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Sphenosuchians
Fossil range: Late Triassic - Late Jurassic
Hesperosuchus BW
Scientific classification

Infraclass:

Archosauromorpha

Superorder:

Crocodylomorpha

Suborder:

Sphenosuchia

Families:

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.

Stratigraphic RangeEdit

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).

PhylogenyEdit

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.

List of sphenosuchian generaEdit

Because of the current uncertainty surrounding sphenosuchian monophyly, no phylogenetic tree is presented in the article; however, the genera currently classified as sphenosuchians are:

Genus Status Age Location Description
Dibothrosuchus Valid Early Jurassic Asia
Dromicosuchus Valid Late Triassic North America
Hallopus Valid Late Jurassic North America Possible synonym of Macelognathus
Hesperosuchus Valid Late Triassic North America
Junggarsuchus Valid Middle Jurassic Asia
Kayentasuchus Valid Early Jurassic North America
Litargosuchus Valid Early Jurassic Africa
Macelognathus Valid Late Jurassic North America
Pedeticosaurus Valid
Phyllodontosuchus Valid Early Jurassic Asia
Pseudohesperosuchus Valid
Redondavenator Valid Late Triassic North America
Saltoposuchus Valid Late Triassic Europe and North America
Sphenosuchus Valid Early Jurassic Africa
Terrestrisuchus Valid Late Triassic Europe



ReferencesEdit

  1. ^ 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.
  2. ^ 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.

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