Eogyrinus
| Eogyrinus | ||||||||||||
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Eogyrinus (reconstruction drawing ) |
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| Temporal occurrence | ||||||||||||
| Upper Carboniferous (Pennsylvania) | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Eogyrinus | ||||||||||||
| Watson , 1926 | ||||||||||||
Eogyrinus (ancient Greek eos = dawn, gyrinos = tadpole) with the only species Eogyrinus attheyi is a taxonomically controversial genus of the "Anthracosauria" or "Embolomeri", a group of primeval vertebrates from the parent group of the Tetrapoda . Almost all the finds date from the Carboniferous of Northumberland , northern England and were found by the coal miners, artisans and amateur paleontologist Thomas Atthey, which was named in honor of the kind. Today Eogyrinus attheyi is usually placed in the genus Pholiderpeton (with the only other species Pholiderpeton scutigerum Huxley, 1869). The species has beenextensively studied and reconstructedby the English zoologist and paleontologist Alec Leonard Panchen .
description
There are quite a number of finds of this species. One specimen, identified as a lectotype by Alfred Romer , comprises a complete skull, adjacent to a series of vertebrae and ribs, a femur and various scales that are assigned to an individual based on their location. There is also another complete and variously fragmented skull, a still articulated section of a spine, and various isolated bones, flakes of skin, and fragments. There are no fully articulated skeletons or substantial parts of them. In addition to the finds from Northumberland, isolated finds from Fenton, Staffordshire and Newarthill, Lanarkshire are attributed to the species.
Eogyrinus attheyi was a large animal with a vaguely crocodile-like habit, its entire body length is estimated to be between four and five meters. As is typical of the embolomeri, the skull was massively ossified with numerous, strong teeth. On the preserved fossils it is usually pressed flat in the dorsoventral direction, but it was arched on the living animal. All the bones of the basic construction plan of the tetrapods can be seen on the skull, in addition to two large eye windows, a small opening for the pineal organ can be seen on the forehead . The upper jaw (palatoquadratum) was movable via a joint in relation to the skull. In addition to the teeth in the upper and lower jaws, the palate was dentate by several pairs of large teeth. There was not one but two vertebral bodies of roughly the same size per vertebral segment. 39 or 40 vertebrae are reconstructed. On the caudal vertebrae there were probably long appendages (poorly preserved throughout), which, as in related species, suggest a rudder seam supported by them. The body surface was covered by dense skin flakes. The distal parts of the extremities are not preserved. A swimming locomotion is reconstructed for the species by a serpentine sideways movement of the trunk and tail, which was probably supported by a wide fin edge on the tail. Based on the teeth, predatory nutrition is considered safe.
Finding circumstances and living space
Almost all of the finds come from the Hannah Pit coal mine in South Newsham, about a kilometer south of Blyth , Northumberland. The finds were discovered between around 1860 and 1880 by the amateur paleontologist Thomas Atthey, who worked in the mine. They come from a black slate with pyrite inclusions immediately above the main coal seam. The liminic sediments are placed in the Westphalian , a period of the Pennsylvanian (formerly: Upper Carboniferous). A freshwater lake is being reconstructed with oxygen-free deep water, presumably a trough-like deepening approx. 8 kilometers in length. In addition to the tetrapods, fossil coelacids up to 6 meters long were discovered in the sediments , which indicates a rather extensive and deep body of water. There are no finds of certain land-living forms. Plant fossils that occurred together with vertebrate fossils include, for example, the genera Sigillaria , Lepidodendron and Calamites , found from coal deposits almost all over the world , which presumably grew on the shore.
Taxonomy and systematics
After the discovery, the finds were initially erroneously attributed to the species Anthracosaurus russellii . In 1912 the material was re-examined by David Meredith Seares Watson and initially assigned to the genus Pteroplax . In 1926 he then separated the larger specimens as a separate species in the new genus Eogyrinus . In 1987, the English paleontologist Jennifer Alice Clack noticed while working on another fossil antharcosaur, Pholiderpeton scutigerum , that this Eogyrinus attheyi was very similar in almost all characteristics , and that she assessed the remaining differences as too small to justify separate genera. It therefore places the species in this genus as Pholiderpeton attheyi . Pholiderpeton was already described by Thomas Henry Huxley in 1869 and thus has priority. If one follows this view, as most experts do , an independent genus Eogyrinus is no longer justified.
Both species are part of a family Eogyrinidae . This name, which is based on a genus that may no longer be valid, remains unchanged in accordance with the zoological rules of nomenclature even if it is recombined. The family Eogyrinidae in the sense of Clack includes the species Palaeoherpeton decorum (Watson), Eobaphetes kansensis Moodie, Leptophractus obsoletus Cope, Neopteroplax conemaughensis Romer and Neopteroplax relictus Romer in addition to these two species . The sister group of the Eogyrinidae is usually the family Anthracosauridae with the only known species Anthracosaurus russelli Huxley, 1863.
Like the entire group, the species is mostly attributed to the amphibians in popular depictions . Whether it actually belongs to the ancestral group of recent amphibians (taxon Lissamphibia) is an open question. Alternatively, numerous researchers also place them with the so-called reptiliomorpha in the parent group of amniotes . Some see them more basic, in the trunk group of the Tetrapoda as a whole. Their relationship to the Seymouriamorpha is important for the assignment .
swell
- AL Panchen (1972): The Skull and Skeleton of Eogyrinus attheyi Watson (Amphibia: Labyrinthodontia). Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences Vol. 263 No. 851: 279-326.
- AL Panchen (1966): The axial skeleton of the labyrinthodont Eogyrinus attheyi. Journal of Zoology 150, Issue 2: 199-222.
- JA Clack (1987): Pholiderpeton scutigerum Huxley, an Amphibian from the Yorkshire Coal Measures. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences Vol. 318 No. 1188: 1-107.
Individual evidence
- ↑ MJF Boyd & S.Turner (1980): Catalog of the Carboniferous Amphibians in the Hancock Museum, Newcastle upon Tyne. Transactions of the Natural History Society of Northumbria 46: 5-24.
- ^ MJ Boyd (1984): The upper carboniferous tetrapod assemblage from Newsham, Northumberland. Paleontology 27 (2): 367-392.
- ↑ Marcello Ruta, Michael I. Coates, Donald LJ Quicke (2003): Early tetrapod relationships revisited. Biological Reviews 78: 251-345.
- ↑ David Marjanović & Michel Laurin (2013): The origin (s) of extant amphibians: a review with emphasis on the “lepospondyl hypothesis”. Geodiversitas 35 (1): 207-272.
- ↑ Michel Laurin & Jason S. Anderson (2004): Meaning of the Name Tetrapoda in the Scientific Literature: An Exchange. Systematic Biology 53 (1): 68-80.