Sphenosuchia
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| Sphenosuchians Fossil range: Late Triassic - Late Jurassic |
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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.
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[edit] Stratigraphic Range
The earliest known members of the group occur (i.e. Hesperosuchus) in the Lower Petrified Forest member of the Chinle Formation, these specimens are Carnian in age. Only one sphenosuchian is currently known from the Middle Jurassic, Junggarsuchus, from the Junggar Basin (Shishugou Formation) of China during either the Bathonian or the Callovian (~165 MA) in age.[1] The youngest sphenosuchian, Macelognathus, is known from the Late Jurassic of North America during the Kimmeridgian, (155 - 150 Ma).
[edit] Phylogeny
The monophyly of the group is debated, although several synapomorphies characterize the clade, including extremely slender limbs, a compact carpus and an elongate coracoid process.
In 2002, Clark and Sues argued that the Spenosuchia formed a clade.[2] More recently, however, Clark et al. (2004) argued for the paraphyly of the group, contending that morphological characters were secondarily lost in more highly derived crocodylomorphs.[1] Further analysis and study is required before the group's monophyly is resolved with certainty — a perfect phylogenetic analysis is, at present, impossible due to a paucity of fossil remains demonstrating phylogenetically informative characters.
[edit] List of sphenosuchian genera
Because of the current uncertainty surrounding sphenosuchian monophyly, no phylogenetic tree is presented in the article; however, the genera currently classified as sphenosuchians are:
Barbarenasuchus
Dibothrosuchus
Dromicosuchus
Dyoplax
Hallopus
Hesperosuchus
Junggarsuchus
Kayentasuchus
Litargosuchus
Macelognathus
Parrishia
Pedeticosaurus
Pseudhesperosuchus
Redondavenator
Saltoposuchus
Sphenosuchus
Terrestrisuchus
Trialestes
[edit] References
- ^ a b Clark, J.M., et al. (2004).A Middle Jurassic 'sphenosuchian' from China and the origin of the crocodylian skull Nature 430:1021-1024.
- ^ Clark, J.M., and Sues, H.-D. (2002). Two new species of basal crocodylomorphs and the status of the Sphenosuchia. Zoological Journal of the Linnean Society 136:77−96.
