Youngina
Encyclopedia
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 Order Eosuchia
(proposed by Broom in 1924). Eosuchia, having become a dustbin for many probably distantly-related primitive diapsid reptiles ranging from the Late Carboniferous
to the Eocene
, Romer proposed that it be replaced by Younginiformes
(that included Younginidae and the Tangasauridae, ranging from the Permian
to the Triassic
).
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 specimen of Youngina was described briefly in the early 20th century. 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
, and more distantly to tangasaurids
(Kenyasaurus, Hovasaurus
, Thadeosaurus
, and Tangasaurus), but the monophyly of younginiforms has not been demonstrated in published analyses of diapsid reptiles, and it is likely this group is paraphyletic. Acerosodontosaurus
is probably closer to other former "younginiforms", rather than being closely related to Youngina.
Youngina could have been a moderately sized early reptile (skull length < 7 centimetres (2.8 in)), comparable to size to some medium-sized monitor lizards such as Gould's monitor
. There were likely no mobile articulations between the palate and braincase, similar to the skull of the tuatara
, contrary to some earlier claims made about the metakinetic mobility of basicranial joints in Youngina and other early diapsid reptiles.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of diapsid reptile from the Late Permian Beaufort Group
Beaufort Group
The Beaufort Group is the third of the main subdivisions of the Karoo Supergroup of geological strata in Southern Africa. It follows conformably after the Ecca Group and consists essentially of sandstones and shales, deposited in the Karoo Basin from the Middle Permian to the early part of the...
(Tropidostoma
Tropidostoma Assemblage Zone
The Tropidostoma Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Tropidostoma, a genus of dicynodont mammal-like reptile, whose fossils have been found in that structure....
-Dicynodon
Dicynodon Assemblage Zone
The Dicynodon Assemblage Zone is a geological stratum and a faunal zone of the Beaufort Group, of the South African Karoo. The name refers to Dicynodon, a genus of mammal-like reptile, that flourished in the Permian Period and whose fossils have been found in that structure....
zones) of the Karoo Red Beds of South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
. This, and a few related forms, make up the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Younginidae, within the Order Eosuchia
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....
(proposed by Broom in 1924). Eosuchia, having become a dustbin for many probably distantly-related primitive diapsid reptiles ranging from the Late Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
to the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
, Romer proposed that it be replaced by Younginiformes
Younginiformes
Younginiformes is a replacement name for the taxon Eosuchia, proposed by Alfred Romer in 1947.The Eosuchia having become rather a dustbin for many probably distantly-related primitive diapsid reptiles ranging from the late Carboniferous to the Eocene, Romer proposed that this be replaced by...
(that included Younginidae and the Tangasauridae, ranging from the Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
to the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
).
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 specimen of Youngina was described briefly in the early 20th century. 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
Acerosodontosaurus is an extinct genus of diapsid reptile....
, and more distantly to tangasaurids
Tangasauridae
Tangasauridae is a family of eosuchian 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 temnospondyls, rhynchosaurs, and gomphodont...
(Kenyasaurus, Hovasaurus
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....
, Thadeosaurus
Thadeosaurus
Thadeosaurus is an extinct genus of diapsid reptile belonging to the Order Eosuchia. Fossils have been found in Madagascar, and date to the late Permian period....
, and Tangasaurus), but the monophyly of younginiforms has not been demonstrated in published analyses of diapsid reptiles, and it is likely this group is paraphyletic. Acerosodontosaurus
Acerosodontosaurus
Acerosodontosaurus is an extinct genus of diapsid reptile....
is probably closer to other former "younginiforms", rather than being closely related to Youngina.
Youngina could have been a moderately sized early reptile (skull length < 7 centimetres (2.8 in)), comparable to size to some medium-sized monitor lizards such as Gould's monitor
Sand goanna
The Sand goanna is a large Australian monitor lizard - also known as Gould's monitor, the Sand monitor, or Racehorse goanna....
. There were likely no mobile articulations between the palate and braincase, similar to the skull of the tuatara
Tuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
, contrary to some earlier claims made about the metakinetic mobility of basicranial joints in Youngina and other early diapsid reptiles.