Chroniosuchidae

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Chroniosuchidae
Chroniosaurus dongusensis from the Upper Permian of Russia.

Chroniosaurus dongusensis from the Upper Permian of Russia.

Temporal occurrence
Middle Perm to Middle Triassic
265 to 230 million years
Locations
  • European Russia, China, Kyrgyzstan
Systematics
Vertebrates (vertebrata)
Jaw mouths (Gnathostomata)
Land vertebrates (Tetrapoda)
Reptiliomorpha
Chroniosuchia
Chroniosuchidae
Scientific name
Chroniosuchidae
Vyushkov , 1957
Genera

The Chroniosuchidae were a group of reptiliomorphic terrestrial vertebrates of the Upper Permian of Russia, whose representatives, given their frequent occurrence in sea sedimentary rocks, probably lived aquatic or amphibious and acted as crocodile-like predators in freshwater lakes - an ecological position similar to that of some groups of large temnospondylians until the appearance of the archosaurs held (Sennikov 1996).

features

The majority of the known forms show a segmented carapace , consisting of a series of broad, articulated, skin bone plates ( osteoderms ). Chroniosuchids anticipate the later formation of similar armor in amniotes such as the crocodylomorphs , aetosaurs , ankylosaurs and armadillos .

Uralerpeton and Suchonica , on the other hand, show relatively narrow osteoderms. a. in the formation of a pair of articulation surfaces pointing backwards and an elongated pi-shaped ventral process , which represents the connection to the spinous process of the associated vertebra, resemble the osteoderms of other Chroniosuchidae (Golubev 1998–1999).

Similar to other terrestrial vertebrates of the Paleozoic Era , the ventral side of the body was covered with a system of partly ossified spindle scales (Ivakhnenko & Tvedokhlebova 1980). In their vertebral structure, Chroniosuchids of the sister group Bystrowianidae resemble the amniotes and some other reptiliomorphs such as the Diadectomorpha and Seymouriamorpha in that the vertebral arch is fused with the pleurocenter (cf. Novikov et al. 2000).

Convergent to the antorbital window of the archosaurs , Chroniosuchids have a skull opening between the eye and nostrils. The contact surfaces of the skull bones involved show that the upper jaw and cheek were movable relative to the roof of the skull - with this form of the skull kinesis , the skull could be laterally widened or narrowed. The foremost osteoderm of the back plate series fitted between the tabular horns of the occiput (Ivakhnenko & Tverdokhlebova 1980, Golubev 2000).

Systematics

Since the revision by Ivakhnenko & Tverdokhlebova (1980), the Chroniosuchids are combined with the Bystrowianids in the Chroniosuchia group and are considered to be relatives of the Anthracosauria .

According to the new description of the Russian Chroniosuchid material by Golubev (1998–2000) and after a find from the Madygen Formation of southwest Kyrgyzstan described in 2010 , the following genera and species are valid:

On the basis of an upper jaw and a lower jaw fragment from the upper perm of China, a further genus and species were described and assigned to the Chroniosuchidae: Phreatochronis qilianensis and Ingentidens corridoricus (Li & Cheng 1999).

Significance for the stratigraphy of the Russian tablet

Chroniosuchidae, along with other terrestrial vertebrates, are used as key forms for the biostratigraphic subdivision of the continental sedimentary rock sequences of the Russian Middle to Upper Permian (table based on Golubev 2000).

series Regional level Tetrapod zoning proven
Chroniosuchia taxa
Zone Subzone
Upper to
Middle Perm 		Vyatkian Archosaurus rossicus  
Scutosaurus karpinskii Chroniosuchus paradoxus
  • C. paradoxus
  • C. licharevi
Jarilinus mirabilis
  • J. mirabilis
Severodvinian Proelginia permiana Chroniosaurus levis
  • C. levis
Chroniosaurus dongusensis
  • C. dongusensis
Deltavjatia vjatkensis  
  • Suchonica vladimiri

literature

  • VK Golubev: Narrow-armored Chroniosuchians (Amphibia, Anthracosauromorpha) from the Late Permian of Eastern Europe. In: Paleontologicheskij Zhurnal. Volume 1998, No. 3, 1998, pp. 64-73.
  • VK Golubev: Revision of the Late Permian chroniosuchians (Amphibia, Anthracosauromorpha) from Eastern Europe. In: Paleontologicheskij Zhurnal. Volume 1998, No. 4, 1998, pp. 68-77.
  • VK Golubev: A new narrow-armored chroniosuchian (Amphibia, Anthracosauromorpha) from the Late Permian of the East Europe. In: Paleontologicheskij Zhurnal. Volume 1999, No. 2, 1999, pp. 43-50.
  • VK Golubev: Permian and Triassic chroniosuchians and biostratigraphy of the Upper Tatarian series in Eastern Europe. In: Trudy Paleontologiceskogo Instituta. Volume 276, 2000, pp. 1-172.
  • MF Ivakhnenko, GI Tverdokhlebova: Systematics, Morphology, and Stratigraphic Significance of the Upper Permian Chroniosuchians from the East of the European Part of the USSR. Izdatelstvo Saratovskogo Universiteta, Saratov 1980.
  • J. Li, Z. Cheng: New anthracosaur and temnospondyl amphibians from Gansu, China. In: Vertebrata PalAsiatica. Volume 37, No. 3, 1999, pp. 234-247.
  • IV Novikov, MA Shishkin, VK Golubev: Permian and Triassic anthracosaurs from Eastern Europe. In: MJ Benton, MA Shishkin, DM Unwin, EN Kurochkin (eds.): The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press, Cambridge 2000, p. 60-70.
  • AG Sennikov: Evolution of the Permian and Triassic tetrapod communities of Eastern Europe. In: Palaeogeography, Palaeoclimatology, Palaeoecology. Volume 120, No. 3-4, 1996, pp. 331-351.
  • Rainer R. Schoch, Sebastian Voigt, Michael Buchwitz: A chroniosuchid from the Triassic of Kyrgyzstan and analysis of chroniosuchian relationships. In: Zoological Journal of the Linnean Society. Volume 160, No. 3, 2010, pp. 515-530.
  • BP Vjushkov: New peculiar animals from strata of the Tatarian Series in the European part of the USSR. In: Doklady Akademiya Nauk SSSR. Volume 113, 1957, pp. 183-186.