Warrenisuchus

Warrenisuchus is an extinct genus of temnospondyl from the Early Triassic of Queensland, Australia. It belongs to a diverse group of Triassic temnospondyls called Capitosauria. The type species Warrenisuchus aliciae was erected in 2009. W. aliciae was originally described as a species of Parotosuchus in 1988, which is known from other species that have been found in Europe, Africa, and Antarctica.^[1] In 2000 it was then assigned to a new genus called Rewanobatrachus along with the newly named species R. gunganj, which was declared the type species of the genus. However, R. gunganj was later reclassified as a species of Watsonisuchus, invalidating the name Rewanobatrachus and requiring that R. aliciae be placed in its own genus, which was named Warrenisuchus.^[2] However, several studies suggest that Warrenisuchus aliciae may be a species of Watsonisuchus as well. Unlike most capitosaurs, Warrenisuchus is known from many juvenile skulls less than 4 centimetres (1.6 in) in length.^[3]

Warrenisuchus Temporal range: Early Triassic, Induan PreꞒ Ꞓ O S D C P T J K Pg N ↓
Skulls at various ontogenic stages
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Order:	†Temnospondyli
Suborder:	†Stereospondyli
Clade:	†Capitosauria
Genus:	†Warrenisuchus Maganuco et al., 2009
Type species
†Warrenisuchus aliciae (Warren and Hutchinson, 1988) (originally Parotosuchus aliciae)

Description

Holotype skull

Warrenisuchus is known from several fossil specimens. The holotype skeleton preserves most of the skull and lower jaws, the pectoral girdle, the forward-most vertebrae and ribs, and the right hind limb and the paratype specimen includes a partial skull and pectoral girdle. All known specimens of Warrenisuchus are very small; the largest skull is only 3.9 centimetres (1.5 in) long and the smallest is 1.1 centimetres (0.43 in) long^[3] (adult capitosaurs can have skulls over a meter in length).^[4] They show many characteristics of juvenile individuals such as large eye sockets, rounded heads (adult capitosaurs typically have triangular heads), loose joints between skull bones, small tabular horns, and pineal foramina close to the back of the eye sockets (as opposed to farther back on the skull table). The smallest specimens seem to represent the stage of development immediately after metamorphosis when gills have been lost and the skull bones have thickened but the vertebrae remain poorly developed.^[3]

Classification

Phylogeny

Below is a cladogram from Maganuco et al. (2009):

Capitosauria

Sclerothorax hypselonotus Warrenisuchus aliciae Edingerella madagascariensis Watsonisuchus gunganj Watsonisuchus magnus Watsonisuchus rewanensis Wetlugasaurus angustifrons Parotosuchus orenburgensis Stanocephalosaurus pronus Cyclotosauridae Cyclotosaurus robustus Tatrasuchus wildi Stenotosaurus stantonensis Xenotosuchus africanus Cherninia denwai Wellesaurus peabodyi Paracyclotosaurus davidi Heylerosauridae Eocyclotosaurus Odenwaldia heidelbergensis Mastodonsauridae Mastodonsaurus giganteus Eryosuchus garjainovi Yuanansuchus laticeps Quasicyclotosaurus campi

Paleoenvironment

Warrenisuchus fossils are the most common components of an amphibian fauna that existed in eastern Australia during the Early Triassic. They are preserved in the Arcadia Formation, which dates back to the Induan stage. Other temnospondyl amphibians from the Arcadia Formation include rhytidosteids and brachyopoids. Another amphibian fauna existed around the same time in western Australia and includes a greater diversity of brachyopoids along with rhytidosteids, trematosaurids, and the capitosaur Edingerella, which was a close relative of Warrenisuchus.^[1]

References

1. Shishkin, M.A. "The patterns of evolution of Early Triassic herpetofauna in Europe and Gondwana: comparison and implications" (PDF). Russian Journal of Herpetology. Proceedings of the 12th Ordinary General Meeting of the Societas Europaea Herpetologica, August 12–16, 2003, St. Petersburg, Russia. 12(Suppl.): 301–303.
2. Maganuco, S.; Steyer, J.S.; Pasini, G.; Boulay, M.; Lorrain, S.; Bénéteau, A.; Auditore, M. (2009). "An exquisite specimen of Edingerella madagascariensis (Temnospondyli) from the Lower Triassic of NW Madagascar; cranial anatomy, phylogeny, and restorations". Memorie della Società Italiana di Scienze Naturalie del Museo Civico di Storia Naturale di Milano. 36 (2): 1–72.
3. Warren, A.A.; Hutchinson, M.N. (1988). "A new capitosaurid amphibian from the Early Triassic of Queensland, and the ontogeny of the capitosaur skull" (PDF). Palaeontology. 31 (3): 857–876.
4. Damiani, R.J. (2001). "Cranial anatomy of the giant Middle Triassic temnospondyl Cherninia megarhina and a review of feeding in mastodonsaurids". Palaeontologica Africana. 37: 41–52.