsp;Desmatosuchia&nbsp;
      |2={{clade
         |label1=&nbsp;Stagonolepidinae&nbsp;
         |1={{clade
            |1=''[[Polesinesuchus aurelioi]]''
            |2=''[[Stagonolepis robertsoni]]'' }}
         |label2=&nbsp;[[Desmatosuchinae]]&nbsp;
         |2={{clade
            |1=''"[[Stagonolepis]]" olenkae''
            |2={{clade
               |1=''[[Neoaetosauroides engaeus]]''
               |2={{clade
                  |1={{clade
                     |1=''[[Calyptosuchus wellesi]]''
                     |2={{clade
                        |1=''[[Adamanasuchus eisenhardtae]]''
                        |2=''[[Scutarx deltatylus]]'' }} }}
                  |label2=&nbsp;Desmatosuchini&nbsp;
                  |2={{clade
                     |1=''[[Gorgetosuchus pekinensis]]''
                     |2={{clade
                        |1=''[[Longosuchus meadei]]''
                        |2={{clade
                           |1=''[[Sierritasuchus macalpini]]''
                           |2={{clade
                              |1=''[[Lucasuchus hunti]]''
                              |2={{clade
                                 |1=''[[Desmatosuchus smalli]]''
                                 |2=''[[Desmatosuchus spurensis]]'' }} }} }} }} }} }} }} }} }} }} }} }}

===Origin and evolution===
[[File:Revueltosaurus.jpg|thumb|right|250px|Life restoration of ''Revueltosaurus callenderi'', a pseudosuchian that may be close to the ancestry of aetosaurs.]]
Although aetosaurs are known exclusively from the Late Triassic, their currently accepted position in archosaur phylogeny indicates that they originated from more basal pseudosuchian archosaurs in the Early or Middle Triassic. Given that aetosaurs are highly specialized with many anatomical features not seen in other pseudosuchians, the group's evolutionary origins are poorly understood. The recent discovery of complete specimens of the Late Triassic pseudosuchian ''[[Revueltosaurus callenderi]]'' indicate that it may have been close to the ancestry of aetosaurs. Several phylogenetic analyses place it as the sister taxon or closest relative of Aetosauria. Like aetosaurs, ''Revueltosaurus'' has two rows of paramedian osteoderms along its back and, in the cheek region of the skull, a [[maxilla]] that fits into a groove of the [[jugal bone]].<ref name=Detal13/> One phylogenetic analysis places ''[[Turfanosuchus dabanensis]]'', a Middle Triassic pseudosuchian, as the sister taxon of ''Revueltosaurus'' and Aetosauria, potentially making it the earliest known "[[stem-based taxon|stem]] aetosaur" ("stem" meaning that it lies on the branch that includes aetosaurs, but is not itself an aetosaur).<ref name=NSASP12>{{cite journal |last=Nesbitt |first=S.J. |author2=Sidor, C.A.|author3= Angielczyk, K.D.|author4= Smith, R.M.|author5= Parker, W. |year=2012 |title=Derivation of the aetosaur osteoderm carapace: evidence from a new, exceptionally preserved "stem aetosaur" from the Middle Triassic (Anisian) Manda Beds of southwestern Tanzania |journal=Journal of Vertebrate Paleontology |volume=32 |issue=Supp. 1 |pages=149 | doi = 10.1080/02724634.2012.10635175|s2cid=220409377 }}</ref> However, other studies have considered ''Turfanosuchus'' part of a different family of pseudosuchians, the [[Gracilisuchidae|gracilisuchids]].<ref>{{Cite journal|last1=Butler|first1=Richard J.|last2=Sullivan|first2=Corwin|last3=Ezcurra|first3=Martín D.|last4=Liu|first4=Jun|last5=Lecuona|first5=Agustina|last6=Sookias|first6=Roland B.|date=10 June 2014|title=New clade of enigmatic early archosaurs yields insights into early pseudosuchian phylogeny and the biogeography of the archosaur radiation|journal=BMC Evolutionary Biology|volume=14|issue=1|pages=128|doi=10.1186/1471-2148-14-128|issn=1471-2148|pmc=4061117|pmid=24916124 |bibcode=2014BMCEE..14..128B |doi-access=free }}</ref>

In 2012 another "stem aetosaur" was described from the Middle Triassic [[Manda Beds]] of Tanzania. It differs from other Middle Triassic pseudosuchians in having a long skull, a small [[antorbital fenestra]] that fits into a large [[Antorbital fenestra|antorbital fossa]] in front of the eye socket, sharp and curved teeth, and osteoderms covering much of its body. Like aetosaurs and ''Revueltosaurus'', it has a maxilla that fits into the jugal. ''Revueltosaurus'', ''Turfanosuchus'', and the unnamed Tanzanian pseudosuchian are all good fits for the hypothesized ancestor of aetosaurs because they both have double rows of leaf-shaped osteoderms along their backs that could potentially have evolved into the tightly fitting paramedian osteoderms of aetosaurs.<ref name=NSASP12/>

==Paleobiology==

===Early interpretations===
In 1904, American paleontologist [[Henry Fairfield Osborn]] described aetosaurs as carnivorous aquatic animals of the order Parasuchia, mentioning that "[Parasuchia] constitutes an independent order, probably freshwater, littoral, carnivorous, short snouted (Aëtosaurus) or long snouted (Phytosaurus, Mystriosuchus) forms, analogous in their habits to the modern Crocodilia".<ref name=OHF04>{{cite journal |doi=10.1086/278383 |last=Osborn |first=H.F. |year=1904 |title=Reclassification of the reptilia |journal=The American Naturalist |volume=38 |issue=446 |pages=93–115|s2cid=84492986 |url=https://zenodo.org/record/1431333 }}</ref> Early aetosaur remains were often found in clays beside skeletons of aquatic animals such as phytosaurs and terrestrial animals such as [[dinosaur]]s and [[trilophosaur]]s. This may have led some paleontologists to believe that the animals had died in swampy environments. Because there were a large number of skeletons of animals that would not normally have inhabited swamps in these clays, some paleontologists even suggested that aetosaurs scavenged off the carcasses of animals that became trapped in the swamps and died. Doubts were later raised over this lifestyle, since aetosaur teeth show little indication of carnivory and the weight of the armor suggests that aetosaurs had "a passive mode of life." However, aetosaurs were still regarded as partly aquatic into the mid-20th century.<ref name=SHJ47/>

[[File:Restorations of Stagonolepis robertsoni, after skeletal by Hartman, 2016.jpg|thumb|Restorations of Stagonolepis robertsoni, after skeletal by Hartman, 2016]]

===Diet===
Aetosaurs were herbivores, likely feeding on [[fern]]s and [[seed fern]]s that were common in the Triassic. The upturned shape of their snout suggests that aetosaurs may have dug up roots and tubers.<ref name=ucmp>{{cite web |url=http://www.ucmp.berkeley.edu/diapsids/pseudosuchia/aetosauria.html |title=Introduction to the Aetosauria |first=K. |last=Ziehn |author2=Sangalang, E.|author3= Fritz-Laylin, L.|author4= Twu, C.|author5= Huynh, A.|author6= Smith, D. |date=1 May 2000 |work=University of California Museum of Paleontology - History of life through time |publisher=Regents of the University of California |access-date=18 August 2010| archive-url= https://web.archive.org/web/20100924001358/http://www.ucmp.berkeley.edu/diapsids/pseudosuchia/aetosauria.html| archive-date= 24 September 2010 | url-status= live}}</ref> Aetosaurs have several anatomical features that may have been adaptations to digging, including a short radius relative to the humerus (seen in many other digging tetrapods) and a large deltopectoral crest on the humerus that served as an attachment for muscles. Aetosaurs also have large hind feet, or [[pes (zoology)|pes]], with large claws that were likely used for skratch-digging. One aetosaur, ''Typothorax'', has an entepicondyle on the humerus, which is the origin of forearm [[Pronation|pronator]] and manual flexor muscles often used in digging. Moreover, it has a large [[olecranon process]] on the ulna which projects backward past the elbow, giving a large area for the insertion of the [[triceps]] muscle.<ref name="Hetal10"/> While many studies have suggested that aetosaurs had a [[fossorial]] or burrowing lifestyle,<ref name=PJM94/> aetosaurs have few of the characteristics that fossorial animals have as adaptations to digging. Therefore, it is likely that aetosaurs were able to dig to some extent, possibly rooting for food, but were unable to burrow.<ref name=Hetal10/>

While features of the limbs indicate that aetosaurs probably dug for food, features of the skull and teeth can indicate what kind of food they were eating. Aetosaurs have many derived features not seen in other crurotarsans, which indicate that they are adapted to a different diet. Unlike the sharp, recurved teeth of other triassic archosaurs, aetosaurs had simple, conical teeth. The tips of the jaws were [[edentulism|edentulous]], or toothless, and probably supported a beak. The teeth have very little wear, suggesting that aetosaurs did not consume stiff and tough plant material. It is more likely that they consumed non-abrasive vegetation such as soft leaves.<ref name=PJM94/>

Alternative theories have been proposed for the diet of aetosaurs. In 1947, [[H J Sawin]] proposed that the aetosaur ''Longosuchus'' was a scavenger based on the close proximity of some specimens to a large number of skeletons that were likely carcasses.<ref name=SHJ47/> A 2009 study of the jaw biomechanics of the South American genus ''Neoaetosauroides'' suggested that the animal may have fed on larvae and insects without hard exoskeletons. This is because ''Neoaetosauroides'' lacks serrations or wear facets on the teeth and has a jaw leverage that is not designed for strong forces such as crushing and chopping. The study recognized that northern aetosaurs such as ''Desmatosuchus'' and ''Stagonolepis'' did have jaws that would have supported a strong musculature, and were likely better suited to eating plant material.<ref name="SBJ02">{{cite journal|last=Small|first=B. J.|year=2002|title=Cranial anatomy of ''Desmatosuchus haplocerus'' (Reptilia: Archosauria: Stagonolepididae)|journal=Zoological Journal of the Linnean Society|volume=136|issue=1|pages=97–111|doi=10.1046/j.1096-3642.2002.00028.x|doi-access=free}}</ref><ref name="DV09">{{cite journal|last=Desojo|first=J.B.|author2=Vizcaíno, S.F.|year=2009|title=Jaw biomechanics in the South American aetosaur ''Neoaetosauroides engaeus''|journal=Paläontologische Zeitschrift|volume=83|issue=4|pages=499–510|doi=10.1007/s12542-009-0032-6|bibcode=2009PalZ...83..499D |s2cid=86520329|hdl=11336/97118|hdl-access=free}}</ref>

===Nests===
[[File:Desmatosuchus BW.jpg|thumb|right|250px|Life restoration of ''Desmatosuchus haplocerus''. This is likely the animal that made the nests discovered there in 1996.]]
At least some aetosaurs built nests and protected their eggs.<ref name=Aetal07>{{cite journal |last=Avanzini |first=M. |author2=Dalla vecchia, F.M. |author3=Mietto, P |author4=Piubelli, D |author5=Preto, N |author6=Rigo, M |author7=Roghi, G |year=2007 |title=A vertebrate nesting site in northeastern Italy reveals unexpectedly complex behavior for late Carnian reptiles |journal=PALAIOS |volume=22 |issue=5 |pages=465–475 |doi=10.2110/palo.2005.p05-137r|bibcode=2007Palai..22..465A |s2cid=131332250 |url=http://doc.rero.ch/record/14081/files/PAL_E1163.pdf }}</ref>

In 1996, geologist [[Stephen Hasiotis]] discovered 220‑million-year-old, fossilized, bowl-like pits in Arizona's Petrified Forest, in part of the [[Chinle Formation]], assumed to be aetosaur and [[phytosaur]] nests. The "nests" are compacted and appear very similar to the nests of the modern day [[crocodile]]s who guard their nests.<ref name=ucmp/> However, it seems that these "nests" are instead the result of sandstone weathering.<ref>Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and Their Kin
Capa
Sterling J. Nesbitt, Julia Brenda Desojo, Randall B. Irmis
Geological Society of London, 2013 - 608 páginas</ref>

A second possible aetosaur nest site is known from northeastern Italy. The nests are preserved as depressions in [[carbonate]] rock that are circular or horseshoe-shaped, with high ridges around the sides. They appear to be unusually complex for nests created by Triassic reptiles. Archosaur footprints were found nearby that resembled aetosaurs, although they were not present in the same layer. Because the tracks were found so close to the nests, it is likely that aetosaurs built them.<ref name="Aetal07"/>

===Development===
The ages of individual aetosaurs can be determined by examining their osteoderms. Some isolated osteoderms have been claimed to belong to juvenile aetosaurs based on their size and shape but these hypotheses have often been questioned. For example, juvenile osteoderms of ''Calyptosuchus'' were later identified as those of the small-bodied pseudosuchian ''[[Revueltosaurus]]'' (which is not an aetosaur), and juvenile osteoderms of ''Desmatosuchus'' have been reinterpreted as those of aetosaur ''Acaenasuchus'', which had a relatively small body size at maturity. Studies of the bone structure of paramedian osteoderms indicate that new bone was deposited along the edges of each plate over the course of an aetosaur's lifetime. This means that [[lines of arrested growth]] on the undersides of paramedian osteoderms can be used to determine an individual's age.<ref name=Detal13/> Comparing the ages of individual specimens with their total body lengths indicates that aetosaurs increased in length at relatively constant rates, but increased in body mass at different rates depending on whether they had wide bodies like ''Typothorax'' or narrow bodies like ''Aetobarbakinoides''. Aetosaurs also seem to have grown more slowly than modern crocodilians.<ref name=TCD13>{{Cite journal | last1 = Taborda | first1 = J. R. A. | last2 = Cerda | first2 = I. A. | last3 = Desojo | first3 = J. B. | doi = 10.1144/SP379.19 | title = Growth curve of Aetosauroides scagliai Casamiquela 1960 (Pseudosuchia: Aetosauria) inferred from osteoderm histology | journal = Geological Society, London, Special Publications | year = 2013 | volume=379 | issue = 1 | pages=413–423| bibcode = 2013GSLSP.379..413T | hdl = 11336/8849 | s2cid = 130820684 | hdl-access = free }}</ref> Analysis of the limb bones of aetosaurs indicates that they grew quickly when young and more slowly when adults. This pattern of growth is seen in most other pseudosuchians.<ref name=Detal13/>

==Biochronology==
Because species of aetosaurs typically have restricted fossil ranges and are abundant in the strata they are found in, they are useful in [[biochronology]]. Osteoderms are the most common remains associated with aetosaurs, so a single identifiable scute can accurately date the layer it is found in.
{{:Template:Aetosaur biochronology timeline}}

One aetosaur, ''Typothorax coccinarum'', has been used to define the [[Revueltian]] [[land vertebrate faunachron]]. A land vertebrate faunachron (LVF) is a time interval that is defined by the first appearance datum (FAD), or first occurrence, of a [[tetrapod]] index fossil and is commonly used to date Late Triassic and [[Early Jurassic]] terrestrial strata.<ref name=LSG91>{{cite journal |last=Lucas |first=S.G. |year=1991 |title=Sequence stratigraphic correlation of nonmarine and marine Late Triassic biochronologies, western United States |journal=Albertiana |volume=9 |pages=11–18}}</ref><ref name=LH93>{{cite book |last=Lucas |first=S.G. |author2=Hunt, A.P. |year=1993 |chapter=Tetrapod biochronology of the Chinle Group (Upper Triassic), western United States |chapter-url=http://econtent.unm.edu/cdm4/document.php?CISOROOT=/bulletins&CISOPTR=1180&REC=4 |title=The Nonmarine Triassic |editor=Lucas, S.G.  |editor2=Morales, M. |series=New Mexico Museum of Natural History and Science Bulletin |volume=3 |pages=327–329}}</ref> Since the FAD of ''T. coccinarum'' is at the beginning of the [[Norian]] stage, the Revueltian LVF starts at the beginning of the Norian around 216 [[Mya (unit)|million years ago]]. The Revueltian ends with the next FAD, which happens to be that of the phytosaur ''[[Redondasaurus]]'' and the start of the [[Apachean (faunachron)|Apachean]] LVF.<ref name=LSG98a/><ref name=Letal07>{{cite book |last=Lucas |first=S.G. |author2=Hunt, A.P. |author3=Heckert, A.B. |author4=Spielmann, J.A. |year=2007 |chapter=Global Triassic tetrapod biostratigraphy and biochronology: 2007 status |chapter-url=http://paleo.cortland.edu/globaltriassic/Bull41/35-Lucas%20et%20al%20(LVF).pdf |title=The Global Triassic |editor=Lucas, S.G. |editor2=Spielmann, J.A. |series=New Mexico Museum of Natural History and Science Bulletin |volume=41 |pages=229–240 |access-date=17 July 2010 |archive-date=27 September 2011 |archive-url=https://web.archive.org/web/20110927060257/http://paleo.cortland.edu/globaltriassic/Bull41/35-Lucas%20et%20al%20(LVF).pdf |url-status=dead }}</ref>

Biochrons for aetosaur genera have been developed for dating strata in the [[Chinle Group]] of the southwestern United States. Up to 13 genera of aetosaurs are known from the Chinle Group, with most occurring in multiple localities and over short time spans. In 1996, paleontologists [[Spencer G. Lucas]] and [[Andrew B. Heckert]] recognized five biochrons based on the presence of aetosaurs throughout the Chinle Group.<ref name=LH96>{{cite journal |last=Lucas |first=S.G. |author2=Heckert, A.B. |year=1996 |title=Late Triassic aetosaur biochronology |journal=Albertiana |volume=17 |pages=57–64}}</ref> The number of biochrons grew to 11 in a 2007 study by Heckert and Lucas along with [[Adrian P. Hunt]] and [[Justin A. Spielmann]]. These biochrons occurred from the [[Otischalkian]] LVF to the Apachean LVF and included genera such as ''Longosuchus'', ''Tecovasuchus'', and ''Typothorax''.<ref name=Hetal07/>

=="Aetogate" naming controversy==
{{main|Rioarribasuchus|Redondasuchus}}
In 2007, paleontologists at the [[New Mexico Museum of Natural History and Science]] in [[Albuquerque, New Mexico]] were accused of [[plagiarism]] in some of their published articles dealing with aetosaurs. In December 2006, the genus ''Rioarribasuchus'' was erected as a replacement name for ''"Desmatosuchus" chamaensis'' in the museum's bulletin.<ref name=LHS06>{{cite book |last=Lucas |first=S.G. |author2=Hunt, A.P.|author3= Spielmann, J.A. |year=2006 |chapter=''Rioarribasuchus'', a new name for an aetosaur from the Upper Triassic of north-central New Mexico |title=The Triassic-Jurassic Terrestrial Transition |editor=Harris |display-editors=etal |series=New Mexico Museum of Natural History and Science Bulletin |publisher=New Mexico Museum of Natural History and Science |location=Albuquerque |pages=37}}</ref> However, four years earlier paleontologist [[William Parker (paleontologist)|William Parker]] reassigned ''"D." chamaensis'' to the newly named genus ''Heliocanthus'' in an unpublished thesis, which was widely disseminated among aetosaur researchers.<ref name=PWG03>{{cite thesis |degree=M.Sc. |title=Description of a new specimen of ''Desmatosuchus haplocerus'' from the Late Triassic of Northern Arizona |last=Parker |first=W.G. |year=2003 |publisher=Northern Arizona University |location=Flagstaff |pages=315}}</ref> Because the name was not formally published, it was considered a ''[[nomen nudum]]'' until January 2007, when Parker's description of ''Heliocanthus'' was published in the ''[[Journal of Systematic Palaeontology]]''.<ref name=PWG07/> The authors of the 2006 paper, Spencer G. Lucas, Adrian P. Hunt, and Justin A. Spielmann, were accused of "intellectual theft" by paleontologists [[Jeff Martz]], [[Mike Taylor (paleontologist)|Mike Taylor]], [[Matt Wedel]], and [[Darren Naish]], who claimed that Lucas et al. knew that Parker would eventually redescribe the species and formally erect a new genus. According to Martz, Taylor, Wedel, and Naish, the authors rushed to publish their own name before Parker could publish his.<ref name=MTWN08>{{cite web |url=http://www.miketaylor.org.uk/dino/nm/timeline.html |title=Timeline of publications and letters |first=Jeff |last=Martz |author2= Taylor, Mark|author3= Wedel, Matt|author4= Naish, Darren |date=1 June 2008 |work=Aetogate: asking for answers in New Mexico |access-date=15 August 2010}}</ref> At the time, Lucas, Hunt, and Spielmann were on the editorial board of the NMMNHS bulletin, while Hunt was also the museum director. 

A coinciding controversy occurred after Spielmann, Hunt, and Lucas published a 2006 paper mentioning that the [[holotype]] of ''Redondasuchus'' was not a left paramedian, but instead a right one.<ref name=Setal06>{{cite book |last=Spielmann |first=J.A. |author2=Hunt, A.P.|author3= Lucas, S.G.|author4= Heckert, A.B. |year=2006 |chapter=Revision of ''Redondasuchus'' (Archosauria: Aetosauria) from the Upper Triassic Redonda Formation, New Mexico, with description of a new species |title=The Triassic-Jurassic Terrestrial Transition |chapter-url=http://www.miketaylor.org.uk/dino/nm/SpielmannEtAl2006-revision-of-redondasuchus.pdf |editor=Harris, H.D. |editor2=Lucas, S.G. |editor3=Spielmann, J.A. |editor4=Lockley, M.G. |editor5=Milner, A.R.C. |editor6= Kirkland, J.L. |publisher=New Mexico Museum of Natural History and Science Bulletin |volume=37 |pages=583–587}}</ref> In 2002, Jeff Martz came to the same conclusion in an unpublished thesis.<ref name=MJW02>{{Cite thesis |degree=M.Sc. |title=The morphology and ontogeny of ''Typothorax coccinarum'' (Archosauria Stagonolepididae) from the Upper Triassic of the American Southwest |url=http://www.miketaylor.org.uk/dino/nm/Martz2002-thesis.pdf |last=Martz |first=J.W. |year=2002 |publisher= Texas Tech University |access-date=3 July 2010}}</ref> He, along with Taylor, Wedel, and Naish, claimed that this was another form of plagiarism, as Martz's 2002 thesis was cited by Spielmann et al. (2006), even if his conclusion on ''Redondasuchus'' was not mentioned.<ref name=MTWN08/>

The allegations were rejected in an internal NMMNHS meeting, reported by Lucas in 2008.<ref>{{Cite web|last=Lucas|first=Spencer|date=3 March 2008|title=Written Responses on Allegations, Suggestions to Improve the NMNHS Bulletin|url=http://www.miketaylor.org.uk/dino/nm/nmnhslucas.pdf|url-status=live|publisher=New Mexico Museum of Natural History and Science|archive-url=https://web.archive.org/web/20080828063004/http://www.miketaylor.org.uk/dino/nm/nmnhslucas.pdf |archive-date=28 August 2008 }}</ref><ref name="MTWN082">{{cite web|last=Martz|first=J.|author2=Taylor, M.|author3=Wedel, M.|author4=Naish, D.|date=10 March 2008|title=Aetogate: Martz's response to Spencer Lucas|url=http://www.miketaylor.org.uk/dino/nm/visit/martz.html|access-date=3 July 2010|work=Miketaylor.org.uk}}</ref><ref name="MTWN102">{{cite web|last=Martz|first=J.|author2=Taylor, M.|author3=Wedel, M.|author4=Naish, D.|date=17 February 2010|title=Aetogate: asking for answers in New Mexico|url=http://www.miketaylor.org.uk/dino/nm/index.html|access-date=3 July 2010|work=Miketaylor.org.uk}}</ref> They were also brought to the attention of an independent party, the Ethics Education Committee of the [[Society of Vertebrate Paleontology]] (SVP) in 2007, and a response was given in 2008. In regard to ''Redondasuchus'', the SVP found no explicit evidence for plagiarism. In the case of ''Heliocanthus'' and ''Rioarribasuchus'', the SVP did not try to resolve the issue, as Lucas et al. and Parker offered conflicting accounts regarding communication and intent. The SVP's response concluded with an update to its ethics policy and recommendations for how similar controversies could be better handled in the future.<ref name=SVP08>{{cite journal|year=2008 |title=Statement from the Executive Committee about the allegations of unethical conduct from J. Martz, W. Parker, M. Taylor and M. Wedel against S. Lucas, A. Hunt, A. Heckert, and J. Spielmann |publisher=Society of Vertebrate Paleontology |url=http://www.vertpaleo.org/society/documents/ExecutiveCommitteestatement.pdf |url-status=dead |archive-url=https://web.archive.org/web/20100714230435/https://www.vertpaleo.org/society/documents/ExecutiveCommitteestatement.pdf |archive-date=14 July 2010 }}</ref><ref>{{Cite web|date=23 May 2008|title=Best practices from the Ethics Education Committee regarding research, publication, and museum work|url=http://www.miketaylor.org.uk/dino/nm/ExecutiveCommitteestatement.pdf|url-status=live|website=Society of Vertebrate Paleontology|archive-url=https://web.archive.org/web/20081011072440/http://www.miketaylor.org.uk/dino/nm/ExecutiveCommitteestatement.pdf |archive-date=11 October 2008 }}</ref><ref>{{Cite web|last=Society of Vertebrate Paleontology Executive Committee|date=23 May 2008|title=Statement from the Executive Committee about the allegations of unethical conduct from J. Martz, W. Parker, M. Taylor and M. Wedel against S. Lucas, A. Hunt, A. Heckert, and J. Spielmann|url=http://www.miketaylor.org.uk/dino/nm/ExecutiveCommitteestatement.pdf|url-status=live|website=Society of Vertebrate Paleontology|archive-url=https://web.archive.org/web/20081011072440/http://www.miketaylor.org.uk/dino/nm/ExecutiveCommitteestatement.pdf |archive-date=11 October 2008 }}</ref> The entire controversy came to be known as "Aetogate", in reference to the famous [[Watergate scandal]] of the 1970s.<ref name="MTWN08" /> It received wide attention from local Albuquerque newspapers and science blogs.<ref name="MTWN10">{{cite web |url=http://www.miketaylor.org.uk/dino/nm/ |title=Press Coverage |first=Jeff |last=Martz |author2= Taylor, Mark|author3= Wedel, Matt|author4= Naish, Darren |date=17 February 2010 |work=Aetogate: asking for answers in New Mexico |access-date=15 August 2010}}</ref> It was also the focus of a news article in a 2008 issue of the journal ''[[Nature (journal)|Nature]]''.<ref name="DR08">{{cite journal |last=Dalton |first=R. |year=2008 |title=Fossil reptiles mired in controversy |journal=Nature |pmid=18235465 |volume=451 |issue=7178 |pages=510 |doi=10.1038/451510a |bibcode=2008Natur.451..510D |doi-access=free }}</ref>

== References ==
{{Reflist}}

==General references==
{{refbegin}}
* [[Michael J. Benton|Benton, M. J.]] (2000). ''[[Vertebrate Palaeontology (Benton)|Vertebrate Paleontology]]'', 2nd ed. Blackwell Science Ltd.
{{refend}}

== External links ==
{{Commons category|Aetosauria|Aetosaur}}
{{Wikispecies|Aetosauria|Aetosaur}}

{{Portal|Paleontology|Reptiles}}
* [https://web.archive.org/web/20060313165459/http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.800.html Archosauromorpha: Suchia (Aetosauridae)] - [[Palaeos]].com
* [https://web.archive.org/web/20060315212944/http://www.dinosauria.com/dml/names/aetoi.htm Aetosauria Translation and Pronunciation Guide] - Ben Creisler
* [http://www.ucmp.berkeley.edu/diapsids/pseudosuchia/aetosauria.html Introduction to the Aetosauria] - [[University of California Museum of Paleontology]]

{{Good article}}
{{Aetosauria}}
{{Taxonbar|from=Q131967}}

[[Category:Aetosaurs| ]]
[[Category:Norian first appearances]]
[[Category:Late Triassic extinctions]]