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35-544: 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 . Neochoristoderes form a monophyletic group, however there is no consensus about

70-436: A basal member of Crocodylinae , more closely related to Crocodylus than to Osteolaemus and the other members of Osteolaeminae , as shown in the cladogram below. Rimasuchus lloydi † Voay robustus † Osteolaemus osborni Osborn's dwarf crocodile Osteolaemus tetraspis Dwarf crocodile Gastralia The possession of gastralia may be ancestral for Tetrapoda and were possibly derived from

105-427: A constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define the species ' family . Crocodiles have more webbing on the toes of the hind feet and can better tolerate saltwater due to specialized salt glands for filtering out salt, which are present, but non-functioning, in alligators. Another trait that separates crocodiles from other crocodilians

140-535: A deviation to the right of the third and fourth neural spines of the neck vertebrae. An immature dromaeosaurid specimen (which had not been described in the scientific literature as of 2001) from Tugrugeen Shireh was observed to have a "bifurcated" gastralium. In the Gorgosaurus libratus holotype ( NMC 2120 ) the 13th and 14th gastralia have healed fractures. Another G. libratus specimen catalogued as TMP94.12.602 bears multiple pathologies, including

175-405: A more robust and shorter snout and could have fed on larger prey. 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

210-436: A variety of broad-snouted species like alligatorids and Borealosuchus . 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

245-451: Is a cladogram showing the relationships of the major extant crocodile groups based on molecular studies, excluding separate extinct taxa: Caiman [REDACTED] Melanosuchus [REDACTED] Paleosuchus [REDACTED] Alligator [REDACTED] Crocodylus [REDACTED] Mecistops [REDACTED] Osteolaemus [REDACTED] Gavialis [REDACTED] Tomistoma [REDACTED] Below

280-659: Is a compound of krokè ( ' pebbles ' ), and drilos/dreilos ( ' worm ' ), although drilos is only attested as a colloquial term for ' penis ' . It is ascribed to Herodotus , and supposedly describes the basking habits of the Egyptian crocodile. The form crocodrillus is attested in Medieval Latin . It is not clear whether this is a medieval corruption or derives from alternative Greco-Latin forms (late Greek corcodrillos and corcodrillion are attested). A (further) corrupted form cocodrille

315-1221: Is a more detailed cladogram of Crocodylidae, based on a 2021 study using paleogenomics that extracted DNA from the extinct Voay . Mecistops cataphractus West African slender-snouted crocodile Euthecodon † Brochuchus † Rimasuchus † Osteolaemus osborni Osborn's dwarf crocodile Osteolaemus tetraspis Dwarf crocodile Voay † Crocodylus anthropophagus † Crocodylus thorbjarnarsoni † Crocodylus palaeindicus † Crocodylus Tirari Desert † Crocodylus johnstoni Freshwater crocodile Crocodylus novaeguineae New Guinea crocodile Crocodylus mindorensis Philippine crocodile Crocodylus porosus Saltwater crocodile Crocodylus siamensis Siamese crocodile Crocodylus palustris Mugger crocodile Crocodylus checchiai † Crocodylus falconensis † Crocodylus suchus West African crocodile Crocodylus niloticus Nile crocodile Crocodylus moreletii Morelet's crocodile Crocodylus rhombifer Cuban crocodile Crocodylus intermedius Orinoco crocodile Crocodylus acutus American crocodile Alternatively, some morphological studies have recovered Mecistops as

350-571: Is found in Old French and was borrowed into Middle English as cocodril(le) . The Modern English form crocodile was adapted directly from the Classical Latin crocodīlus in the 16th century, replacing the earlier form. The use of -y- in the scientific name Crocodylus (and forms derived from it) is a corruption introduced by Laurenti (1768). Crocodylidae was named as a family by Georges Cuvier in 1807. It belongs to

385-432: Is likely that at least some neochoristoderes were too. 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. 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

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420-595: 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. Nearly all neochoristodere remains occur at high latitudes, suggesting a preference for temperate climates . Champsosaurus fossils are known in the Canadian Arctic and Greenland . Crocodile Crocodiles ( family Crocodylidae ) or true crocodiles are large, semiaquatic reptiles that live throughout

455-406: Is that the upper and lower jaws of the crocodiles are the same width, and the teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed; therefore, all teeth are visible, unlike an alligator, which possesses in the upper jaw small depressions into which the lower teeth fit. Also, when the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into

490-726: Is their much higher levels of aggression . Crocodile size , morphology , behaviour and ecology differ somewhat among species . However, they have many similarities in these areas as well. All crocodiles are semiaquatic and tend to congregate in freshwater habitats such as rivers , lakes , wetlands and sometimes in brackish water and saltwater . They are carnivorous animals, feeding mostly on vertebrates such as fish , reptiles , birds and mammals , and sometimes on invertebrates such as molluscs and crustaceans , depending on species and age. All crocodiles are tropical species that, unlike alligators, are very sensitive to cold . They separated from other crocodilians during

525-676: The Cedar Mountain Formation of the United States and an indeterminate partial skeleton from the Kuwajima Formation of Japan. 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

560-465: The Eocene epoch, about 55 million years ago. Many species are at the risk of extinction , some being classified as critically endangered . The word crocodile comes from Ancient Greek κροκόδιλος (krokódilos)  'lizard', used in the phrase ho krokódilos tou potamoú , ' the lizard of the ( Nile ) river ' . There are several variant Greek forms of the word attested, including

595-478: The six pack in humans). However, the terminology for these gastral-like structures remains confused. Both types, along with sternal ribs ( ossified costal cartilages ), have been referred to as abdominal ribs, a term with limited usefulness that should be avoided. Gastralia are also present in a variety of extinct animals, including theropod and prosauropod dinosaurs , pterosaurs , plesiosaurs , choristoderes and some primitive pelycosaurs . In dinosaurs,

630-650: 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. Choristoderes reappear in the fossil record in the Campanian of North America under the genus Champsosaurus . This genus survives

665-603: 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. 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

700-430: The T. rex have led to an understanding that Tyrannosaurus bodies were more barrel-chested – and heavier – than previously thought. The term "gastralia" was proposed by Georg Baur in 1898. They had previously been termed "abdominal ribs", but because the term "abdominal ribs" has been applied to various structures, and the gastralia are not true ribs, this is not considered an appopriate term. In turtles, where

735-538: The earliest-branching lineages of ornithischians, retained them. Sauropods have been considered to lack gastralia. Elements interpreted as gastralia have been rarely found in sauropods, but it has been argued that these elements are more convincingly interpreted as sternal ribs. Modern birds lack gastralia, but they were present in early lineages of birds, as in other theropods. The Allosaurus fragilis specimen USNM 8367 contained several gastralia which preserve evidence of healed fractures near their middle. Some of

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770-591: The ecological niche for these choristoderes to occupy a similar ecological niche. The oldest known neochoristodere is Mengshanosaurus , from the Berriasian - Valanginian aged Mengyin Formation of China. 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

805-417: The elements articulate with each other in a sort of zig-zag along the midline and may have aided in respiration . Gastralia are known to be present in primitive ornithischian and sauropodomorph dinosaurs. However gastralia are only known from heterodontosaurid ornithschians, and gastralia are lost in eusauropodan sauropods . Discoveries about how the gastralia fit together in the skeleton of Sue

840-463: 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

875-566: 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. Competition from crocodilians has been at times implicated in

910-521: The fractures were poorly healed and "formed pseudoarthroses." An apparent subadult male Allosaurus fragilis was reported by Laws to have extensive pathologies. The possible subadult A. jimmadseni specimen MOR 693 also had pathological gastralia. The left scapula and fibula of an Allosaurus fragilis specimen catalogued as USNM 4734 are both pathological, both probably due to healed fractures. The holotype of Neovenator salerii had many pathologies, including pseudoarthrotic gastralia and

945-728: The gastralia are incorporated into the plastron , each pair of gastralia gets a distinct name: the hyoplastra, hypoplastra, xiphiplastra, and in some taxa the mesoplastra. Gastralia were ancestrally present in amniotes, but have been lost in many groups. Among extant taxa, they are only present in crocodylians and the tuatara , and in modified form as part of the plastron of turtles. Gastralia are rarely preserved in therapsids , but have been identified in some dinocephalians and gorgonopsians and several anomodonts . However, they were probably genuinely absent in some dicynodonts , therocephalians , and cynodonts . Most ornithischian dinosaurs lacked gastralia, but heterodontosaurids , one of

980-454: The gharial are similar in appearance, they belong to separate biological families . The gharial, with its narrow snout , is easier to distinguish, while morphological differences are more difficult to spot in crocodiles and alligators. The most obvious external differences are visible in the head, with crocodiles having narrower and longer heads, with a more V-shaped than a U-shaped snout compared to alligators and caimans. Another obvious trait

1015-685: The larger superfamily Crocodyloidea , which also includes additional extinct crocodile relatives. These all belong to the order Crocodilia , which also includes alligators and gharials . Crocodylidae is cladistically defined as a crown group composed of the last common ancestor of the Nile crocodile ( Crocodylus niloticus ), the Dwarf crocodile ( Osteolaemus tetraspis ), and all of its descendants. It contains two subfamilies : Crocodylinae and Osteolaeminae . Crocodylinae contains 13-14 living species, as well as 6 extinct species. Osteolaeminae

1050-525: The later form krokódeilos ( κροκόδειλος ) found cited in many English reference works. In the Koine Greek of Roman times, krokodilos and krokodeilos would have been pronounced identically, and either or both may be the source of the Latinized form crocodīlus used by the ancient Romans. It has been suggested, but it is not certain that the word crocodilos or crocodeilos

1085-409: 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

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1120-551: 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. 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. As most choristoderes are thought to have been ovoviviparous or viviparous , it

1155-524: The tropics in Africa , Asia , the Americas and Australia . The term “crocodile” is sometimes used more loosely to include all extant members of the order Crocodilia , which includes the alligators and caimans (both members of the family Alligatoridae ), the gharial and false gharial (both members of the family Gavialidae ) as well as other, extinct, taxa. Although crocodiles, alligators, and

1190-437: The ventral scales found in animals like rhipidistians , labyrinthodonts , and Acanthostega , and may be related to ventral elements of turtle plastrons . Similar, but not homologous cartilagenous elements, are found in the ventral body walls of lizards and anurans . These structures have been referred to as inscriptional ribs, based on their alleged association with the inscriptiones tendinae (the tendons that form

1225-576: Was named by Christopher Brochu in 2003 as a subfamily of Crocodylidae separate from Crocodylinae, and contains the two extant genera Osteolaemus and Mecistops , along with several extinct genera. The number of extant species within Osteolaeminae is currently in question. Recent molecular studies using DNA sequencing have shown crocodiles to be more closely related to the gavialids rather than to alligators , contrary to prior theories based on morphological studies alone. Below

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