''Dibothrosuchus'' is a

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 ...

sphenosuchia Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Middle Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms ...

n, a type of basal

crocodylomorph Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably mor ...

, the

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 ...

that comprises the

crocodilia Crocodilia () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...

ns and their closest kin. It is known from several partial skeletons and skulls. These fossils were found in

Lower Jurassic The Early Jurassic Epoch (in chronostratigraphy corresponding to the Lower Jurassic Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic–Jurassic extinction event, 201.3 Ma&nb ...

(Lower Pliensbachian, circa 186 million years old) rocks of

Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population of 47.2 million (as of 2020). The capital of the province is Kunming. The province borders the Chinese provinces ...

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 ...

. ''Dibothrosuchus'' was a small terrestrial crocodylomorph that probably had a keen sense of hearing, and thus was probably a vocal animal like modern crocodilians.

History and description

''Dibothrosuchus'' was named in 1965 by D.J. Simmons based on a partial skull and skeleton collected by Father Oehler of

Fu Jen Catholic University Fu Jen Catholic University (FJU, FJCU or Fu Jen; or ) is a private education, private Catholic university in Xinzhuang District, Xinzhuang, New Taipei City, Taiwan. The university was founded in 1925 in Beijing at the request of Pope Pius XI and ...

from

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

s near Huangchiatien. The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

is ''D. elaphros''. Additional remains of this genus were recovered in 1985 by a joint Chinese-US expedition. Fossils of ''Dibothrosuchus'' come from the Zhangjiawa Formation, being originally assigned to the Reds Beds of the

Lufeng Formation The Lufeng Formation (formerly Lower Lufeng Series) is a Lower Jurassic sedimentary rock formation found in Yunnan, China. It has two units: the lower Dull Purplish Beds/Shawan Member are of Hettangian age, and Dark Red Beds/Zhangjia'ao Member a ...

, thus being geologically younger than other crocodylomorphs from the region. At least three partial skeletons and two skulls are known, along with isolated bones. ''Dibothrosuchus'' was first described as an ornithosuchid

thecodont Thecodontia (meaning 'socket-teeth'), now considered an obsolete taxonomic grouping, was formerly used to describe a diverse "order" of early archosaurian reptiles that first appeared in the latest Permian period and flourished until the end of t ...

, but it was later reclassified as a sphenosuchid sphenosuchian. A second species, ''D. xingsuensis'', was named by Wu in 1986. After reexamination of the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

Wu and

Chatterjee Chatterjee (), also known as Chattopadhyay is a Bengali Hindu surname, used by the Kulin group of the Bengali Brahmin caste. Together with Banerjees, Mukherjees, Bhattacharjees, and Gangulys, Chatterjees form the Kulin Brahmins, the highest ...

found ''D. xingsuensis'' to be a synonym of ''D. elaphros'', leaving only one species in the genus. Dibothrosuchus elaphros

''Dibothrosuchus'' was not a large animal. From the tip of the snout to the

occipital condyle The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the Atlas (anatomy), atlas vertebra. The condyles are oval or reniform (kidney-shaped) in shape ...

, the skull of

IVPP The Institute of Vertebrate Paleontology and Paleoanthropology (IVPP; ) of China is a research institution and collections repository for fossils, including many dinosaur and pterosaur specimens (many from the Yixian Formation). As its name sugges ...

V 7907 is only long, and the body length of the individual is estimated as . In general form, ''Dibothrosuchus'' was a slender, long-tailed and long-limbed

quadruped Quadrupedalism is a form of locomotion in which animals have four legs that are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four legs is said to be a quadruped (fr ...

with a pointed snout. Unlike modern crocodilians, it was a terrestrial animal. The upper jaws had five small teeth per

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 ...

(snout-tip bones) and seventeen per

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 ...

, with a small hole between the maxilla and premaxilla for an enlarged tooth in the lower jaw to fit. At least eleven teeth were present on each side of the lower jaw. Several small ridges were present on the top of the skull. The various parts of the skull that supported hearing were well-developed, indicating that ''Dibothrosuchus'' had a keen sense of hearing and was probably a vocal animal that could communicate with others of the same genus, like modern crocodilians. Two rows of armor plates ran along the midline of the spine.

References

{{Taxonbar, from=Q744899 Early Jurassic reptiles of Asia Early Jurassic crocodylomorphs Terrestrial crocodylomorphs Prehistoric pseudosuchian genera