''Youngina'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

diapsid Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years a ...

reptile from the

Late Permian Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

Beaufort Group ('' Tropidostoma''-'' Dicynodon'' zones) of the Karoo Red Beds of

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. It is bounded to the south by of coastline that stretch along the Atlantic Ocean, South Atlantic and Indian Oceans; to the ...

. This, and a few related forms, make up the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Younginidae, within the Order

Eosuchia Eosuchians are an extinct order of diapsid reptiles. Depending on which taxa are included the order may have ranged from the late Carboniferous to the Eocene but the consensus is that eosuchians are confined to the Permian and Triassic. Eosuchi ...

(proposed by Broom in 1914). Eosuchia, having become a

wastebasket taxon Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined ...

for many probably distantly-related primitive diapsid reptiles ranging from the Late Carboniferous to the

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, Romer proposed that it be replaced by

Younginiformes Younginiformes is a replacement name for the taxon Eosuchia, proposed by Alfred Romer in 1947. The Eosuchia having become a wastebasket taxon for many probably distantly-related primitive diapsid reptiles ranging from the late Carboniferous to ...

(that included Younginidae and the Tangasauridae, ranging from the

Permian The Permian ( ) is a geologic period and System (stratigraphy), stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last ...

to the

Triassic The Triassic ( ) is a geologic period and system (stratigraphy), system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago (Year#Abbreviations yr and ya, Mya), to the beginning of the Jurassic Period 201.36 ...

''Youngina'' is known from several specimens. Many of these were attributed to as separate genera and species (such as ''Youngoides'' and ''Youngopsis''), but it was later realized that they were not distinct from ''Y. capensis''. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

specimen of ''Youngina'' was described briefly in

1914 This year saw the beginning of what became known as World War I, after Archduke Franz Ferdinand of Austria, heir to the Austrian throne was Assassination of Archduke Franz Ferdinand, assassinated by Serbian nationalist Gavrilo Princip. It als ...

. The "''Youngoides romeri''" specimen was first attributed to ''Youngina'', but later given its eponymous and separate designation in a later paper. ''Acanthotoposaurus'' is also a junior synonym of ''Youngina''. ''Youngina'' was once thought to be closely related to ''

Acerosodontosaurus ''Acerosodontosaurus'' is an extinct genus of neodiapsid reptiles that lived during the Upper Permian of Madagascar. The only species of ''Acerosodontosaurus'', ''A. piveteaui'', is known from a natural mold of a single partial skeleton including ...

'', and more distantly to tangasaurids (''

Kenyasaurus ''Kenyasaurus'' is an extinct genus of basal (phylogenetics), basal tangasaurid known from the Early Triassic geological timescale, period of Coast Province, southeastern Kenya. It contains a single species, ''Kenyasaurus mariakaniensis''. Disco ...

'', ''

Hovasaurus ''Hovasaurus'' is an extinct genus of diapsid reptile belonging to the order Eosuchia. It lived in what is now Madagascar during the Late Permian and Early Triassic, being a survivor of the Permian–Triassic extinction event and the paleontolog ...

'', '' Thadeosaurus'', and ''

Tangasaurus ''Tangasaurus'' is an extinct genus of aquatic basal tangasaurid neodiapsid known from the Late Permian period (late Changhsingian stage) of Tanga, northeastern Tanzania. It contains a single species, ''Tangasaurus mennelli''. Discovery ''Ta ...

''), but the monophyly of has not been demonstrated in published analyses of diapsid reptiles, and it is likely this group is paraphyletic. ''

'' is probably closer to other former ', rather than being closely related to ''Youngina''. Below is a

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

from the analysis of Reisz ''et al.'' (2011) showing the phylogenetic position of ''Youngina'' among early diapsids: ''Youngina'' could have been a moderately sized early reptile (skull length < ), comparable to size to some medium-sized monitor lizards such as Gould's monitor. The braincase anatomy was redescribed in 2010, and ''Youngina'' shows a mosaic of features found in more primitive diapsids and more derived taxa such as archosauromorphs and lepidosauromorphs suggesting a non-orthogenetic evolution of these characters. Though the palatobasal articulation is open, it was probably immobile, similar to the skull of the

tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...

, contrary to some earlier claims made about the metakinetic mobility of basicranial joints in ''Youngina'' and other early diapsid reptiles.

References

{{Taxonbar, from=Q143325 Prehistoric neodiapsids Prehistoric reptile genera Lopingian reptiles of Africa Lopingian genera Permian South Africa Fossils of South Africa Fossil taxa described in 1914 Taxa named by Robert Broom