Champsosaurus
Champsosaurus Temporal range:
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C. natator skeleton, Canadian Museum of Nature, Ottawa, Ontario | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | †Choristodera |
Suborder: | †Neochoristodera |
Genus: | †Champsosaurus Cope, 1877 |
Species | |
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Synonyms | |
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Champsosaurus is an extinct genus of crocodile-like choristodere reptile, known from the Late Cretaceous and early Paleogene periods of North America and Europe (Campanian–Paleocene). The name Champsosaurus is thought to come from champsai, (χαμψαι) said in an Ancient Greek source to be an Egyptian word for "crocodiles", and sauros, (σαύρος) Greek for "lizard". The morphology of Champsosaurus resembles that of gharials, with a long, elongated snout. It was native to freshwater environments where it likely preyed on fish, similar to living gharials.
History of research
Champsosaurus was the first member of the
Brown in 1905 named two species of Champsosaurus. One was C. ambulator, named from the specimen AMNH 983, a fragmentary skeleton with a partial skull found in the Hell Creek Formation of Montana. The other was C. laramiensis, named from AMNH 982, a nearly complete skeleton and skull, also found in the Hell Creek Formation.[3] Parks in 1927 named C. albertensis from ROM 806, a partial skeleton lacking the skull, found in the Horseshoe Canyon Formation in Alberta, Canada.[5] Parks in 1933 named the species C. natator from an incomplete skeleton with a fragmentary skull (TMP 81.47.1) found in the Belly River Group in the Red Deer River valley in Alberta.[4] In 1979, Denise Sigogneau-Russell named the species C. dolloi from remains found in the Paleocene of Belgium.[6] In 1972, Bruce Erickson named the species C. gigas from SMM P71.2.1, a partial skeleton and skull found in the Sentinel Butte Formation, Golden Valley County, North Dakota.[7] Erickson subsequently in 1981 named the species C. tenuis from SMM P79.14.1, a partial skeleton and skull found in the Bullion Creek Formation, North Dakota. In 1998 K. Q. Gao and Richard Carr Fox described the species C. lindoei from UALVP 931, a nearly complete skeleton with skull and jaws from the Dinosaur Park Formation in Alberta. The publication also thoroughly reviewed Champsosaurus, rediagnosing most species except for C. ambulator and C. laramiensis.[8]
Fossils of Champsosaurus have been found in
Taxonomy
Sixteen species of Champsosaurus have been named, of which seven are presently considered valid.[2] The type species Champsosaurus annectens Cope, 1876 is considered to be dubious.[2] The only named European species C. dolloi Sigogneau-Russell 1979 was considered to be too fragmentary to warrant a new species by Gao and Fox in 1998.[2]
Species | Author | Year | Status | Temporal range | Location | Formations | Notes & description |
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Champsosaurus ambulator | Brown | 1905 | Valid | Maastrichtian-Paleocene | United States (Montana) | Hell Creek, Tullock | Distinguished from C. laramiensis by having robust limbs and limb girdles[2] |
Champsosaurus laramiensis | Brown | 1905 | Maastrichtian-Paleocene | United States (Montana, New Mexico) Canada (Saskatchewan) | Hell Creek, Frenchman, Tullock, Puerco, Torrejonian | Synonyms C. australis Cope, 1881, C. puercensis Cope, 1881, C. saponensis Cope, 1881 distinguished from C. ambulator by having gracile limbs and long bones.[2] | |
Champsosaurus albertensis | Parks | 1927 | Campanian-Maastrichtian | Canada (Alberta) | Horseshoe Canyon | Distinguished from other species of Champsosaurus based on proportionately short epipodials, though Gao and Fox (1998) suggest that this may not be taxonomically significant.[2] | |
Champsosaurus natator | Parks | 1933 | middle-late Campanian | Canada (Alberta) | Dinosaur Park | Relatively large species (~ 2 metres in length) syn. C. profundus Cope, 1876, C. brevicollis Cope, 1876, C. inelegans Parks, 1933, C. inflatus Parks, 1933 distinguished by " (1) a more robust skull than the contemporaneous C. lindoei; (2) laterally swollen lower temporal bar; (3) lower temporal fenestra expanded mediolaterally; (4) expansion of the postfrontal separating the postorbitals from the frontals"[2] | |
Champsosaurus gigas | Erickson | 1972 | Paleocene | United States (North Dakota) Canada (Saskatchewan) | Sentinel Butte, Ravenscrag | Largest species of the genus, reaching a length of approximately 3 metres. Distinguished by "(1) parietal table strongly projecting laterally at anterior margin of superior temporal fenestra; (2) posterior part of parietal table narrower than in other species of comparable size; (3) postorbital extending anteromedially to meet frontal and parietal, preventing postfrontal-parietal contact"[2] | |
Champsosaurus tenuis | Erickson | 1981 | Paleocene | United States (North Dakota) | Bullion Creek | Distinguished by "(1) An extremely long and slender snout; (2) postcranial skeleton with narrow shoulder girdle; (3) clavicles short and deeply concave anteriorly; (4) limbs reduced in length"[2] | |
Champsosaurus lindoei | Gao and Fox | 1998 | middle-late Campanian | Canada (Alberta), United States (Montana) | Dinosaur Park, Two Medicine.[11] | Relatively small member of the genus characterised by "(1) snout significantly more slender in proportion to the skull size, and the bulla on the snout is proportionately larger; (2) the pterygoid flange is weekly developed with reduced number of teeth; (3) inferior temporal arch is nearly straight, and is not swollen laterally; (4) subtemporal fenestra is rectangular, not oval".[2] |
Description
Most species grew to about 1.50 m (5 ft) long,[12] though Champsosaurus gigas, the largest species, reached 3–3.5 m (10–12 ft) in length.[13][14][12]
Anatomy
The skull of Champsosaurus is
Internal cranial anatomy
The
Teeth
Champsosaurus, like many of its fellow neochoristoderes, features teeth with striated enamel of the tooth crown with enamel infolding at the base. Anterior teeth are typically sharper and more slender than posterior teeth. Like other choristoderes, Champsosaurus possessed palatal teeth (teeth present on the bones of the roof of the mouth), with longitudinal rows present on the pterygoid, palatine and vomer, alongside a small row on the flange of the pterygoid. The palatine teeth of Champsosaurus are located on raised platforms of bone, though the wideness of the platforms, the sharpness and orientation of teeth vary between species. The orientation of the teeth varies in the jaw, with the posterior teeth being orientated backward. The palatal teeth, likely in combination with a fleshy tongue probably aided in gripping and swallowing prey.[18]
Skin
Skin impressions of Champsosaurus have been reported. They consist of small (0.6-0.1 mm) pustulate and rhomboid scales, with the largest scales being located on the lateral sides of the body, decreasing in size dorsally, no osteoderms were present.[15]
Classification
Champsosaurus belongs to the Neochoristodera, a clade within Choristodera, the members of which are characterised by elongated snouts and expanded temporal arches. The group first appeared during the Early Cretaceous in Asia, and are suggested to have evolved in the regional absence of aquatic crocodyliformes.[19] While Neochoristodera is a well supported grouping, the relationships of the members of the group to each other are uncertain, with the clade having been recovered as a polytomy in recent analyses.[20]
Phylogeny of Choristodera after Dong and colleagues (2020).[20]
Choristodera |
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Paleobiology
Champsosaurus is thought to have been highly specialised for aquatic life.
See also
References
- ^ Cope ED (1876). "On some extinct reptiles and Batrachia from the Judith River and Fox Hills beds of Montana". Proceedings of the Academy of Natural Sciences of Philadelphia. 1876: 340–359.
- ^ a b c d e f g h i j k Dudgeon, Thomas William (2019). The internal cranial anatomy of Champsosaurus lindoei and its functional implications (PDF). Earth Sciences (M.Sci.). Ottawa, Ontario: Carleton University.
- ^ a b B. Brown. 1905. The osteology of Champsosaurus Cope. American Museum of Natural History, Memoirs 9:1–264
- ^ a b W. A. Parks. 1933. New species of Champsosaurus from the Belly River Formation of Alberta, Canada. Transactions of Royal Society of Canada 27:121–137
- ^ W. A. Parks. 1927. Champsosaurus albertensis, a new species of rhynchocephalian from the Edmonton Formation of Alberta. University of Toronto Studies of Geological Survey 25:1–48
- ^ Sigogneau-Russell D. 1979. Les champsosaures Européens: mise au point sur le champsosaure d'erquelinnes (landenien inferieur, Belgique). Annales de Paliontologit (Vertibris) 65: 7–62.
- ^ B. R. Erickson. 1972. The lepidosaurian reptile Champsosaurus in North America. The Science Museum of Minnesota, Monograph (Paleontology) 1:1–91
- ^ .
- S2CID 131740273.
- ISSN 0031-0182.
- ISSN 0024-4082.
- ^ ISBN 0-7513-0955-9
- ^ Hoganson, J.W.; J. Campbell (1995). "Restoration and display of a crocodilie-like Champsosaurus gigas skeleton at the North Dakota Heritage Center" (PDF). NDGS Newsletter. 22 (3): 8–10.
- ^ "Champsosaurus gigas" (PDF). Department of Mineral Resources, North Dakota. Archived from the original (PDF) on 17 October 2020.
- ^ .
- PMID 31905243.
- PMID 32346021.
- PMID 26573112.
- ^ .
- ^ S2CID 219047160.
- ^ S2CID 244917425.
- ISSN 0024-1164.
- S2CID 84966652.