Proceratosauridae is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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 ...

tyrannosauroid Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinen ...

theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...

s from the Middle Jurassic to the Early Cretaceous.

Distinguishing features

Unlike the advanced

tyrannosaurids Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera i ...

but similar to primitive

tyrannosauroids Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...

like '' Dilong'', proceratosaurids were generally small (with the exception of the possible proceratosaurids ''

Yutyrannus ''Yutyrannus'' (meaning "feathered tyrant") is a genus of proceratosaurid tyrannosauroid dinosaur which contains a single known species, ''Yutyrannus huali''. This species lived during the early Cretaceous period in what is now northeastern Ch ...

'' and ''

Sinotyrannus ''Sinotyrannus'' (meaning "Chinese tyrant") is an extinct genus of large tyrannosauroid theropod dinosaurs known from the Early Cretaceous Jiufotang Formation of Liaoning, China. This genus contains a single species, ''Sinotyrannus kazuoensis'' ...

'') and had fairly long, three-fingered arms capable of grasping prey. In comparison to other members of Tyrannosauroidea, proceratosaurids can be distinguished by the following features according to phylogenetic analyses by Averianov ''et al''. (2010) and Loewen ''et al''. (2013) : * A sagittal cranial crest formed by the

nasals In phonetics, a nasal, also called a nasal occlusive or nasal stop in contrast with an oral stop or nasalized consonant, is an occlusive consonant produced with a lowered velum, allowing air to escape freely through the nose. The vast majorit ...

starting at the junction of 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 ...

and nasals. * Extremely elongated external nares, with posterior margins posterior to the anterior margin of the antorbital fossa and maxillary fenestrae. * A short ventral margin of the premaxilla. * The depth of the antorbital fossa ventral to the

antorbital fenestra An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with Archosauriformes, archosauriforms, first appearing during the Triassic Period. Among Extant ...

being much greater than that of 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 ...

below the antorbital fossa. * A ventrally concave

ischium The ischium (; : is ...

. * A convex tubercule on the anterior margin of the pubis just ventral to contact with the ilium. * A short and shallow concave step on the anterior margin of the maxilla.

Classification

The family belongs to the

tyrannosaur Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...

lineage. It was first named in 2010 by Oliver Rauhut and colleagues in their re-evaluation of the

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

, ''

Proceratosaurus ''Proceratosaurus'' ( ) is a genus of theropod dinosaur that lived during the Middle Jurassic in what is now England. The holotype and only known specimen consists of a mostly complete skull with an accompanying lower jaw and a bone, found nea ...

''. Their study supported the idea that ''Proceratosaurus'' is a coelurosaur, a

, and most closely related to the Chinese tyrannosauroid ''

Guanlong ''Guanlong'' (冠龍) is a genus of extinct proceratosaurid tyrannosauroid dinosaur from the Late Jurassic of China. The taxon was first described in 2006 by Xu Xing ''et al.'', who found it to represent a new taxon related to ''Tyrannosaurus' ...

''. They defined the

containing these two dinosaurs as all theropods closer to ''Proceratosaurus'' than to ''Tyrannosaurus'', ''

Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...

'', ''

Compsognathus ''Compsognathus'' (; Ancient Greek, Greek ''kompsos''/κομψός; "elegant", "refined" or "dainty", and ''gnathos''/γνάθος; "jaw") is a genus of small, bipedalism, bipedal, carnivore, carnivorous theropoda, theropod dinosaur. Members o ...

'', ''

Coelurus ''Coelurus'' ( ) is a genus of coelurosaurian dinosaur from the Late Jurassic period (mid-late Kimmeridgian faunal stage, 155–152 million years ago). The name means "hollow tail", referring to its hollow tail vertebrae (Greek κοῖλ� ...

'', ''

Ornithomimus ''Ornithomimus'' (; "bird mimic") is a genus of ornithomimid theropod dinosaurs from the Campanian and Maastrichtian ages of Late Cretaceous Western North America. ''Ornithomimus'' was a swift, bipedal dinosaur which fossil evidence indicates wa ...

'', or ''

Deinonychus ''Deinonychus'' ( ; ) is a genus of Dromaeosauridae, dromaeosaurid Theropoda, theropod dinosaur with one described species, ''Deinonychus antirrhopus''. This species, which could grow up to long, lived during the early Cretaceous Period (ge ...

''. Later studies included the Russian ''

Kileskus ''Kileskus'' (meaning ''lizard'' in the Khakas language) is a genus of tyrannosauroid dinosaur known from partial remains found in Middle Jurassic (Bathonian stage) Itat Formation of Sharypovsky District, Krasnoyarsk Krai (Russia). Fossils r ...

'' and the Chinese ''

'' in the family. Recently, Proceratosauridae has been found to include ''Proceratosaurus'', ''Guanlong'', ''Kileskus'', ''Sinotyrannus'', and the genera ''Stokesosaurus'', ''Juratyrant'', and ''Dilong'' previously recognized as non-proceratosaurid tyrannosauroids. In their re-evaluation of ''

'', Rauhut ''et al.'' stated that tooth taxa from the Late Jurassic and Early Cretaceous previously assigned to the

dromaeosaurid Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...

subfamily Velociraptorinae may instead be proceratosaurid in nature, due to the similarity between the teeth of the two groups and the fact that velociraptorines are otherwise unknown from the fossil record until the Late Cretaceous. This would mean that ''

Nuthetes ''Nuthetes'' is the name given to a genus of coelurosaurian theropod dinosaur, either a dromaeosaurid or a tyrannosauroid, known only from fossil teeth and jaw fragments found in rocks of the middle Berriasian (Early Cretaceous) age in the Chert ...

'' and other dubious genera are potential proceratosaurids. Below is the cladogram by Loewen ''et al.'' in 2013. Proceratosaurus holotype

An analysis by Brusatte ''et al.'' in 2016 provides both parsimony and

Bayesian Thomas Bayes ( ; c. 1701 – 1761) was an English statistician, philosopher, and Presbyterian minister. Bayesian ( or ) may be either any of a range of concepts and approaches that relate to statistical methods based on Bayes' theorem Bayes ...

phylogenetic analyses, with ''

'' being placed within Proceratosauridae as a sister taxon to ''Sinotyrannus'' and ''

Juratyrant ''Juratyrant'' (meaning "Jurassic tyrant") is a tyrannosauroid dinosaur genus from the late Jurassic period (early Tithonian age) of England. The genus contains a single species, ''Juratyrant langhami'', which was once classed as a species of '' ...

'' and ''

Stokesosaurus ''Stokesosaurus'' (meaning "Stokes' lizard") is a genus of small (around in length), carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States. History From 1960 onwards Utah geologist William ...

'' being placed as more advanced tyrannosauroids in each instance. The Bayesian analysis is shown below. Below is a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

from Naish and Cau (2022):.

References

{{Taxonbar, from=Q134304 Dinosaur families

Distinguishing features

Classification

See also

References