Aetosaurus

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Aetosaurus
Temporal range: Late Triassic,
Carnian–Norian
Aetosaurus ferratus.JPG
Assemblage of fossil A. ferratus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Order:† Aetosauria
Family:† Stagonolepididae
Subfamily:† Aetosaurinae
Genus:† Aetosaurus
Fraas, 1887
Species
  • †A. arcuatus(Marsh, 1896)
  • †A. crassicaudaFraas, 1907
  • †A. ferratusFraas, 1877 (type)
Synonyms
  • Stegomus arcuatus Marsh, 1896

Aetosaurus is an extinct genus of pseudosuchian reptile belonging to the order Aetosauria. It is generally considered to be the most primitive aetosaur. [1] Three species are currently recognized: A. ferratus, the type species from Germany and Italy; [2] A. crassicauda from Germany; [3] and A. arcuatus from eastern North America. [4] Additional specimens referred to Aetosaurus have been found in the Chinle Group of the southwestern United States, [5] [6] and the Fleming Fjord Formation of Greenland. [7] Specimens of Aetosaurus occur in Norian-age strata.

Contents

Description

Aetosaurus was a small, primitive aetosaur. Unlike more derived aetosaurs such as Desmatosuchus or Typothorax , the carapace was long and narrow and lacked spikes. The paramedian scutes that covered the back (with one row on each side of the vertebrae) are considerably wider than they are long. The lateral scutes, which are beneath the paramedian and formed a row on either side of the animal, do not bear any spikes or other projections. [4]

Behaviour

A 2023 study based on a fossil assemblage found in Kaltental, suggested that juvenile A. ferratus were likely gregarious animals, possibly to increase their chances of survival and to deter predators. [8] [9]

Species

Reconstructed skull of A. ferratus Aetosaurus ferratus skull.png
Reconstructed skull of A. ferratus

Aetosaurus was first named, with the description of the type species A. ferratus, in 1877 by German paleontologist Oscar Fraas. At the time, Aetosaurus was known from 22 articulated skeletons that had been found in the Lower Stubensandtein of Germany. [2] Thirty years later, Fraas' son Eberhard described a second species, A. crassicauda, also from Germany. [3] A. crassicauda can be distinguished from A. ferratus by its larger size; A. crassicauda reached a maximum length of 150 centimetres (59 in) while A. ferratus reached a length of up to 90 centimetres (35 in). [1]

In addition to the Stubensandtein in Germany, A. ferratus is also known from the Calcare di Zorzino Formation in Cene, Italy. [10] Specimens of Aetosaurus that have been recovered from the Fleming Fjord Formation in Greenland likely represent A. ferratus. [7] Some material from the Chinle Group in the southwestern United States probably represent A. ferratus, as well. [5] [6]

In 1998, the genus Stegomus was synonymized with Aetosaurus. [4] In 1896, paleontologist Othniel Charles Marsh named Stegomus arcuatus from a cast of an aetosaur known as YPM 1647 from the New Haven Formation in the Fair Haven Heights neighborhood of New Haven. [11] This cast consisted of the dorsal carapace. Several other casts preserving the surface of the skull and tail have been found in the Passaic Formation of Hunterdon and Somerset counties, New Jersey [12] [13] and an outcrop of the Lower Sanford Formation at the Triangle Brick Co. Quarry in Durham County, North Carolina. [14] Stegomus arcuatus was found to be synonymous with Aetosaurus on the basis of several similarities, including a lack of spikes and a distinctive radial pattern of grooves on some of the caudal scutes. [4]

Photograph of YPM 1647, a specimen of A. arcuatus Stegomus arcuatus Marsh.JPG
Photograph of YPM 1647, a specimen of A. arcuatus
Skeletal drawing of A. ferratus by Marsh Aetosaurus.jpg
Skeletal drawing of A. ferratus by Marsh

A. arcuatus has paramedian scutes that are much wider than they are long, even in comparison to other species of Aetosaurus. There is very little pitting on the surface of the scutes, although the porosity of the sandstone that makes up the casts has been mistaken for pitting. [15] The tail narrows significantly past the base. The carapace is "waisted", meaning that it narrows in front of the pelvis. [4]

The following cladogram is simplified after an analysis presented by Julia B. Desojo, Martin D. Ezcurra and Edio E. Kischlat (2012). [16]

Aetosauria

Related Research Articles

<span class="mw-page-title-main">Aetosaur</span> Extinct order of heavily armoured reptiles

Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, 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 fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.

<i>Stagonolepis</i> Extinct genus of reptiles

Stagonolepis is an extinct genus of stagonolepidid aetosaur known from the Late Triassic Hassberge Formation of Germany, the Drawno Beds of Poland, and the Lossiemouth Sandstone of Scotland. Supposed fossils from North and South America have been placed into their own genera, Calyptosuchus and Aetosauroides, respectively.

<i>Desmatosuchus</i> Extinct genus of reptiles

Desmatosuchus is an extinct genus of archosaur belonging to the Order Aetosauria. It lived during the Late Triassic.

Calyptosuchus is an extinct genus of aetosaur from the Late Triassic of North America. Like other aetosaurs, it was heavily armored and had a pig-like snout used to uproot plants.

<i>Acaenasuchus</i> Genus of reptiles

Acaenasuchus is an extinct genus of pseudosuchian, endemic to what would be presently be known as Arizona during the Late Triassic, specifically during the Carnian and Norian stages of the Triassic. Acaenasuchus had a stratigraphic range of approximately 11.5 million years. Acaenasuchus is further categorized as one of the type fauna that belong to the Adamanian LVF, based on the fauna of the Blue Mesa Member of the Chinle Petrified Forest Formation of Arizona, where Acaenasuchus was initially discovered.

<i>Aetosauroides</i> Extinct genus of reptiles

Aetosauroides is an extinct genus of aetosaur from the Late Triassic of South America. It is one of four aetosaurs known from South America, the others being Neoaetosauroides, Chilenosuchus and Aetobarbakinoides. Three species have been named: the type species A. scagliai, A. subsulcatus and A. inhamandensis. Fossils have been found in the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina and the Santa Maria Formation in the Paraná Basin in southeastern Brazil. The strata date to the late Carnian and early Norian stages, making Aetosauroides one of the oldest aetosaurs.

<i>Typothorax</i> Extinct genus of reptiles

Typothorax is an extinct genus of typothoracine aetosaur that lived in the Late Triassic. Its remains have been found in North America. Two species are known: T. coccinarum, the type species, and T. antiquum.

Coahomasuchus is an extinct genus of aetosaurine aetosaur. Remains of the genus have been found from deposits in Texas and North Carolina that date to the Otischalkian faunachron of the Late Triassic. It was small for an aetosaur, being less than 1.5 metres long. The dorsal plates are distinctively flat and unflexed, and have a faint sub-parallel to radial ornamentation. The genus lacked spines or keels on these plates, features seen in many other aetosaurs. Coahomasuchus was very similar in appearance to the closely related Aetosaurus.

Lucasuchus is an extinct genus of aetosaur. Fossils have been found from the Bull Canyon Formation of the Dockum Group outcropping in the Revuelto Creek locality in Quay County, New Mexico. All specimens date back to the Norian stage of the Late Triassic. The genus was named in 1995 after the American paleontologist Spencer G. Lucas.

<i>Paratypothorax</i> Genus of reptiles

Paratypothorax is an extinct genus of aetosaur, known from a single species, Paratypothorax andressorum. It was a broadly distributed member of the group found in Germany, North America, and possibly parts of Gondwana. The best specimens come from Germany, though for more than a century they were mistakenly considered phytosaur armor. Paratypothorax was a large and wide-bodied typothoracine aetosaur, as well as the namesake of the tribe Paratypothoracisini.

Tecovasuchus is an extinct genus of aetosaur. It is known primarily from osteoderms found from the Tecovas Formation in Texas, which is Late Triassic in age, dating back to the lower Norian. Material is also known from several other localities of the Chinle Group in New Mexico and Arizona, such as older Carnian outcrops and younger Rhaetian outcrops. Specimens of Tecovasuchus have been collected from the Tecovas Formation, the Bluewater Creek Formation, and the Los Esteros Member of the Santa Rosa Formation.

<span class="mw-page-title-main">Aetosaurinae</span> Extinct subfamily of reptiles

Aetosaurinae is one of the two main clades of aetosaurs, the other being Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to Aetosaurus than Desmatosuchus. Aetosaurinae currently comprises Aetosaurus, similar forms such as Coahomasuchus and Stenomyti, and the widespread and successful aetosaur clade Typothoracinae.

Redondasuchus is an extinct genus of aetosaur. It may be a junior synonym of Typothorax coccinarum, another aetosaur. Redondasuchus is a member of the clade Typothoracisinae within the subfamily Aetosaurinae, and lived during the middle Norian stage of the Late Triassic. Material belonging to the genus has been found from the Redonda Formation in east-central New Mexico. The type species, R. reseri, was named in 1991 after having been referred to as a species of Typothorax since 1985. A second species, R. rineharti, was described in 2006.

Aetobarbakinoides is an extinct genus of stagonolepidid aetosaur known from the Late Triassic of Rio Grande do Sul state, southern Brazil. Fossils have been found from the Santa Maria Supersequence of the late Carnian and early Norian stages, making Aetobarbakinoides one of the oldest aetosaurs. The type species, A. brasiliensis, was named in 2012, and is notable for being described primarily by features of the vertebrae; most other aetosaurs are diagnosed by features in bony plates called osteoderms, which are by far the most common material. Although placed in a basal phylogenetic position among aetosaurs, Aetobarbakinoides is closely related to both desmatosuchines and typothoracisines, two derived clades of aetosaurs.

The Bull Canyon Formation is a geological formation of Late Triassic (Norian) age in eastern New Mexico and the Texas Panhandle. It is one of several formations encompassed by the Dockum Group.

The Colorado City Formation is a Late Triassic geologic formation in the Dockum Group of Texas, United States. It has previously been known as the Iatan Member, Colorado City Member or 'Pre-Tecovas Horizon'.

Gorgetosuchus is an extinct genus of aetosaur from the Late Triassic of the North Carolina, represented by the type species Gorgetosuchus pekinensis. It is mainly known from osteoderms, including the front half of an articulated carapace. Gorgotesuchus is typically considered a basal desmatosuchin, though alternative interpretations exist.

<i>Scutarx</i> Extinct genus of reptiles

Scutarx is an extinct genus of Aetosauriformes, most commonly regarded by its species name Scutarx deltatylus. Scutarx lived around 230 million years ago during the Carnian and Norian stage of the Late Triassic. Scutarx are “medium sized” paramedian osteoderms belonging to the clade Aetosauria, a heavily armored and more herbivorous cousin of crocodiles.

Apachesuchus is an extinct genus of aetosaur from the Late Triassic of New Mexico. It is only known from several paramedian osteoderms discovered in Quay County in eastern New Mexico. This area belongs to the late Norian-age Quay Member of the Redonda Formation. Unique among aetosaurs, its osteoderms are nearly completely smooth, without strong pits or grooves. The left dorsal paramedian has a relatively high width-to-length ration, suggesting that Apachesuchus is a wide-bodied aetosaur within the clade Typothoracinae.

<span class="mw-page-title-main">Aetosauriformes</span> Extinct clade of reptiles

Aetosauriformes is an extinct clade of early-diverging pseudosuchians. It includes the aetosaurs, a group of heavily armoured and at least partially herbivorous pseudosuchians, as well as the closely related genera Acaenasuchus, Euscolosuchus and Revueltosaurus.

References

  1. 1 2 Heckert, A.B.; Lucas, S.G. (1999). "A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs". Journal of Vertebrate Paleontology. 19 (1): 50–68. Bibcode:1999JVPal..19...50H. CiteSeerX   10.1.1.563.9516 . doi:10.1080/02724634.1999.10011122.
  2. 1 2 Fraas, O. (1877). "Aetosaurus ferratus Fr. Die gepanzerte Vogel-Echse aus dem Stubensandstein bei Stuttgar". Festschrift zur Feier des 400jährigen Jubiläums der Eberhard-Karls-Universät zu Tübingen, Wurttembergische Naturwissenschaftliche Jahreshefte. 33 (3): 1–22.
  3. 1 2 Fraas, E. (1907). "Aëtosaurus crassicauda n. sp., nebst Beobachtungen tiber das Becken der Aëtosaurier". Jahreshefte des Vereins für Vaterländische Naturkunde Württemberg. 42: 101–109.
  4. 1 2 3 4 5 Lucas, S.G.; Heckert, A.B.; Huber, P. (1998). "Aetosaurus (Archosauromorpha) from the Upper Triassic of the Newark Supergroup, eastern United States, and its biochronological significance" (PDF). Palaeontology. 41 (6): 1215–1230. Archived from the original (PDF) on 2012-03-09.
  5. 1 2 Heckert, A.B.; Lucas, S.G. (1998). "First occurrence of Aetosaurus (Reptilia: Archosauria) in the Upper Triassic Chinle Group (USA) and its biochronological significance". Neues Jahrbuch für Geologie und Paläontologie. 1998 (10): 604–612. doi:10.1127/njgpm/1998/1998/604.
  6. 1 2 Small, B.J. (1998). "The occurrence of Aetosaurus in the Chinle Formation (Late Triassic, USA) and its biostratigraphic significance". Neues Jahrbuch für Geologie und Paläontologie. 1998 (3): 289–300.
  7. 1 2 Jenkins, F.A. Jr.; Shubin, N.H.; Amaral, W.W.; Gatesy, S.M.; Schaff, C.R.; Clemmensen, L.B.; Downs, W.R.; Davidson, A.R.; Bonde, N.; Osbaeck, F.F. (1994). "Late Triassic continental vertebrates and depositional environments of the Fleming Fjord Formation, Jameson Land, East Greenland". Meddelelser om Grønland, Geoscience. 32: 1–25.
  8. ↑ Teschner, Elżbieta M.; Konietzko-Meier, Dorota; Desojo, Julia B.; Schoch, Rainer R.; Klein, Nicole (2023-02-12). "Triassic Nursery? Evidence of gregarious behavior in juvenile pseudosuchian archosaurs as inferred by humeral histology of Aetosaurus ferratus (Norian; southern Germany)". Journal of Vertebrate Paleontology. 42 (2): e2168196. doi:10.1080/02724634.2023.2168196. ISSN   0272-4634. S2CID   256864004.
  9. ↑ Lazaro, Enrico de (2023-02-13). "Aetosaurs Were Gregarious, Paleontologists Say | Sci.News". Sci.News: Breaking Science News. Retrieved 2023-02-14.
  10. ↑ Wild, R. (1989). "Aëtosaurus (Reptilia:Thecodontia) from the Upper Triassic (Norian) of Cene near Bergamo, Italy, with a revision of the genus" (PDF). Revista del Museo Civico di Scienze Naturali "Enrico Caffi". 14: 1–24.
  11. ↑ Marsh, O.C. (1896). "A new belodont reptile (Stegomus) from the Connecticut River Sandstone". American Journal of Science. 2 (7): 59–62. Bibcode:1896AmJS....2...59M. doi:10.2475/ajs.s4-2.7.59.
  12. ↑ Jepsen, G.L. (1948). "A Triassic armored reptile from New Jersey". State of New Jersey Department of Conservation Miscellaneous Geological Paper: 1–20.
  13. ↑ Baird, D. (1986). "Some Upper Triassic reptiles, footprints and an amphibian from New Jersey". The Mosasaur. 3: 125–135.
  14. ↑ Parker, J.M. (1966). "Triassic reptilian fossil from Wake County, North Carolina". Journal of the Elisha Mitchell Society. 82: 92.
  15. ↑ Lull, R.S. (1953). "Triassic life of the Connecticut Valley revised". Bulletin of the Connecticut Geologic and Natural History Survey. 81: 1–336.
  16. ↑ Julia B. Desojo, Martin D. Ezcurra and Edio E. Kischlat (2012). "A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late Triassic of southern Brazil" (PDF). Zootaxa. 3166: 1–33. doi:10.11646/zootaxa.3166.1.1. ISSN   1175-5334.
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