Sphenosuchia

Sphenosuchians Fossil range: Late Triassic - Late Jurassic

Scientific classification
Infraclass:	Archosauromorpha
Superorder:	Crocodylomorpha
Suborder:	Sphenosuchia
Families:	Sphenosuchidae

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 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).

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.

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:

Genera[]

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Genus	Status	Age	Location	Unit	Notes
Dibothrosuchus	Valid	Early Jurassic	China	Lower Lufeng Series
Dromicosuchus	Valid	Late Triassic	USA	Newark Supergroup
Dyoplax	Valid	Late Triassic(Carnian)	Germany	Schilfsandstein Formation	A possible sphenosuchian; alternatively, it could be an erpetosuchid.
Hesperosuchus	Valid	Late Triassic(Carnian)	USA	Chinle Formation
Junggarsuchus	Valid	Middle Jurassic	China	Shishugou Formation
Kayentasuchus	Valid	Early Jurassic(Sinemurian - Pliensbachian)	USA	Kayenta Formation
Litargosuchus	Valid	Early Jurassic	South Africa	Elliot Formation
Parrishia	Nomen dubium	Late Triassic	USA	Dockum Group	An indeterminate sphenosuchian known only from undiagnostic vertebrae
Phyllodontosuchus	Valid	Early Jurassic	China	Lower Lufeng Series
Pseudhesperosuchus	Valid	Late Triassic(Norian)	Argentina	Los Colorados Formation
Redondavenator	Valid	Late Triassic	USA	Redonda Formation
Saltoposuchus	Valid	Late Triassic(Norian)	Germany Switzerland UK	Löwenstein Formation Trossingen FormationLossiemouth Sandstone
Sphenosuchus	Valid	Early Jurassic	South Africa	Elliot Formation
Terrestrisuchus	Valid.	Late Triassic	UK
Trialestes	Valid	Late Triassic	Argentina	Ischigualasto Formation

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.

[CETAL04-1] Clark, J.M., et al. (2004).A Middle Jurassic 'sphenosuchian' from China and the origin of the crocodylian skull Nature 430:1021-1024.

[CS02-2] 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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