The coal measures Amphibia of North America / by Roy Lee Moodie.

  • Roy Lee Moodie
Date:
1916
Catalogue details

Licence: In copyright

Credit: The coal measures Amphibia of North America / by Roy Lee Moodie. Source: Wellcome Collection.

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    (d) The teeth of the Coal Measures Amphibia (194) are remarkably similar in the various forms. They are always slender, pleurodont denticles arranged in a single row on the jaws or as tubercular eruptions on the palate bones, with a large pulp- cavity and the enamel often striated. The food of the creatures must have been small Crustacea, worms, insects, and succulent vegetation, such as is the food of the modern Amphibia. (e) The occiput is formed of partially ossified (465) ex- and basi-occipitals, though these elements are never firmly united by ossific union. Often a pair of condyles occur, one on either exoccipital. The occiput was usually, however, car- tilaginous and no trace of its structure is preserved. (/) The mandible is usually as long as the skull and is slender. It is composed of 6 elements so far as known (465); these are the articular, the surangular, the angular, the coronoid, the dentary, and the splenial. Other elements may be present, but the anatomy of this portion of the animals is not very completely known. The bones are sculptured and cut by lateral-line canals (458) in a few forms. Whether the articular operated on an osseous or cartilaginous quadrate is unknown, though certain specimens seem to indicate an osseous condition for that element. The anterior symphysis was doubtless ligamentous, the halves always separating before fossilization. The dentary always bears a single row of pleurodont teeth, which may vary greatly in size and number. (g) The hyoid apparatus is well preserved in a few forms (123). Doubtless it was present in all of them, though it has seldom been preserved. The condition of the hyobranchial apparatus in Cocytinus gyrinoides (text-fig. 16) from the Coal Measures of Linton, Ohio, seems to indicate that the species was a perennibranchiate salamander (123). It is well known from the studies of Credner that the Euro- pean Branchiosauria, in the young, possessed external branchiag (187) supported by lateral basibranchials. The gill-arches seem to have been slightly calcified or ossified in a few cases, and they supported denticle-like projections which bore the gill-filaments. When the Branchiosauria had attained a length of 100 mm. or more they lost their gills (187). This change was accompanied by the reduc- tion of the tail, expansion of the pelvis, and increase in ossification of the skull and skeletal elements. Gills have not yet been detected among the American Branchiosauria. {h) The eye in a few species had a large amount of black pigment, as indicated by the blackening of the stone in the Mazon Creek nodules. Professor Cope (107) thought that this would indicate a nocturnal and crepuscular habit for these verte- brates, since the pigmentum nigrum of the choroid is largely developed. Other than this suggestion nothing is known of the soft parts of the head. (f) The alimentary canal (text-fig. 7) is beautifully preserved as a cast in three specimens of the American branchiosaur species Eumicrerpeton parvum Moodie (471) from the Mazon Creek beds. The nodules which contain these interesting little fossils measure less than 3 inches in long diameter. The fossil salamanders, about 30 mm. in length, are preserved on their backs and occur as nearly as is possible in the center of the nodule.