Chroniosaurus

Live reconstruction of C. dongusensis

• Orenburg district, Voruralgebiet, Russia

• Chroniosaurus dongusensis
• Chroniosaurus levis

Chroniosaurus is a genus of primitive reptiliomorpher land vertebrates, whose fossils have been discovered in continental sedimentary rocks of the Upper Permian of Russia. In the most frequently occupied representatives of Chroniosuchia typical of this group associated with the spine skin bony plates ( osteoderms ) formed an armor that covered most of the back of the body.

Features

The Permian Chroniosuchiden differ only in a few features from each other: Compared to Suchonica and Uralerpeton had located in front of the pelvic girdle osteoderms of Chroniosaurus a high ratio of ( transverse ) width ( axial ) length. In contrast to the equally wide skin bone plates of Jarilinus and Chroniosuchus the ornamentation of the exterior was mainly characterized by round to oval pustules ( Golubev, 1998a, b, 1999). The skull had partly also a pustular sculpture, and exhibited in comparison to Chroniosuchus long eye relief ( Tverdokhlebova 1972, Golubev 1998b, 2000).

Unlike what is shown in reconstructions of Chroniosaurus, the hinge joints between successive plates were partly a considerable degree of lateral bending of the segmented armor to ( Golubev, 1998a ). The belly of the fuselage was occupied as Chroniosuchus and some Temnospondyliern with a system ossified spindle scales ( Ivakhnenko & Tverdokhlebova 1980).

Types and biostratigraphic significance

• Type species Chroniosaurus dongusensis Tverdokhlebova, 1972
• Chroniosaurus levis Golubev, 1998, synonym Jugosuchus Boreus

Especially the location Dongus - 6 in the Orenburg Oblast has produced in association obtained partial skeletons of C. dongusensis that represent the most well-known finds of Chroniosuchiern ( cf. Golubev 2000).

C. levis differs from C. dongusensis only in that the pustules of the ornamented exterior of the osteoderms often comb-like ( pectinate ) are fused together. Since so than C. levis reported findings occur as C. dongusensis in slightly younger sedimentary rock layers and is between the two species morphologically defined an ancestor - descendant relationship than likely, they are also used for biostratigraphic subdivision. The Proelginia - permiana zone of Severodvinian horizon, a rock unit of the Russian Permian sequence is, therefore, divided into an older Chroniosaurus - dongusensis subzone and a younger Chroniosaurus - levis - subzone ( Golubev 1998b ).