Thursday, February 21, 2013

[PaleoIchthyology • 2013] 'ปลาพุทธบุตร' ไทยอิกธิส พุทธบุตรเอนซิส ภูน้ำจั้น | Thaiichthys (Lepidotes) buddhabutrensis • Osteology and relationships of Thaiichthys nov. gen.: a Ginglymodi from the Late Jurassic – Early Cretaceous of Thailand



Thaiichthys (Lepidotes) buddhabutrensis 
(Cavin, Suteethorn, Khansubha, Buffetaut and Tong, 2003)


Abstract 
The osteology of Thaiichthys buddhabutrensis, nov. gen., from the Late Jurassic – Early Cretaceous of Thailand is described on the basis of a collection of well-preserved specimens. The mode of preservation of the material allows describing the external anatomy, as well as some elements of the internal anatomy (braincase, elements of the vertebral column). Most of the cranial and postcranial skeleton shows a rather conservative anatomy for ‘semionotiformes’, but the jaw apparatus displays specializations. Variations observed in the ossification pattern of the skull roof and of the cheek, in the morphology of the median dorsal scales and in fin rays’ count indicate that caution should be applied when these characters are used in diagnoses and in phylogenetic analyses. A phylogenetic analysis including a set of gars, of ‘semionotiformes’, of Macrosemiiformes and of Halecomorphi shows the following features: (1) the monophyly of Holostei; (2) sister-pair relationships between Tlayuamichin/Semiolepis, Isanichthys/’Lepidotes’ latifrons and Araripelepidotes/Pliodetes; (3) the latter pair, together with Thaiichthys and possibly ‘Lepidotes’ mantelli, are resolved as stem Lepisosteiformes; and (4) the ‘semionotiformes’ (a group gathering species of Semionotus and Lepidotes) do not form a clade.

Keywords: Lepidotes; semionotiformes; phylogenetic relationships; gars; South-East Asia



Super Division HOLOSTEI sensu Grande, 2010
Division GINGLYMODI sensu Grande, 2010
Order LEPISOSTEIFORMES sensu Grande, 2010

Genus THAIICHTHYS gen. nov.
Type species. Thaiichthys buddhabutrensis (Cavin, Suteethorn, Khansubha, Buffetaut and Tong, 2003).

Derivation of name.  From Thailand and Greek, ichthys, fish.


Figure 2. Mode of preservation of specimens of Thaiichthys buddhabutrensis in the site of Phu Nam Jun. Arrows indicate features described in the text. A, KS12-26. B, KS12-238. C, KS12-128. D, KS12-168. Scale bars represent 20 mm.

Lionel Cavin, Uthumporn Deesri and Varavudh Suteethorn. 2013. Osteology and relationships of Thaiichthys nov. gen.: a Ginglymodi from the Late Jurassic – Early Cretaceous of Thailand. Palaeontology. 56 (1): 183–208. doi:10.1111/j.1475-4983.2012.01184.x

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