# Aetosaurus

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Extinct genus of reptiles

Aetosaurus Temporal range: Late Triassic, Carnian–Norian PreꞒ Ꞓ O S D C P T J K Pg N Assemblage of fossil A. ferratus Scientific classification Kingdom: Animalia Phylum: Chordata Class: Reptilia Clade: Pseudosuchia Order: †Aetosauria Family: †Stagonolepididae Subfamily: †Aetosaurinae Genus: †Aetosaurus Fraas, 1877 Species †A. arcuatus (Marsh, 1896) †A. crassicauda Fraas, 1907 †A. ferratus Fraas, 1877 (type) Synonyms Stegomus arcuatus Marsh, 1896

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

## Description

*Aetosaurus* was a small, primitive aetosaur. Unlike more [derived](/source/Synapomorphy) aetosaurs such as *[Desmatosuchus](/source/Desmatosuchus)* or *[Typothorax](/source/Typothorax)*, the [carapace](/source/Carapace) was long and narrow and lacked spikes. The paramedian [scutes](/source/Scute) 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](/source/Kaltental), suggested that juvenile *A. ferratus* were likely [gregarious](/source/Gregarious) animals, possibly to increase their chances of survival and to deter predators.[8][9]

## Species

Reconstructed skull of *A. ferratus*

*Aetosaurus* was first named, with the description of the type species *A. ferratus*, in 1877 by German [paleontologist](/source/Paleontologist) [Oscar Fraas](/source/Oscar_Fraas). At the time, *Aetosaurus* was known from 22 articulated skeletons that had been found in the [Lower Stubensandtein](/source/Lower_Stubensandtein) of Germany.[2] Thirty years later, Fraas' son [Eberhard](/source/Eberhard_Fraas) 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](/source/Zorzino_Limestone) in [Cene](/source/Cene%2C_Lombardy), 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](/source/Othniel_Charles_Marsh) named *Stegomus arcuatus* from a [cast](/source/Fossil#Casts_and_molds) of an aetosaur known as [YPM](/source/Peabody_Museum_of_Natural_History) 1647 from the [New Haven Formation](/source/New_Haven_Formation) in the [Fair Haven Heights neighborhood](https://en.wikipedia.org/w/index.php?title=Fair_Haven_Heights_neighborhood&action=edit&redlink=1) 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](/source/Passaic_Formation) of [Hunterdon](/source/Hunterdon_County%2C_New_Jersey) and [Somerset counties](/source/Somerset_County%2C_New_Jersey), [New Jersey](/source/New_Jersey)[12][13] and an outcrop of the Lower [Sanford Formation](/source/Sanford_Formation) at the [Triangle Brick Co. Quarry](https://en.wikipedia.org/w/index.php?title=Triangle_Brick_Co._Quarry&action=edit&redlink=1) in [Durham County, North Carolina](/source/Durham_County%2C_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*

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](/source/Pelvis).[4]

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

Aetosauria Aetosauroides scagliai Stagonolepididae Aetosaurus ferratus Coahomasuchus kahleorum Neoaetosauroides engaeus Calyptosuchus wellesi Stagonolepis robertsoni Aetobarbakinoides brasiliensis Typothoracisinae Typothorax Redondasuchus Paratypothoracisini Tecovasuchus chatterjeei Rioarribasuchus chamaensis Paratypothorax andressorum Desmatosuchinae Sierritasuchus macalpini Longosuchus meadei Lucasuchus hunti Acaenasuchus geoffreyi Desmatosuchus Desmatosuchus haplocerus Desmatosuchus smalli

## References

1. ^ [***a***](#cite_ref-HL99_1-0) [***b***](#cite_ref-HL99_1-1) Heckert, A.B.; Lucas, S.G. (1999). ["A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs"](https://www.researchgate.net/publication/254314124). *Journal of Vertebrate Paleontology*. **19** (1): 50–68. [Bibcode](/source/Bibcode_(identifier)):[1999JVPal..19...50H](https://ui.adsabs.harvard.edu/abs/1999JVPal..19...50H). [CiteSeerX](/source/CiteSeerX_(identifier)) [10.1.1.563.9516](https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.563.9516). [doi](/source/Doi_(identifier)):[10.1080/02724634.1999.10011122](https://doi.org/10.1080%2F02724634.1999.10011122).

1. ^ [***a***](#cite_ref-FO77_2-0) [***b***](#cite_ref-FO77_2-1) 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.

1. ^ [***a***](#cite_ref-FE07_3-0) [***b***](#cite_ref-FE07_3-1) Fraas, E. (1907). "*Aëtosaurus crassicauda* n. sp., nebst Beobachtungen tiber das Becken der Aëtosaurier". *Jahreshefte des Vereins für Vaterländische Naturkunde Württemberg*. **42**: 101–109.

1. ^ [***a***](#cite_ref-LHH98_4-0) [***b***](#cite_ref-LHH98_4-1) [***c***](#cite_ref-LHH98_4-2) [***d***](#cite_ref-LHH98_4-3) [***e***](#cite_ref-LHH98_4-4) 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"](https://web.archive.org/web/20120309062222/http://palaeontology.palass-pubs.org/pdf/Vol%2041/Pages%201215-1230.pdf) (PDF). *Palaeontology*. **41** (6): 1215–1230. Archived from the original on 2012-03-09.

1. ^ [***a***](#cite_ref-HL98_5-0) [***b***](#cite_ref-HL98_5-1) 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](/source/Doi_(identifier)):[10.1127/njgpm/1998/1998/604](https://doi.org/10.1127%2Fnjgpm%2F1998%2F1998%2F604).

1. ^ [***a***](#cite_ref-SBJ98_6-0) [***b***](#cite_ref-SBJ98_6-1) 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.

1. ^ [***a***](#cite_ref-Jetal94_7-0) [***b***](#cite_ref-Jetal94_7-1) 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.

1. **[^](#cite_ref-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](/source/Doi_(identifier)):[10.1080/02724634.2023.2168196](https://doi.org/10.1080%2F02724634.2023.2168196). [ISSN](/source/ISSN_(identifier)) [0272-4634](https://search.worldcat.org/issn/0272-4634). [S2CID](/source/S2CID_(identifier)) [256864004](https://api.semanticscholar.org/CorpusID:256864004).

1. **[^](#cite_ref-9)** Lazaro, Enrico de (2023-02-13). ["Aetosaurs Were Gregarious, Paleontologists Say | Sci.News"](https://www.sci.news/paleontology/gregarious-aetosaurus-ferratus-11649.html). *Sci.News: Breaking Science News*. Retrieved 2023-02-14.

1. **[^](#cite_ref-WR89_10-0)** Wild, R. (1989). ["*Aëtosaurus* (Reptilia:Thecodontia) from the Upper Triassic (Norian) of Cene near Bergamo, Italy, with a revision of the genus"](https://www.museoscienzebergamo.it/web/images/stories/museo/Rivista_museo/14_volume/riv_14_wild.pdf) (PDF). *Revista del Museo Civico di Scienze Naturali "Enrico Caffi"*. **14**: 1–24.

1. **[^](#cite_ref-MOC96_11-0)** Marsh, O.C. (1896). ["A new belodont reptile (*Stegomus*) from the Connecticut River Sandstone"](https://zenodo.org/record/1450162). *American Journal of Science*. **2** (7): 59–62. [Bibcode](/source/Bibcode_(identifier)):[1896AmJS....2...59M](https://ui.adsabs.harvard.edu/abs/1896AmJS....2...59M). [doi](/source/Doi_(identifier)):[10.2475/ajs.s4-2.7.59](https://doi.org/10.2475%2Fajs.s4-2.7.59).

1. **[^](#cite_ref-JGL48_12-0)** Jepsen, G.L. (1948). "A Triassic armored reptile from New Jersey". *State of New Jersey Department of Conservation Miscellaneous Geological Paper*: 1–20.

1. **[^](#cite_ref-BD86_13-0)** Baird, D. (1986). "Some Upper Triassic reptiles, footprints and an amphibian from New Jersey". *The Mosasaur*. **3**: 125–135.

1. **[^](#cite_ref-PJM66_14-0)** Parker, J.M. (1966). "Triassic reptilian fossil from Wake County, North Carolina". *Journal of the Elisha Mitchell Society*. **82**: 92.

1. **[^](#cite_ref-LRS53_15-0)** Lull, R.S. (1953). "Triassic life of the Connecticut Valley revised". *Bulletin of the Connecticut Geologic and Natural History Survey*. **81**: 1–336.

1. **[^](#cite_ref-Aetobarbakinoides_16-0)** 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"](https://www.mapress.com/zootaxa/2012/f/z03166p033f.pdf) (PDF). *Zootaxa*. **3166**: 1–33. [doi](/source/Doi_(identifier)):[10.11646/zootaxa.3166.1.1](https://doi.org/10.11646%2Fzootaxa.3166.1.1). [ISSN](/source/ISSN_(identifier)) [1175-5334](https://search.worldcat.org/issn/1175-5334).

## External links

- [*Aetosaurus*](https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=38269) in the [Paleobiology Database](/source/Paleobiology_Database)

- [Paleontology portal](https://en.wikipedia.org/wiki/Portal:Paleontology)

v t e Aetosauria Kingdom: Animalia Phylum: Chordata Class: Sauropsida Clade: Pseudosuchia Clade: Aetosauriformes Pseudosuchia see Pseudosuchia Aetosauria see below↓ Aetosauria †Aetosauria Aetosauroides Stagonolepididae Aetosaurinae Aetosaurus Coahomasuchus? Stenomyti? Typothoracinae? Apachesuchus Chilenosuchus? Gorgetosuchus? Kryphioparma Redondasuchus Typothorax Paratypothoracini Garzapelta? Kocurypelta Kuttysuchus Paratypothorax Rioarribasuchus Tecovasuchus Venkatasuchus Desmatosuchia Stagonolepidinae? Polesinesuchus Stagonolepis Desmatosuchinae sensu lato Adamanasuchus? Aetobarbakinoides? Calyptosuchus? Chilenosuchus? Neoaetosauroides? Olkasuchus Scutarx? Desmatosuchini (Desmatosuchinae sensu stricto) Desmatosuchus Gorgetosuchus? Longosuchus Lucasuchus Sierritasuchus Category

Taxon identifiers Aetosaurus Wikidata: Q3496825 Wikispecies: Aetosaurus GBIF: 3238743 Open Tree of Life: 6148465 Paleobiology Database: 38269

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Adapted from the Wikipedia article [Aetosaurus](https://en.wikipedia.org/wiki/Aetosaurus) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Aetosaurus?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.