Chroniosaurus
| Chroniosaurus | ||||||||||||
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Live reconstruction of C. dongusensis |
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| Temporal occurrence | ||||||||||||
| Upper Perm | ||||||||||||
| 260.5 to 255 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Chroniosaurus | ||||||||||||
| Tverdokhlebova , 1972 | ||||||||||||
| species | ||||||||||||
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Chroniosaurus is a genus of primeval reptiliomorphic terrestrial vertebrates whose fossils were discovered in continental sedimentary rocks of the Upper Permian of Russia . In the most frequently documented representative of Chroniosuchia , the skin bone plates ( osteoderms )that are typical of this group and are connected to the spine formeda shell that covered most of the back of the body.
features
The Permian Chroniosuchids differ from each other only in a few features: Compared to Suchonica and Uralerpeton , the Chroniosaurus osteoderms located in front of the pelvic girdle had a high ratio of (transversal) width to (axial) length. In contrast to the equally wide skin bone plates of Jarilinus and Chroniosuchus , the ornamentation on the outside was mainly characterized by rounded to oval pustules (Golubev 1998a, b, 1999). The skull also had a pustular sculpture in part and showed a large eye relief compared to Chroniosuchus (Tverdokhlebova 1972, Golubev 1998b, 2000).
In contrast to what is shown in reconstructions of Chroniosaurus , the joint connections between successive plates sometimes allowed a considerable amount of lateral bending of the segmented shell (Golubev 1998a). As in Chroniosuchus and some Temnospondylians, the ventral side of the trunk was covered with a system of ossified spindle scales (Ivakhnenko & Tverdokhlebova 1980).
Species and biostratigraphic meaning
- Type species Chroniosaurus dongusensis Tverdokhlebova, 1972
- Chroniosaurus levis Golubev, 1998, synonym Jugosuchus boreus
Especially the locality Dongus-6 in the Oblast Orenburg produced partial skeletons of C. dongusensis that were preserved in the association and represent the most complete known finds of Chroniosuchiern (cf. Golubev 2000).
C. levis differs from C. dongusensis only in that the pustules on the ornamented outside of the osteoderms are often fused together like a comb (pectinate). Since the finds identified as C. levis occur in somewhat younger sedimentary rock layers than C. dongusensis and an ancestor-descendant relationship is considered probable between the two morphologically defined species, they are also used for biostratigraphic subdivision. The Proelginia -permiana zone of Severodvinian horizon, a rock unit of the Russian Permian -Abfolge is therefore in an older dongusensis chroniosaurus- -Subzone and a younger chroniosaurus-levis -Subzone subdivided (Golubev 1998b).
literature
- Golubev, VK (1998a). Narrow-armored Chroniosuchians (Amphibia, Anthracosauromorpha) from the Late Permian of Eastern Europe. Paleontologicheskij Zhurnal 1998 (3): 64-73. Russian version including illustrations
- Golubev, VK (1998b). Revision of the Late Permian chroniosuchians (Amphibia, Anthracosauromorpha) from Eastern Europe. Paleontologicheskij Zhurnal 1998 (4): 68- 77. Russian version including illustrations
- Golubev, VK (1999). A new narrow-armored chroniosuchian (Amphibia, Anthracosauromorpha) from the Late Permian of the East Europe. Paleontologicheskij Zhurnal 1999 (2): 43-50.
- Golubev, VK (2000). Permian and Triassic chroniosuchians and biostratigraphy of the Upper Tatarian series in Eastern Europe. Trudy Paleontologiceskogo Instituta 276: 1- 172.
- Ivakhnenko, MF, GI Tverdokhlebova (1980). Systematics, Morphology, and Stratigraphic Significance of the Upper Permian Chroniosuchians from the East of the European Part of the USSR. Saratov, Izdatelstvo Saratovskogo Universiteta.
- Tverdokhlebova, GI (1972). New batrachosaurian genus from the Upper Permian of the southern Cis-Urals. Paleontologicheskij Zhurnal (1972): 95-103.