Sphenosuchia

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.

Stratigraphic range

The earliest known members of the group (i.e. Hesperosuchus) are early Norian in age, found in the Blue Mesa Member of the Chinle Formation. 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) age, and the Hallopodidae are known from the Late Jurassic of North America.

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 found a possible sphenosuchian clade of Dibothrosuchus, Sphenosuchus, and possibly Hesperosuchus and Saltoposuchus, with several other genera in unresolved positions (Kayentasuchus, Litargosuchus, Pseudhesperosuchus, and Terrestrisuchus). 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. 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.

Below is a cladogram modified from Nesbitt (2011). Sphenosuchians are marked by the green bracket.

Genera

Genus	Status	Age	Location	Unit	Notes	Images
Dibothrosuchus	Valid	Early Jurassic	China	Lower Lufeng Series		File:Dibothrosuchus BW.jpg
Dromicosuchus	Valid	Late Triassic	USA	Newark Supergroup
Dyoplax	Valid	Late Triassic (Carnian)	Germany	Schilfsandstein Formation	A possible sphenosuchian; alternatively, it could be an erpetosuchid.	File:Dyoplax holotype.jpg
Hesperosuchus	Valid	Late Triassic (Carnian)	USA	Chinle Formation
Junggarsuchus	Valid	Middle Jurassic	China	Shishugou Formation		File:Junggarsuchus sloani.jpg
Kayentasuchus	Valid	Early Jurassic (Sinemurian - Pliensbachian)	USA	Kayenta Formation
Litargosuchus	Valid	Early Jurassic	South Africa	Elliot Formation		File:Litargosuchus leptorhynchus.jpg
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 Formation Lossiemouth Sandstone		File:Saltoposuchus BW.jpg
Sphenosuchus	Valid	Early Jurassic	South Africa	Elliot Formation
Terrestrisuchus	Valid.	Late Triassic	UK			File:Terrestrisuchus BW.jpg
Trialestes	Valid	Late Triassic	Argentina	Ischigualasto Formation