Crocodylomorpha

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Crocodylomorpha

The Crocodylomorpha are an important group of archosaur

Archosaur

Archosaurs are a group of diapsid reptiles represented by modern birds and crocodilians. This group also includes extinct non-avian dinosaurs, pterosaurs and relatives of crocodiles....
s that include the crocodilia

Crocodilia

Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria....
ns and their extinct relatives.

During Mesozoic

Mesozoic

The Mesozoic Era is one of three Geologic time scale of the Phanerozoic eon . The division of time into eras dates back to Giovanni Arduino, in the 18th century, although his original name for the era now called the 'Mesozoic' was 'Secondary' ....
and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were supplanted during the early Jurassic by various aquatic and marine forms. The Later Jurassic, Cretaceous, and Tertiary saw a wide diversity of terrestrial and semi-aquatic lineages.

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Encyclopedia

The Crocodylomorpha are an important group of archosaur

Archosaur

Crocodilia

Mesozoic

Evolutionary history

When their extinct species and stem group are examined, the crocodylian lineage (clade Crurotarsi

Crurotarsi

The Crurotarsi are a group of Archosauria, whose name was erected as a Cladistics#Cladistic classification by Paul Sereno in 1991 to supplant the old term Pseudosuchia....
) proves to have been a very diverse and adaptive group of reptiles. Not only are they an ancient group of animals, at least as old as the dinosaur

Dinosaur

Dinosaurs were the dominant vertebrate animals of Landform ecosystems for over 160 million years, from the late Triassic Period until the end of the Cretaceous Period , when most of them became extinct in the Cretaceous?Tertiary extinction event....
s, they also evolved into a great variety of forms. The earliest forms, the sphenosuchia

Sphenosuchia

Sphenosuchia is the name of 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....
ns, evolved during the Late Triassic

Triassic

The Triassic is a geologic period that extends from about 251 to 199 annum . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic....
, and were highly gracile

Gracile

Gracile can refer to:* Gracile fasciculus* Gracile nucleus* "Gracile syndrome", associated with a BCS1L mutationGracile is the name for various plant species, including:...
terrestrial forms built like greyhounds. During the Jurassic

Jurassic

The Jurassic is a geologic period that extends from about annum to Ma, that is, from the end of the Triassic to the beginning of the Cretaceous....
and the Cretaceous marine forms in the family Metriorhynchidae
Metriorhynchidae

Metriorhynchids were a clade of fully-aquatic crocodyliforms that lived in seas of the Jurassic and Cretaceous periods. Their fore-legs were reduced and paddle-like, and unlike living crocodilians, they lost their osteoderms ....
such as Metriorhynchus
Metriorhynchus

Metriorhynchus is an extinct genus of marine crocodyliformes that lived in the oceans during the Middle Jurassic to Late Jurassic. Metriorhynchus was named by the Germans palaeontologist Christian Erich Hermann von Meyer in 1830....
evolved forelimbs that were paddle-like and had a tail similar to modern fish. Dakosaurus andiniensis, a species closely related to Metriorhynchus, had a skull that was adapted to eat large marine reptiles. Several terrestrial species during the Cretaceous

Cretaceous

The Cretaceous , usually abbreviated K for its German translation Kreide, is a geologic period from circa to million years ago . In the geologic timescale, the Cretaceous follows on the Jurassic period and is followed by the Paleogene period....
evolved herbivory, such as Simosuchus clarki and Chimaerasuchus paradoxus. A number of lineages during the Tertiary and Pleistocene became wholly terrestrial predators.

Phylogenetic definition

The Crocodylomorpha are defined phylogenetically by Sereno 2005 as "The most inclusive clade

Clade

A clade is a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants.The term "monophyletic group" is used in this article in the conventional sense of "an a...
containing Crocodylus niloticus (Laurenti 1768) but not Poposaurus gracilis
Poposaurus

Poposaurus is a genus of reptile from the Late Triassic. It was a Crurotarsi archosaur which lived in what is now Wyoming, Utah, Arizona, New Mexico and Texas....
Mehl 1915, Gracilisuchus stipanicicorum
Gracilisuchus

Gracilisuchus is an extinct genus of tiny crurotarsan from the Middle Triassic. It was a suchian close to the ancestry of crocodiles, and was at one time thought to be a dinosaur, but this hypothesis has since been rejected....
Romer 1972, Prestosuchus chiniquensis
Prestosuchus

Prestosuchus is an extinct genus of a group of rauisuchians called prestosuchids. Like its prestosuchid cousins, Prestosuchus had a deep skull, and serrated teeth....
Huene 1942, Aetosaurus ferratus
Aetosaurus

Aetosaurus is an extinct genus of archosaur reptile belonging to the aetosaur order. Remains of Aetosaurus were found in South Africa....
Fraas 1877."

This a stem-based definition and therefore includes all taxa closer to extant crocodilians than to other crurotarsan

Crurotarsi

The Crurotarsi are a group of Archosauria, whose name was erected as a Cladistics#Cladistic classification by Paul Sereno in 1991 to supplant the old term Pseudosuchia....
clades.

Taxonomy and phylogeny

Historically, all known living and extinct crocodiles were indiscriminately lumped into the order

Order (biology)

In Biological classification used in biology, the order is a taxonomic rank between class and family . The superorder is a rank between class and order....
Crocodilia. But it is now known that this is erroneous, based on the uniqueness of the crocodilian morphology

Morphology (biology)

The term morphology in biology refers to form, structure and configuration of an organism. This includes aspects of the outward appearance as well as the form and structure of the internal parts like bones and organs....
. Thus, the order Crocodilia is nowadays restricted to the living species and close extinct relatives such as Mekosuchus
Mekosuchus

Mekosuchus is a genus of extinct Australasian crocodile within the subfamily Mekosuchinae. It is believed to have been made extinct by the arrival of man on the Oceania islands where it lived ....
.

The old Crocodilia was subdivided into the suborders:

Eusuchia
Eusuchia

Eusuchia is a clade of crocodyliforms that first appears in the Early Cretaceous Geologic time scale#Terminology. All living crocodilian species are eusuchians, as are many extinct forms....
: true crocodilies (which includes crown-group Crocodylia)
Mesosuchia
Mesosuchia

"Mesosuchia" is an obsolete name for a group of terrestrial animal, semi-aquatic, or fully aquatic Crocodylomorpha reptiles. The marine crocodile Metriorhynchus had paddle-like forelimbs, Dakosaurus andiniensis had a skull that was adapted to eat large sea reptiles, and Shamosuchus was adapted for eating molluscs and gastropods....
: 'middle' crocodiles
Thalattosuchia
Thalattosuchia

Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution....
: sea crocodiles
Protosuchia
Protosuchia

Protosuchians are early crocodilians that were small in size and Terrestrial animal....
: first crocodiles

Mesosuchia is a paraphyletic group as it does not include eusuchians (which nest within Mesosuchia). Mesoeucrocodylia

Mesoeucrocodylia

Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
was the name given to the clade that contains mesosuchians and eusuchians (Whetstone and Whybrow, 1983).

Phylogeny

Here is the consensus of Larsson & Sues (2007) and Sereno et al. (2003):

Crocodyliformes |--Protosuchia

Protosuchia

Protosuchians are early crocodilians that were small in size and Terrestrial animal....
`--o Mesoeucrocodylia
Mesoeucrocodylia

Mesoeucrocodylia is the name of the clade that includes Eusuchia and the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day....
|--Thalattosuchia

Thalattosuchia

Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution....
`--+--Notosuchia

Notosuchia

Notosuchia is a suborder of Mesoeucrocodylia that lived during the Cretaceous. It was a clade of terrestrial crocodilians that evolved a range of feeding behaviours, including: herbivory , terrestrial hypercarnivory , and omnivory ....
`--+-Sebecia `--o Neosuchia
Neosuchia

Neosuchia is an unranked clade within Mesoeucrocodylia that includes all modern extant Crocodilia in the crown group Eusuchia and their closest fossil relatives....
|--Atoposauridae

Atoposauridae

Atoposauridae is a Family of crocodile-like archosaurs. Members of the family have been found from France, Spain, Portugal, Germany, the United Kingdom, the United States, and Thailand....
`--+--+--Pholidosaurus | `--+--Dyrosauridae

Dyrosauridae

Dyrosauridae is a family of extinct neosuchian Crocodyliformes that lived from the Late Cretaceous to the Eocene. Fossils of this group have been found in almost every continent, specifically Africa, Asia, Europe, North America and South America....
| `--+--Sarcosuchus
Sarcosuchus

Sarcosuchus , meaning 'flesh crocodile' and commonly called "SuperCroc", is an extinct genus of crocodyliform and distant relative of the crocodile....
| `--Terminonaris
Terminonaris

Terminonaris is a genus of pholidosauridae mesoeucrocodylian that lived in the Late Cretaceous . Its remains are known from North America. Originally known under the generic name Teleorhinus, it was once believed to be a teleosaurid ....
`--+--Goniopholididae

Goniopholididae

Goniopholididae is an extinct family of moderate-sized semi-aquatic crocodyliforms similar to extant crocodiles. They lived between the Early Jurassic and the Late Cretaceous....
`--+--Bernissartia
Bernissartia

Bernissartia is an extinct genus of crocodyliform that was 60 cm long.Bernissartia is one of the smallest crocodyliforms that ever lived....
`--Eusuchia

Eusuchia

Eusuchia is a clade of crocodyliforms that first appears in the Early Cretaceous Geologic time scale#Terminology. All living crocodilian species are eusuchians, as are many extinct forms....

The previous definitions of Crocodilia and Eusuchia do not accurately resemble the evolution of the group. The only order-level taxon that is currently considered valid is Crocodilia in the present definition. Prehistoric crocodiles are represented by many taxa, but since few major groups of the ancient forms are recognizable, a decision where to delimit new order-level clades is not yet possible. (Benson & Clark, 1988).

External links

- webpages by Ross Elgin on the University of Bristol
University of Bristol

The University of Bristol is a university in Bristol, England. It received its Royal Charter in 1909, although its predecessor institution, University College, Bristol, had been in existence since 1876....
server

classification (used here)

from Palaeos
Palaeos

Palaeos.com is a web site on biology, paleontology, cladistics and geology and which covers the history of Earth. The site is well-respected and has been used as a reference by professional paleontologists such as Michael J....

- hyperlinked cladogram at Mikko's Phylogeny Archive
Mikko's Phylogeny Archive

Mikko's Phylogeny Archive is an amateur paleontology website maintained by Mikko Haaramo, a student at the University of Helsinki's Department of Geology, Division of Geology and Palaeontology....
Sereno, P. C
Paul Sereno

Paul Callistus Sereno is an United States paleontology who is the discoverer of several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco and Niger....
. 2005. [version 1.0, 2005 November 7]