Crocodylomorpha

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Crocodylomorphs
Temporal range: Late Triassic Present, 235–0  Ma [1]
Terrestrisuchus.jpg
Skeleton of Terrestrisuchus , an early saltoposuchid crocodylomorph
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Paracrocodylomorpha
Clade: Loricata
Clade: Crocodylomorpha
Hay, 1930
Subgroups

Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably more ecologically diverse than modern crocodillians. The earliest and most primitive crocodylomorphs are represented by "sphenosuchians", a paraphyletic assemblage containing small-bodied, slender forms with elongated limbs that walked upright, which represents the ancestral morphology of Crocodylomorpha. These forms persisted until the end of the Jurassic. [4] During the Jurassic, crocodylomorphs morphologically diversified into numerous niches, with the subgroups Neosuchia (which includes modern crocodilians) and the extinct Thalattosuchia adapting to aquatic life, while some terrestrial groups adopted herbivorous and omnivorous lifestyles. Terrestrial crocodylomorphs would continue to co-exist alongside aquatic forms until becoming extinct during the Miocene.

Contents

Evolutionary history

Life restoration of Hesperosuchus Hesperosuchus BW.jpg
Life restoration of Hesperosuchus

The earliest lineages of Crocodylomorpha are placed into the paraphyletic "Sphenosuchia", which are charactersed by slender bodies with elongate legs. The oldest known crocodylmorph is Trialestes , known from the Late Triassic (Carnian-Norian) of Argentina, around 231–225 million years ago, [5] the last groups of "sphenosuchians" persisted until the end of the Jurassic. [4] During the Jurassic, crocodylomorphs diversified, including the emergence of herbivorous and omnivorous forms, [6] as well as the aquatically adapted Neosuchia and Thalattosuchia, with Thalattosuchia and several groups of neosuchians becoming adapted to a marine lifestyle over the Jurassic and Cretaceous [7] During the Cretaceous, the Notosuchia were a diverse group across the Southern Hemisphere occupying many diverse ecologies. [8] Modern crocodilians, a subgroup of Neosuchia, emerged during the Late Cretaceous. [7] Crocodylomorph diversity was severely reduced by the end-Cretaceous extinction event. [8] The last group of terrestrially adapted crocodylomorphs was the Sebecidae, a group of large predatory notosuchians which persisted in South America until the middle Miocene around 12 million years ago. [9] [7]

Taxonomy and phylogeny

Historically, all known living and extinct crocodiles were indiscriminately lumped into the order Crocodilia. However, beginning in the late 1980s, many scientists began restricting the order Crocodilia to the living species and close extinct relatives such as Mekosuchus . The various other groups that had previously been known as Crocodilia were moved to Crocodylomorpha and the slightly more restrictive Crocodyliformes. [10] Crocodylomorpha has been given the rank of superorder in some 20th and 21st century studies. [11]

The old Crocodilia was subdivided into the suborders:

Mesosuchia is a paraphyletic group as it does not include eusuchians (which nest within Mesosuchia). Mesoeucrocodylia was the name given to the clade that contains mesosuchians and eusuchians (Whetstone and Whybrow, 1983).

Phylogeny

Below is a cladogram modified from Nesbitt (2011) [12] and Bronzati (2012). [13]

Crocodylomorpha 

The previous definitions of Crocodilia and Eusuchia did not accurately convey evolutionary relationships within the group. The only order-level taxon that is currently considered valid is Crocodilia in its present definition. Prehistoric crocodiles are represented by many taxa, but since few major groups of the ancient forms are distinguishable, a conclusion on how to define new order-level clades is not yet possible. (Benson & Clark, 1988).

Biology

The Crocodylomorpha comprise a variety of forms, shapes, and sizes, which occupied a range of habitats. As with most amniotes, Crocodylomorphs were and are oviparous, laying eggs in a nest or mound, known from strata as old as the Late Jurassic. [14] Adult size varies widely, from about 55 cm long in Knoetschkesuchus to much larger dimensions, as in Sarcosuchus . Most crocodylomorphs were carnivores, but many lineages evolved to be obligate piscivores, such as the extant gharials.

Related Research Articles

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

Goniopholis is an extinct genus of goniopholidid crocodyliform that lived in Europe and North America during the Late Jurassic and Early Cretaceous. Like other goniopholidids, it resembled living crocodilians, and probably had a similar ecology as semi-aquatic ambush predators.

<i>Machimosaurus</i> Genus of reptiles

Machimosaurus is an extinct genus of machimosaurid crocodyliform from the Late Jurassic and Early Cretaceous. The type species, Machimosaurus hugii, was found in Switzerland. Other fossils have been found in England, France, Germany, Portugal, Switzerland and Tunisia. Machimosaurus rex is the largest named teleosauroid and thalattosuchian, with an estimated length of up to 7.15 m (23.5 ft). Machimosaurus is the largest known crocodyliform of the Jurassic.

<span class="mw-page-title-main">Pseudosuchia</span> Clade of reptiles

Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as a subset of the group.

<span class="mw-page-title-main">Metriorhynchidae</span> Extinct family of reptiles

Metriorhynchidae is an extinct family of specialized, aquatic metriorhynchoid crocodyliforms from the Middle Jurassic to the Early Cretaceous period of Europe, North America and South America. The name Metriorhynchidae was coined by the Austrian zoologist Leopold Fitzinger in 1843. The group contains two subfamilies, the Metriorhynchinae and the Geosaurinae. They represent the most marine adapted of all archosaurs.

<span class="mw-page-title-main">Thalattosuchia</span> Clade of marine crocodylomorphs

Thalattosuchia is a clade of mostly marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are colloquially referred to as marine crocodiles or sea crocodiles, though they are not members of Crocodilia and records from Thailand and China suggest that some members lived in freshwater. The clade contains two major subgroupings, the Teleosauroidea and Metriorhynchoidea. Teleosauroids are not greatly specialised for oceanic life, with back osteoderms similar to other crocodyliformes. Within Metriorhynchoidea, the Metriorhynchidae displayed extreme adaptions for life in the open ocean, including the transformation of limbs into flippers, the development of a tail fluke, and smooth, scaleless skin, and probably gave live birth, seemingly uniquely among archosaurs.

<span class="mw-page-title-main">Sphenosuchia</span> Suborder of reptiles

Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Middle Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, a group which includes all living crocodilians.

<i>Terrestrisuchus</i> Genus of terrestrial crocodylomorph

Terrestrisuchus is an extinct genus of very small early crocodylomorph that was about 76 centimetres (30 in) long. Fossils have been found in Wales and Southern England and date from near the very end of the Late Triassic during the Rhaetian, and it is known by type and only known species T. gracilis. Terrestrisuchus was a long-legged, active predator that lived entirely on land, unlike modern crocodilians. It inhabited a chain of tropical, low-lying islands that made up southern Britain, along with similarly small-sized dinosaurs and abundant rhynchocephalians. Numerous fossils of Terrestrisuchus are known from fissures in limestone karst which made up the islands it lived on, which formed caverns and sinkholes that preserved the remains of Terrestrisuchus and other island-living reptiles.

<i>Litargosuchus</i> Extinct genus of reptiles from the early Jurassic of South Africa

Litargosuchus is a sphenosuchian crocodylomorph, a basal member of the crocodylomorph clade from the Early Jurassic of South Africa. Its genus name Litargosuchus is derived from Greek meaning "fast running crocodile" and its species name leptorhynchus refers to its gracile snout. Litargosuchus, along with all of South Africa's crocodylomorph taxa, are confined to the upper Elliot Formation (UEF) in South Africa.

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

Pelagosaurus is an extinct genus of thalattosuchian crocodyliform that lived during the Toarcian stage of the Lower Jurassic, around 183 Ma to 176 Ma, in shallow epicontinental seas that covered much of what is now Western Europe. The systematic taxonomy of Pelagosaurus has been fiercely disputed over the years, and was assigned to Thalattosuchia after its systematics within Teleosauridae were disputed. Pelagosaurus measured 2–3 m (6.6–9.8 ft) long.

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

Junggarsuchus is an extinct genus of sphenosuchian crocodylomorph from the Middle or Late Jurassic period of China. The type and only species is J. sloani. The generic name of Junggarsuchus comes from the Junggar Basin, where the fossil was found, and the Greek word "souchos" meaning crocodile. The specific name, "sloani" is in honor of C. Sloan, who is credited with finding the holotype.

<span class="mw-page-title-main">Notosuchia</span> Extinct suborder of reptiles

Notosuchia is a suborder of primarily Gondwanan mesoeucrocodylian crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ; if Sebecosuchia is included within Notosuchia its existence is pushed into the Middle Miocene, about 11 million years ago. Fossils have been found from South America, Africa, Asia, and Europe. Notosuchia was a clade of terrestrial crocodilians that evolved a range of feeding behaviours, including herbivory (Chimaerasuchus), omnivory (Simosuchus), and terrestrial hypercarnivory (Baurusuchus). It included many members with highly derived traits unusual for crocodylomorphs, including mammal-like teeth, flexible bands of shield-like body armor similar to those of armadillos (Armadillosuchus), and possibly fleshy cheeks and pig-like snouts (Notosuchus). The suborder was first named in 1971 by Zulma Gasparini and has since undergone many phylogenetic revisions.

Cricosaurus is an extinct genus of marine crocodyliforms of the Late Jurassic. belonging to the family Metriorhynchidae. The genus was established by Johann Andreas Wagner in 1858 for three skulls from the Tithonian of Germany. The name Cricosaurus means "Ring lizard", and is derived from the Greek Krikos- ("ring") and σαῦρος -sauros ("lizard"). It was a relatively small reptile, with C. suevicus and C. araucanensis measuring 2 m (6.6 ft) and 3.2 m (10 ft) in total body length, respectively.

Calsoyasuchus is a genus of crocodylomorph that lived in the Early Jurassic. Its fossilized remains were found in the Sinemurian-Pliensbachian-age Kayenta Formation on Navajo Nation land in Coconino County, Arizona, United States. Formally described as C. valliceps, it is known from a single incomplete skull which is unusually derived for such an early crocodile relative. This genus was described in 2002 by Ronald Tykoski and colleagues; the specific name means "valley head" and refers to a deep groove along the midline of the nasal bones and frontal bones. It has often been interpreted as the earliest diverging member of Goniopholididae, but other studies have recovered it in various other positions.

<span class="mw-page-title-main">Goniopholididae</span> Extinct family of reptiles

Goniopholididae is an extinct family of moderate-sized semi-aquatic neosuchian crocodyliformes. Their bodyplan and morphology are convergent on living crocodilians. They lived across Laurasia between the Middle Jurassic and the Late Cretaceous.

<span class="mw-page-title-main">Neosuchia</span> Clade of reptiles

Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus than to Notosuchus terrestris. Members of Neosuchia generally share a crocodilian-like bodyform adapted to freshwater aquatic life, as opposed to the terrestrial habits of more basal crocodylomorph groups. The earliest neosuchian is suggested to be the Early Jurassic Calsoyasuchus, which lived during the Sinemurian and Pliensbachian stages in North America. It is often identified as a member of Goniopholididae, though this is disputed, and the taxon may lie outside Neosuchia, which places the earliest records of the group in the Middle Jurassic.

<span class="mw-page-title-main">Crocodyliformes</span> Clade of reptiles

Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the only pseudosuchians to survive the K-Pg extinction event.

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

Pholidosaurus is an extinct genus of neosuchian crocodylomorph. It is the type genus of the family Pholidosauridae. Fossils have been found in northwestern Germany. The genus is known to have existed during the Berriasian-Albian stages of the Early Cretaceous. Fossil material found from the Annero and Jydegård Formations in Skåne, Sweden and on the island of Bornholm, Denmark, have been referred to as a mesoeucrocodylian, and possibly represent the genus Pholidosaurus.

<span class="mw-page-title-main">Loricata</span> Extinct clade of reptiles

Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as Postosuchus and Prestosuchus. More specifically, Loricata includes Crocodylomorpha and most "rauisuchians", a paraphyletic grade of large terrestrial pseudosuchians which were alive in the Triassic period and ancestral to crocodylomorphs.

Almadasuchus is an extinct genus of crocodylomorph known from the early Late Jurassic Puesto Almada Member of the e Cañadón Calcáreo Formation of Patagonia, Argentina. It contains a single species, Almadasuchus figarii. It is known from the holotype MPEF-PV 3838, a well-preserved posterior region of the skull as well as other skull and postcranial remains. Almadasuchus was recovered from Puesto Almada, 30 m above the fish beds, dated as Oxfordian in age.

<span class="mw-page-title-main">Coelognathosuchia</span> Extinct clade of reptiles

Coelognathosuchia is an extinct clade of neosuchian crocodyliforms that includes all taxa more closely related to the family Pholidosauridae than to Bernissartia fagesii or Eusuchia. Martin et al. (2014) named the clade after finding goniopholidids and pholidosaurids to group together in their phylogenetic analysis of crocodyliform evolutionary relationships. In their analysis, Pholidosauridae was monophyletic and Goniopholididae was paraphyletic, being an assemblage of successively more basal taxa within Coelognathosuchia. Coelognathosuchia itself was positioned near the base of the larger clade Neosuchia as the sister group to a clade containing the Early Cretaceous neosuchian Bernissartia and Eusuchia, the group that includes all modern crocodilians and their closest extinct relatives.

References

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