Monjurosuchus

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Monjurosuchus
Temporal range: Early Cretaceous Hauterivian–Aptian
Fossil specimen, on display at the National Museum of Natural Science
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: †Choristodera
Genus: †Monjurosuchus
Endo, 1940
Species
  • †M. splendens Endo, 1940 (type)

Monjurosuchus is a

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 webbed feet.

Description and history

Restoration of a Japanese specimen, which may represent a second species

Monjurosuchus was first found in China as part of the Early Cretaceous

neotype preserving soft tissue.[1] In 2007, remains were described from the Okurodani Formation of the Tetori Group of Japan. The Japanese material represents a different species of Monjurosuchus that has not yet been named.[2]

Monjurosuchus was a small choristodere, reaching a total body length of 30–40 cm (0.98–1.31 ft).

squamosal
bone at the back of the skull.

Fossil of Monjurosuchus splendens in the Hong Kong Science Museum.

Specimens from China preserve soft tissue, including scales and webbing between the toes of the feet. The scales of Monjurosuchus were small, giving the animal soft skin. Two rows of larger scutes run along its back. The rest of the scales on the back are small, while the scales on the underside are slightly smaller. The skin of Monjurosuchus has a similar appearance to the living Chinese crocodile lizard Shinisaurus.[1]

The feet of Monjurosuchus are webbed, with skin covering all parts of the foot but the short claws. The limbs were robust and the hips are wide. The long, slender tail shows no adaptations for its presumed semi-aquatic lifestyle.

arthropod cuticle, indicating that Monjurosuchus may have fed on invertebrates.[1]

Classification

Beijing Museum of Natural History

Monjurosuchus is a

Monjurosuchidae. Unlike Monjurosuchus, neochoristoderes have small, dorsally facing eyes and long snouts. Philydrosaurus, another Early Cretaceous Chinese choristodere, was grouped with Monjurosuchus in Monjurosuchidae.[4] A 2007 phylogenetic analysis of choristoderes found only weak support for this family, as Philydrosaurus seemed to be a more basal choristodere than Monjurosuchus. A close relationship was found between Monjurosuchus and the Miocene Lazarussuchus, but this was only weakly supported.[2]

Phylogeny from the analysis of Dong and colleagues (2020):[5]

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. ^
    S2CID 86064702
    .
  2. ^ a b 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. ^ Dudgeon, Thomas William (2019). The internal cranial anatomy of Champsosaurus lindoei and its functional implications (PDF). Earth Sciences (M.Sci.). Ottawa, Ontario: Carleton University.
  4. doi:10.1111/j.1096-3642.2005.00191.x
    .
  5. S2CID 219047160
    .
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