Philydrosaurus

Philydrosaurus Temporal range: Aptian PreꞒ Ꞓ O S D C P T J K Pg N
Fossil specimen preserving skin impressions, National Museum of Natural Science
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Choristodera
Genus:	†Philydrosaurus Gao and Fox, 2005
Species
†P. proseilus Gao and Fox, 2005 (type)

Philydrosaurus is an extinct genus of choristoderan which existed in China during the Early Cretaceous. The type species P. proseilus was named in 2005. Philydrosaurus was found from the Jiufotang Formation and is slightly younger than Monjurosuchus, which was found from the Yixian Formation.[1]

Description

Distinct ridges cover the prefrontal and postfrontal bones of the skull, distinguishing Philydrosaurus from related genera. The lower temporal fenestra, usually present as a hole in the back of the skull of choristoderes, is closed by bone in Philydrosaurus. The eye sockets are large and spaced close together, similar to Monjurosuchus and Lazarussuchus. Philydrosaurus is considered more basal than these choristoderes because its eyes are not as closely spaced and face laterally rather than dorsally. The skull is similar in shape to that of Cteniogenys, the most basal choristodere. The shortness of the skull and the laterally facing eye sockets likely represent the ancestral condition for choristoderes, but the closed lower temporal fenestra links the genus with more advanced forms.[2]

Paleobiology

A skeleton of Philydrosaurus has been found with associated post-hatchling stage juveniles, suggesting that they engaged in post-hatching parental care.[3]

Phylogeny

Phylogeny from the analysis of Dong and colleagues (2020):[4]

Choristodera

Cteniogenys sp. Heishanosaurus pygmaeus Coeruleodraco jurassicus Neochoristodera Ikechosaurus pijiagouensis Ikechosaurus sunailinae Tchoiria namsari Tchoiria klauseni Champsosaurus C. gigas C. albertensis Simoedosaurus S. lemoinei S. dakotensis "Allochoristodera" Monjurosuchus splendens Philydrosaurus P. proseilus P. proseilus Lazarussuchus L. inexpectatus Lazarussuchus sp. L. dvoraki Khurendukhosaurus orlovi Hyphalosaurus sp. Hyphalosaurus lingyuanensis Shokawa ikoi

References

1. Gao, K.-Q.; Fox, R.C. (2005). "A new choristodere (Reptilia: Diapsida) from the Lower Cretaceous of western Liaoning Province, China, and phylogenetic relationships of Monjurosuchidae" (PDF). Zoological Journal of the Linnean Society. 145 (3): 427–444. doi:10.1111/j.1096-3642.2005.00191.x.
2. Matsumoto, R.; Evans, S.E.; Manabe, M. (2007). "The choristoderan reptile Monjurosuchus from the Early Cretaceous of Japan" (PDF). Acta Palaeontologica Polonica. 52 (2): 329–350.
3. Lü J, Kobayashi Y, Deeming DC, Liu Y (20 October 2014). "Post-natal parental care in a Cretaceous diapsid from northeastern China" (PDF). Geosciences Journal. 19 (2): 273–280. doi:10.1007/s12303-014-0047-1. S2CID 49570935.
4. Dong, Liping; Matsumoto, Ryoko; Kusuhashi, Nao; Wang, Yuanqing; Wang, Yuan; Evans, Susan E. (2020-08-02). "A new choristodere (Reptilia: Choristodera) from an Aptian–Albian coal deposit in China". Journal of Systematic Palaeontology. 18 (15): 1223–1242. doi:10.1080/14772019.2020.1749147. ISSN 1477-2019. S2CID 219047160.