Ctenosauriscus koeneni (F. Huene, 1902 )

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

Ctenosauriscus koeneni (F. Huene, 1902)

Holotype.

GZG. V. 4191 , partial vertebral column including three partial cervical vertebrae, at least 13 or 14 dorsal vertebrae, three sacral vertebrae, nine anterior caudal vertebrae, five incomplete cervical ribs, eight partial dorsal ribs, and unidentified bone fragments possibly representing part of the pectoral girdle (Fig. 4 A ). The specimen is preserved on four sandstone blocks that together comprise part and counterpart.

Type locality.

Bremke Valley, quarry east of the village of Reinhausen, about 10 km SE of Göttingen, Göttingen district, Lower Saxony.

Type horizon.

Lower part of Solling Formation, Middle Buntsandstein Subgroup. Age: Early Triassic (Olenekian: Spathian).

Diagnosis.

Diagnosed by the following combination of features: posterior cervical, dorsal, sacral and anterior caudal vertebrae with elongated neural spines forming symmetrical ‘ sail’ (shared with other ctenosauriscids); dorsal neural spines distinctly elongated, with height of longest neural spine more than 12 times length that of corresponding vertebral centrum (probably shared with Arizonasaurus babbitti ); neural spines with strongly anteroposteriorly expanded apices, reaching 190 % of anteroposterior length of bases (probably shared with Hypselorhachis mirabilis ); and pre- and postzygapophyses of dorsal vertebrae large and robust, extending far beyond anterior and posterior articular faces of centra (probably shared with Hypselorhachis mirabilis ) ( Butler et al. 2011).

Comments.

Although Kuhn’s (1964) replacement of Ctenosaurus F. Huene, 1902 by Ctenosauriscus is technically unjustified ( Maisch 2025) the replacement name has become firmly entrenched in the literature and we retain it in the interest of nomenclatural stability.

Ctenosauriscus koeneni was initially considered a late-surviving early synapsid because it superficially resembles Dimetrodon in possessing greatly elongated neural spines along much of the vertebral column (F. Huene 1902, 1914, 1942). Krebs (1969) first interpreted it as a pseudosuchian based on the structure of the vertebrae and noted its close resemblance to (the then still unnamed) Hypselorhachis mirabilis , which is known from an anterior dorsal vertebra with an unusually tall neural spine from the Lifua Member of the Manda Beds (Middle Triassic: Anisian – Ladinian) in Tanzania ( Butler et al. 2009). Furthermore, Arizonasaurus babbitti , from the Holbrook Member of the Moenkopi Formation (Middle Triassic: Anisian) of Arizona, also has greatly elongated neural spines on at least the anterior dorsal vertebrae ( Nesbitt 2005).

A set of three partial neural spines ( SMNS 91405 ), a partial anterior dorsal vertebra ( SMNS 91402 ), and an incomplete left ilium ( SMNS 91401 ) from the stratigraphically slightly younger Röt Formation (Upper Buntsandstein Subgroup; Anisian: Aegean) of Waldhaus in Baden-Württemberg possibly belong to a ctenosauriscid but cannot be confidently assigned to Ctenosauriscus koeneni due to the lack of corresponding skeletal elements ( Butler et al. 2011).

References.

F. Huene (1902, 1914, 1942), Krebs (1969), Nesbitt (2005), Butler et al. (2009, 2011).

Figures

Figure 4. Reptiles from the Upper Buntsandstein Subgroup. A. Poposauroid pseudosuchian Ctenosauriscus koeneni, holotype (GZG. V. 4191), partial vertebral column. Scale bar: 10 cm. From Butler et al. (2011) – CC BY 4.0. B. Tanystropheid tanysaurian Amotosaurus rotfeldensis, holotype (SMNS 50830), disarticulated remains of postcranial skeleton. Scale bar: 5 cm.