''Youngina'' (named after John Young (1823–1900)) 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 ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 earliest traditionally identified diapsids, the araeosc ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

from the

Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...

Beaufort Group The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup in South Africa. It is composed of a lower Adelaide Subgroup and an upper Tarkastad Subgroup. It follows conformably after the Ecca Group and unconformably under ...

(''

Tropidostoma ''Tropidostoma'' is a medium-sized herbivorous oudenodontid dicynodont therapsid that lived during the Late Permian (Lopingian) period in South Africa. The first ''Tropidostoma'' fossil was described by Harry Govier Seeley in 1889. Later two su ...

''-'' 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. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

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

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 ...

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 purpose of classifying organisms that do not fit anywhere else. They are typically defined by e ...

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

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

to the

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

, Romer proposed that it be replaced by

Younginiformes Younginiformes is a group of diapsid reptiles known from the Permian-Triassic of Africa and Madagascar. It has been used as a replacement for " Eosuchia". Younginiformes (including '' Acerosodontosaurus'', '' Hovasaurus'', '' Kenyasaurus'', '' Ta ...

(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 251.902 Mya. It is the s ...

to the

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 ...

Taxonomy

''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 (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen of ''Youngina'', discovered by

Broom A broom (also known as a broomstick) is a cleaning tool, consisting of usually stiff fibers (often made of materials such as plastic, hair, or corn husks) attached to, and roughly parallel to, a cylindrical handle, the broomstick. It is thus a ...

himself, was described briefly in

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

. 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 In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of ''Youngina''.

Description

''Youngina'' was a relatively small reptile, with a skull length of and a total body length of . The

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, brain-pan, or brainbox, is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calv ...

anatomy was redescribed in 2010. ''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 The tuatara (''Sphenodon punctatus'') is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephal ...

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

Phylogeny

''Youngina'' was once thought to be closely related to ''

Acerosodontosaurus ''Acerosodontosaurus'' is an Extinction, extinct genus of Neodiapsida, neodiapsid Reptile, reptiles that lived during the Late Permian of Madagascar. The only species of ''Acerosodontosaurus'', ''A. piveteaui'', is known from a natural wiktionary ...

'', 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 basal diapsid reptile. 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 paleontologically youngest member of t ...

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

Tangasaurus ''Tangasaurus'' is an extinct genus of aquatic animal, aquatic basal (phylogenetics), basal tangasaurid neodiapsid known from the Late Permian geological timescale, period (late Changhsingian stage) of Tanga Region, Tanga, northeastern Tanzania. ...

''), 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 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 the analysis of Reisz ''et al.'' (2011) showing the

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 ...

position of ''Youngina'' among early diapsids:

References

External links

* {{Taxonbar, from=Q143325 Diapsids 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