Philydrosaurus
Encyclopedia
Philydrosaurus is an extinct genus of choristodera
n which existed in China
during the Early Cretaceous
. The type species
P. proseilus was named in 2005. Philydrosaurus is closely related to the choristodere Monjurosuchus
, and both have been placed in the same family Monjurosuchidae
. Philydrosaurus was found from the Jiufotang Formation
and is slightly younger than Monjurosuchus, which was found from the Yixian Formation
.
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 fenestra links the genus with more advanced forms.
Choristodera
Choristodera is an order of semi-aquatic diapsid reptiles which ranged from the Middle Jurassic, or possibly Late Triassic, to at least the early Miocene. Choristoderes have been found in North America, Asia, and Europe. The most common fossils are typically found from the Late Cretaceous to the...
n which existed in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
during the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
P. proseilus was named in 2005. Philydrosaurus is closely related to the choristodere Monjurosuchus
Monjurosuchus
Monjurosuchus is a genus of choristoderan reptile that lived in what is now China and Japan during the Early Cretaceous. It has large eyes, a rounded skull, robust legs with short claws, and a long, thin tail. Fossils have been found that preserve soft tissue, showing that it had soft skin and...
, and both have been placed in the same family Monjurosuchidae
Monjurosuchidae
Monjurosuchidae is a family of prehistoric reptiles belonging to the order Choristodera. Until the description of Philydrosaurus in 2005, the only genus in the family was Monjurosuchus. Both lived in what is now China during the Early Cretaceous....
. Philydrosaurus was found from the Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
and is slightly younger than Monjurosuchus, which was found from the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
.
Description
Distinct ridges cover the prefrontalPrefrontal bone
The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and extinct lungfish, amphibians and reptiles...
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
Lazarussuchus
Lazarussuchus is a genus of basal choristodere, a type of amphibious reptile, from the late Oligocene and early Miocene of France and the Czech Republic. Two species have been named: the type species L. inexpectatus from the late Oligocene of France; and L...
. Philydrosaurus is considered more basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
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
Cteniogenys
Cteniogenys is a genus of choristodere, a morphologically diverse group of aquatic reptiles. It had a wide distribution temporally and geographically, from the Middle Jurassic and Late Jurassic of western Europe, to the Late Jurassic-age Morrison Formation of western North America, to the Late...
, 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 fenestra links the genus with more advanced forms.