Younginidae is an extinct

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 ...

neodiapsid Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade ...

reptiles 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, ...

and

Early Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is ...

. In a

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...

context, younginids are near the base of the

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...

Neodiapsida Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade S ...

. Younginidae includes the species ''

Youngina capensis ''Youngina'' is an extinct genus of diapsid reptile from the Late Permian Beaufort Group ('' Tropidostoma''-''Dicynodon'' zones) of the Karoo Red Beds of South Africa. This, and a few related forms, make up the family Younginidae, within the Ord ...

'' from the Late Permian of

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

and '' Thadeosaurus colcanapi'' from the Late Permian and Early Triassic of

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

. '' Heleosuchus griesbachi'' from the Late Permian of South Africa may also be a member of the family. Younginidae was traditionally assigned to Eosuchia, an order containing an assemblage of basal diapsids now thought to represent an evolutionary grade rather than a true clade. In 1945

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

Alfred Romer Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution. Biography Alfred Romer was born in White Plains, New York, the son of Harry Houston Romer an ...

reclassified Younginidae within a new group,

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 ...

, grouping it with the families

Tangasauridae Tangasauridae is a family of diapsids. Specimens have been found that are of Late Permian to Early Triassic in age from the Sakamena Group of western Madagascar. They lived alongside other taxa present from the Sakamena Group, including temnos ...

and

Prolacertidae Prolacertidae is an extinct family of archosauromorph reptiles that lived during the Early Triassic epoch. It was named in 1935 by the British palaeontologist Francis Rex Parrington to include the species ''Prolacerta broomi'' of South Africa ...

. Romer considered Younginidae to include many genera that are no longer classified as younginids: ''

Paliguana ''Paliguana'' is an extinct genus of lizard-like lepidosauromorph reptile from the earliest Triassic Katberg Formation (Beaufort Group) in the upper ''Lystrosaurus'' Assemblage Zone of South Africa South Africa, officially the Republic ...

'', '' Palaegama'', and ''

Saurosternon ''Saurosternon'' is an extinct genus of neodiapsid reptile from the Late Permian of South Africa. It is based on a partial skeleton split between two slabs of sandstone from the ''Daptocephalus'' Assemblage Zone. ''Saurosternon'' was one of th ...

'' are now considered basal lepidosauromorphs, '' Galesphyrus'' and '' Heleosuchus'' are diapsids of uncertain affinities (''

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

''), '' Heleophilus'' is now a millerettid, and '' Heleosaurus'' is now thought to be a

varanopid Varanopidae is an extinct family of amniotes that resembled monitor lizards and may have filled a similar niche, hence the name. Typically, they are considered synapsids that evolved from an '' Archaeothyris''-like synapsid in the Late Carbonifer ...

synapsid. Like Eosuchia, Younginiformes is no longer considered valid; for example, the phylogenetic analysis of Reisz ''et al.'' place younginids close to

Sauria Sauria is the clade containing the most recent common ancestor of archosaurs (such as crocodilians, dinosaurs, etc.) and lepidosaurs ( lizards and kin), and all its descendants. Since most molecular phylogenies recover turtles as more closely ...

, the clade including the still-living

archosauromorph Archosauromorpha ( Greek for "ruling lizard forms") is a clade of diapsid reptiles containing all reptiles more closely related to archosaurs (such as crocodilians and dinosaurs, including birds) rather than lepidosaurs (such as tuataras, l ...

and lepidosauromorph reptiles, while the younginiform family Tangasauridae takes a more basal position in Neodiapsida. 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 that analysis:

References

{{Taxonbar, from=Q8058609 Prehistoric reptile families Prehistoric reptiles of Africa Lopingian first appearances Early Triassic extinctions Prehistoric neodiapsids