Friday, 3 April 2015

Ionoscopiform Fish from the Middle Triassic of Guizhou Province, China.

Halecomorphs are Neopterygid Fish (Ray-finned Fish) related to Ginglymodians (Gars) and Teleosts (almost all modern Ray-finned Fish). They are split into three groups, the extant Amiiformes, which contain a single living species, the Bowfin, Amia calva, the Paraseminotiformes, which are known from the Early Triassic and possibly the Permian, and the Ionoscopiformes which are known from the Middle Triassic to the Early Cretaceous. To date only a single Ionoscopiform has been described from the Triassic, Robustichthys from the Middle Triassic Panxian Biota of Guizhou Province, China, although potential Ionoscopiformes have been described from the Middle Triassic of Austria and Italy.

In a paper published in the journal Vertebrata PalAsiatica on 21 January 2015, Xu Guang-Hi of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences and the State Key Laboratory of Palaeobiology and Stratigraphy at the Nanjing Institute of Geology and Palaeontology and Shen Chen-Chen, also of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, describe a second species of Ionoscopiform Fish from the Middle Triassic Panxian Biota of Guizhou Province, China.

The new species is named Panxianichthys imparilis, where ‘Panxianichthys’ means ‘Panxian-Fish’ and ‘imparilis’ meaning ‘peculiar and unusual’. It is described from two specimens, both about 200 mm in length, though which is the largest depends on how they are measured, since the smaller specimen has a more intact tail.

Panxianichthys imparilis, first specimen. Photograph (top) and interpretive drawing (bottom). Xu & Shen (2015).

The new species comes from the same deposits as Robustichthys, Member II of the Guanling Formation at Xinmin in Panxian County, though it is judged to be slightly younger; these deposits have produced a variety of Fish, Marine Reptiles and Invertebrates, which are collectively referred to as the ‘Panxian Biota’ or ‘Panxian Fauna’. Importantly, while Panxianichthys is slightly younger than Robustichthys, it is judged to be slightly more primitive, which is to say it shows less of the derived features seen in Ionoscopiform Fish but not non-Ionoscopiform Halecomorphs, suggesting that it may be closer to the first Ionoscopiform Fish, making it useful for understanding the origin and evolution of the group.

Panxianichthys imparilis, second specimen. Photograph (top) and interpretive drawing (bottom). Xu & Shen (2015).

See also…

A freshwater Coccolepidid Fish from the Late Jurassic of Patagonia.
In 1943 palaeontologist Alejandro Bordas described a number of fossil freshwater Fish from a location in...

An Ichthyodectiform Fish from the Early Cretaceous of Queensland, Australia.
Ichthyodectiforms were large, predatory Fish from the Late Jurassic and Cretaceous, distantly related to modern Mooneyes, Elephantfish, Featherbacks, Arowanas and Butterflyfish. The typically...

A Flying Fish from the Middle Triassic of Guizhou Province, China.
Modern Flying Fish, Exocoetidae, are known in the fossil record as far back as the Eocene, and may have originated slightly earlier, though it is unlikely that they are much older than this, since they are known to be related to other groups considered to be quite...


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