Neochoristodera

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Neochoristodera
Temporal range: Early Cretaceous - Eocene, 145–56  Ma
Champsosaurus natator.jpg
Skeletal mount of Champsosaurus
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order:† Choristodera
Suborder:† Neochoristodera
Evans & Hecht, 1993
Genera
Synonyms

Champsosauriformes Hay 1930

Neochoristodera is a lineage of specialised crocodile-like fully aquatic choristodere reptiles. Noted for their long jaws and large size, these animals were predominant across the Northern Hemisphere, occurring in freshwater and coastal environments across the Cretaceous and early Cenozoic.

Contents

Systematics

Neochoristoderes form a monophyletic group, however there is no consensus about the relationships of the genera, which have been recovered as a polytomy in recent studies. Neochoristodera contains the named genera Champsosaurus , Ikechosaurus , Kosmodraco , Liaoxisaurus , Mengshanosaurus , Simoedosaurus and Tchoiria . Various taxa of uncertain affinities within this group are known, including a partial femur of a choristodere, possibly of a neochoristodere from the Cedar Mountain Formation of the United States and an indeterminate partial skeleton from the Kuwajima Formation of Japan. [2]

Evolution

Skeleton of Tchoiria Tchoiria skeleton.PNG
Skeleton of Tchoiria

Neochoristoderes first appear in the Early Cretaceous of Asia, where they co-exist with other choristodere groups like monjurosuchids and hyphalosaurids. Here, a regional absence of aquatic crocodilians, possibly due to colder temperatures, seems to have opened the ecological niche for these choristoderes to occupy a similar ecological niche. [3] [4] The oldest known neochoristodere is Mengshanosaurus , from the Berriasian-Valanginian aged Mengyin Formation of China. [5]

Other than a possible specimen from the Cedar Mountain Formation, a large gap occurs between these Early Cretaceous faunas and the Late Cretaceous ones. There are no fossils of neochoristoderes in the Asian Late Cretaceous, but the subsequent distribution of Simoedosaurus in the Paleocene and Eocene implies that there were Asian taxa around this time, seeing as Simoedosauridae is predominantly Asian and Simoedosaurus only propagated widely after the KT event. [6]

Fossils of Simoedosaurus Simoedosaurus lemoinei Cernay.JPG
Fossils of Simoedosaurus

Choristoderes reappear in the fossil record in the Campanian of North America under the genus Champsosaurus . This genus survives the KT event unscathed and diversifies in the aftermath, being soon after joined by Simoedosaurus . Both taxa remain at high latitudes in North America and Europe until the Eocene, when they mysteriously disappear. [7]

In 2021, fossil remains of indetermine neochoristoderes were described from several sites from the Navesink Formation of New Jersey, marking the first known occurrence of neochoristoderes from the former landmass Appalachia. Niche modeling based on the presumed niche of Champsosaurus indicates that neochoristoderes may have had a widespread distribution in Appalachia, but the majority of this habitat was not located in areas conducive for Cretaceous fossilization, leading to only a small margin of optimal habitat in New Jersey that preserved choristodere remains. [8]

Competition from crocodilians has been at times implicated in the extinction of neochoristoderes. There appears to be a niche partitioning between neochoristoderes and long-snouted crocodilians such as gharials, which are absent from freshwater sites in Laurasia until well after neochoristoderes disappear, but competition between both groups, if it even existed, is currently unaccounted for. Ultimately, both Champsosaurus and Simoedosaurus co-existed with a variety of broad-snouted species like alligatorids and Borealosuchus . [9] [10]

Biology

Lateral and dorsal views of a Champsosaurus skeletal mount Large williston champsosaurus.jpg
Lateral and dorsal views of a Champsosaurus skeletal mount

Neochoristoderes are thought to be fully aquatic. They possess laterally flattened, muscular tails and paddle-like limbs, their torsos are dorsoventrally flattened with short but massive ribs and their gastralia are heavily ossified, facilitating sinking. While they have their nostrils at the end of the snout as in crocodiles, they are oriented towards the tip instead of dorsally; their eye sockets are similarly forward-facing, implying that these animals did not surface often and probably simply rose the snout in a snorkel-like fashion. As in most choristoderes the skin lacks scutes, instead having small, non-overlapping scales. [11] In Champsosaurus adult females are thought to have particularly ossified limbs and pelvises, implying that they could crawl unto land, while adult males and juveniles could not. [12] As most choristoderes are thought to have been ovoviviparous or viviparous, it is likely that at least some neochoristoderes were too. [13]

Champsosaurus skull Champsosaurus laramiensis.JPG
Champsosaurus skull

Most neochoristoderes have exceptionally large temporal fenestrae, suggesting powerful bite forces; Champsosaurus is estimated to have a bite force around 1194 to 1910 N, as opposed to the modern gharial's 310-497 N. [14] In spite of this, most are thought to have had a diet similar to that of modern gharials due to the long and slender jaws, though Simoedosaurus has a more robust and shorter snout and could have fed on larger prey. [15]

Compared with other choristoderes, which have rather simple teeth, neochoristoderes have teeth completely enveloped in striated enamel with an enamel infolding at the base, labiolingually compressed and hooked, the exception being Ikechosaurus which has still rather simple teeth aside from the start of an enamel infolding. There is some tooth differentiation, with the anterior teeth being larger than the posterior ones. As with most choristoderes, neochoristoderes have palatal teeth, indicating food manipulation in the mouth. [16]

Nearly all neochoristodere remains occur at high latitudes, suggesting a preference for temperate climates. [17] Champsosaurus fossils are known in the Canadian Arctic and Greenland. [18]

Related Research Articles

<i>Champsosaurus</i> Extinct genus of reptiles

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.

<span class="mw-page-title-main">Choristodera</span> Extinct order of reptiles

Choristodera is an extinct order of semiaquatic diapsid reptiles that ranged from the Middle Jurassic, or possibly Triassic, to the late Miocene. Choristoderes are morphologically diverse, with the best known members being the crocodile-like neochoristoderes such as Champsosaurus. Other choristoderans had lizard-like or long necked morphologies. Choristoderes appear to have been confined to the Northern Hemisphere, having been found in North America, Asia, and Europe, and possibly also North Africa. Choristoderes are generally thought to be derived neodiapsids that are close relatives or members of Sauria.

<i>Simoedosaurus</i> Extinct genus of reptiles

Simoedosaurus is an extinct reptile known from the Paleocene of North America, Europe and western Asia, and a member of the Choristodera, a group of aquatic reptiles that lived in the Northern Hemisphere from the Jurassic to the early Cenozoic.

<i>Hyphalosaurus</i> Genus of extinct freshwater aquatic reptiles

Hyphalosaurus is a genus of freshwater aquatic reptiles, belonging to the extinct order Choristodera. They lived during the early Cretaceous period, about 122 million years ago. The genus contains two species, H. lingyuanensis and H. baitaigouensis, both from the Yixian Formation of Liaoning Province, China. They are among the best-known animals from the Jehol Biota, with thousands of fossil specimens representing all growth stages in scientific and private collections.

<span class="mw-page-title-main">Dinosaur Park Formation</span> Uppermost member of the Belly River Group geologic unit in Alberta, Canada

The Dinosaur Park Formation is the uppermost member of the Belly River Group, a major geologic unit in southern Alberta. It was deposited during the Campanian stage of the Late Cretaceous, between about 76.5 and 74.4 million years ago. It was deposited in alluvial and coastal plain environments, and it is bounded by the nonmarine Oldman Formation below it and the marine Bearpaw Formation above it.

Pachystropheus is a genus of prehistoric reptile, possibly a choristodere (champsosaur), from the Rhaetian of southwestern England. It was named by Erika von Huene in 1935; Huene described Pachystropheus as a champsosaur, but this was overlooked for decades until its redescription by Storrs and Gower in 1993. This reevaluation would extend the fossil record of champsosaurs back 45 million years. However, other authors consider attribution of Pachystropheus to Choristodera problematic, stating that it depends on vertebral and girdle characters that are also found in the skeletons of aquatic reptiles other than choristoderes; most of the diagnostic features of choristoderes are skull features, but the presence of these cannot be confirmed in Pachystropheus, as there is no confirmed skull material for this taxon. Silvio Renesto (2005) found similarities in the postcranial skeleton of Pachystropheus and the thalattosaur genus Endennasaurus; according to Renesto, these similarities may indicate that Pachystropheus and Endennasaurus are close relatives, but they might as well simply be a case of a convergent evolution triggered by the aquatic lifestyle of both taxa.

<i>Lazarussuchus</i> Extinct genus of reptiles

Lazarussuchus is an extinct genus of amphibious reptile, known from the Cenozoic of Europe. It is the youngest known member of Choristodera, an extinct order of aquatic reptiles that first appeared in the Middle Jurassic. Fossils have been found in Late Paleocene, Late Oligocene, Early Miocene and Late Miocene deposits in France, Germany, and the Czech Republic. Two species have been named: the type species L. inexpectatus ("unexpected") from the late Oligocene of France. and L. dvoraki from the early Miocene of the Czech Republic. It was not a large animal; the skull of L. inexpectatus was only about 4.53 centimeters long (1.78 in), with the total preserved body and tail length being just over 30 centimetres. A complete specimen of Lazarussuchus with preserved soft tissue was found from the Late Paleocene of France, but has not been assigned to a species.

<i>Cteniogenys</i> Genus of reptiles

Cteniogenys is a genus of choristodere, a morphologically diverse group of aquatic reptiles. It is part of the monotypic family Cteniogenidae. The type and only named species, C. antiquus, was named in 1928 by Charles W. Gilmore. The holotype, VP.001088, was collected in the Morrison Formation, Wyoming in 1881 by William H. Reed. More specimens have been discovered since then, including specimens from the Late Jurassic of Portugal and Middle Jurassic of Britain, which have not been assigned to species.

The Kuwajima Formation is an Early Cretaceous geologic formation in Japan. Its precise age is uncertain due to a lack of identifying fossils, and it was previously considered likely Valanginian to Hauterivian in age. However, it is now considered to probably be Barremian in age. Dinosaurs and other vertebrates has been recovered from the Kaseki-kabe "Fossil-bluff" locality in the uppermost part of the formation.

The Akaiwa Formation is an Early Cretaceous (Hauterivian-Barremian) geologic formation in central Honshu, Japan. Indeterminate ornithischian fossils are known from the formation. Fossil ornithopod tracks have been reported from the formation. As well as the turtle Kappachelys

<i>Monjurosuchus</i> Extinct genus of reptiles

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 webbed feet.

Irenosaurus is a genus of choristodere, a type of amphibious reptile. It is known from a single fragmentary postcranial skeleton (PIN 3386/2), discovered in the Aptian-age Lower Cretaceous Hühteeg Formation at Hüren Dukh, central Mongolia. The type species is I. egloni, which was originally described as a new species of the related choristodere Tchoiria in 1983 by Efimov. Efimov transferred the species to the new genus Irenosaurus in 1988. Evans and Hecht (1993) questioned the separation of the taxon from Tchoiria namsarai from the same locality on the grounds that the differences between the two may not have been greater than those of various species of the choristodere Champsosaurus. A later review by Efimov and Storrs (2000) retained the two as separate, noting that some characteristics of Irenosaurus are more like Khurendukhosaurus, also known from the same site, at the same time recognizing the difficulties of distinguishing three genera from the same locality. Irenosaurus was a small choristodere, approximately 1 to 1.5 metres long. It is known from what are interpreted as lake deposits.

<i>Khurendukhosaurus</i> Extinct genus of reptiles

Khurendukhosaurus is a genus of choristodere, a type of amphibious reptile. It is known from Lower Cretaceous rocks of Mongolia and Russia. Two species have been named. The type species, K. orlovi, was named in 1984 by Sigogneau–Russell and Efimov for the fragmentary postcranial skeleton PIN 3386/3. This specimen was discovered in the Albian-age Lower Cretaceous Khuren Dukh Formation Formation at Hüren Dukh, central Mongolia. The lake deposits at this site also contain fossils of the choristoderes Irenosaurus and Tchoiria. Other postcranial bones of K. orlovi have been found at this site as well.

<i>Tchoiria</i> Extinct genus of diapsid reptiles

Tchoiria () is a genus of neochoristoderan reptile from the Early Cretaceous of Mongolia. The name Tchoiria comes from the city of Choir which is nearby to where the holotype was found. Tchoiria is thought to have a similar diet to another neochoristoderan reptile, Champsosaurus, due to morphology of the skull. It would hunt in freshwater environments, like the living gharials, where it would prey on many different types of fish and turtles.

<i>Philydrosaurus</i> Extinct genus of reptiles

Philydrosaurus is an extinct genus of choristoderan which existed in China during the Early Cretaceous. The type species P. proseilus was named in 2005. Philydrosaurus was found from the Jiufotang Formation and is slightly younger than Monjurosuchus, which was found from the Yixian Formation.

<i>Ikechosaurus</i> Extinct genus of reptiles

Ikechosaurus is an extinct genus of choristodere reptile which existed in China and Mongolia during the Early Cretaceous. It contains the species Ikechosaurus sunailinae and Ikechosaurus gaoi. It belongs to the crocodilian-like clade Neochoristodera and was initially assigned to the Champsosauridae by Sigogneau-Russell (1981). Compared to other neochoristoderes, Ikechosaurus has a rather simple dentition, lacking the speciations seen in latter species. It also has parasphenoid palatal teeth, a feature not seen in any other choristodere.

<i>Aegisuchus</i> Extinct genus of reptiles

Aegisuchus is an extinct monospecific genus of giant, flat-headed crocodyliform within the family Aegyptosuchidae. It was found in the Kem Kem Formation of southeast Morocco, which dates back to the Cenomanian age of the Late Cretaceous epoch. The type species Aegisuchus witmeri was named in 2012 by paleontologists Casey Holliday and Nicholas Gardner, who nicknamed it "Shieldcroc" for the shield-like shape of its skull. A. witmeri is known from a single partial skull including the braincase and skull roof.

<i>Coeruleodraco</i> Extinct genus of choristoderan

Coeruleodraco is an extinct genus of choristoderan known from the Late Jurassic (Oxfordian) Tiaojishan Formation in China. Coeruleodraco is significant as the most complete Jurassic choristodere taxon, as the only other named Jurassic choristodere Cteniogenys is based on fragmentary remains. Although similar to Philydrosaurus in its proportions and postcranial characters, it is distinct in retaining several apparently plesiomorphic characters, including a short snout, paired external nares and an open lower temporal fenestra.

Heishanosaurus is an extinct genus of choristodere reptile from the Early Cretaceous of China. The type and currently only known species is Heishanosaurus pygmaeus. It is unusual as it is much more primitive than other known choristoderes from the Early Cretaceous of Asia, and retains many plesiomorphic characters.

<i>Kosmodraco</i> Extinct genus of reptiles

Kosmodraco is a genus of large bodied choristodere from the Paleocene of North America. Originally described as a species of Simoedosaurus, it was found to represent a distinct genus in 2022. Multiple fossil skulls show a relatively short and robust snout and a skull that is considerably wider behind the eyes. Two species are currently recognized, K. dakotensis and K. magnicornis.

References

  1. ↑ Brownstein, C. D. (2022). "High morphological disparity in a bizarre Paleocene fauna of predatory freshwater reptiles". BMC Ecology and Evolution. 22 (1): 34. doi:10.1186/s12862-022-01985-z. PMC   8935759 . PMID   35313822.
  2. ↑ The first record of a long-snouted choristodere (Reptilia, Diapsida) from the Early Cretaceous of Ishikawa Prefecture, Japan. Historical Biology 27(5):1-12. December 2014. doi : 10.1080/08912963.2014.898296
  3. ↑ The first record of a long-snouted choristodere (Reptilia, Diapsida) from the Early Cretaceous of Ishikawa Prefecture, Japan Article in Historical Biology 27(5):1-12 · December 2014 doi : 10.1080/08912963.2014.898296
  4. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  5. ↑ 袁 梦, 李大庆; YUAN Meng, LI Da-Qing (2021). "A juvenile skull of the longirostrine choristodere (Diapsida:Choristodera), Mengshanosaurus minimus gen. et sp. nov., with comments on neochoristodere ontogeny". Vertebrata PalAsiatica. 59 (3): 213–228. doi:10.19615/j.cnki.2096-9899.210607. ISSN   2096-9899.
  6. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  7. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  8. ↑ Dudgeon, Thomas W.; Landry, Zoe; Callahan, Wayne R.; Mehling, Carl M.; Ballwanz, Steven (September 2021). Mannion, Philip (ed.). "An Appalachian population of neochoristoderes (Diapsida, Choristodera) elucidated using fossil evidence and ecological niche modelling". Palaeontology. 64 (5): 629–643. doi:10.1111/pala.12545. ISSN   0031-0239. S2CID   237761128.
  9. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  10. ↑ The first record of a long-snouted choristodere (Reptilia, Diapsida) from the Early Cretaceous of Ishikawa Prefecture, Japan Article in Historical Biology 27(5):1-12 · December 2014 doi : 10.1080/08912963.2014.898296
  11. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  12. ↑ Yoshihiro Katsura, Fusion of sacrals and anatomy in Champsosaurus (Diapsida, Choristodera), doi : 10.1080/08912960701374659
  13. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  14. ↑ omateus.googlepages.com/Jacobsetal2009CretaceousSkeletoncoas.pdf
  15. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
  16. ↑ Morphology and function of the palatal dentition in Choristodera Article in Journal of Anatomy 228(3):n/a-n/a · November 2015 doi : 10.1111/joa.12414
  17. ↑ The first record of a long-snouted choristodere (Reptilia, Diapsida) from the Early Cretaceous of Ishikawa Prefecture, Japan Article in Historical Biology 27(5):1-12 · December 2014 doi : 10.1080/08912963.2014.898296
  18. ↑ R. Matsumoto and S. E. Evans. 2010. Choristoderes and the freshwater assemblages of Laurasia. Journal of Iberian Geology 36(2):253-274
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