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{{automatic taxobox
{{automatic taxobox
| fossil_range = [[Late Cretaceous]], {{fossilrange|85.8|earliest=93.5}}
| fossil_range = [[Late Cretaceous]], {{fossilrange|83.6}}
| image = Aralosaurus skull.png
| image = Aralosaurus skull.png
| image_caption = Skull of ''Aralosaurus''. Known material white
| image_caption = Skull of ''Aralosaurus''. Known material white. This is the former reconstruction of ''Aralosaurus'' depicting incorrectly the animal as a Gryposaur-like Hadrosaurinae.<ref name="Godefroit & al.2004"/>
| taxon = Aralosaurus
| taxon = Aralosaurus
| authority = [[Anatoly Konstantinovich Rozhdestvensky|Rozhdestvensky]], 1968
| authority = [[Anatoly Konstantinovich Rozhdestvensky|Rozhdestvensky]], 1968
Line 9: Line 9:
}}
}}


'''''Aralosaurus''''' was a [[genus]] of [[Hadrosauridae|hadrosaurid]] [[dinosaur]] that lived during the [[Late Cretaceous]] in what is now [[Kazakhstan]]. It is known only by a posterior half of a skull (devoid of its mandible) and some post-cranial bones<ref name="Rozhdestvensky 1968">{{cite journal|last=Rozhdestvensky|first=A.K.|title=Gadrozavry Kazakhstana [Hadrosaurs of Kazakhstan]. [Upper Paleozoic and Mesozoic Amphibians and Reptiles]|journal=Akademia Nauk SSSR, Moscow|year=1968|volume=|pages=97-141|url=http://www.dinochecker.com/papers/Hadrosaurs_of_Kazakhstan_Rozhdestvensky_1968.pdf|}}</ref> found in the [[Bostobe Formation]] in rocks dated from the Upper [[Santonian]]-Lower [[Campanian]] boundary, at about 83.6 Ma (millions of years).<ref name="Prieto-Márquez & al.2013">{{cite journal|last=Prieto-Márquez|first=A.|author2=Dalla Vecchia, F.M.|author3=Gaete, R.|author4=Galobart, À.|title=Diversity, Relationships, and Biogeography of the Lambeosaurine Dinosaurs from the European Archipelago, with Description of the New Aralosaurin ''Canardia garonnensis''|journal=PLos ONE|year=2013|volume=8(7): e69835|pages=1-44|doi=10.1371/journal.pone.0069835|}}</ref> Only one [[species]] is known, ''Aralosaurus tuberiferus'', described by [[Anatoly Konstantinovich Rozhdestvensky]] in 1968. The genus name means [[Aral Sea]] lizard, because it was found to the northeast of the Aral Sea.<ref name="Rozhdestvensky 1968"/> The specific epithet ''tuberiferus'' means bearing a tuber because the posterior part of the [[nasal bone]] rises sharply in front of the [[Orbit (anatomy)|orbits]] like an outgrowth.<ref name="Rozhdestvensky 1968"/> ''Aralosaurus'' was originally reconstituted with a nasal arch similar to that of North American ''[[Kritosaurus]]'' (a comparison based on a specimen now placed in the genus ''[[Gryposaurus]]'').<ref name="Rozhdestvensky 1968"/> For many years, ''Aralosaurus'' was thus placed in the clade of the [[Hadrosaurinae]]. This classification was invalidated in 2004, following the re-examination of the skull of the animal which allowed to identify in ''Aralosaurus'' many typical characters of [[Lambeosaurinae]]. In particular, this study revealed that ''Aralosaurus'' had a hollow bony structure located far in front of the orbits, which communicated with the [[respiratory tract]].<ref name="Godefroit & al.2004">{{cite journal|last1=Godefroit|first1=P.|author2=Alifanov, V.|author3=Boltsky, Y.|title=A re-appraisal of "Aralosaurus tuberiferus" (Dinosauria, Hadrosauridae) from the Late Cretaceous of Kazakhstan|journal=Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre|date=2004|issue=74|pages=139-154|url=http://biblio.naturalsciences.be/rbins-publications/bulletin-of-the-royal-belgian-institute-of-natural-sciences-earth-sciences/bulletin-of-the-royal-belgian-institute-of-natural-sciences-earth-sciences/godefroit_reappraisal_2004|}}</ref> This structure being broken at its base, its shape and size unfortunately remains undetermined.<ref name="Godefroit & al.2004"/> More recently, ''Aralosaurus'' has been identified as the most basal Lambeosaurinae, and placed with its close relative ''[[Canardia]]'' from the upper [[Maastrichtian]] of [[France]] in the new clade of [[Aralosaurini]].<ref name="Prieto-Márquez & al.2013"/>
'''''Aralosaurus''''' (meaning "[[Aral Sea]] lizard", because it was found in the [[Aral Sea]] - [[Greek language|Greek]] ''sauros'' = lizard) was a [[genus]] of [[hadrosaurid]] [[dinosaur]] which lived during the Late [[Cretaceous]] [[Bostobe Formation]] of what is now [[Kazakhstan]].<ref name="ageofdinosaursaralosaurus"/> ''Aralosaurus'' was characterized by a small, bony peak on its nose, much like its relatives ''[[Maiasaura]]'' and ''[[Gryposaurus]]''.<ref name="ageofdinosaursaralosaurus">"Aralosaurus". In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 126. {{ISBN|0-7853-0443-6}}.</ref> It was described by Soviet paleontologist A. Rozhdestvensky in 1968.<ref>A. K. Rozhdestvensky. 1968. Gadrozavry Kazakhstana [Hadrosaurs of Kazakhstan]. [Upper Paleozoic and Mesozoic Amphibians and Reptiles]. Akademia Nauk SSSR, Moscow 97-141</ref>


=Discovery=
''Aralosaurus'' was a [[herbivore]] that lived in the late [[Cretaceous]] period, sometime between 93.5 and 85.8 million years ago.<ref name="Holtz2008">Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' [http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf Winter 2011 Appendix.]</ref> Several relatives, such as ''[[Jaxartosaurus]]'' have also been found in the surrounding area where ''Aralosaurus'' was found.
The partial [[skull]] of ''Aralosaurus'' was discovered in 1957 near the Shakh-Shakh locality during a [[Soviet people|Soviet]] expedition in central Kazakhstan (which at the time was part of the [[Soviet Union|USSR]]). In addition to the skull (which lacks most of the [[snout]] and the entire [[Jaw|mandible]]), the material also included isolated [[tooth|teeth]] and postcranial elements most often fragmentary ([[ulna]], [[Radius (bone)|radius]], [[femur]], [[tibia]], [[fibula]], [[Talus bone|astragalus]], [[Metatarsal bones|metatarsals]]). The only complete elements were a [[humerus]] and a metatarsal. It is only in 1968 that Rozhdestvensky described and named the animal. He estimated the size of the skull at about 65 cm and the size of the animal at about 6.5 m long. As the cranial sutures are far from fusioned, this specimen was probably immature. At the time, Rozhdestvensky argued that the skull of ''Aralosaurus'' presented the greatest ressemblance with the skull of ''[[Kritosaurus]]'' with the presence of a nasal arch in front of the [[Orbit (anatomy)|orbits]] (the comparisons were based with specimens attributed today to ''[[Gryposaurus]]'', not to ''Kritosaurus''). So, the animal was classified among the [[Hadrosaurinae]], which are hadrosaurs devoid of cranial crest or with a solid bony crest.<ref name="Rozhdestvensky 1968"/>
In 2004, the skull of ''Aralosaurus'' was re-examined by Godedroit and colleagues, and according to them, the bone fragments identified by Rozhdestvensky as the middle part of the nasal arch and the posterior portion of the [[premaxilla]] seem to have been lost. These fragments were originally found isolated while the rest of the skull was articulated (including a posterior fragment of the nasal). So that it is no longer possible today to confirm the presence of a nasal arch in ''Aralosaurus''. On the other hand, this study shows that ''Aralosaurus'' was not a gryposaur-like hadrosaurine, because the puported nasal boss was in fact a fragment of a hollow structure. Indeed, Godefroit and colleagues did not find any hadrosaurines diagnostic characters in ''Aralosaurus''. On the contrary, the skull of ''Aralosaurus'' presents several features (in the [[maxilla]], [[Parietal bone|parietal]], [[Squamosal bone|squamosal]] and especially the [[Nasal bone|nasal]]) which indicates its inclusion among the [[Lambeosaurinae]]. Notably, the posterior fragment of the nasal, which is clearly articulated to the rest of the skull, rises just in front of the orbits and forming or participating to a hollow crest-like structure. As this structure is broken at its base, it is not possible to deduce its size and shape. However, in rostral view, the nasal is clearly hollow, it is deeply excavated rostrally by a broad groove that communicates directly with the ventral side of the posterior part of the bone. It is therefore clear that in ''Aralosaurus'' the nasal crest surrounded part of the [[respiratory system]]. The extension of the nasal cavity inside a hollow crest is typically a lambeosaurine feature, thus confirming the inclusion of ''Aralosaurus'' among them.<ref name="Godefroit & al.2004"/> ''Aralosaurus'' also exhibits several cranial characters which indicate that it was a [[Basal (phylogenetics)|basal]] member of the group. Although having a hollow nasal structure, the latter was located in front of the orbits, a primitive position in lambeosaurines. In the most advanced representatives of the group, the nasal migrates to a caudodorsal position because of the important development of the [[Premaxilla|premaxillae]] in these forms. In addition, in more derived lambeosaurines, the skull roof is modified to form a fixation zone for the hollow crest, whereas in ''Aralosaurus'' the skull roof does not present any particular modification. The shape and the size of the crest-like structure of ''Aralosaurus'' is unknown. Unfortunately, the fragments that was previously interpreted as a part of a gryposaur-like nasal arch and could have helped to reconstruct the circumnarial region of ''Aralosaurus'', have been lost.<ref name="Godefroit & al.2004"/>. So, the discovery of more complete specimens is necessary for a better knowledge of the shape and the size of this hollow structure.


==Description==
=Description=
Beside the participation of the nasal in a hollow structure in front of the orbits, ''Aralosaurus'' is also distinguished by the morphology of its [[maxilla]]. ''Aralosaurus'' has a maxilla with an enlarged rostrodorsal region that forms a prominent subrectangular flange that rises vertically above the rostroventral [[Process (anatomy)|process]].<ref name="Prieto-Márquez & al.2013"/> Recently, this trait has also been found in ''[[Canardia]]'' from the upper Maastrichtian of France, which is closely related to ''Aralosaurus''. However, the maxilla of ''Aralosaurus'' differs from the French form in exhibiting a clearly inclined [[ectopterygoid]] shelf whereas in ''Canardia'' the same element is subhorizontal (it is parallel to the posterior segment of the dental row).<ref name="Prieto-Márquez & al.2013"/> The maxilla of ''Aralosaurus'' carries 30 rows of teeth<ref name="Rozhdestvensky 1968"/> while ''Canardia'' has at least 26 rows (part of the dental row is not preserved in the latter).<ref name="Prieto-Márquez & al.2013"/> The maxillary teeth of ''Aralosaurus'' bear a single central ridge, while the only known tooth of the [[mandible|lower jaw]] has a fine secondary ridge placed in front of the central ridge.<ref name="Rozhdestvensky 1968"/> A condition also observed in ''Canardia'' and in many other hadrosaurs.<ref name="Prieto-Márquez & al.2013"/>. ''Aralosaurus'' differs also from ''Canardia'' by the shape of the [[Prefrontal bone|prefrontal]] in dorsal view. In ''Aralosaurus'', the rostroventral process of the prefrontal is broad and laterally well-exposed whereas in ''Canardia'' the same bone process is rostrocaudally narrow.<ref name="Prieto-Márquez & al.2013"/>. In addition, the prefrontal of ''Aralosaurus'' does not have the dorsomedial flange present in ''Canardia''.<ref name="Prieto-Márquez & al.2013"/> Godefroit and colleagues also report the presence of primitive characters in ''Aralosaurus'' such as the [[Frontal bone|frontal]] that participates in the upper margin of the orbit, and a prefrontal oriented laterally and not participating in the lateral wall of the hollow crest.<ref name="Godefroit & al.2004"/>
''Aralosaurus'' was about the size of an [[elephant]]. Although only one near complete [[skull]] has been found,<ref name="ageofdinosaursaralosaurus"/> this allowed to identify it due to the presence of a beak with nearly 1,000 small teeth in 30 rows.<ref name="ageofdinosaursaralosaurus"/> These teeth were used for breaking up [[plant]] matter by chewing, a feature common in herbivorous dinosaurs, but unusual for [[reptiles]].The back of an ''Aralosaurus'' skull was wide, a feature suggestive of large [[jaw muscles]] used to power its chewing apparatus.<ref name="ageofdinosaursaralosaurus"/>


=Phylogeny=
The nasal peak before the eyes was common to most hadrosaurs. This bump may have also been used as a weapon in duels between males by [[head butting]] into one another, much like modern day animals such as [[Sheep|rams]] and [[goat]]s. It had a thick tail, bulky body and powerful hind legs, all also common with other hadrosaurs.
The following cladogram was produced by Albert Prieto-Márquez and his colleagues in 2013, it shows the phylogeny of [[Lambeosaurinae]]. ''Aralosaurus'' is closely related to ''Canardia'' and both genera are included in the tribe of [[Aralosaurini]], which are identified as the most basal members of Lambeosaurinae.

<center>{{clade| style=font-size:85%;line-height:85%
|label1=&nbsp;'''[[Lambeosaurinae]]'''&nbsp;
|1={{clade
|label1='''[[Aralosaurini]]'''
|1={{clade
|1='''''Aralosaurus'''''
|2=''[[Canardia]]''}}
|2={{clade
|1=''[[Jaxartosaurus]]''
|2={{clade
|label1=[[Tsintaosaurini]]
|1={{clade
|1=''[[Tsintaosaurus]]''
|3=''[[Pararhabdodon]]'' }}
|2={{clade
|label1=[[Parasaurolophini]]
|1={{clade
|1=''[[Charonosaurus]]''
|label2=''[[Parasaurolophus]]''
|2={{clade
|1=''[[Parasaurolophus cyrtocristatus]]''
|2={{clade
|1=''[[Parasaurolophus tubicen]]''
|2=''[[Parasaurolophus walkeri]]'' }} }} }}
|label2=[[Lambeosaurini]]
|2={{clade
|label1=''[[Lambeosaurus]]''
|1={{clade
|1=''[[Lambeosaurus lambei]]''
|2=''[[Lambeosaurus magnicristatus]]'' }}
|2={{clade
|label1=''[[Corythosaurus]]''
|1={{clade
|1=''[[Corythosaurus casuarius]]''
|2=''[[Corythosaurus intermedius]]'' }}
|2={{clade
|1=[[Hypacrosaurus|"Hypacrosaurus" ''stebingeri'']]
|2={{clade
|1=''[[Hypacrosaurus]]''
|2=''[[Olorotitan]]''
|3={{clade
|1=''[[Arenysaurus]]''
|2=''[[Blasisaurus]]'' }}
|4={{clade
|1=''[[Magnapaulia]]''
|2={{clade
|1=''[[Velafrons]]''
|2={{clade
|1=''[[Amurosaurus]]''
|2=''[[Sahaliyania]]'' }} }} }} }} }} }} }} }} }} }} }} }}</center>

=Paleobiogeography=
''Aralosaurus'' lived about 20 millions years before its close relative ''Canardia''. The later inhabited the Ibero-Armorican Island, which was the westernmost island of the Late Cretaceous [[Europe|European]] [[Archipelago]].<ref name="Csiki-Sava & al.2015">{{cite journal|last=Csiki-Sava|first=Z.|author2=Buffetaut, E.|author3=Ősi, A.|author4=Pereda-Suberbiola, X.|author5=Brusatte, S.L.|title=Island life in the Cretaceous-faunal composition, biostratigraphy, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago|journal=ZooKeys|year=2015|volume=469|pages=1-161|url=https://zookeys.pensoft.net/article/4474/download/pdf/|doi=10.3897/zookeys.469.8439||pmc=4296572}}</ref> As no lambeosaurines were known in the rich localities of late [[Campanian]] and early [[Maastrichtian]] ages of the Ibero-Armorican Island, it was suggested that the descendants of ''Aralosaurus'' had to reach this island rather late, perhaps at the end of the early Maastrichtian or during the late Maastrichtian.<ref name="Prieto-Márquez & al.2013"/> The discovery later in Spain of numerous lambeosaurines remains in the highest levels of the lower Maastrichtian argues for the first hypothesis.<ref name="Fondevilla & al.2018">{{cite journal|last=Fondevilla|first=V.|author2=Dalla Vecchia, F.M.|author3=Gaete, R.|author4=Galobart, À.|author5=Moncunill-Solé, B.|author6=Köhler, M.|title=Ontogeny and taxonomy of the hadrosaur (Dinosauria, Ornithopoda) remains from Basturs Poble bonebed (late early Maastrichtian, tremp Syncline, Spain)|journal=Plos ONE|year=2018|volume=13(10): e0206287|pages=1-33|doi=10.1371/journal.pone.0206287|}}</ref><ref name="Prieto-Márquez & al.2019">{{cite journal|last=Prieto-Márquez|first=A.|author2=Fondevilla, V.|author3=Sellés, A.G.|author4=Wagner, J.R.|author5=Galobart, À.|title=''Adynomosaurus arcanus'', a new lambeosaurine dinosaur from the Late Cretaceous Ibero-Armorican Island of the European Archipelago|journal=Cretaceous Research|year=2019|volume=96|pages=19-37|doi=10.1016/j.cretres.2018.12.002|}}</ref> This [[Migration (ecology)|migration]] was probably carried out in several stages, firstly by temporary terrestrial links between the landmass of Western Asia and the eastern islands of the European archipelago, then between the different European islands up to the Ibero-Armorican Island.<ref name="Csiki-Sava & al.2015"/> ''Canardia'' was a rather archaic form for its time and the Ibero-Armorican Island was perhaps an ultimate refuge for the [[Aralosaurini]].<ref name="Prieto-Márquez & al.2013"/>
=Paleoecology=
The [[sediment]]s of the Bostobe Formation consist mainly of [[clay]]s and [[sandstone]]s, and correspond to [[floodplain]] and [[Estuary|estuarine]] environments in a [[Subtropics|subtropical]] to [[Tropical climate|tropical]] [[climate]].<ref name="Averianov & al.2015">{{cite journal|last=Averianov|first=A.|author2=Dyke, G.|author3=Danilov, I.|author4=Skutschas, P.|title=The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous of Kazakhstan|journal=ZooKeys|year=2015|volume=483|pages=59-80|doi=10.3897/zookeys.483.9058|}}</ref> These different [[biotope]]s were located on the west coast of the [[Asia|Asian]] continent of the time, on the edge of the ancient [[Turgai Sea]] which connected the [[Tethys Ocean|Tethys]] to the [[Arctic Ocean]].<ref name="Averianov & al.2015"/> The shallow marine waters west of this fluvial coastal plain were the site of intense organic productivity due to [[upwelling]] conditions caused by strong winds from the mainland.<ref name="Averianov & al.2015"/> These winds were also the cause of a significant [[aridification]] of the climate in this region during the Santonian and early Campanian, causing a change in the [[flora]] of [[Flowering plant|angiosperms]], with a rarefaction of broad-leaved forms and a proliferation of small and narrow-leaved species of the family [[Ulmaceae]]. Angiosperms accounted for 75% of the flora of these biotopes, the rest being [[Pinophyta|conifers]] and rare [[ginkgo]]s and [[Cycadales|cycads]].<ref name="Averianov & al.2015"/>

The locality of Shakh Shakh, where ''Aralosaurus'' was found, yielded a diverse fauna including many fish ([[Chondrichthyes|chondrichthyans]], [[Chondrostei|chondrosteans]], and [[Holostei|holosteans]]),<ref name="Averianov & al.2015"/> [[Frog|Anura]],<ref name="Averianov & al.2015"/>, at least six species of [[turtle]]s<ref name="Averianov & al.2015"/> some of which had a carapace at least 75 cm long,<ref name="Danilov & al.2015">{{cite journal|last=Danilov|first=I.G.|author2=Vitek, N.S.|author3=Averianov, A.O.|author4=Glinskiy, V.N.|title=A new soft-shelled trionychid turtle of the genus ''Khunnuchelys'' from the Upper Cretaceous Bostobe Formation of Kazakhstan|journal=Acta Palaeontologica Polonica|year=2015|volume=60(1)|pages=155-161|doi=10.4202/app.2013.0045|}}</ref> a [[Scincomorpha|scincomorph]],<ref name="Averianov & al.2015"/> [[Crocodilia|crocodylians]],<ref name="Averianov & al.2015"/> [[pterosaur]]s (''[[Aralazhdarcho]]''),<ref name="Averianov 2007a">{{cite journal|last=Averianov|first=A.O.|title=New records of azhdarchids [Pterosauria, Azhdarchidae) from the Late Cretaceous of Russia, Kazakhstan, and Central Asia|journal=Paleontological Journal|year=2007|volume=41(2)|pages=189-197|doi=10.1134/S0031030107020098|}}</ref> birds,<ref name="Averianov & al.2015"/> mammals,<ref name="Averianov & al.2015"/> and several undetermined dinosaur species ([[Ankylosauridae]], [[Sauropoda]], [[Tyrannosauroidea]], [[Ornithomimidae]], [[Therizinosauroidea]], [[Troodontidae]], and [[Dromaeosauridae]]).<ref name="Dyke & Malakhov 2004">{{cite journal|last=Dyke|first=G.J.|author2=Malakhov, D.V.|title=Abundance and taphonomy of dinosaur teeth and other vertebrate remains from the Bostobynskaya Formation, north-east Aral Sea region, Republic of Kazakhstan|journal=Cretaceous research|year=2004|volume=25|pages=669-674|doi=10.1016/j.cretres.2004.06.004|}}</ref><ref name="Averianov 2007b">{{cite journal|last=Averianov|first=A.O.|title=Theropod dinosaurs from Late Cretaceous depositsin the northeastern Aral Sea region, Kazakhstan|journal=Cretaceous research|year=2007|volume=28|pages=532-544|doi=10.1016/j.cretres.2006.08.008|}}</ref><ref name="Averianov 2015">{{cite journal|last=Averianov|first=A.|title=Frontals bones of non-avian theropod dinosaurs from the Upper Cretaceous (Santonian-?Campanian) Bostobe Formation of the northeastern Aral Sea region, Kazakhstan|journal=Canadian Journal of Earth Sciences|year=2015|volume=53(2)|pages=168-175|doi=10.1139/cjes-2015-0099|}}</ref><ref name="Averianov & al.2015"/> Elsewhere in this formation, the site of Akkurgan is distinguished by the presence of the two basal [[Hadrosauroidea|hadrosauroids]] ''[[Arstanosaurus]]''<ref name="Shilin & Suslov 1982">{{cite journal|last=Shilin|first=F.V.|author2=Suslov, Y.V.|title=A hadrosaur from the northeastern Aral Region|journal=Paleontological Journal|year=1982|volume=1982(1)|pages=132-136|}}</ref> and ''[[Batyrosaurus]]'',<ref name="Godefroit & al.2012">{{cite book|last=Godefroit|first=P.|author2=Escuillié, F.|author3=Bolotsky, Y.L.|author4=Lauters, P.|year=2012|chapter=A new Basal Hadrosauroid Dinosaur from the Upper Cretaceous of Kazakhstan|pages=335-358|title=Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems|editor1-last=Godefroit|editor1-first=P.|publisher=Indiana University Press|location=Bloomington and Indianapolis|isbn=978-0-253-35721-2|}}</ref> as well as the pterosaur ''[[Samrukia]]'' (whose jaw was first attributed to an [[Caenagnathidae|Caenagnathid]] [[Oviraptorosauria|oviraptorosaur]], then to a giant bird),<ref name="Naish & al.2012">{{cite journal|last=Naish|first=D.|author2=Dyke, G.|author3=Cau, A.|author4=Escuillié, F.|author5=Godefroit, P.|title=A gigantic bird from the Upper Cretaceous of Central Asia|journal=Biology Letters|year=2012|volume=8(1)|pages=97-100|doi=10.1098/rsbl.2011.0683|}}</ref><ref name="Buffetaut 2011">{{cite journal|last=Buffetaut|first=E.|title=''Samrukia nessovi'', from the Late Cretaceous of Kazakhstan: A large pterosaur, not a giant bird|journal=Annales de Paléontologie|year=2011|volume=97(3-4)|pages=133-138|doi=10.1016/j.annpal.2011.10.001|}}</ref> which could be a junior synonym of ''Aralazhdarcho''.<ref name="Averianov & al.2015"/>


==See also==
==See also==

Revision as of 09:37, 23 September 2019

Aralosaurus
Temporal range: Late Cretaceous, 83.6 Ma
↓
Skull of Aralosaurus. Known material white. This is the former reconstruction of Aralosaurus depicting incorrectly the animal as a Gryposaur-like Hadrosaurinae.[1]
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Ornithopoda
Family: †Hadrosauridae
Subfamily: †Lambeosaurinae
Genus: †Aralosaurus
Rozhdestvensky, 1968
Type species
†Aralosaurus tuberiferus
Rozhdestvensky, 1968

Aralosaurus was a genus of hadrosaurid dinosaur that lived during the Late Cretaceous in what is now Kazakhstan. It is known only by a posterior half of a skull (devoid of its mandible) and some post-cranial bones[2] found in the Bostobe Formation in rocks dated from the Upper Santonian-Lower Campanian boundary, at about 83.6 Ma (millions of years).[3] Only one species is known, Aralosaurus tuberiferus, described by Anatoly Konstantinovich Rozhdestvensky in 1968. The genus name means Aral Sea lizard, because it was found to the northeast of the Aral Sea.[2] The specific epithet tuberiferus means bearing a tuber because the posterior part of the nasal bone rises sharply in front of the orbits like an outgrowth.[2] Aralosaurus was originally reconstituted with a nasal arch similar to that of North American Kritosaurus (a comparison based on a specimen now placed in the genus Gryposaurus).[2] For many years, Aralosaurus was thus placed in the clade of the Hadrosaurinae. This classification was invalidated in 2004, following the re-examination of the skull of the animal which allowed to identify in Aralosaurus many typical characters of Lambeosaurinae. In particular, this study revealed that Aralosaurus had a hollow bony structure located far in front of the orbits, which communicated with the respiratory tract.[1] This structure being broken at its base, its shape and size unfortunately remains undetermined.[1] More recently, Aralosaurus has been identified as the most basal Lambeosaurinae, and placed with its close relative Canardia from the upper Maastrichtian of France in the new clade of Aralosaurini.[3]

Discovery

The partial skull of Aralosaurus was discovered in 1957 near the Shakh-Shakh locality during a Soviet expedition in central Kazakhstan (which at the time was part of the USSR). In addition to the skull (which lacks most of the snout and the entire mandible), the material also included isolated teeth and postcranial elements most often fragmentary (ulna, radius, femur, tibia, fibula, astragalus, metatarsals). The only complete elements were a humerus and a metatarsal. It is only in 1968 that Rozhdestvensky described and named the animal. He estimated the size of the skull at about 65 cm and the size of the animal at about 6.5 m long. As the cranial sutures are far from fusioned, this specimen was probably immature. At the time, Rozhdestvensky argued that the skull of Aralosaurus presented the greatest ressemblance with the skull of Kritosaurus with the presence of a nasal arch in front of the orbits (the comparisons were based with specimens attributed today to Gryposaurus, not to Kritosaurus). So, the animal was classified among the Hadrosaurinae, which are hadrosaurs devoid of cranial crest or with a solid bony crest.[2]

In 2004, the skull of Aralosaurus was re-examined by Godedroit and colleagues, and according to them, the bone fragments identified by Rozhdestvensky as the middle part of the nasal arch and the posterior portion of the premaxilla seem to have been lost. These fragments were originally found isolated while the rest of the skull was articulated (including a posterior fragment of the nasal). So that it is no longer possible today to confirm the presence of a nasal arch in Aralosaurus. On the other hand, this study shows that Aralosaurus was not a gryposaur-like hadrosaurine, because the puported nasal boss was in fact a fragment of a hollow structure. Indeed, Godefroit and colleagues did not find any hadrosaurines diagnostic characters in Aralosaurus. On the contrary, the skull of Aralosaurus presents several features (in the maxilla, parietal, squamosal and especially the nasal) which indicates its inclusion among the Lambeosaurinae. Notably, the posterior fragment of the nasal, which is clearly articulated to the rest of the skull, rises just in front of the orbits and forming or participating to a hollow crest-like structure. As this structure is broken at its base, it is not possible to deduce its size and shape. However, in rostral view, the nasal is clearly hollow, it is deeply excavated rostrally by a broad groove that communicates directly with the ventral side of the posterior part of the bone. It is therefore clear that in Aralosaurus the nasal crest surrounded part of the respiratory system. The extension of the nasal cavity inside a hollow crest is typically a lambeosaurine feature, thus confirming the inclusion of Aralosaurus among them.[1] Aralosaurus also exhibits several cranial characters which indicate that it was a basal member of the group. Although having a hollow nasal structure, the latter was located in front of the orbits, a primitive position in lambeosaurines. In the most advanced representatives of the group, the nasal migrates to a caudodorsal position because of the important development of the premaxillae in these forms. In addition, in more derived lambeosaurines, the skull roof is modified to form a fixation zone for the hollow crest, whereas in Aralosaurus the skull roof does not present any particular modification. The shape and the size of the crest-like structure of Aralosaurus is unknown. Unfortunately, the fragments that was previously interpreted as a part of a gryposaur-like nasal arch and could have helped to reconstruct the circumnarial region of Aralosaurus, have been lost.[1]. So, the discovery of more complete specimens is necessary for a better knowledge of the shape and the size of this hollow structure.

Description

Beside the participation of the nasal in a hollow structure in front of the orbits, Aralosaurus is also distinguished by the morphology of its maxilla. Aralosaurus has a maxilla with an enlarged rostrodorsal region that forms a prominent subrectangular flange that rises vertically above the rostroventral process.[3] Recently, this trait has also been found in Canardia from the upper Maastrichtian of France, which is closely related to Aralosaurus. However, the maxilla of Aralosaurus differs from the French form in exhibiting a clearly inclined ectopterygoid shelf whereas in Canardia the same element is subhorizontal (it is parallel to the posterior segment of the dental row).[3] The maxilla of Aralosaurus carries 30 rows of teeth[2] while Canardia has at least 26 rows (part of the dental row is not preserved in the latter).[3] The maxillary teeth of Aralosaurus bear a single central ridge, while the only known tooth of the lower jaw has a fine secondary ridge placed in front of the central ridge.[2] A condition also observed in Canardia and in many other hadrosaurs.[3]. Aralosaurus differs also from Canardia by the shape of the prefrontal in dorsal view. In Aralosaurus, the rostroventral process of the prefrontal is broad and laterally well-exposed whereas in Canardia the same bone process is rostrocaudally narrow.[3]. In addition, the prefrontal of Aralosaurus does not have the dorsomedial flange present in Canardia.[3] Godefroit and colleagues also report the presence of primitive characters in Aralosaurus such as the frontal that participates in the upper margin of the orbit, and a prefrontal oriented laterally and not participating in the lateral wall of the hollow crest.[1]

Phylogeny

The following cladogram was produced by Albert Prieto-Márquez and his colleagues in 2013, it shows the phylogeny of Lambeosaurinae. Aralosaurus is closely related to Canardia and both genera are included in the tribe of Aralosaurini, which are identified as the most basal members of Lambeosaurinae.

 Lambeosaurinae 

Paleobiogeography

Aralosaurus lived about 20 millions years before its close relative Canardia. The later inhabited the Ibero-Armorican Island, which was the westernmost island of the Late Cretaceous European Archipelago.[4] As no lambeosaurines were known in the rich localities of late Campanian and early Maastrichtian ages of the Ibero-Armorican Island, it was suggested that the descendants of Aralosaurus had to reach this island rather late, perhaps at the end of the early Maastrichtian or during the late Maastrichtian.[3] The discovery later in Spain of numerous lambeosaurines remains in the highest levels of the lower Maastrichtian argues for the first hypothesis.[5][6] This migration was probably carried out in several stages, firstly by temporary terrestrial links between the landmass of Western Asia and the eastern islands of the European archipelago, then between the different European islands up to the Ibero-Armorican Island.[4] Canardia was a rather archaic form for its time and the Ibero-Armorican Island was perhaps an ultimate refuge for the Aralosaurini.[3]

Paleoecology

The sediments of the Bostobe Formation consist mainly of clays and sandstones, and correspond to floodplain and estuarine environments in a subtropical to tropical climate.[7] These different biotopes were located on the west coast of the Asian continent of the time, on the edge of the ancient Turgai Sea which connected the Tethys to the Arctic Ocean.[7] The shallow marine waters west of this fluvial coastal plain were the site of intense organic productivity due to upwelling conditions caused by strong winds from the mainland.[7] These winds were also the cause of a significant aridification of the climate in this region during the Santonian and early Campanian, causing a change in the flora of angiosperms, with a rarefaction of broad-leaved forms and a proliferation of small and narrow-leaved species of the family Ulmaceae. Angiosperms accounted for 75% of the flora of these biotopes, the rest being conifers and rare ginkgos and cycads.[7]

The locality of Shakh Shakh, where Aralosaurus was found, yielded a diverse fauna including many fish (chondrichthyans, chondrosteans, and holosteans),[7] Anura,[7], at least six species of turtles[7] some of which had a carapace at least 75 cm long,[8] a scincomorph,[7] crocodylians,[7] pterosaurs (Aralazhdarcho),[9] birds,[7] mammals,[7] and several undetermined dinosaur species (Ankylosauridae, Sauropoda, Tyrannosauroidea, Ornithomimidae, Therizinosauroidea, Troodontidae, and Dromaeosauridae).[10][11][12][7] Elsewhere in this formation, the site of Akkurgan is distinguished by the presence of the two basal hadrosauroids Arstanosaurus[13] and Batyrosaurus,[14] as well as the pterosaur Samrukia (whose jaw was first attributed to an Caenagnathid oviraptorosaur, then to a giant bird),[15][16] which could be a junior synonym of Aralazhdarcho.[7]

See also

References

  1. ^ a b c d e f Godefroit, P.; Alifanov, V.; Boltsky, Y. (2004). "A re-appraisal of "Aralosaurus tuberiferus" (Dinosauria, Hadrosauridae) from the Late Cretaceous of Kazakhstan". Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre (74): 139–154. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  2. ^ a b c d e f g Rozhdestvensky, A.K. (1968). "Gadrozavry Kazakhstana [Hadrosaurs of Kazakhstan]. [Upper Paleozoic and Mesozoic Amphibians and Reptiles]" (PDF). Akademia Nauk SSSR, Moscow: 97–141. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  3. ^ a b c d e f g h i j Prieto-Márquez, A.; Dalla Vecchia, F.M.; Gaete, R.; Galobart, À. (2013). "Diversity, Relationships, and Biogeography of the Lambeosaurine Dinosaurs from the European Archipelago, with Description of the New Aralosaurin Canardia garonnensis". PLos ONE. 8(7): e69835: 1–44. doi:10.1371/journal.pone.0069835. {{cite journal}}: Cite has empty unknown parameter: |1= (help)CS1 maint: unflagged free DOI (link)
  4. ^ a b Csiki-Sava, Z.; Buffetaut, E.; Ősi, A.; Pereda-Suberbiola, X.; Brusatte, S.L. (2015). "Island life in the Cretaceous-faunal composition, biostratigraphy, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago". ZooKeys. 469: 1–161. doi:10.3897/zookeys.469.8439. PMC 4296572. {{cite journal}}: Cite has empty unknown parameter: |1= (help)CS1 maint: unflagged free DOI (link)
  5. ^ Fondevilla, V.; Dalla Vecchia, F.M.; Gaete, R.; Galobart, À.; Moncunill-Solé, B.; Köhler, M. (2018). "Ontogeny and taxonomy of the hadrosaur (Dinosauria, Ornithopoda) remains from Basturs Poble bonebed (late early Maastrichtian, tremp Syncline, Spain)". Plos ONE. 13(10): e0206287: 1–33. doi:10.1371/journal.pone.0206287. {{cite journal}}: Cite has empty unknown parameter: |1= (help)CS1 maint: unflagged free DOI (link)
  6. ^ Prieto-Márquez, A.; Fondevilla, V.; Sellés, A.G.; Wagner, J.R.; Galobart, À. (2019). "Adynomosaurus arcanus, a new lambeosaurine dinosaur from the Late Cretaceous Ibero-Armorican Island of the European Archipelago". Cretaceous Research. 96: 19–37. doi:10.1016/j.cretres.2018.12.002. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  7. ^ a b c d e f g h i j k l m Averianov, A.; Dyke, G.; Danilov, I.; Skutschas, P. (2015). "The paleoenvironments of azhdarchid pterosaurs localities in the Late Cretaceous of Kazakhstan". ZooKeys. 483: 59–80. doi:10.3897/zookeys.483.9058. {{cite journal}}: Cite has empty unknown parameter: |1= (help)CS1 maint: unflagged free DOI (link)
  8. ^ Danilov, I.G.; Vitek, N.S.; Averianov, A.O.; Glinskiy, V.N. (2015). "A new soft-shelled trionychid turtle of the genus Khunnuchelys from the Upper Cretaceous Bostobe Formation of Kazakhstan". Acta Palaeontologica Polonica. 60(1): 155–161. doi:10.4202/app.2013.0045. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  9. ^ Averianov, A.O. (2007). "New records of azhdarchids [Pterosauria, Azhdarchidae) from the Late Cretaceous of Russia, Kazakhstan, and Central Asia". Paleontological Journal. 41(2): 189–197. doi:10.1134/S0031030107020098. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  10. ^ Dyke, G.J.; Malakhov, D.V. (2004). "Abundance and taphonomy of dinosaur teeth and other vertebrate remains from the Bostobynskaya Formation, north-east Aral Sea region, Republic of Kazakhstan". Cretaceous research. 25: 669–674. doi:10.1016/j.cretres.2004.06.004. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  11. ^ Averianov, A.O. (2007). "Theropod dinosaurs from Late Cretaceous depositsin the northeastern Aral Sea region, Kazakhstan". Cretaceous research. 28: 532–544. doi:10.1016/j.cretres.2006.08.008. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  12. ^ Averianov, A. (2015). "Frontals bones of non-avian theropod dinosaurs from the Upper Cretaceous (Santonian-?Campanian) Bostobe Formation of the northeastern Aral Sea region, Kazakhstan". Canadian Journal of Earth Sciences. 53(2): 168–175. doi:10.1139/cjes-2015-0099. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  13. ^ Shilin, F.V.; Suslov, Y.V. (1982). "A hadrosaur from the northeastern Aral Region". Paleontological Journal. 1982(1): 132–136. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  14. ^ Godefroit, P.; Escuillié, F.; Bolotsky, Y.L.; Lauters, P. (2012). "A new Basal Hadrosauroid Dinosaur from the Upper Cretaceous of Kazakhstan". In Godefroit, P. (ed.). Bernissart Dinosaurs and Early Cretaceous Terrestrial Ecosystems. Bloomington and Indianapolis: Indiana University Press. pp. 335–358. ISBN 978-0-253-35721-2. {{cite book}}: Cite has empty unknown parameter: |1= (help)
  15. ^ Naish, D.; Dyke, G.; Cau, A.; Escuillié, F.; Godefroit, P. (2012). "A gigantic bird from the Upper Cretaceous of Central Asia". Biology Letters. 8(1): 97–100. doi:10.1098/rsbl.2011.0683. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
  16. ^ Buffetaut, E. (2011). "Samrukia nessovi, from the Late Cretaceous of Kazakhstan: A large pterosaur, not a giant bird". Annales de Paléontologie. 97(3-4): 133–138. doi:10.1016/j.annpal.2011.10.001. {{cite journal}}: Cite has empty unknown parameter: |1= (help)
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