Rugosuchus
Encyclopedia
Rugosuchus is an extinct genus
of neosuchia
n crocodyliform 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 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.
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 ostracod
e, bivalve, and fish fossils.
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 maxilla
e, 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 premaxilla
e 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.
Wu et al.. noted that their new genus was not an eusuchia
n 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
. 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.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of neosuchia
Neosuchia
Neosuchia is an unranked 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 than to Notosuchus terrestris...
n crocodyliform from the late Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of China
People's Republic of China
China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...
. It is known from most of a skull, a partial postcranial skeleton, and a second partial skeleton including part of the hips
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
. It was described by 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.
Description and history
Rugosuchus is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
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
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
. 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
Nong'an County
Nong'an County is a county of Jilin, People's Republic of China. It is under the administration of Changchun, the provincial capital.-Administrative Divisions:There are 10 towns and 11 townships.Towns:...
, Jilin
Jilin
Jilin , is a province of the People's Republic of China located in the northeastern part of the country. Jilin borders North Korea and Russia to the east, Heilongjiang to the north, Liaoning to the south, and Inner Mongolia to the west...
, in the Song-Liao Basin. The formation
Rock formation
This is a list of rock formations that include isolated, scenic, or spectacular surface rock outcrops. These formations are usually the result of weathering and erosion sculpting the existing rock...
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 ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
e, bivalve, and fish fossils.
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 maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e, 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 premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
e 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.
Wu et al.. noted that their new genus was not an eusuchia
Eusuchia
Eusuchia is a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. All living crocodilian species are eusuchians, as are many extinct forms.-Description:...
n because of the form of the palatal bones, but it was probably more closely related to the eusuchians than other extinct crocodyliforms like Goniopholis
Goniopholis
Goniopholis is an extinct genus of crocodyliform that lived in North America, Europe and Asia during the Late Jurassic and Early Cretaceous. Being semi-aquatic it is very similar to modern crocodiles...
by having more than two rows of bony armor
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
running its length, and by the form of the armor. They interpreted Rugosuchus as similar to Bernissartia
Bernissartia
Bernissartia is an extinct genus of crocodyliform that lived in the Early Cretaceous, around 130 million years ago.At only in length, Bernissartia is one of the smallest crocodyliforms that ever lived. It resembled modern species in many respects, and was probably semi-aquatic...
, Shamosuchus
Shamosuchus
Shamosuchus is an extinct genus of neosuchian crocodile that lived during the Late Cretaceous period in what is now the Gobi desert of Mongolia, approximately 85 to 65 million years ago. The teeth were adapted to crush bivalves, gastropods and other animals with a shell or exoskeleton . The genus...
and the unnamed "Glen Rose Form", but not as derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
. However, a more recent phylogenetic analysis
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
by Turner and Buckley (2008) places it with the "Glen Rose Form" in a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
with Eusuchia, more derived than Bernissartia.