''Rugosuchus'' (meaning "uneven or wrinkled

crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large, semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term "crocodile" is sometimes used more loosely to include ...

", in reference to texturing on its upper jaw bones) is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 Crocodylomorpha, crocodylomorphs more closely related to ''Croc ...

crocodyliform Crocodyliformes is a clade of Crurotarsi, crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the first members of Crocodylomorpha to possess many of the features that define later relatives. They are the ...

from the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. It is known from most of a skull, a partial postcranial skeleton, and a second partial skeleton including part of the

hips In vertebrate anatomy, the hip, or coxaLatin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) (: ''coxae'') in medical terminology, refers to either an anatomical region or a joint ...

. 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.

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

vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...

e, a partial hip, and a fragment of

thigh bone The femur (; : femurs or femora ), or thigh bone is the only bone in the thigh — the region of the lower limb between the hip and the knee. In many four-legged animals the femur is the upper bone of the hindleg. The top of the femur fits 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 () is a county of Jilin Province, Northeast China, it is under the administration of the prefecture-level city of Changchun, the capital of Jilin. The westernmost county-level division of Changchun City, it borders Dehui to the eas ...

Jilin ) , image_skyline = Changbaishan Tianchi from western rim.jpg , image_alt = , image_caption = View of Heaven Lake , image_map = Jilin in China (+all claims hatched).svg , mapsize = 275px , map_al ...

, 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 thought to be latest Early Cretaceous, based on

ostracod Ostracods, or ostracodes, are a Class (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

, and fish fossils. However, most of later studies consider it as late Cretaceous instead. 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 In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

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 The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

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 is a clade of neosuchian Crocodylomorpha, crocodylomorphs that first appeared in the Early Cretaceous, which includes modern Crocodilia, crocodilians. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survi ...

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'' (meaning "angled scale") is an extinct genus of goniopholidid crocodyliform that lived in Europe and North America during the Late Jurassic and Early Cretaceous. Like other goniopholidids, it resembled living crocodilians, and pro ...

'' 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 ''Bernissartia'' ('of Bernissart') is an extinct genus of neosuchian 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 ...

'', '' Shamosuchus'' and the unnamed "Glen Rose Form", but not as derived. However, a more recent

phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...

by Turner and Buckley (2008) places it with the "Glen Rose Form" in a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

with Eusuchia, more derived than ''Bernissartia''.

References

{{Taxonbar, from=Q7378610 Paralligatoridae Prehistoric pseudosuchian genera Cretaceous reptiles of Asia Cretaceous crocodylomorphs of Asia