The Coal Measures Amphibia of North America

by Roy Lee Moodie

The fossils at the "upper beds" are localized into special strata. At one place in the upper part of the deposit, in a reddish shale, one finds that insects are more abundant than they are lower down. The Crustacea seem to come from apparently the same shale. At the lower end of the deposit certain definite species of Pecopteris are localized. It is an interesting fact that one seldom finds a Neuropteris at the "upper beds." The most abundant fossils are the various species of Pecopteris and Annularia. When specimens of Neuropteris are found they are usually discovered at the lower end of the exposures. In one place behind the "island" very blue nodules, hard and flinty and with sometimes well-preserved specimens of Pecopteris, are found quite definitely localized. These nodules are apt to assume an irregular shape. These localizations of the fossils are, of course, what we would expect from our knowledge of the recent fauna and flora. There is, to be sure, more or less intermingling of the species. The myriapods, so far as they have been found, are also localized. Mr. Carr found 3 within a space of a few feet, but again these are found widely scattered. The exposures at the "upper beds" are about a quarter of a mile long. They disappear under a heavy ledge of sandy limestone.

At the "lower beds" ([plate 1, fig. 6]) , those further down the creek, conditions are quite different from those just described, although of the same horizon: the banks of the creek are higher and almost perpendicular, so that the chances of collection from the shales are fewer. The bed of the creek, however, is wider and there are more nodules washed out. The most abundant fossil at this place is Neuropteris. The nodules at the upper end of the exposure are all, almost without exception, barren of fossils. The exposures here are of about the same extent as the "upper beds," though the species are not so varied. Judging from the collections made while there, Arthropoda are more abundant at the "lower beds."

Bradley (Geol. Surv. Illinois, IV, 196, 1870) mentions the occurrence of these nodules at or near Morris. Other than these places the nodules have been thrown out of a coal mine near Braidwood, Illinois. Doubtless close search would reveal other localities where the shale is cut through in mining. The beds at both places are slightly folded. This is true especially of the "upper beds," where a conspicuous fold caused the beds to disappear in the bed of the creek and to reappear farther down stream. This is directly across the large "ox-bow" bend of the creek.

The beds at Mazon Creek were first explored in 1857 by Mr. Joseph Evans, who sent his specimens to Berlin, Germany, where they excited great interest. It was he who collected the type specimen of Amphibamus grandiceps Cope. Since the time of Mr. Evans many have collected at Mazon Creek, and without doubt the fossil-bearing nodules from this locality are more widely scattered in the museums of the world than are organic remains from any other one horizon.

So far as we know there was no upland vertebrate life at that time. The forms at present known were confined to the water or the margins of the water. The absence of knowledge of upland and terrestrial deposits of this time doubtless accounts for the absence of known vertebrates. It is, however, especially interesting to speculate on the ancestral types of the land vertebrates, and it must be admitted that the Coal Measures Amphibia as at present known throw the ancestry of land-living vertebrates far back into geological time.

(m) The Cannelton slates of Beaver County, Pennsylvania, have furnished 3 species of Amphibia and fragments of other species are represented in the U. S. National Museum ([462]). The species so far known are: Tuditanus minimus Moodie, Erpetosaurus sculptilis Moodie, Erpetosaurus minutus Moodie.

They are the first evidence of the occurrence of amphibian remains in these deposits. The Cannelton specimens are found in a thin stratum of slate which forms part of the Middle Cannelton Coal. The Cannelton slate, in which the fossils occur, forms the roof of the Middle Kittanning Coal, which is only 20 to 30 feet above the Lower Kittanning bed (I. C. White), so it becomes evident that the deposition of the Cannelton slates was at only a slightly later period than that of the shales in which the Mazon Creek nodules occur, since the Mazon Creek shales form the roof of the Morris, which "is probably somewhat lower than the Lower Kittanning of Pennsylvania." From the Cannelton slates are known the remains of plants, insects, crustacea, especially "Eurypterids found in shale immediately below the Darlington (Upper Kittanning) Cannel Coal, near Cannelton, Darlington Township, Beaver County, Pennsylvania, Horizon, Allegheny River Series" (Hall, 1884). In these shales occur also, fishes and the 3 species of amphibians referred to above. The Amphibia known from this region are small, the largest of them not exceeding 6 inches in length.

Fig. 4. Portion of "West Virginia-Ohio-Pennsylvania, Wellsville Quadrangle" of the U.S. Geological Survey, to show topography and situation of Linton coal mines. Some fossil amphibians doubtless came from across the line in Columbiana County.