Shamosuchus

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Shamosuchus
Temporal range: Late Cretaceous, 83.6–72.1  Ma [1]
Shamosuchus djadochtaensis.PNG
Holotype specimen
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Clade: Neosuchia
Family:† Paralligatoridae
Genus:† Shamosuchus
Mook, 1924
Type species
†Shamosuchus djadochtaensis
Mook, 1924

Shamosuchus is an extinct genus of neosuchian crocodyliform that lived during the Late Cretaceous (Campanian) period in what is now the Djadochta Formation of Mongolia, approximately 75 million to 71 million years ago.

Contents

Description

Skull and diagram of referred specimen Shamosuchus.png
Skull and diagram of referred specimen

Shamosuchus reached up to 4 m long and had a rostrum of moderate length. [2] In S. djadochtaensis, a perinarial fossa extended along the ventrolateral region of the narial opening. Where the premaxilla and maxilla articulate, the alveolar margin is continuous and is characterised by the absence of a notch for receiving the opposing mandibular tooth. [3]

Taxonomy

The genus was named in 1924 by Charles C. Mook. [4] Paralligator was synonymized with Shamosuchus by several authors. [5] [6] [7] However, recent cladistic analysis of Paralligatoridae found the former genus to be distinct from the latter. [8]

Phylogeny

Below are the results of a phylogenetic analysis by Pol et al., 2009 showing the position of Shamosuchus within Neosuchia: [3]

Neosuchia

Palaeobiology

The eye and nasal openings were not raised above the skull as in modern crocodilians, so that the animal would have to raise its head completely out of the water to breathe. As this cranial morphology does not suit an ambush predator, it lends support to the idea of a diet of aquatic invertebrates. The morphology of the teeth of Shamosuchus suggests they were adapted to crush bivalves, gastropods, and other animals with a shell or exoskeleton. [4]

References

  1. ↑ Rio, Jonathan P.; Mannion, Philip D. (6 September 2021). "Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem". PeerJ . 9 e12094. doi: 10.7717/peerj.12094 . PMC   8428266 . PMID   34567843.
  2. ↑ G. Storrs, M. B. Efimov. (2000). "Mesozoic crocodyliforms of north-central Eurasia". In book: The Age of Dinosaurs in Russia and Mongolia (pp.402-419) Publisher: Cambridge University PressEditors: Michael J. Benton, Michael A. Shishkin, David M. Unwin, Evgenii N. Kurochkin
  3. 1 2 Pol, Diego; Turner, Alan H.; Norell, Mark A. (30 June 2009). "Morphology of the Late Cretaceous Crocodylomorph Shamosuchus djadochtaensis and a Discussion of Neosuchian Phylogeny as Related to the Origin of Eusuchia". Bulletin of the American Museum of Natural History . 324: 1–103. doi:10.1206/0003-0090-324.1.1 . Retrieved 21 October 2025– via BioOne Digital Library.
  4. 1 2 Mook, C. C. (1924). "A new crocodilian from Mongolia" (PDF). American Museum Novitates (117): 1–5.
  5. ↑ Efimov, M. B. (1983). "Review of fossil crocodiles of Mongolia". Transactions of the Joint Soviet–Mongolia Paleontological Expedition. 24: 76–95.
  6. ↑ Rozhdestvenskiy, A. K. (1974). "History of the dinosaur fauna of Asia and other continents and questions concerning paleogeography". Transactions of the Joint Soviet–Mongolia Paleontological Expedition. 1: 107–131.
  7. ↑ Storrs, G. W.; Efimov, M. B. (2000). "Mesozoic crocodyliforms of north-central Eurasia". In Michael J. Benton; Mikhail A. Shishkin; David M. Unwin; Evgenii N. Kurochkin (eds.). The Age of Dinosaurs in Russia and Mongolia. Cambridge University Press. pp. 402–419.
  8. ↑ Turner, A. H. (2015). "A Review of Shamosuchus and Paralligator (Crocodyliformes, Neosuchia) from the Cretaceous of Asia". PLOS ONE . 10 (2) e0118116. Bibcode:2015PLoSO..1018116T. doi: 10.1371/journal.pone.0118116 . PMC   4340866 . PMID   25714338.
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