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Philydrosaurus - A Reptile of the Cretaceous

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  • Neal Robbins
          This link has a drawing that gives an idea of how Philydrosaurus looked. Another illustration is under it. The images can be reached by scrolling
    Message 1 of 1 , Sep 16, 2013
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          This link has a drawing that gives an idea of how Philydrosaurus looked. Another illustration is under it. The images can be reached by scrolling down. Clicking on the pictures will enlarge them.
       
          Philydrosaurus proseilus was a reptile of the Cretaceous. The systematic paleontology of it is:
       
      Reptilia Laurenti 1768
      Diapsida Osborn 1903
      Choristodera Cope 1876
      Monjurosuchidae Endo 1940
      Philydrosaurus Gao and Fox 2005
      Philydrosaurus prosileus Gao and Fox 2005
       
          The holotype (PKUP V2001) is a partial skeleton (almost complete skull and mandibles) in association with a partial postcranial skeleton. These fossil remains were found in the Jiufotang Formation at Shangheshou in Liaoning, China. They date to the Aptian age (125.45 - 112.03 million years ago) of the Cretaceous. [Note - The source of this information is The Paleobiology Database.]
          Ke-Qin Gao, Chang-Fu Zhou, Lianhai Hou, and Richard Fox wrote an article titled Osteology and ontogeny of Early Cretaceous Philydrosaurus (Diapsiada: Choristodera) based on new specimens from Liaoning Province, China. It was published in 2013 in Cretaceous Research 45: 91-102. This quote from the abstract says:
       
      Choristoderes are a group of extinct diapsid reptiles that once occupied the freshwater systems in the Northern Hemisphere from the Middle Jurassic through the Miocene. The Early Cretaceous monjurosuchid Philydrosaurus from western Liaoning, China, represents a transitional morphotype between a broad-snouted (crocodile-like) and a narrow-snouted (gavial-like) skull during the evolution of Choristodera. New specimens of the taxon from the Early Cretaceous Jiufotang Formation include an incomplete braincase and a nearly complete juvenile skeleton of this transitional monjurosuchid. In the braincase floor, the foramen internus canalis caroticus externus opens in a groove lateral to the constricted lateral aspect of the parasphenoid, and ventral exposure of this foramen differs from Champsosaurus, in which parasphenoid/pterygoid fusion completely encloses the canal. On the occiput, the vagus nerve foramen penetrates the basioccipital, while the two formina for the hypoglossal nerve open at the exoccipital/basioccipital suture. Comparative study of the new juvenile specimen with adult Philydrosaurus reveals previously unknown developmental changes of the cranial and postcranial skeleton of this monjurosuchid. Ontogenetically, Philydrosaurus underwent a dramatic change of skull proportions, including elongation of the antorbital and postorbital regions, and elongation of the jaws, with a great increase of the number of marginal teeth. The lower temporal fenestra is entirely closed in early ontogeny, as in large, full grown adults.
       
          This link has the abstract, along with some fossil photos and drawings. Clicking on the pictures will enlarge them.
       
          Neal Robbins
       
       
       
       
       
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