Rugosuchus

Rugosuchus (meaning "uneven or wrinkled crocodile", in reference to texturing on its upper jaw bones) is an extinct genus of neosuchian crocodyliform[1] from the late Early Cretaceous of China. It is known from most of a skull, a partial postcranial skeleton, and a second partial skeleton including part of the hips. It was described by Xiao-Chun Wu and colleagues in 2001, with R. nonganensis as the type species. At the time of its description, it was the most complete crocodyliform from northeastern China, and only the second known.

Rugosuchus
Temporal range: Early Cretaceous
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Family: Paralligatoridae
Genus: Rugosuchus
Wu et al., 2001
Type species
Rugosuchus nonganensis
Wu et al., 2001

Description and history

Rugosuchus is based on IGV 33, most of a skull. Wu et al. assigned two other specimens to this genus: IGV 31, much of a skeleton lacking a skull and most of the limbs; and IGV 32, three vertebrae, a partial hip, and a fragment of thigh bone. These three specimens had been collected in 1958 by the Petroleum Geological Survey of the Song-Liao Basin, and remained unstudied for many years. The locality is near Fulongquan, Nong'an County, Jilin, in the Song-Liao Basin. The formation is not known for certain, but is probably the Nenjiang Formation. The age of the Nenjiang Formation has been debated, but as of the description of Rugosuchus was though to be latest Early Cretaceous, based on ostracode, bivalve, and fish fossils.[2]

Skull IGV 33 is thought to have come from an adult, based on the fusion of bones. It is somewhat elongate, being about 28 centimeters (11 in) long but only an estimated 13 centimeters (5 in) at its widest. The maxillae, the main tooth-bearing bones of the upper jaw, had unusual elongate depressions on their sides, nine or ten per maxilla. Other skull bones had heavily textured surfaces, as is seen on other crocodyliforms. The premaxillae at the tip of the snout had five teeth each, and the maxillae 16 or 17, with wide spacing; because the jaws are closed, the teeth of the lower jaw cannot be observed.[2]

Wu et al. noted that their new genus was not an eusuchian because of the form of the palatal bones, but it was probably more closely related to the eusuchians than other extinct crocodyliforms like Goniopholis by having more than two rows of bony armor running its length, and by the form of the armor. They interpreted Rugosuchus as similar to Bernissartia, Shamosuchus and the unnamed "Glen Rose Form", but not as derived.[2] However, a more recent phylogenetic analysis by Turner and Buckley (2008) places it with the "Glen Rose Form" in a clade with Eusuchia, more derived than Bernissartia.[3]

References

  1. ^ Crocodyliformes and Neosuchia are clades that include all living crocodilians and successively smaller subsets of their closest extinct relatives.
  2. ^ a b c Xiao-Chun Wu; Zheng-Wu Cheng; Russell, Anthony P. (2001). "Cranial anatomy of a new crocodyliform (Archosauria: Crocodylomorpha) from the Lower Cretaceous of Song-Liao Plain, northeastern China" (pdf). Canadian Journal of Earth Sciences. 38 (12): 1653–1663. Bibcode:2001CaJES..38.1653W. doi:10.1139/cjes-38-12-1653.
  3. ^ Turner, Alan H.; Buckley, Gregory A. (2008). "Mahajangasuchus insignis (Crocodyliformes: Mesoeucrocodylia) cranial anatomy and new data on the origin of the eusuchian-style palate". Journal of Vertebrate Paleontology. 28 (2): 382–408. doi:10.1671/0272-4634(2008)28[382:MICMCA]2.0.CO;2.
Aegyptosuchidae

Aegyptosuchidae is an extinct family of eusuchian crocodyliforms from the Cretaceous period of Africa. They are characterized by their large size and flat heads. The family includes two genera, Aegyptosuchus and Aegisuchus.

Anteophthalmosuchus

Anteophthalmosuchus (meaning "forward-pointing eye crocodile") is an extinct genus of goniopholidid mesoeucrocodylian from the Early Cretaceous of southern England, eastern Spain, and western Belgium.

Batrachomimus

Batrachomimus is an extinct genus of neosuchian crocodyliform known from the Late Jurassic of northeastern Brazil. It contains a single species, Batrachomimus pastosbonensis, which was first described and named by Felipe C. Montefeltro, Hans C. E. Larsson, Marco A. G. de França and Max C. Langer in 2013. It is known from a nearly complete skull, osteoderms and limb bones. Batrachomimus belongs to the family Paralligatoridae and predates all other members of the family and its immediate sister group, Eusuchia, by 30 million years.

Calsoyasuchus

Calsoyasuchus (meaning "[Dr. Kyril] Calsoyas' crocodile") is a genus of goniopholidid mesoeucrocodylian that lived in the Early Jurassic. Its fossilized remains were found in the Sinemurian-Pliensbachian-age Kayenta Formation on Navajo Nation land in Coconino County, Arizona, United States. Formally described as C. valliceps, it is known from a single incomplete skull which is unusually derived for such an early crocodile relative. This genus was described in 2002 by Ronald Tykoski and colleagues; the species name means "valley head" and refers to a deep groove along the midline of the nasal bones and frontal bones.

Coelosuchus

Coelosuchus is an extinct genus of goniopholidid mesoeucrocodylian. Fossils have been found from the Graneros Shale of the Benton Group in Wyoming, and are of Cenomanian age. It was slightly over 1 meter in length.

Eusuchia

The Eusuchia ("true crocodiles") are a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades died out 35 and 11 million years ago, all living crocodilian species are eusuchians, as are many extinct forms.

Goniopholididae

Goniopholididae is an extinct family of moderate-sized semi-aquatic crocodyliforms superficially similar to living crocodiles (but see below). They lived between the Early Jurassic and the Late Cretaceous.

Goniopholis

Goniopholis is an extinct genus of goniopholidid crocodyliform that lived in Europe and Africa during the Late Jurassic and Early Cretaceous. Being semi-aquatic it is very similar to modern crocodiles. It ranged from 2–4 metres in length, and would have had a very similar lifestyle to the American alligator or Nile crocodile.

Hulkepholis

Hulkepholis is an extinct genus of goniopholidid mesoeucrocodylian from the Early Cretaceous of southern England and eastern Spain. It contains two species, the type species, Hulkepholis willetti, and also H. plotos. Hulkepholis is most closely related to both species of Anteophthalmosuchus (including "Dollo's goniopholidid").

Nannosuchus

Nannosuchus (meaning "dwarf crocodile") is an extinct genus of goniopholidid mesoeucrocodylian from the Berriasian of England.

Neosuchia

Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus (the Nile Crocodile) than to Notosuchus terrestris. Neosuchia is very diverse and may be polyphyletic, as the clade has undergone many revisions since it was first named in 1988. Neosuchians first appear in the Early Jurassic with the earliest known goniopholid Calsoyasuchus, which lived during the Sinemurian and Pliensbachian stages.

Paluxysuchus

Paluxysuchus is an extinct genus of neosuchian crocodyliform known from the Early Cretaceous Twin Mountains Formation (late Aptian stage) of north-central Texas. It contains a single species, Paluxysuchus newmani. Paluxysuchus is one of three crocodyliforms known from the Early Cretaceous of Texas, the others being Pachycheilosuchus and an unnamed species referred to as the "Glen Rose Form". Paluxysuchus has a long, flat skull that is probably transitional between the long and narrow skulls of many early neosuchians and the short and flat skulls of later neosuchians.

Paralligatoridae

Paralligatoridae is an extinct family of neosuchian crocodyliforms that existed during the Jurassic and Cretaceous periods. It includes the genera Paralligator, Brillanceausuchus, Kansajsuchus, Shamosuchus, Scolomastax, Sabresuchus, Rugosuchus, Batrachomimus and Wannchampsus, as well as the yet-unnamed "Glen Rose form".

Pholidosauridae

Pholidosauridae is an extinct family of aquatic neosuchian mesoeucrocodylian crocodylomorphs. Fossils have been found in Europe (Denmark, England, France, Germany, Spain and Sweden), Africa (Algeria, Niger, Mali, Morocco and Tunisia), North America (Canada and the United States) and South America (Brazil and Uruguay). The pholidosaurids first appeared in the fossil record during the Bathonian stage of the Middle Jurassic and became extinct during the Late Turonian stage of the Late Cretaceous.Sarcosuchus is one of the best known pholidosaurs. It is believed to have attained lengths of up to 12 metres (39 ft 4 in) and weighed up to 8 tonnes (7.9 long tons; 8.8 short tons). One genus, Suchosaurus, once thought to be a pholidosaur, has since been shown to be a spinosaurid theropod dinosaur.

Sunosuchus

Sunosuchus is an extinct genus of goniopholidid mesoeucrocodylian. Fossils are known from China, Kyrgyzstan, and Thailand and are Jurassic in age, although some may be Early Cretaceous. Four species are currently assigned to the genus: the type species S. miaoi and the species S. junggarensis, S. shartegensis, and S. shunanensis. All species are from China. Goniopholis phuwiangensis, also from Thailand, was reassigned to Sunosuchus by Andrade et al. (2011). The material from Kyrgyzstan has not been assigned to any species.

Symptosuchus

Symptosuchus is an extinct genus of goniopholidid mesoeucrocodylian. It is known from the Late Cretaceous of Argentina. Argentine paleontologist Florentino Ameghino named the genus in 1899, along with the type species S. contortidens. It was formally described by Carlos Rusconi in 1934.

Tethysuchia

Tethysuchia is an extinct clade of neosuchian mesoeucrocodylian crocodylomorphs from the late Middle Jurassic (Bathonian stage) to the Early Eocene (Ypresian stage) of Asia, Europe, North America and South America. It was named by the French paleontologist Eric Buffetaut in 1982 as a suborder. Tethysuchia was considered to be a synonym of Dyrosauridae or Pholidosauridae for many years. In most phylogenetic analyses the node Dyrosauridae+Pholidosauridae was strongly supported. De Andrade et al. (2011) suggested that Tethysuchia be resurrected for that node. They defined it as a node-based taxon "composed of Pholidosaurus purbeckensis (Mansel-Pleydell, 1888) and Dyrosaurus phosphaticus (Thomas, 1893), their common ancestor and all its descendants". In their analysis they found that the support for Tethysuchia is actually stronger than the support for Thalattosuchia. The following cladogram shows the position of Tethysuchia among the Neosuchia sensu this study.

Wahasuchus

Wahasuchus is a genus of extinct mesoeucrocodylian of the Middle Campanian age found in the Quseir Formation, Egypt. The generic name derives from the Arabic word واحة (waha), which means "oasis", and souchos from the Greek in honor of crocodile-headed god of ancient Egypt. The specific egyptensis (Lat.) means from Egypt.Fossils of skull and jaw fragments, dorsal vertebrae, and fragmentary appendicular remains have been recovered.

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