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...

Follow Sciency Thoughts on Facebook.

An early Ray-Finned fish from the Middle Triassic Luoping Biota of Yunnan Province, China.

Neopterygian (Ray-Finned) Fish first appeared in the Late Permian, and became the most abundant group of fish during the Mesozoic; they remain such today. Neopterygians cane be divided into three groups, the Teleosts, fish with expandable mouthparts, which are the most abundant fish today, and two other groups, the Semiontids (which include the modern Gars) and Halecomorphs (which include the modern Bowfin), which were abundant during the Mesozoic but are now represented by only a few species. The relationships of the early Neoptergyians are unclear, but the Semiontids and Halecomorphs are generally thought to be more closely related to each other than either is to the Teleosts; together they are collectively referred to as Holosteians.

A fisherman with an Alligator Gar, Atractosteus spatula, one of North America's largest fish and a surviving Semiontid Fish. The Megafishes Project.

In a paper in the April edition of the journal Acta Palaeonotologica Polonica a team of palaeontologists led by Wen Wen of the Chengdu Institute of Geology and Mineral Resources announce the discovery of an early Neopterygian Fish that does not fit clearly into any of these groups, and the implications of this.

The new species is named as Luoxiongichthys hyperdorsalis, meaning 'The humpbacked fish from Luoxing'. It has a distinctive forward curving hump on its back that Wen Wen et al. compare to a 'reverse shark’s dorsal fin'. This is unlikely to have been advantageous to the fish when swimming, and was probably used for display.

Luoxiongichthys hyperdorsalis. Top, photograph of original specimen. Middle, interpretive drawing based upon photograph. Bottom, reconstruction of living fish. From Wen Wen et al. (2012).

Luoxiongichthys hyperdorsalis was described from a single specimen found in the Daaozi Section of the Guanling Formation, at Daaozi Village in Luoping County, about 25 km northeast of the town of Luoxiong. This is a muddy limestone that has produced a large number of excellently preserved vertebrates, invertebrates and plants from the Middle Triassic, collectively refered to as the Luoping Biota.

The location of the section that produces the Luoping Biota. From Wen Wen et al. (2012).

Luoxiongichthys hyperdorsalis does not fit easily into any group of Neopterygian Fish, but appears to be more closely related to the Semiontids and Halecomorphs than to the Teleosts, supporting the theory that these groups are related, and probably more closely related to the the Semiontids than to the Halecomorphs. Several early Semiontids have also been shown to have humped backs, supporting this relationship.

Diagram showing the probable relationships of Luoxiongichthys hyperdorsalis to other groups of fish. From Wen Wen et al. (2012).

See also News species of Velvetfish from the Kimberly Coast of Western Australia, Live birth in a Middle Triassic Coelacanth, The pelvic girdles of two primitive boney fish from China, New species of Deepwater Tilefish from the Philippines and and Boney Fish on Sciency Thoughts YouTube.

Follow Sciency Thoughts on Facebook.