Aetosaur Awesomeness!

Aetosauria: a clade of armoured pseudosuchians from the Upper Triassic continental beds

Authors:

1. Julia B. Desojo (a)
2. Andrew B. Heckert (b)
3. Jeffrey W. Martz (c)
4. William G. Parker (d,e)
5. Rainer R. Schoch (f)
6. Bryan J. Small (g)
7. Tomasz Sulej (h)

Affiliations:

a. CONICET, Comisión Nacional de Investigación Científica y Técnica, Sección Paleontología Vertebrados, Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’, Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina

b. Department of Geology, Appalachian State University, ASU Box 32067, Boone, NC 28608-2067, USA

c. Department of Earth Sciences, Denver Museum of Nature and Science, 2001 Colorado Blvd, Denver, CO 80205, USA

d. Division of Resource Management, Petrified Forest National Park, PO Box 2217, Petrified Forest, AZ 86028, USA

e. Department of Geological Sciences, University of Texas, Austin, TX 78712, USA

f. Staatliches Museum für Naturkunde, Rosenstein 1, 70191 Stuttgart, Germany

g. Museum of Texas Tech University, 3301 4th St., Lubbock, TX 79409-3191, USA

h. Instytut Paleobiologii, PAN, Twarda 51/55, 00-818 Warszawa, Poland

Abstract:

Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species ranging from 1 to 6 m in length, and with a body mass ranging from less than 10 to more than 500 kg, are known. Aetosauroides scagliai was recently recovered as the most basal aetosaur, placed outside of Stagonolepididae (the last common ancestor of Desmatosuchus and Aetosaurus). Interrelationships among the basal aetosaurs are not well understood but two clades with relatively apomorphic armour – the spinose Desmatosuchinae and the generally wide-bodied Typothoracisinae – are consistently recognized. Paramedian and lateral osteoderms are often distinctive at the generic level but variation within the carapace is not well understood in many taxa, warranting caution in assigning isolated osteoderms to specific taxa. The aetosaur skull and dentition varies across taxa, and there is increasing evidence that at least some aetosaurs relied on invertebrates and/or small vertebrates as a food source. Histological evidence indicates that, after an initial period of rapid growth, lines of arrested growth (LAGs) are common and later growth was relatively slow. The common and widespread Late Triassic ichnogenus Brachychirotherium probably represents the track of an aetosaur.