Euparkeriidae 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 ...

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 ...

of small carnivorous archosauriforms which lived from the Early

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

to the Middle Triassic (

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

). While most other early archosauriforms walked on four limbs, euparkeriids were probably facultative

bipeds Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) Limb (anatomy), limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from ...

that had the ability to walk on their hind limbs at times. The most well known member of Euparkeriidae is the species '' Euparkeria capensis'', which was named by paleontologist

Robert Broom Robert Broom Fellow of the Royal Society, FRS FRSE (30 November 1866 6 April 1951) was a British- South African medical doctor and palaeontologist. He qualified as a medical practitioner in 1895 and received his DSc in 1905 from the University ...

from the Karoo Basin of

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

in 1913 and is known from several nearly complete skeletons. The family name was first proposed by German paleontologist Friedrich von Huene in 1920; Huene classified euparkeriids as members of

Pseudosuchia Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

, a traditional name for crocodilian-line

archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

s from the Triassic (Pseudosuchia means "false crocodiles"). However,

phylogenetic 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 dat ...

analyses performed in the 21st century place Euparkeriidae as a group of

Archosauriformes Archosauriformes (Ancient Greek, Greek for 'ruling lizards', and Latin for 'form') is a clade of diapsid reptiles encompassing Archosaur, archosaurs and some of their close relatives. It was defined by Jacques Gauthier (1994) as the clade stemmin ...

, a position outside Pseudosuchia and close to the ancestry of both crocodile-line archosaurs and bird-line archosaurs (which include

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 and

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

s). However, they are probably not direct ancestors of archosaurs. Several other species apart from ''Euparkeria'' have been assigned to the family, but many are dubious or have been determined to have been placed in the family incorrectly. One study has suggested that Euparkeriidae may not represent a true evolutionary grouping or

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 ...

. Instead, the family may represent an

evolutionary grade A grade is a taxon united by a level of morphological or physiological complexity. The term was coined by British biologist Julian Huxley, to contrast with clade, a strictly phylogenetic unit. Phylogenetics The concept of evolutionary grades ...

of small archosauriforms (making it

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

) or a group of species that each evolved small body sizes through

evolutionary convergence Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

(making it

polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...

). However, other studies consider the family valid, albeit difficult to diagnose. Euparkeriidae is defined as the most inclusive clade containing ''Euparkeria capensis'' but not ''

Crocodylus niloticus The Nile crocodile (''Crocodylus niloticus'') is a large crocodilian native to freshwater habitats in Africa, where it is present in 26 countries. It is widely distributed in sub-Saharan Africa, occurring mostly in the eastern, southern, and ce ...

'' (the nile crocodile) or ''

Passer domesticus The house sparrow (''Passer domesticus'') is a bird of the sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pale brown and grey, ...

'' (the house sparrow).

Description

Euparkeriids, as well as several other advanced archosauriformes or early archosaurs ('' Dorosuchus'', '' Dongusuchus'', gracilisuchids) were lightly built and agile terrestrial carnivores which likely competed with

cynodont Cynodontia () is a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 Megaannum, mya), and extensively diversified after the Permian–Triassic extinction event. Mammals are cynodonts, as are their extin ...

s for food. They had gracile but well-

ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

femurs which were capable of, but not well adapted for, bipedalism and

cursorial A cursorial organism is one that is adapted specifically to run. An animal can be considered cursorial if it has the ability to run fast (e.g. cheetah) or if it can keep a constant speed for a long distance (high endurance). "Cursorial" is often ...

ity. Most taxa which can be assigned to Euparkeriidae are incomplete, and shared

synapomorphies In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...

(defining characteristics) are difficult to assess between members of the family. The only uniting trait observable in ''Euparkeria'', '' Halazhaisuchus'', and '' Osmolskina'' (the only genera believed to be valid euparkeriids) relates to their

osteoderm Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct amph ...

s. Euparkeriids had two rows of small keeled osteoderms with characteristically pointed anterior processes, although some osteoderms referred to ''Osmolskina'' are shorter and blunter than those characteristic of the other genera. ''Euparkeria'' and ''Osmolskina'' are united by several more traits which may characterize the family but are unknown in the rather incomplete ''Halazhaisuchus''. These include an anterolaterally opening pit on the front of the maxilla, four premaxillary teeth, two exits for the

hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated b ...

on the exoccipital, and separate interparietals (or postparietals). ''Osmolskina'', ''Halazhaisuchus'', and the dubious (but likely euparkeriid) '' "Turfanosuchus" shageduensis'' form a clade within Euparkeriidae united by the presence of a pronounced tuber on the

scapula The scapula (: scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on either side ...

for the m. triceps.

Classification

Besides ''Euparkeria'', the most completely known putative euparkeriid is ''Osmolskina czatkowicensis''. Several hundred isolated bones have been found in

Poland Poland, officially the Republic of Poland, is a country in Central Europe. It extends from the Baltic Sea in the north to the Sudetes and Carpathian Mountains in the south, bordered by Lithuania and Russia to the northeast, Belarus and Ukrai ...

and referred to this genus. A 2010

analysis found that ''Osmolskina'' was more distantly related to ''Euparkeria'' than had previously been suspected, although in 2016 it was reinstated as a member of the family. '' Dorosuchus neoetus'', a Russian archosauriform known mostly by hind limb bones, has also been proposed as a possible euparkeriid, but has subsequently been placed outside the family. Three species from

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 ...

have also been proposed as euparkeriids: ''Halazhaisuchus qiaoensis'', ''"Turfanosuchus" shageduensis'', and '' Wangisuchus tzeyii.'' Sookias ''et al.'' (2014) analysed many species that have been considered euparkeriids, finding many outside the group while recovering a slightly supported monophyletic family including ''" Turfanosuchus"'' ''shageduensis'', ''Halazhaisuchus'', and ''Euparkeria''. However, ''"Turfanosuchus"'' ''shageduensis'' and ''Wangisuchus'' were both also found to be ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium,'' it may be impossible to determine whether a ...

''. Their

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 ...

is shown below. Sookias (2016) also performed another study on Euparkeriidae using both parsimony and Bayesian analysis. This study found ''Halazhaisuchus'', ''Osmolskina'', and ''"Turfanosuchus" shageduensis'' to all be valid members of a monophylectic (albeit poorly supported) Euparkeriidae, and more closely related to each other than to ''Euparkeria''. ''Dorosuchus'' was placed outside Euparkeriidae. The strict consensus tree of the parsimony analysis is given below: The Bayesian analysis resolved the trichotomy within Euparkeriidae and recovered ''Halazhaisuchus'' and '' Osmolskina'' as sister taxa. However, other parts of the tree lost much resolution creating a large polytomy of large groups above Erythrosuchidae. This analysis is given below:

References

External links

Euparkeriidae
from Palaeos.com (technical) {{Taxonbar, from=Q946970 Archosauriformes Prehistoric reptile families Triassic reptiles Early Triassic first appearances Middle Triassic extinctions Taxa named by Friedrich von Huene