Aetosaurus ferratus O. Fraas, 1877

Sues, Hans-Dieter & Schoch, Rainer R., 2025, Synopsis of the Triassic reptiles from Germany, Fossil Record 28 (2), pp. 411-483 : 411-483

Aetosaurus ferratus O. Fraas, 1877

Lectotype.

SMNS 5770 , ‘ Specimen XVI, ’ nearly complete skeleton (Fig. 17 A ), part of a single block with a group of 24 skeletons ranging in length from 20 to 82 cm. The skull of the lectotype was separated from the block and underwent additional preparation for the revision by Schoch (2007).

Type locality.

Former quarry in the “ Billert, ” at the confluence of the Elsenbach and Nesenbach creeks, Stuttgart-Kaltental, Baden-Wu ̈ rttemberg ( Schoch 2007).

Type horizon.

Lower Stubensandstein (S 1), Lo ̈ wenstein Formation (equivalent of Arnstadt Formation), Middle Keuper Subgroup. Age: Late Triassic (Norian: Lacian). Oskar Fraas (1887: 2) noted that the block was discovered three meters above the main sandstone unit, within a local occurrence of mudstone (“ erste Hangendletten ”).

Referred material (only from Germany).

Lower Stubensandstein (S 1): SMNS 5771 (partial dermal armor and limb bones from type locality and horizon); SMNS 18554 (articulated skeleton lacking skull and pectoral girdle from Blankenhorn Castle near Eibensbach). Middle Stubensandstein (S 2; at Pfaffenhofen): SMNS 11837 ( holotype of Aetosaurus crassicauda E. Fraas, 1907 ); SMNS 12670 (set of isolated dorsal osteoderms and a fragment of the ventral dermal armor); SMNS 14882 (articulated portion of tail with dermal armor and 14 caudal vertebrae).

Diagnosis.

Distinguished by the following autapomorphies: premaxilla lacking apical transverse expansion; maxilla extending to midlevel of external naris; jugal shorter than orbit; size of supratemporal fenestra one fifth size of orbit; quadratojugal process extending into infratemporal fenestra; three supraorbital elements; ratio of width to length for paramedian dorsal osteoderms 2 to 3.5; paramedian dorsal osteoderms slightly flexed transversely; and ventral dermal armor in mid-trunk region comprising up to 12 osteoderms per transverse row ( Schoch 2007).

Comments.

F. Huene (1920), Walker (1961), and Schoch (2007) documented the skeletal structure of Aetosaurus ferratus in detail. Recent histological work has shown that the famous aggregation of skeletons ( SMNS 5770 ; O. Fraas 1877; E. Fraas 1896), which includes the lectotype of Aetosaurus ferratus , probably represents a group of juvenile individuals ( Teschner et al. 2023). Schoch (2007) suggested that the holotype of Aetosaurus crassicauda E. Fraas, 1907 ( SMNS 11837 ) merely represents a larger individual of Aetosaurus ferratus .

References.

O. Fraas (1877), E. Fraas (1896, 1907), F. Huene (1920), Walker (1961), Heckert and Lucas (2000), Schoch (2007), Parker (2016), Teschner et al. (2023).

Figures

Figure 17. Reptiles from the Middle Keuper Subgroup. A. Stagonolepidid pseudosuchian Aetosaurus ferratus, lectotype (SMNS 5770, individual XVI), skull and part of cervical region in lateral view. Scale bar: 2 cm. B. Stagonolepidid pseudosuchian Paratypothorax andressorum, holotype (SMNS 5721), right paramedian dorsal osteoderm in dorsal view. Scale bar: 5 cm. C. Stagonolepidid pseudosuchian Paratypothorax andressorum (SMNS 19003), skull and dorsal armor. Scale bar: 20 cm.