Wednesday, June 8, 2016

[Paleontology • 2016] New Material of the Pterosaur Gladocephaloideus et al., 2012 from the Early Cretaceous of Liaoning Province, China, with Comments on Its Systematic Position


Fig 11. Life reconstruction of Gladocephaloideus jingangshanensis
(drawn by Zhao Chuang).

Abstract

Although there are nine genera of ctenochasmatoids reported from the Jehol Biota, at present each is known from a specimen that has either a skull or a relatively complete postcranial skeleton. A nearly complete juvenile specimen of Gladocephaloideus from the Lower Cretaceous Jiufotang Formation of Sihedang, Lingyuan of Liaoning Province is the most complete ctenochasmatoid preserved to date with a skull and postcranial skeleton. Based on the holotype (IG-CAGS 08–07) and the nearly complete new specimen (JPM 2014–004), the diagnosis of Gladocephaloideus is amended: approximately 50 teeth in total with sharp tips; small nasoantorbital opening, occupying approximately 13% of total skull length; ratio of prenarial rostrum length to skull length approximately 0.63; deep groove along the mid-line of the mandibular symphysis; length to width ratio of the longest cervical vertebra = 4.1; ratio of femur length to tibia length = 0.61; tibia as long as the wing-phalange 1. Phylogenetic analysis recovers Gladocephaloideus within the clade Ctenochasmatidae. Gladocephaloideus has a closer relationship to the Chinese Pterofiltrus rather than to other ctenochasmatid pterosaurs. Microstructure of limb bones implies that JPM 2014–004 represents an early juvenile of Gladocephaloideus jingangshanensis, and that the type specimen is not a fully grown specimen either. We assume that the holotype may equate to the late juvenile or sub-adult developmental stage of Gladocephaloideus.


Systematic paleontology

Pterosauria Kaup, 1834 
Pterodactyloidea Plieninger, 1901 
Archaeopterodactyloidea Kellner, 2003 
Ctenochasmatoidea Unwin, 1995 

Gladocephaloideus Lü, Ji, Wei, Liu, 2012 
Gladocephaloideus jingangshanensis Lü, Ji, Wei, Liu, 2012

Specimen: A nearly complete skeleton with a skull and lower jaws (JPM-2014-004). The specimen is housed in the collections of Jinzhou Paleontological Museum, Jinzhou City, Liaoning Province of China.

Locality and horizon: Sihedang, Lingyuan of Liaoning Province, Jiufotang Formation. 

Amended diagnosis: A ctenochasmatoid pterosaur distinguished by the following unique combination of characters: rostrum relatively slender, the distal end of the parietal crest large; about 50 teeth in total, and all the teeth with sharp tips; nasoantorbital opening small, reaching approximately 13% of skull length; ratio of prenarial rostrum length to skull length approximately 0.63; deep groove along the mid-line on the dorsal surface of the mandibular symphysis; length to width ratio of the longest cervical vertebra = 4.1; ratio of femur length to tibia length = 0.61; tibia as long as wing-phalange 1; length ratio of metatarsal III to tibia about 0.4.



Conclusion

The new material of Gladocephaloideus provides much more information on the postcranial morphology, such as the length ratios of femur to tibia, length-to-width ratio of the cervical vertebra, and the length relationships of wing phalanges and tibia. The dense, slender, sharp teeth suggest that Gladocephaloideus is a fish eater (Fig 11). Phylogenetic analysis shows that Gladocephaloideus is more closely related to Pterofiltrus than to other ctenochasmatoids, and they form a clade. The description of a new specimen of Gladocephaloideus from the Jiufotang Formation and the holotype IG-CAGS 08–07 from the Yixian Formation substantially expand the geographic range of this taxon, and increase the known diversity of the pterosaur assemblage from this area. Therefore, the discovery of new material of Gladocephaloideus indicates that the toothed pterosaurs from western Liaoning are widely distributed and more diverse than previous thought. Bone microstructure indicates that JPM 2014–004 represents an early juvenile stage of Gladocephaloideus jingangshanensis and the holotype, IG-CAGS-08-07, is also not fully mature. The holotype bone tissues document an initial stage of skeletal maturation equivalentto a late juvenile or sub-adult stage.


Junchang Lü, Martin Kundrát and Caizhi Shen. 2016. New Material of the Pterosaur Gladocephaloideus et al., 2012 from the Early Cretaceous of Liaoning Province, China, with Comments on Its Systematic Position. PLoS ONE. 11(6): e0154888. DOI: 10.1371/journal.pone.0154888

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