Stegotherium: Difference between revisions
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In 1902, after a skull of ''Scaetops simplex'' was found in association with ''Stegotherium tessellatum'' osteoderms, Ameghino considered the two species synonymous, and proposed a new species ''Stegotherium variegatum'' based on osteoderms found in [[Chubut Province]].<ref name=A02/> In 1904, after the discovery of additional remains of ''S. variegatum'', [[William Berryman Scott]] re-evaluated ''Scaetops simplex'' as a species of ''Stegotherium'' different from ''S. tessellatum''.<ref name=V94>{{Cite journal | last1 = Vizcaíno | first1 = S.F. | title = Mecánica masticatoria de Stegotherium tessellatum Ameghino (Mammalia, Xenarthra) del Mioceno temprano de Santa Cruz (Argentina). Algunos aspectos paleoecológicos relacionados | volume = 231(3)| pages = 283–290 |journal = Ameghiniana |year = 1994}}</ref> |
In 1902, after a skull of ''Scaetops simplex'' was found in association with ''Stegotherium tessellatum'' osteoderms, Ameghino considered the two species synonymous, and proposed a new species ''Stegotherium variegatum'' based on osteoderms found in [[Chubut Province]].<ref name=A02/> In 1904, after the discovery of additional remains of ''S. variegatum'', [[William Berryman Scott]] re-evaluated ''Scaetops simplex'' as a species of ''Stegotherium'' different from ''S. tessellatum''.<ref name=V94>{{Cite journal | last1 = Vizcaíno | first1 = S.F. | title = Mecánica masticatoria de Stegotherium tessellatum Ameghino (Mammalia, Xenarthra) del Mioceno temprano de Santa Cruz (Argentina). Algunos aspectos paleoecológicos relacionados | volume = 231(3)| pages = 283–290 |journal = Ameghiniana |year = 1994}}</ref> |
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In 2008, two important studies on the genus were published. The first, led by Fernicola and Vizcaíno, reviewed the material and species assigned to the genus. They proposed two new species, ''S. caroloameghinoi'', with MACN-A 10443a, an osteoderm from the dorsal carapace, as holotype, and ''S. pascuali'' using MACN A-12680d, an osteoderm from the dorsal carapace, as holotype. This review also kept, not without some doubt, ''S. simplex'' as a valid taxon.<ref name=F08/> The second study from 2008, led by González Ruiz and Scillato-Yané, proposed |
In 2008, two important studies on the genus were published. The first, led by Fernicola and Vizcaíno, reviewed the material and species assigned to the genus. They proposed two new species, ''S. caroloameghinoi'', with MACN-A 10443a, an osteoderm from the dorsal carapace, as holotype, and ''S. pascuali'' using MACN A-12680d, an osteoderm from the dorsal carapace, as holotype. This review also kept, not without some doubt, ''S. simplex'' as a valid taxon.<ref name=F08/> The second study from 2008, led by González Ruiz and Scillato-Yané, proposed ‘’''Stegotherium tauberi''’’ as a species, based on YPM PU 15565, a fairly complete specimen including a fragmentary dorsal carapace, a complete skull, several vertebra and a right foot, previously assigned to ''S. tessellatum''.<ref name=G08/> |
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In 2009, another species was named by González Ruiz and Scillato-Yané, '' |
In 2009, another species was named by González Ruiz and Scillato-Yané, ''S. notohippidensis'', with the [[holotype]] being MLP 84-III-5-10, a collection of 130 osteoderms from Argentina.<ref name=G09/> |
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The name ''Stegotherium'' is composed from the [[Greek language|Greek]] words ''stegè''/στέγη, meaning "roof", and ''therion''/θηρίον, meaning "beast", and hence means "roof(ed) beast", in allusion to its carapace. |
The name ''Stegotherium'' is composed from the [[Greek language|Greek]] words ''stegè''/στέγη, meaning "roof", and ''therion''/θηρίον, meaning "beast", and hence means "roof(ed) beast", in allusion to its carapace.{{Citation needed|date=April 2022}} |
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== Description == |
== Description == |
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== Species == |
== Species == |
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The genus ''Stegotherium'' is unambiguously known from six species, ''S. tessellatum'', ''S. variegatum'', ''S. caroloameghinoi'', ''S. pascuali'', ''S. tauberi'' and ''S. notohippidensis''. A seventh species, ''S. simplex'', is generally considered too fragmentary, but has generally been considered valid with reservations by most recent scholars. |
The genus ''Stegotherium'' is unambiguously known from six species, ''S. tessellatum'', ''S. variegatum'', ''S. caroloameghinoi'', ''S. pascuali'', ''S. tauberi'' and ''S. notohippidensis''. A seventh species, ''S. simplex'', is generally considered too fragmentary, but has generally been considered valid with reservations by most recent scholars. As osteoderms are the most abundant fossils of ''Stegotherium'' known, they are commonly used as the main determinate of which species a given fossil belongs too. |
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===''Stegotherium tessellatum''=== |
===''Stegotherium tessellatum''=== |
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''S. tessellatum'' is the type species of ''Stegotherium''. Fossils of |
''S. tessellatum'' is the type species of ''Stegotherium''. Fossils of it have been recovered in the Santacrucian of the Santa Cruz Formation. It had quadrangular osteoderms, with a single large foramen in the exterior margin, devoid of longitudinal ridge of any kind in the central region. While non-osteoderm remains have been historically referred to this species in literature, they are now assigned to ''S. tauberi''.<ref name=F08/> |
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===''Stegotherium simplex''=== |
===''Stegotherium simplex''=== |
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''S. simplex'' is only known from its holotype, a fragmentary mandible with two [[Dental alveolus|alveoli]], found in the |
''S. simplex'' is only known from its holotype, a fragmentary mandible with two [[Dental alveolus|alveoli]], found in the Santa Cruz Formation and dated from the Santacrucian period. It is the only species in the genus whose osteoderms, usually considered diagnostic for armadillo fossils, are unknown. Its only diagnosis characteristic could be the presence of two [[wikt:molariform|molariform]] teeth on the mandible, while ''S. tessellatum'' had six;<ref name=F19/> the validity of the species has been debated since 1902,<ref name=F08/><ref name=G08/><ref name=G09/> and the holotype is probably lost.<ref name=F19>{{Cite journal | last1 = Fernicola| first1 = J.C. | last2 = Vizcaíno| first2 = S.F. | title = Cingulates (Mammalia, Xenarthra) of the Santa Cruz Formation (Early-Middle Miocene) from the Rio Santa Cruz, Argentine Patagonia | volume = 19(2)| pages = 85–101|journal = Publicación Electrónica de la Asociación Paleontológica Argentina|year = 2019}}</ref> |
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===''Stegotherium variegatum''=== |
===''Stegotherium variegatum''=== |
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''S. variegatum'' is known from the |
''S. variegatum'' is known from the Colhuehuapian Sarmiento Formation. The species is mainly known from fossilized quadrangular osteoderms, whose exposed surface showed several piliferous pits around a single granulated central figure, and a longitudinal ridge surrounded, in all of its length, by depressions.<ref name=F08/> |
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===''Stegotherium caroloameghinoi''=== |
===''Stegotherium caroloameghinoi''=== |
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''S. caroloameghinoi'' is known from the |
''S. caroloameghinoi'' is known from the Sarmiento Formation of [[Argentina]], in rocks dating from the Colhuehuapian period. It is only known from osteoderms. Those were rectangular, with a granular textured dorsal surface. Piliferous pits are placed around a central figure, crossed by a median longitudinal ridge, and one to three smaller anterior figures.{{Citation needed paragraph|date=April 2022}} |
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The |
The specific name, ''caroloameghinoi'', is meant to honour [[Carlos Ameghino]], who discovered the holotype of ''Stegotherium'' and was a prominent figure in the history of paleontology in Patagonia.<ref name=F08/> |
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===''Stegotherium pascuali''=== |
===''Stegotherium pascuali''=== |
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''S. pascuali'' is known from the |
''S. pascuali'' is known from the Colhuehuapian period in the Sarmiento Formation. It is known by fossilized osteoderms, whose various shapes all shared the same grainy-textured central figure surrounded by piliferous pits, without anterior figures. Two foramina, absent in ''S. variegatum'' and ''S. caroloameghinoi'', and a ridge absent in ''S. tessellatum'', were present on the osteoderms, completing the diagnostic characteristics.<ref name=F08/> |
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It was named to honour the Argentinian paleontologist [[Rosendo Pascual]].<ref name=F08>{{Cite journal | last1 = Fernicola| first1 = J.C. | last2 = Vizcaíno| first2 = S.F. | title = Revisión del género Stegotherium Ameghino, 1887 (Mammalia, Xenarthra, Dasypodidae) | volume = 245(2)| pages = 321–332|journal = Ameghiniana |year = 2008}}</ref> |
It was named to honour the Argentinian paleontologist [[Rosendo Pascual]].<ref name=F08>{{Cite journal | last1 = Fernicola| first1 = J.C. | last2 = Vizcaíno| first2 = S.F. | title = Revisión del género Stegotherium Ameghino, 1887 (Mammalia, Xenarthra, Dasypodidae) | volume = 245(2)| pages = 321–332|journal = Ameghiniana |year = 2008}}</ref> |
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[[File:Stegotherium shell.jpg|thumb|Shell of ''Stegotherium'', now associated with ''S. tauberi.'']] |
[[File:Stegotherium shell.jpg|thumb|Shell of ''Stegotherium'', now associated with ''S. tauberi.'']] |
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''S. tauberi'' is known from the |
''S. tauberi'' is known from the Santa Cruz Formation, in rocks dated from the Santacrucian period. It is distinguished from other species of ''Stegotherium'' by osteoderms more rugged and with a sharper ridge than ''S. variegatum''. Those osteoderms had a large foramen in the anterior-central region, along with several smaller foramina assembled in a transversal row in the anterior region. The presence of a longitudinal ridge on the osteoderms also distinguishes them. Some of the non-osteoderm material used by González Ruiz and Scillato-Yané to describe ''S. tauberi'' was assigned by Fernicola and Vizcaíno to ''S. tessellatum''; both species are, however, considered valid by the current consensus.{{Citation needed paragraph|date=April 2022}} |
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Its species name, ''tauberi'', honours Adán Alejo Tauber, an Argentinian paleontologist who worked on the Santa Cruz Formation.<ref name=G08/> |
Its species name, ''tauberi'', honours Adán Alejo Tauber, an Argentinian paleontologist who worked on the Santa Cruz Formation.<ref name=G08/> |
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===''Stegotherium notohippidensis''=== |
===''Stegotherium notohippidensis''=== |
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''S. notohippidensis'' is found in sediments from the "Notohippidian" period (traditionally considered as the lower part of the |
''S. notohippidensis'' is found in sediments from the "Notohippidian" period (traditionally considered as the lower part of the Santacrucian period) of the Santa Cruz Formation. |
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Its osteoderms had several foramina in their anterior region, larger than ''S. variegatum'' and ''S. tauberi''. In addition, the longitudinal ridge present in the osteoderms of other species of ''Stegotherium'' was absent in ''S. notohippidensis''. |
Its osteoderms had several foramina in their anterior region, larger than ''S. variegatum'' and ''S. tauberi''. In addition, the longitudinal ridge present in the osteoderms of other species of ''Stegotherium'' was absent in ''S. notohippidensis''.{{Citation needed paragraph|date=April 2022}} |
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The species name, "''notohippidensis''" means, in [[New Latin]], "from the Notohippidian", which was itself named after the large herbivore ''[[Notohippus]]'', considered to be characteristic of this period.<ref name=G09/> |
The species name, "''notohippidensis''" means, in [[New Latin]], "from the Notohippidian", which was itself named after the large herbivore ''[[Notohippus]]'', considered to be characteristic of this period.<ref name=G09/> |
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The morphology of the jaws of ''Stegotherium'' shows that most of the mastication muscles were specialized for a horizontal and propalinal movement; the teeth were reduced but could still be used for masticating relatively soft food. Those important specializations pushed most scholars to consider ''Stegotherium'' as a specialized [[myrmecophagy|myrmecophage]], similar ecologically to [[anteater]]s and to the less specialized [[giant armadillo]].<ref name=V94/> |
The morphology of the jaws of ''Stegotherium'' shows that most of the mastication muscles were specialized for a horizontal and propalinal movement; the teeth were reduced but could still be used for masticating relatively soft food. Those important specializations pushed most scholars to consider ''Stegotherium'' as a specialized [[myrmecophagy|myrmecophage]], similar ecologically to [[anteater]]s and to the less specialized [[giant armadillo]].<ref name=V94/> |
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The area where ''Stegotherium'' lived was, during the Early Miocene, a forested [[savannah]] with a mild climate.<ref name=V94/> It lived alongside a diversity of related [[Cingulata|cingulates]], such as the [[Euphractinae]] ''[[Prozaedyus]]'', the basal [[Chlamyphoridae]] ''[[Proeutatus]]'', the [[Dasypodidae]] ''[[Stenotatus]]'', the [[Peltephilidae|horned armadillo]] ''[[Peltephilus]]'' and several genera of [[glyptodonts]], such as ''[[Asterostemma (mammal)|Asterostemma]]'', ''[[Propalaehoplophorus]]'', ''[[Cochlops]]'' and ''[[Eucinepeltus]]''.<ref>{{cite book |last1=Vizcaíno |first1=S. F.|last2=Kay |first2=R.F.|last3=Bargo |first3=M. S.|date=2012 |editor-last1=Vizcaíno |editor-first1=S. F.|editor-last2=Kay|editor-first2=R. F.|editor-last3=Bargo|editor-first3=M. S.|title=Early Miocene Paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation|publisher=Cambridge University Press|pages=194–215|chapter=Paleobiology of Santacrucian glyptodonts and armadillos (Xenarthra, Cingulata)|isbn=9780511667381|doi=10.1017/CBO9780511667381}}</ref> |
The area where ''Stegotherium'' lived was, during the Early Miocene, a forested [[savannah]] with a mild climate.<ref name=V94/> It lived alongside a diversity of related [[Cingulata|cingulates]], such as the [[Euphractinae|Euphractine]] ''[[Prozaedyus]]'', the basal [[Chlamyphoridae|Chlamyphorid]] ''[[Proeutatus]]'', the [[Dasypodidae|Dasypodid]] ''[[Stenotatus]]'', the [[Peltephilidae|horned armadillo]] ''[[Peltephilus]]'' and several genera of [[glyptodonts]], such as ''[[Asterostemma (mammal)|Asterostemma]]'', ''[[Propalaehoplophorus]]'', ''[[Cochlops]]'' and ''[[Eucinepeltus]]''.<ref>{{cite book |last1=Vizcaíno |first1=S. F.|last2=Kay |first2=R.F.|last3=Bargo |first3=M. S.|date=2012 |editor-last1=Vizcaíno |editor-first1=S. F.|editor-last2=Kay|editor-first2=R. F.|editor-last3=Bargo|editor-first3=M. S.|title=Early Miocene Paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation|publisher=Cambridge University Press|pages=194–215|chapter=Paleobiology of Santacrucian glyptodonts and armadillos (Xenarthra, Cingulata)|isbn=9780511667381|doi=10.1017/CBO9780511667381}}</ref> |
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The specialisation of ''Stegotherium'' may have caused the extinction of the genus during the Santacrucian, as it may have suffered from the large-scale environmental and climatic changes occurring in Patagonia during this period, the result of the [[Andean orogeny|rise]] of the [[Andes]], causing an [[aridization]] that may have caused the rarefaction of [[ant]] and [[termite]] colonies it fed upon, and [[cooling]] making it harder for the animal to regulate its own body temperature.<ref name=V94/> After the Santacrucian, the genus is only known by one [[Colloncuran]] fossilized osteoderm, MLP 91-IV-1-66 from the [[Collón Curá Formation]], tentatively assigned to ''Stegotherium'' sp. and different from all currently known species of ''Stegotherium'', although other [[Colloncuran]] osteoderms of indeterminate Stegotheriini have also been recovered in the [[Chubut Province]].<ref name=GR10>{{cite thesis |type=Doctor |last=Gonzalez-Ruiz|first=Laureano |date=October 2010|title=1. Los Cingulata (Mammalia, Xenarthra) del Mioceno temprano y medio de Patagonia (edades Santacrucense y “Friasense”). Revisión sistemática y consideraciones bioestratigráficas|publisher=Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata}}</ref> |
The specialisation of ''Stegotherium'' may have caused the extinction of the genus during the Santacrucian, as it may have suffered from the large-scale environmental and climatic changes occurring in Patagonia during this period, the result of the [[Andean orogeny|rise]] of the [[Andes]], causing an [[aridization]] that may have caused the rarefaction of [[ant]] and [[termite]] colonies it fed upon, and [[cooling]] making it harder for the animal to regulate its own body temperature.<ref name=V94/> After the Santacrucian, the genus is only known by one [[Colloncuran]] fossilized osteoderm, MLP 91-IV-1-66 from the [[Collón Curá Formation]], tentatively assigned to ''Stegotherium'' sp. and different from all currently known species of ''Stegotherium'', although other [[Colloncuran]] osteoderms of indeterminate Stegotheriini have also been recovered in the [[Chubut Province]].<ref name=GR10>{{cite thesis |type=Doctor |last=Gonzalez-Ruiz|first=Laureano |date=October 2010|title=1. Los Cingulata (Mammalia, Xenarthra) del Mioceno temprano y medio de Patagonia (edades Santacrucense y “Friasense”). Revisión sistemática y consideraciones bioestratigráficas|publisher=Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata}}</ref> |
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Revision as of 13:57, 5 April 2022
| Stegotherium | |
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| Skeleton of Stegotherium tauberi (without carapace) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Cingulata |
| Family: | Dasypodidae |
| Subfamily: | Dasypodinae |
| Genus: | †Stegotherium Ameghino, 1887 |
| Type species | |
| Stegotherium tessellatum Ameghino, 1887
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| Species | |
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| Synonyms | |
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Stegotherium is an extinct genus of long-nosed armadillo, belonging to the Dasypodidae family alongside the nine-banded armadillo. It is currently the only genus recognized as a member of the tribe Stegotheriini. It lived during the Early Miocene of Patagonia and was found in Colhuehuapian rocks from the Sarmiento Formation, Santacrucian rocks from the Santa Cruz Formation,[2] and potentially also in Colloncuran rocks from the Middle Miocene Collón Curá Formation.[3] Its strange, almost toothless and elongated skull indicates a specialization for myrmecophagy, the eating of ants, unique among cingulates.[4]
History
Stegotherium tessellatum was described originally in 1887 by Florentino Ameghino based on the remains of a carapace collected by his brother Carlos in the Santa Cruz Province of Argentina. The same paper also described another genus and species of armadillo, Scaetops simplex, known from a fragmentary mandible. In 1894, Stegotherium, at that time only known from osteoderms, was temporarily considered by Lydekker as a synonym of Peltephilus. This status was contested and proven wrong a year later by Ameghino.
In 1902, after a skull of Scaetops simplex was found in association with Stegotherium tessellatum osteoderms, Ameghino considered the two species synonymous, and proposed a new species Stegotherium variegatum based on osteoderms found in Chubut Province.[5] In 1904, after the discovery of additional remains of S. variegatum, William Berryman Scott re-evaluated Scaetops simplex as a species of Stegotherium different from S. tessellatum.[6]
In 2008, two important studies on the genus were published. The first, led by Fernicola and Vizcaíno, reviewed the material and species assigned to the genus. They proposed two new species, S. caroloameghinoi, with MACN-A 10443a, an osteoderm from the dorsal carapace, as holotype, and S. pascuali using MACN A-12680d, an osteoderm from the dorsal carapace, as holotype. This review also kept, not without some doubt, S. simplex as a valid taxon.[7] The second study from 2008, led by González Ruiz and Scillato-Yané, proposed ‘’Stegotherium tauberi’’ as a species, based on YPM PU 15565, a fairly complete specimen including a fragmentary dorsal carapace, a complete skull, several vertebra and a right foot, previously assigned to S. tessellatum.[1]
In 2009, another species was named by González Ruiz and Scillato-Yané, S. notohippidensis, with the holotype being MLP 84-III-5-10, a collection of 130 osteoderms from Argentina.[4]
The name Stegotherium is composed from the Greek words stegè/στέγη, meaning "roof", and therion/θηρίον, meaning "beast", and hence means "roof(ed) beast", in allusion to its carapace.[citation needed]
Description
Stegotherium was an unusual armadillo, whose most striking feature was the elongated skull, often compared to the skull of an anteater. The posterior area of the jaws, the only one to bear teeth, was compressed compared to Dasypus, while the nasal area and the anterior parts of both jaws, completely toothless, were long and slender. The teeth were cylindricals and greatly reduced, both in number and in size, and were all contained in the posterior area of the lower and upper jaws.[6] While S. tauberi had six teeth in its lower mandible, the dubious S. simplex only had two.[7]
The body of Stegotherium was roughly the size of the modern species of Dasypus,[7] and its carapace was composed of at least 23 mobile bands of osteoderms.[1] The osteoderms of Stegotherium, 3 to 7.5 mm thick[7] and 20 mm long,[5] were characterized by the presence of a number of piliferous foramina around their posterior and lateral margins, a granular appearance, and a compact bone structure.[8]
Species
The genus Stegotherium is unambiguously known from six species, S. tessellatum, S. variegatum, S. caroloameghinoi, S. pascuali, S. tauberi and S. notohippidensis. A seventh species, S. simplex, is generally considered too fragmentary, but has generally been considered valid with reservations by most recent scholars. As osteoderms are the most abundant fossils of Stegotherium known, they are commonly used as the main determinate of which species a given fossil belongs too.
Stegotherium tessellatum
S. tessellatum is the type species of Stegotherium. Fossils of it have been recovered in the Santacrucian of the Santa Cruz Formation. It had quadrangular osteoderms, with a single large foramen in the exterior margin, devoid of longitudinal ridge of any kind in the central region. While non-osteoderm remains have been historically referred to this species in literature, they are now assigned to S. tauberi.[7]
Stegotherium simplex
S. simplex is only known from its holotype, a fragmentary mandible with two alveoli, found in the Santa Cruz Formation and dated from the Santacrucian period. It is the only species in the genus whose osteoderms, usually considered diagnostic for armadillo fossils, are unknown. Its only diagnosis characteristic could be the presence of two molariform teeth on the mandible, while S. tessellatum had six;[9] the validity of the species has been debated since 1902,[7][1][4] and the holotype is probably lost.[9]
Stegotherium variegatum
S. variegatum is known from the Colhuehuapian Sarmiento Formation. The species is mainly known from fossilized quadrangular osteoderms, whose exposed surface showed several piliferous pits around a single granulated central figure, and a longitudinal ridge surrounded, in all of its length, by depressions.[7]
Stegotherium caroloameghinoi
S. caroloameghinoi is known from the Sarmiento Formation of Argentina, in rocks dating from the Colhuehuapian period. It is only known from osteoderms. Those were rectangular, with a granular textured dorsal surface. Piliferous pits are placed around a central figure, crossed by a median longitudinal ridge, and one to three smaller anterior figures.[This paragraph needs citation(s)]
The specific name, caroloameghinoi, is meant to honour Carlos Ameghino, who discovered the holotype of Stegotherium and was a prominent figure in the history of paleontology in Patagonia.[7]
Stegotherium pascuali
S. pascuali is known from the Colhuehuapian period in the Sarmiento Formation. It is known by fossilized osteoderms, whose various shapes all shared the same grainy-textured central figure surrounded by piliferous pits, without anterior figures. Two foramina, absent in S. variegatum and S. caroloameghinoi, and a ridge absent in S. tessellatum, were present on the osteoderms, completing the diagnostic characteristics.[7]
It was named to honour the Argentinian paleontologist Rosendo Pascual.[7]
Stegotherium tauberi
S. tauberi is known from the Santa Cruz Formation, in rocks dated from the Santacrucian period. It is distinguished from other species of Stegotherium by osteoderms more rugged and with a sharper ridge than S. variegatum. Those osteoderms had a large foramen in the anterior-central region, along with several smaller foramina assembled in a transversal row in the anterior region. The presence of a longitudinal ridge on the osteoderms also distinguishes them. Some of the non-osteoderm material used by González Ruiz and Scillato-Yané to describe S. tauberi was assigned by Fernicola and Vizcaíno to S. tessellatum; both species are, however, considered valid by the current consensus.[This paragraph needs citation(s)]
Its species name, tauberi, honours Adán Alejo Tauber, an Argentinian paleontologist who worked on the Santa Cruz Formation.[1]
Stegotherium notohippidensis
S. notohippidensis is found in sediments from the "Notohippidian" period (traditionally considered as the lower part of the Santacrucian period) of the Santa Cruz Formation. Its osteoderms had several foramina in their anterior region, larger than S. variegatum and S. tauberi. In addition, the longitudinal ridge present in the osteoderms of other species of Stegotherium was absent in S. notohippidensis.[This paragraph needs citation(s)]
The species name, "notohippidensis" means, in New Latin, "from the Notohippidian", which was itself named after the large herbivore Notohippus, considered to be characteristic of this period.[4]
Paleoecology
The morphology of the jaws of Stegotherium shows that most of the mastication muscles were specialized for a horizontal and propalinal movement; the teeth were reduced but could still be used for masticating relatively soft food. Those important specializations pushed most scholars to consider Stegotherium as a specialized myrmecophage, similar ecologically to anteaters and to the less specialized giant armadillo.[6]
The area where Stegotherium lived was, during the Early Miocene, a forested savannah with a mild climate.[6] It lived alongside a diversity of related cingulates, such as the Euphractine Prozaedyus, the basal Chlamyphorid Proeutatus, the Dasypodid Stenotatus, the horned armadillo Peltephilus and several genera of glyptodonts, such as Asterostemma, Propalaehoplophorus, Cochlops and Eucinepeltus.[10]
The specialisation of Stegotherium may have caused the extinction of the genus during the Santacrucian, as it may have suffered from the large-scale environmental and climatic changes occurring in Patagonia during this period, the result of the rise of the Andes, causing an aridization that may have caused the rarefaction of ant and termite colonies it fed upon, and cooling making it harder for the animal to regulate its own body temperature.[6] After the Santacrucian, the genus is only known by one Colloncuran fossilized osteoderm, MLP 91-IV-1-66 from the Collón Curá Formation, tentatively assigned to Stegotherium sp. and different from all currently known species of Stegotherium, although other Colloncuran osteoderms of indeterminate Stegotheriini have also been recovered in the Chubut Province.[3]
References
- ^ a b c d e González Laureano Raúl, Scillato-Yané Gustavo Juan. Una nueva especie de Stegotherium Ameghino (Xenarthra, Dasypodidae, Stegotheriini) del Mioceno de la provincia de Santa Cruz (Argentina). Ameghiniana, 2008 Dic; 45(4): 641-648.
- ^ Stegotherium at Fossilworks.org
- ^ a b Gonzalez-Ruiz, Laureano (October 2010). 1. Los Cingulata (Mammalia, Xenarthra) del Mioceno temprano y medio de Patagonia (edades Santacrucense y “Friasense”). Revisión sistemática y consideraciones bioestratigráficas (Doctor). Facultad de Ciencias Naturales y Museo Universidad Nacional de La Plata.
- ^ a b c d González Ruiz, L. R. L.; Scillato-Yané, G. J. (2009). "A new Stegotheriini (Mammalia, Xenarthra, Dasypodidae) from the "Notohippidian" (early Miocene) of Patagonia, Argentina". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 252: 81–90. doi:10.1127/0077-7749/2009/0252-0081.
- ^ a b Ameghino, F. (1902). "Première contribution a la connaissance de la faune mammalogique des couches a Colpodon". Boletin de la Academia Nacional de Ciencias en Córdoba, República Argentina. 17: 71–141.
- ^ a b c d e Vizcaíno, S.F. (1994). "Mecánica masticatoria de Stegotherium tessellatum Ameghino (Mammalia, Xenarthra) del Mioceno temprano de Santa Cruz (Argentina). Algunos aspectos paleoecológicos relacionados". Ameghiniana. 231(3): 283–290.
- ^ a b c d e f g h i j Fernicola, J.C.; Vizcaíno, S.F. (2008). "Revisión del género Stegotherium Ameghino, 1887 (Mammalia, Xenarthra, Dasypodidae)". Ameghiniana. 245(2): 321–332.
- ^ Ciancio, M.R.; Krmpotic, C.M.; Scarano, A.C.; Epele, M.B. (2019). "Internal Morphology of Osteoderms of Extinct Armadillos and Its Relationship with Environmental Conditions". Journal of Mammalian Evolution. 26(1): 71–93.
- ^ a b Fernicola, J.C.; Vizcaíno, S.F. (2019). "Cingulates (Mammalia, Xenarthra) of the Santa Cruz Formation (Early-Middle Miocene) from the Rio Santa Cruz, Argentine Patagonia". Publicación Electrónica de la Asociación Paleontológica Argentina. 19(2): 85–101.
- ^ Vizcaíno, S. F.; Kay, R.F.; Bargo, M. S. (2012). "Paleobiology of Santacrucian glyptodonts and armadillos (Xenarthra, Cingulata)". In Vizcaíno, S. F.; Kay, R. F.; Bargo, M. S. (eds.). Early Miocene Paleobiology in Patagonia: high-latitude paleocommunities of the Santa Cruz Formation. Cambridge University Press. pp. 194–215. doi:10.1017/CBO9780511667381. ISBN 9780511667381.
