Dibothrosuchus
Encyclopedia
Dibothrosuchus is a genus
of sphenosuchia
n, a type of basal
crocodylomorph
, the clade
that comprises the crocodilia
ns and their closest kin. It is known from several partial skeletons and skulls. These fossils were found in Lower Jurassic rocks of Yunnan
, China
. Dibothrosuchus was a small terrestrial crocodylomorph that probably had a keen sense of hearing
, and thus was likely a vocal animal like modern crocodilians.
a partial skull and skeleton collected by Father Oehler of Fu Jen Catholic University
from mudstone
s near the village of Dawa. The type species
is D. elaphros. Additional remains of this genus were recovered in 1985 by a joint Chinese-US expedition. Fossils of Dibothrosuchus come from the lower Lufeng Formation
(the Dark Red Beds). At least three partial skeletons and two skulls are known, along with isolated bones. Dibothrosuchus was first described as an ornithosuchid
thecodont
, 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
Wu and Chatterjee
found D. xingsuensis to be a synonym of D. elaphros, leaving only one species in the genus.
Dibothrosuchus was not a large animal. From the tip of the snout to the occipital condyle
, the skull of IVPP
V 7907 is only 164 millimetres (6.5 in) long, and the body length of the individual is estimated as 1.3 metres (4.3 ft). In general form, Dibothrosuchus was a slender, long-tailed and long-limbed quadruped
with a pointed snout. Unlike modern crocodilians, it was a terrestrial animal. The upper jaws had five small teeth per premaxilla
(snout-tip bones) and seventeen per maxilla
, 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 likely was 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.
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 sphenosuchia
Sphenosuchia
Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Late Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, which include all living crocodilians.-Stratigraphic...
n, a type of basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
crocodylomorph
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
, the clade
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...
that comprises the crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
ns and their closest kin. It is known from several partial skeletons and skulls. These fossils were found in Lower Jurassic rocks of Yunnan
Yunnan
Yunnan is a province of the People's Republic of China, located in the far southwest of the country spanning approximately and with a population of 45.7 million . The capital of the province is Kunming. The province borders Burma, Laos, and Vietnam.Yunnan is situated in a mountainous area, with...
, 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...
. Dibothrosuchus was a small terrestrial crocodylomorph that probably had a keen sense of hearing
Hearing (sense)
Hearing is the ability to perceive sound by detecting vibrations through an organ such as the ear. It is one of the traditional five senses...
, and thus was likely a vocal animal like modern crocodilians.
History and description
Dibothrosuchus was named in 1965 by D.J. Simmons 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...
a partial skull and skeleton collected by Father Oehler of Fu Jen Catholic University
Fu Jen Catholic University
Fu Jen Catholic University is a co-educational Catholic university located in Xinzhuang District, New Taipei City, Republic of China...
from mudstone
Mudstone
Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...
s near the village of Dawa. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is D. elaphros. Additional remains of this genus were recovered in 1985 by a joint Chinese-US expedition. Fossils of Dibothrosuchus come from the lower Lufeng Formation
Lower Lufeng Series
The Lower Lufeng Series is a Lower Jurassic sedimentary rock formation found in Yunnan, China. It has two units: the lower Dull Purplish Beds are of Hettangian age, and Dark Red Beds are of Sinemurian age. It is known for its fossils of early dinosaurs...
(the Dark Red Beds). At least three partial skeletons and two skulls are known, along with isolated bones. Dibothrosuchus was first described as an ornithosuchid
Ornithosuchidae
Ornithosuchidae is an extinct family of reptiles from the Triassic period that were distantly related to crocodilians. They are classified as crurotarsan archosaurs. Ornithosuchids were quadrupedal and facultatively bipedal, meaning they had the ability to walk on two legs for short periods of time...
thecodont
Thecodont
Thecodont , now considered an obsolete term, was formerly used to describe a diverse range of early archosaurs that first appeared in the Latest Permian and flourished until the end of the Triassic period...
, 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
Holotype
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...
Wu and Chatterjee
Sankar Chatterjee
Sankar Chatterjee is a paleontologist, and is the Paul W. Horn Professor of Geosciences at Texas Tech University and Curator of Paleontology at the Museum of Texas Tech University. He earned his Ph. D. from the University of Calcutta in 1970 and was a Post-doctoral Fellow at the Smithsonian...
found D. xingsuensis to be a synonym of D. elaphros, leaving only one species in the genus.
Dibothrosuchus was not a large animal. From the tip of the snout to the occipital condyle
Occipital condyle
The occipital condyles are undersurface facets of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra....
, the skull of IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V 7907 is only 164 millimetres (6.5 in) long, and the body length of the individual is estimated as 1.3 metres (4.3 ft). In general form, Dibothrosuchus was a slender, long-tailed and long-limbed quadruped
Quadruped
Quadrupedalism is a form of land animal locomotion using four limbs or legs. An animal or machine that usually moves in a quadrupedal manner is known as a quadruped, meaning "four feet"...
with a pointed snout. Unlike modern crocodilians, it was a terrestrial animal. The upper jaws had five small teeth per 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....
(snout-tip bones) and seventeen per 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...
, 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 likely was a vocal animal that could communicate with others of the same genus, like modern crocodilians. Two rows of armor plates
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...
ran along the midline of the spine.