Sclerosaurus armatus Meyer

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

Sclerosaurus armatus Meyer in Fischer, 1857

Holotype.

Unnumbered in collections of the Institut für Geo- und Umweltwissenschaften of Albert-Ludwigs-Universität, Freiburg. Part and counterpart blocks preserving a partial postcranial skeleton.

Type locality.

Quarry at Warmbach near Rheinfelden, Baden, Baden-Württemberg.

Type horizon.

Plattensandstein Formation, Upper Buntsandstein Subgroup. Age: Middle Triassic (Anisian: Aegean).

Referred material.

NMB Bs. 28, part and counterpart blocks with a nearly complete, largely articulated skeleton preserved as natural mold. Holotype of “ Labyrinthodon ” ruetimeyeri Wiedersheim, 1878 (= Aristodesmus ruetimeyeri Seeley, 1896 ). Former quarry at Riehen, Kanton Basel-Stadt, Switzerland. Röt Formation, Upper Buntsandstein Subgroup (Anisian: Aegean).

Diagnosis.

Distinguished by the following features: long, posterolaterally projecting spike on pedicle formed by supratemporal; quadratojugal with pair of dorsoventrally flattened spines and additional spine posteroventral to paired spines; crowns of posterior dentary teeth aligned mesiolingually, slightly overlapping each other; narrow band of dermal armor comprising two or three rows of osteoderms extending on either side of body midline; osteoderms with external sculpturing composed of irregular pits; distal end of femur with intercondylar canal; and robust astragalocalcaneum ( Sues and Reisz 2008).

Comments.

Using casts prepared from the holotype and NMB Bs. 28, Sues and Reisz (2008) provided a detailed anatomical description. With a total length of approximately 50 cm, NMB Bs. 28 is the largest procolophonid currently known. F. Huene (1912) initially classified Sclerosaurus armatus as a procolophonid but later reinterpreted it as a pareiasaur (F. Huene 1932 a). Lee (1995) recovered Sclerosaurus armatus as the sister-taxon to a clade comprising pareiasaurs and turtles in his phylogenetic analysis but considered the possibility that it was a large-bodied ‘ aberrant’ procolophonid. Sues and Reisz (2008) redescribed Sclerosaurus armatus and recovered it as a leptopleuronine procolophonid in their analysis. Cisneros (2008) considered it most closely related to Scoloparia glyphanodon , from the Evangeline Member of the Wolfville Formation (Carnian) of Nova Scotia ( Canada), based on the shared presence of dermal armor. However, the dermal osteoderms of Sclerosaurus armatus extend along the midline of the back whereas one specimen of Scoloparia glyphanodon has a nuchal ‘ shield’ composed of small osteoderms. Both conditions are autapomorphic for their respective taxa and should not be coded as the same character-state.

References.

Fischer (1857), Meyer (1859), Wiedersheim (1878), Seeley (1896), F. Huene (1911 a, 1912, 1932 a), Lee (1995), Cisneros (2008), Sues and Reisz (2008).