Erythrosuchidae

Erythrosuchids Temporal range: Early - Middle Triassic, 249.7–237Ma PreꞒ Ꞓ O S D C P T J K Pg N
Skull of Shansisuchus shansisuchus at the Paleozoological Museum of China.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauriformes
Family:	†Erythrosuchidae Broom, 1905
Genera
see below

Erythrosuchidae (meaning "red crocodiles") are a family of large basal archosauromorph carnivores that lived from the later Early Triassic (Olenekian) to the early Middle Triassic (Anisian).

Description

Erythrosuchids were unusually large and robust archosaurs. Several features set them apart from other archosauriformes and are also seen in later, more derived archosaurs. For example, they lack teeth on the palate, which are found in other early archosauriformes such as Doswellia and euparkeriids. In erythrosuchids, the centra (central parts of vertebrae) are deeply indented on either side, differing considerably from the usual cylindrical shape of the centra in other early archosauriformes, but similar to later archosaurs.^[1]

The heads of erythrosuchids are generally large and deep. One distinguishing feature of erythrosuchids is the shape of the margin of their upper jaw. In all erythrosuchids, the lower margin of the premaxilla, the bone at the tip of the upper jaw, is lower than the lower margin of the maxilla, the bone behind the premaxilla. This forms a characteristic "step" which makes erythrosuchids easily distinguishable from all other early archosauriformes, which have smooth jaw margins that are either straight or gradually curved.^[1]

Erythrosuchids are notable for being the first archosauriforms to have a triradiate pelvic girdle with three projecting areas formed from three bones: an illium and an elongated pubis and ischium.^[2] Although it is small, the fourth trochanter, a ridge on the femur that serves as a muscle attachment in archosaurs, first appears in erythrosuchids. The triradiate pelvis and fourth trochanter are both features which indicate that erythrosuchids had an erect stance similar to later archosaurs. More basal archosauriforms such as proterosuchids lacked these features and probably had a more sprawling posture.^[3]

Classification

Erythrosuchids were formerly classified as thecodonts of the suborder Proterosuchia. This classification is no longer used by paleontologists, who now employ a cladistic approach. In this, erythrosuchids constitute an Archosauriformes clade that is an outgroup to the Archosauria proper. The presence of certain archosaurian features such as the triradiate pelvic girdle, the fourth trochanter, and the third metatarsal longer than the fourth, indicate that erythrosuchids are closer to the true archosaurs than the Proterosuchidae, which lack these features. Thus the Erythrosuchidae occupy a transitional evolutionary position between the most primitive archisauriformes and more advanced Triassic archosaurs.

Status and Range

They were the apex predators of their day, with lengths of 2.5 to over 5 meters. Their fossil remains are known only (so far) from South Africa (Beaufort Group of the Karoo Basin), China, and the Perm region of Russia.

Genera

Genus	Status	Age	Location	Description	Images
Chalishevia	Valid.	Middle Triassic.	Eastern Europe.
Erythrosuchus	Valid.	Early Triassic.	South Africa.
Fugusuchus	Valid.	Early Triassic.	China.
Garjainia	Valid.	Early Triassic.	Eastern Europe.
Guchengosuchus	Valid.	Early Triassic.	China.
Shansisuchus	Valid.	Middle Triassic.	China.
Vjushkovia	Valid.	Middle Triassic.	Eastern Europe.

Phylogeny

Cladogram from Parrish (1992):^[1]

Paleobiology

The large contemporary kannemeyeriid dicynodonts doubtless constituted much of erythrosuchids' prey. However, the first erythrosuchids appear in the fossil record slightly earlier than the kannemeyeriids do, so it must be assumed that they also fed on other animals as well.

References

• Benton, M. J. (2000), Vertebrate Paleontology, 2nd Ed. Blackwell Science Ltd (2004) 3rd edition
• Carroll, R. L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.

External links

Wikimedia Commons has media related to Erythrosuchidae.

• Erythrosuchidae
• Erythrosuchidae - list of species (Mikko's Phylogeny Archive)