Youngosuchus
Encyclopedia
Youngosuchus is an extinct genus
of archosauriform from the Middle Triassic
of China
. The type species
is Y. sinensis. Y. sinensis was first described in 1973 as a new species of the erythrosuchid Vjushkovia
. In 1985, it was reassigned as its own genus of rauisuchid. Some more recent studies support the original classification of Youngosuchus sinensis as an erythrosuchid, but others still classify it as a rauisuchian.
, China. The skeleton, referred to as IVPP V 3239, includes a complete skull, cervical vertebrae, ribs, the pectoral girdle, and forelimbs. Youngosuchus has a large, deep skull with sharp recurved teeth. Osteoderm
s are not present on the skeleton, a possible indication that Youngosuchus did not have the body armor present in other early archosauriforms.
, better known as C.C. Young. Young described it as Vjushkovia sinensis, a third species of the erythrosuchid genus Vjushkovia. Erythrosuchids are basal
archosauriforms that are closely related to Archosauria, the group that includes living crocodile
s and bird
s. In 1985, Russian paleontologists N.N. Kalandadze and Andreii Sennikov erected Youngosuchus as a new genus for V. sinensis, naming it after Young. They considered the two other species of Vjushkovia to members of the erythrosuchid genus Garjainia, and reclassified Y. sinensis as a rauisuchid. Rauisuchids are more derived
than erythrosuchids because they lie within Archosauria, specifically within the clade
Crurotarsi
.
Youngosuchus lacks several common erythrosuchid features. The skull table of Youngosuchus is flat, while in erythrosuchids the same region is slightly depressed. The depression of erythrosuchids is a remnant of the pineal foramen that was present in more primitive reptiles. The lack of a depression in the skull table of Youngosuchus suggests that it belongs to a more derived group than erythrosuchids. Another difference between Youngosuchus and erythrosuchids can be seen in the antorbital fenestra, a hole in the skull in front of the eyes. In Youngosuchus, the fenestra is large and triangular, but lacks the depressed upper and front margins seen in the skulls of erythrosuchids.
The assignment of Youngosuchus to Rauisuchidae is not widely accepted. Paleontologist J. Michael Parrish kept Y. sinensis as a species of Vjushkovia in his 1992 study of erythrosuchids, and continued to recognize Vjushkovia as a valid taxon distinct from Garjainia. Sennikov, along with paleontologist David J. Gower
, rejected Parrish's conclusions in 2000 by considering V. triplocostata, the type species of Vjushkovia, a junior synonym of Garjainia prima. In his 2000 overview of rauisuchia
ns, Gower did not consider Y. sinensis to be a synonym of G. prima, instead suggesting that it was a rauisuchid.
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 archosauriform from the Middle Triassic
Middle Triassic
In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided. It spans the time between 245 ± 1.5 Ma and 228 ± 2 Ma...
of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. 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 Y. sinensis. Y. sinensis was first described in 1973 as a new species of the erythrosuchid Vjushkovia
Vjushkovia
Vjushkovia is an extinct genus of erythrosuchid archosauromorph....
. In 1985, it was reassigned as its own genus of rauisuchid. Some more recent studies support the original classification of Youngosuchus sinensis as an erythrosuchid, but others still classify it as a rauisuchian.
Description
Youngosuchus is known from a well-preserved skeleton recovered from the Kelamayi Formation in the Junggur Basin of XinjiangXinjiang
Xinjiang is an autonomous region of the People's Republic of China. It is the largest Chinese administrative division and spans over 1.6 million km2...
, China. The skeleton, referred to as IVPP V 3239, includes a complete skull, cervical vertebrae, ribs, the pectoral girdle, and forelimbs. Youngosuchus has a large, deep skull with sharp recurved teeth. Osteoderm
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...
s are not present on the skeleton, a possible indication that Youngosuchus did not have the body armor present in other early archosauriforms.
Classification
The skeleton of Youngosuchus was first described in 1973 by Chinese paleontologist Yang ZhongjianYang Zhongjian
Yang Zhongjian , courtesy name Keqiang , also known as C.C. Young, was one of China's foremost paleontologists. He has been called the 'Father of Chinese vertebrate paleontology'...
, better known as C.C. Young. Young described it as Vjushkovia sinensis, a third species of the erythrosuchid genus Vjushkovia. Erythrosuchids are 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:...
archosauriforms that are closely related to Archosauria, the group that includes living crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s and bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
s. In 1985, Russian paleontologists N.N. Kalandadze and Andreii Sennikov erected Youngosuchus as a new genus for V. sinensis, naming it after Young. They considered the two other species of Vjushkovia to members of the erythrosuchid genus Garjainia, and reclassified Y. sinensis as a rauisuchid. Rauisuchids are more 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...
than erythrosuchids because they lie within Archosauria, specifically within the 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...
Crurotarsi
Crurotarsi
The Crurotarsi are a group of archosauriformes, represented today by the crocodiles,...
.
Youngosuchus lacks several common erythrosuchid features. The skull table of Youngosuchus is flat, while in erythrosuchids the same region is slightly depressed. The depression of erythrosuchids is a remnant of the pineal foramen that was present in more primitive reptiles. The lack of a depression in the skull table of Youngosuchus suggests that it belongs to a more derived group than erythrosuchids. Another difference between Youngosuchus and erythrosuchids can be seen in the antorbital fenestra, a hole in the skull in front of the eyes. In Youngosuchus, the fenestra is large and triangular, but lacks the depressed upper and front margins seen in the skulls of erythrosuchids.
The assignment of Youngosuchus to Rauisuchidae is not widely accepted. Paleontologist J. Michael Parrish kept Y. sinensis as a species of Vjushkovia in his 1992 study of erythrosuchids, and continued to recognize Vjushkovia as a valid taxon distinct from Garjainia. Sennikov, along with paleontologist David J. Gower
David J. Gower
David J. Gower is a palaeontologist.Since 2004 he is a herpetology researcher at the Museum of Natural History in London.-External links:* *...
, rejected Parrish's conclusions in 2000 by considering V. triplocostata, the type species of Vjushkovia, a junior synonym of Garjainia prima. In his 2000 overview of rauisuchia
Rauisuchia
Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
ns, Gower did not consider Y. sinensis to be a synonym of G. prima, instead suggesting that it was a rauisuchid.