Ymeria denticulata (lat.) Is a species of extinct mandibular from the Ichthyostegidae family of the tetrapodomorph clade ( Tetrapodomorpha ), the only one of the genus Ymeria [3] . The taxon is known from the Devonian sediments ( Famennian layer [3] ) by the partially preserved skull of the holotype , including the lower jaw and palate , also by the remains of the shoulder girdle [2] .
| † Ymeria denticulata | |||||||||||||||||||||||||||||||||||||||||
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| International scientific name | |||||||||||||||||||||||||||||||||||||||||
Ymeria denticulata Clack et al. , 2012 [2] | |||||||||||||||||||||||||||||||||||||||||
| Geochronology Famennian age 372.2—358.9 Ma
◄ Nowadays◄ Cretaceous-Paleogene extinction◄ Triassic extinction◄ Mass Permian Extinction◄ Devonian extinction◄ Ordovician-Silurian extinction◄ Cambrian explosion | |||||||||||||||||||||||||||||||||||||||||
Content
Study History
Fossils of the Devonian four-legged animals, similar to the genus Ichthyostega , have been known on the island of Imer since 1929. A skull of the genus Ymeria was discovered in 1947 by a team of paleontologists from Denmark and Sweden on the southern slope of Mount Celsius ( Mt. Celsius ) on the island of Imer in the northeastern part of the administrative territory of Greenland (Denmark) [2] . The Swedish paleontologist, academician Erik Jarvik (1907-1998), a member of the 1947 expedition, could not attribute the found skull to either the genus Ichthyostega or the genus Acanthostega . For a long time, the remains remained undefined. In 1988, the English paleontologist Professor Jennifer Clack ( University of Cambridge ) was the first scientist to suggest that the material found was a new, third, species of four-legged animal from Greenland [4] . As a result of additional studies in 2012, a new genus and species Ymeria denticulata were described [2] .
Systematics
When describing the new species, the authors did not indicate either a class or a detachment to which it can be assigned, since the holotype MGUH VP 6088 combines both plesiomorphic and apomorphic characters. Researchers see the new taxon as a basal group for tetrapods. More than 10 genera of tetrapods are known from the Devonian sediments: Ichthyostega Säve-Söderbergh, 1932 [5] ; Acanthostega Jarvik, 1952 [6] , Tulerpeton Lebedev, 1984 [7] ; Metaxygnathus Campbell & Bell, 1977 ; Elginerpeton Ahlberg, 1991 ; Obruchevichthys Ahlberg, 1991 ; Ventastega Ahlberg et al. 1994 ; Hynerpeton Daeschler et al. 1994 ; Densignathus Daeschler, 2000 ; Sinostega Zhu et al. , 2002 [8] ; Jakubsonia Lebedev, 2004 [2] [9] . Ymeria denticulata most closely resembles two other genera found in Greenland: Ichthyostega and Acanthostega [2] [10] [11] .
In 2015, Jennifer Clack and AR Milner confirmed the assignment of the genus to the family Ichthyostegidae from the clade of tetrapodomorphs (Tetrapodomorpha) [12] .
Etymology
The generic name Ymeria is given by the name of the island of Imer , where type material was discovered that comes from the character of the German-Scandinavian mythology of the giant Ymir , from whom this world was created. The species name denticulata draws attention to the serrated surface of the lower jaw [2] .
Notes
- ↑ Due to the limitations of MediaWiki, the maxillary tetra podomorph taxon indicates the maxillary infratype (Gnathostomata) instead of the Dipnotetrapodomorpha clade, cited in the source: Betancur-RR et al. The tree of life and a new classification of bony fishes // PLOS Currents Tree of Life. - 2013. - DOI : 10.1371 / currents.tol.53ba26640df0ccaee75bb165c8c26288 .
- ↑ 1 2 3 4 5 6 7 Clack, JA; Ahlberg, PE; Blom, H .; and Finney, SM A new genus of Devonian tetrapod from North-East Greenland, with new information on the lower jaw of Ichthyostega (Eng.) // Palaeontology: journal. - 2012. - Vol. 55 , no. 1 . - P. 73-86 . - DOI : 10.1111 / j.1475-4983.2011.01117.x .
- ↑ 1 2 Ymeria denticulata . Paleobiology Database Classic . (Retrieved August 27, 2016) .
- ↑ Clack, JA 1988. New material of the early tetrapod Acanthostega from the Upper Devonian of East Greenland. Palaeontology 31 : 699-724.
- ↑ Säve-Söderbergh, G. 1932. Preliminary note on Devonian stegocephalians from East Greenland. Meddelelser om Grønland 98 : 1-211.
- ↑ Jarvik, E. 1952. On the fish-like tail in the ichthyostegid stegocephalians. Meddelelser om Grønland 114 : 1–90.
- ↑ Lebedev, OA 1984. The first find of a Devonian tetrapod vertebrate in the USSR. Doklady Akademii Nauk SSSR, Palaeontology 278 : 1470-1473.
- ↑ Zhu, M., Ahlberg, PE, Zhao, W. and Jia, L. 2002. First Devonian tetrapod from Asia. Nature 420 : 760-761.
- ↑ Lebedev, OA 2004. A new tetrapod Jakubsonia livnensis from the Early Famennian Devonian) of Russia and palaeoecological remarks on the Late Devonian tetrapod habitats. Acta Universitatis Latviensis, Series Earth and Environment Sciences 679 : 79-98.
- ↑ Ahlberg, PE, Luksevics, E. and Lebedev, OA The first tetrapod finds from the Devonian Upper Famennian of Latvia. // Philosophical Transactions of the Royal Society of London B. - 1994. - Vol. 343. - P. 303—328.
- ↑ Ahlberg, PE and Clack, JA Lower jaws, lower tetrapods - a review based on the Devonian genus Acanthostega. // Transactions of the Royal Society of Edinburgh, Earth Sciences. - 1998. - Vol. 89. - P. 11–46.
- ↑ JA Clack and AR Milner. 2015. Handbook of Paleoherpetology, Part 3A1: Basal Tetrapoda.
Literature
- Blom, H. Taxonomic revision of the Late Devonian tetrapod Ichthyostega from Greenland. // Palaeontology. - 2005. - Vol. 48. - P. 111-134.
- Blom, H., Clack, JA and Ahlberg, PE Localities, distribution and stratigraphical context of the Late Devonian tetrapods of East Greenland. // Meddelelser om Grønland, Geoscience. - 2005. - Vol. 43. - P. 1-50.
- Jarvik, E. Basic Structure and Evolution of Vertebrates. - New York: Academic Press, 1980. - Vol. 1 - 575 pp.
- Jarvik, E. The Devonian tetrapod Ichthyostega. - Fossils and Strata, 1996. - Vol. 40 - P. 1-206.