Diagnoza

A small archosauriform. Cervical centra 12–13 mm in adult length, smaller than in any other known archosauriforms except euparkeriids. From known euparkeriids it differs in having more elongate and cylindrical cervical centra, and costal articulations barely protruding from the body of the centrum, while resembling the East European rauisuchids Tsylmosaurus, Vytshegdosuchus, and Dongusuchus except in smaller size. Weak development of ventral crests makes the vertebrae most similar to those of Tsylmosuchus, but posteroventral obliquity of the centrum is less. In cervicals the centrum length to posterior depth index is about 2.07 except at the transition between cervical and dorsal series where it drops to 1.8. In caudals it ranges from 1.9 to 3.7 and increases down the tail.

Porównanie

The vertebrae of Collilongus rarus approximate prolacertiform type vertebrae in the proportions of the cervical centra, but their short, tall neural spines contrast with the elongated crest-like prolacertiform type cervical neural spines. Prolacertiform vertebrae in the Czatkowice 1 material belong to animals of much smaller size (about 6 mm cervical centrum length and a length-to-height proportion of about 4.0). The other archosauriform type dorsal, sacral, and caudal vertebrae are tentatively associated with the cervicals. Their conspecificity is highly likely. All the vertebrae in this series are mature as shown by the completely closed neurocentral sutures.

In their elongate shape, the cervical vertebrae of Collilongus most closely resemble those of Olenekian rauisuchids from Russia, and particularly those of the group including Tsylmosuchus, Vytshegdosuchus, Dongusuchus, and Energosuchus. There were considered six species: T. samariensis, T. jakovlevi, T. donensis, V. zheshartensis, D. efremov, and E. garjanovi, to be consecutive members of the same phylogenetic line, ranging from Early Olenekian to Ladinian. This hypothesis is based on the common possession of elongate cervical vertebrae with a central axis sloping posteroventrally at 6–20°; a concave ventral centrum profile; and diapophyses and parapophyses that hardly protrude from the centrum. As these taxa are represented by isolated bones, no other feature can be used to unite them. Just two species, T. jacovlevi and V. zheshartensis, include fragmentary ilia with a supra-acetabular buttress that approximates the rauisuchid condition, and this forms the basis for the rauisuchid attribution of the whole group. Collilongus cervical vertebrae are much smaller and less sloping (1 to 9°), less waisted, and slightly less ventrally concave, but otherwise quite similar to those of any of these apparent rauisuchids. However, no synapomorphy can be named to support their relationships.

Autekologia

Terrestrial

Występowanie geograficzne

Only locus typicus

Zasięg czasowy

Only stratum typicum

Materiały muzealne

Institute of Paleobiology PAN, Warsaw (ZPAL)

Literatura

Borsuk−Białynicka, M. and Sennikov, A.G. 2009. Archosauriform postcranial remains from the Early Triassic karst deposits of

southern Poland. Palaeontologica Polonica 65, 283–328.