Labidosaurikos meachami
From Palaeos
Labidosaurikos meachami is a large, multiple-tooth-rowed captorhinid. It is the basalmost member of the subfamily Moradisaurinae. It is known from one single, however almost complete and virtually perfectly preserved skull coming from Lower Permian terrestrial deposits of central Oklahoma.
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Scientific History
L. meachami has been discovered as early as in 1939 but has not been named and introduced to paleontology until 1950. Finally a detailed description of the skull has been published in 1995.
Skull
The heavily ornamented skull of L. meachami measures about 28 cm in length. Given that the trunk length in Captorhinus is approximately 3.6-fold the skull length, the overall body length in L. meachami was as much as 1.3 m. L. meachami shows almost the whole range of features which define the moradisaurines. Its snout is, compared to the posterior part of the skull, very narrow. Its dentigerous bones form wide tooth plates equipped with batteries of relatively small subconical teeth. The supratemporal is comparativley large and sculptured. The postparietal is not entirely overlapped dorsally by the parietal and its exposed portion is sculptured as well. Both supratemporal and postparietal contribute to the skull table in a way that the parietal is excluded from the posterior rim of that table. L. meachami, however, differs from the other well known moradisaurine Moradisaurus in retaining a band of small denticles on the posterior egde of the transverse flange ("wing") of the pterygoid. Another difference to Moradisaurus is the lateral wall of the mandible being only modestly bulged, however this bulge is still much more pronounced than in smaller moradisaurines such as Kahneria or Gecatogomphius.
Teeth
The only premaxillary tooth preserved is the largest tooth of the upper jaw and slightly recurved. The anteriormost dentary tooth is the largest of the lower jaw, however, only its base is preserved. The teeth of the maxillary and dentary tooth plates are arranged in six and five, respectively, longitudinal rows in which the teeth of two adjacent rows each alternate resulting in a chessboard-like pattern. Most of these teeth show distinctive wear facets. The teeth of the most labial row are exclusively worn on the lingual side whereas wear in the most lingual row is restricted to the labial side. Almost all teeth of the median rows are worn on both labial and lingual sides. This wear pattern is apparently the result of interdigitation of the tooth rows of upper and lower jaw. Thus it is very likely that the teeth were used for grinding fibrous plants.
A second species ?
A second species of Labidosaurikos, L. barkeri, has been described from the deepest part of the "Choza Formation" (upper part of Clear Fork Group) of North Texas in 1954 but has been questioned as early as 1959. It differs from L. meachami in having one less row of teeth in both maxillary and dentary. The material, however, is fragmentary. Given that the Texas specimens seem to be immature the number of tooth rows could be related to age. Because no further unequivocal difference between L. meachami and L. barkeri is as yet reported a revisional examination of the Texas fossils is needed to verify the validity of L. barkeri.
Some facts
| †Labidosaurikos meachami Stovall 1950 | |
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Family: Captorhinidae
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Stratigraphic Range: Lower Permian: Leonardian |
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References
DODICK, J.T. and MODESTO, S.P. (1995): The Cranial Anatomy of the Captorhinid Reptile Labidosaurikos meachami from the Lower Permian of Oklahoma. Palaeontology 38 (3): 687-711
OLSON, E.C. (1954): Fauna of the Vale and Choza: 9 Captorhinomorpha. Fieldiana Geology 10 (19): 211-218
SELTIN, R.J. (1959): A review of the family Captorhinidae. Fieldiana Geology 10 (34):461-509
STOVALL, J.W. (1950): A New Cotylosaur from North Central Oklahoma. American Journal of Science 248 (1): 46-54
Credits
--Zidane 13:51, 26 May 2008 (PDT)
