''Umzantsia'' is an extinct genus of limbed stegocephalians ('

tetrapod Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...

s', in the broad sense) from the Devonian 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 ...

. It contains a single species, ''Umzantsia amazana''. The genus is based on ~360 million year old skull and shoulder bones from the

Waterloo Farm lagerstätte The Waterloo Farm lagerstätte is a Famennian lagerstätte in South Africa that constitutes the only known record of a near-polar Devonian coastal ecosystem. History and discovery The Waterloo Farm Lagerstätte is an approximately 360 millio ...

, a locality on the south-eastern coast of South Africa. In the Devonian, this area of Gondwana was located within the

Antarctic Circle The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. So ...

. Together with the find of '' Tutusius umlambo'' from the same locality, this provides the first evidence that Devonian limbed vertebrates were not restricted to the

tropics The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referr ...

as was formerly believed, and suggests that they may have been global in distribution. Waterloo Farm fossils have been metamorphosed and intensely flattened, with the bone tissue replaced by secondary metamorphic mica that is partially altered to kaolinite and chlorite during uplift. They also provide the first evidence of Devonian limbed vertebrates from the continent of Africa, and only the second and third such taxa from Gondwana.

Etymology

The generic name is derived from

isiXhosa Xhosa (, ) also isiXhosa as an endonym, is a Nguni language and one of the official languages of South Africa and Zimbabwe. Xhosa is spoken as a first language by approximately 8.2 million people and by another 11 million as a secon ...

“uMzantsi”, meaning “south” (also “South Africa”), referring to its place of origin. The specific name “amazana” means “water ripples”, referring to its distinctive dermal ornament.

Description

Dermal bones of ''Umzantsia'' carry a distinctive ornamentation consisting of fine parallel ridges reminiscent of water ripples. This allows the identification of a number of cranial bones and a

cleithrum The cleithrum (plural cleithra) is a membrane bone which first appears as part of the skeleton in primitive bony fish, where it runs vertically along the scapula. Its name is derived from Greek κλειθρον = "key (lock)", by analogy with "cla ...

from one bedding plane which are probably derived from a single individual. The dermal ornamentation covers about 80% of the cleithrum of ''Umzantsia''; this fishlike characteristic contrasts with the un-ornamented cleithra of most other Devonian limbed vertebrates, suggesting a phylogenetic position transitional between proper limbed vertebrates (traditionally called tetrapods) and more basal taxa such as ''

Tiktaalik ''Tiktaalik'' (; Inuktitut ) is a monospecific genus of extinct sarcopterygian (lobe-finned fish) from the Late Devonian Period, about 375 Mya (million years ago), having many features akin to those of tetrapods (four-legged animals). It may ha ...

''. The only other contemporary 'tetrapod' with dermal ornamentation on the cleithrum is ''

Parmastega ''Parmastega'' is an extinct genus of tetrapod from the Devonian, dated to the earliest Famennian age (about 372 million years ago), in contrast to later fossils known from late Famennian (365–359 million years ago). These later fossils are c ...

,'' though ornamentation covers far less of the cleithrum in that taxon. The cleithrum tapers to a point anteroventrally and carries a single attachment scar for the

scapulocoracoid The scapulocoracoid is the unit of the pectoral girdle that contains the coracoid and scapula. The coracoid itself is a beak-shaped bone that is commonly found in most vertebrates with a few exceptions. The scapula is commonly known as the ''shoulde ...

, which extends along the anteroventral process, forms a v-shaped dorsal peak, and ends posteriorly in a projecting buttress. The blade of the cleithrum carries a semicircular posterodorsal extension. The jugal (cheek bone beneath the eye) extends anterior to the orbit and contacts the prefrontal. The jugal has a very short orbital margin and lacks a distinct dorsal postorbital process. A decayed lower jaw from a different individual of the same species was also described.

References

{{Taxonbar, from=Q61893422 Prehistoric tetrapods