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Doragnathus Дорагнат
Doragnathus

Genus: Doragnathus SMITHSON, 1980
Etymology:In reference to the Dora Opencast site, and gnathus
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Species: D.woodi SMITHSON, 1980
Etymology: The animal is named after Mr. Stanley Wood, who discovered the bonebed at the Dora Opencast Site which has yielded the majority of the material attributed to Doragnathus.

Holotype:NUZ 77.5.26 - Incomplete left ramus of lower jaw.

Locality:Dora Opencast Site, Cowdenbeath, Fife Province, Scotland, Northern United Kingdom.

Horizon: Dora Bone Bed, Limestone Coal Group.

Age:Lower Lower Namurian, Lower Silesian Series, Pendleian Stage, Serpukhovian Epoch, Early Carboniferous (Early Late Mississippian).
Note: Localized seatrock, beneath a coal seam below the Lochgelly Blackband Ironstone, upper part of the Limestone Coal Group.

Referred Material: RSM GY 1975.5.3: Fragmentary lower jaw.

RSM GY 1881.43.24: Fragmentary lower jaw of a small individual.

RSM GY 1881.107.51: Fragmentary lower jaw.

NUS 78.1.26: Left premaxilla.

NUZ 77.8.28: Maxilla.

Locality: Pitcorthie, Scotland, Northern United Kingdom.

Age: Carboniferous.

Material: RSM GY 1881.43.24: Fragmentary maxilla.

****

MILNER, SMITHSON, MILNER, COATES & ROLFE 1986
Locality: Dora opencast site near Cowdenbeath, Fife Province, Scotland, Northern United Kingdom.

Horizon: Dora Bone Bed, Limestone Coal Group.

Age: Lower Lower Namurian, Lower Silesian Series, Pendleian Stage, Serpukhovian Epoch, Early Carboniferous (Early Late Mississippian).
Note: Localized seatrock, beneath a coal seam below the Lochgelly Blackband Ironstone, upper part of the Limestone Coal Group.

Material: Fragmentary remains of at least 20 individuals.

****

SMITHSON, 1985

Locality: Locality 2, Inchkeith, Fifth or Fourth, Fife Province, Scotland, Northern United Kingdom.

Horizon: ‘Middle’ Oil Shale Group.

Age: Asbian Stage, Upper Middle Visean Epoch, Middle Dinantian series, Gzelian Epoch, Early Carboniferous (Middle Mississippian).

Material: ?

****

Locality: Ramsay colliery, Loanhead, Edinburgh, mid-Lothian Province, Scotland, Northern United Kingdom.

Horizon: Rumbles Ironstone/Burghlee Ironstone, Limestone Group.

Age: Lower Lower Namurian, Lower Silesian Series, Pendleian Stage, Serpukhovian Epoch, Early Carboniferous (Early Late Mississippian).

Material: MCZ 1511:

****

Locality: Niddrie Colliery, Niddrie, Edinburgh, mid-Lothian Province, Scotland, Northern United Kingdom.

Horizon: Rumbles Ironstone/Burghlee Ironstone, Limestone Group.

Age: Lower Lower Namurian, Lower Silesian Series, Pendleian Stage, Serpukhovian Epoch, Early Carboniferous (Early Late Mississippian).

Material: Not given:

****

Diagnosis:Labyrinthodont amphibian with a long, shallow lower jaw which terminates with a distinct rctroarticular process; small Meckelian fenestra at the mesial exposure of the splenial/post splcnial suture; denlary with room for more than eighty closely spaced, strongly incurved teeth, labyrinthine unfolding of enamel found only below the margin of the gums; a row of slim needle-like replaceable teeth on the coronoid series.

Comments:It was assigned to Trimerorhachidae by Carroll (1988).


Cranial remains of a labyrimhodont amphibian Doragnaihia waodi gen. et sp. nov.. from localities in the Visean and Namurian of the Scottish Carboniferous, are described. The structure of the lower jaw resembles that of the earliest known Amphibia, but its dentition is unusual, comprising large numbers of strongly incurved, closely spaced marginal teeth together with a row of small needle-like coronoid teeth. The relationships of Doragnathus are discussed. A specimen of Doragnathus from Pitcorthie represents the earliest recorded labyrimhodont in the British Carboniferous.

Thh Scottish Midland Valley is one of the few areas in the world from which fossil Amphibia have been found in Carboniferous sediments older than those equivalent in age to the British Coal Measures (Westphalian and Stephanian). Thirteen pre-Coal Measure genera have so far been described from a total of eleven Scottish localities. Most discoveries were made in the latter half of the last century, but recently a diverse amphibian fauna was discovered in a bone bed at the Dora Opencast Site, near Cowdenbcath. Fife (Andrews, Browne. Panchen. and Wood 1977: Smithson. in press). With the exception of an almost complete skeleton of Crassigyrinus SCOtiCUS (Panchen. in press) the Cowdenbeath fauna is represented by dissociated skeletal elements of at least six amphibian genera. The most common of these is a hitherto undescribed labyrimhodont represented by a large number of incomplete jaw specimens. The new form has also been found at Pitcorthie and Niddrie (Smithson, in press) and recently by Mr. Stanley Wood and the author on the island of Inchkeith. in the Firth of Forth.

Labyrinthodonts are rare components of the Scottish Lower Carboniferous amphibian assemblage, and until recently they had been recorded at only three of the eight Lower Carboniferous localities. The recognition that a jaw specimen from Pitcorthie in the collection of the Royal Scottish Museum was that of a labyrimhodont and not, as had previously been thought, a lepospondyl. and the discovery of similar material on the Island of Inchkeith, has improved this position. Although these new specimens are incomplete and poorly preserved, material from the Upper Carboniferous deposits at Cowdenbcath and Niddrie allows a description of a number of aspects of the cranial anatomy of the new labyrimhodont to be given.

The fossiliferous deposits on the island of Inchkeith and at Pitcorthie occur in strata of Visean age. The middle of the exposed sequence on Inchkeith is thought to be equivalent to the horizon of the Burdiehousc Limestone (Davis 1936). The fossiliferous sediments at Pitcorthie almost certainly occur within the Anstruther Beds(Forsyth and Chisholm 1973). These lie below the Cuniger Rock Marine Band which has been placed, on palynological evidence, well below the Burdichouse Limestone (Neves el at. 1973). Thus the amphibian remains from Pitcorthie are older than those from the Burdiehouse Limestone, and the labyrinthodonl remains are the earliest recorded in the British Carboniferous.

Where necessary material was prepared with a dental mallet and industrial 'Airbrasivc' unit, and a solution of "Perspex' dissolved in chloroform was used to repair breaks in specimens.



References:
Smithson, T. R., 1980, A new Labyrinthodont Amphibian from the Carboniferous of Scotland: Paleontology, v. 23, part 4, p. 915-923.

Smithson, T. R., 1985, Scottish Carboniferous amphibian localities: Scottish Journal of Geology, v. 21, n. 2, p. 123-142.

Milner, A. R., Smithson, T. R., Milner, A. C., Coatees, M. I., and Rolfe, W. D. I., 1986, The Search for early Tetrapods: Modern Geology, v. 10, p. 1-28.

Carroll. R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York 1-698


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Категория: Labyrinthodontia Лабиринтодонты | Добавил: dinoweb (2013-07-16) W
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