  THE MICROSAURIAN FAMILY ICHTHYCANTHIDÆ, FROM THE COAL MEASURES OF OHIO. Family ICHTHYCANTHIDÆ new family. This family is the most recently recognized group of the Linton fauna. Its members, of which there are two known species, are distinct from all other Coal Measures Amphibia in the possession of an osseous tarsus (483, 484), with its associated reptile-like limb bones. There are preserved fine scutellÆ in a large patch near the vertebral column. The vertebral spines are broad and heavy, with the vertebral centra amphicoelous. Cope, Proc. Am. Phil. Soc., p. 573, Feb. 3, 1877 (Pal. Bull. 24). Baur, BeitrÄge zur Morphogenie des Carpus und Tarsus der Vertebraten, I Theil, p. 16, 1888. Cope, Trans. Am. Phil. Soc., XVI, p. 289, fig. 1, 1888. Moodie, Science, n. s., XLI, No. 1044, p. 34, 1915. Moodie, Am. Jour. Sci., XXXIX, pp. 509-512, fig. 2, May, 1915. Type: Ichthycanthus ohiensis Cope. The generic characters are derived from the characters presented by the posterior dorsal and caudal vertebrÆ, with adjacent parts. The posterior limbs are well developed, with distinct tibia and fibula, osseous tarsus, and 5 digits. Ribs elongate, simple, curved. Abdominal armature consisting of bristle-like rods in anteriorly directed chevrons. Dorsal vertebrÆ not elongate, with simple neural spines. Tail large, its vertebrÆ ossified, and furnished with slender chevron bones which terminate in a hÆmal spine. Neural spines broad and directed backwards; the caudal series somewhat resembling that of a fish. All the centra are amphicoelous. This genus differs from all those with enlarged and sculptured neural spines, and from those with abdominal scutes. It is equally distinct from those without ribs, abdominal rods, or limbs. It is possible that some of the species referred to Tuditanus, in which these parts are unknown, may belong to it, or that it may be established on a small species of Leptophractus, a genus known only as yet from the skull. With our present imperfect knowledge of the Linton forms it seems best to refer I. ohiensis and I. platypus to this distinct genus, Ichthycanthus. Ichthycanthus ohiensis Cope. Cope, Proc. Am. Phil. Soc., 1877, p. 573 (Pal. Bull. 24). Type: Specimen in the American Museum of Natural History. Horizon and locality: Linton, Ohio, Coal Measures. Collected by Dr. J. S. Newberry, in the summer of 1876. The centra of the dorsal vertebrÆ are about as long as deep, and their sides are deeply concave; there are 4 anterior to the pelvis which are without ribs. The caudal vertebrÆ are robust, and 7, from the first, support a small tubercle-like diapophysis. The chevron bones are short and acuminate; the neural spines are a little shorter, narrow, and truncate, and directed backwards at the same angle as the chevron bones. They are much reduced on the eighteenth caudal vertebra, The abdominal rods are quite slender. The hind limb is quite stout for this order. The femur is regularly expanded at both extremities, but the distal is deeply and openly grooved, distinguishing the condyles, while the proximal end is plane. There is no trochanter visible. The ulna and radius are well separated, and are three-fifths the length of the femur. There is a large fibular tarsal bone of a subquadrate outline. In immediate contact with it is probably the external digit with 5 phalanges or segments; the ungual is simply conic. The femur is as long as 5 dorsal vertebrÆ. The ribs have expanded, undivided heads, and extend to the abdominal armature.
Ichthycanthus platypus Cope. Cope, Proc. Am. Phil. Soc., pp. 574, 575, 1877. Cope, Trans Am. Phil. Soc., XVI, p. 289, fig. 1, 1888. Baur, BeitrÄge zur Morphogenie des Carpus und Tarsus der Vertebraten, I Theil, p. 16, 1888. Moodie, Science, n.s., XLI, No. 1044, p. 34, 1915. Moodie, Am. Jour. Sci., XXXIX, pp. 509-512, fig. 2, 1915. Type: Specimen No. 79540, and obverse, Department of Geology, Columbia University. (Plate 23, fig. 1.) Horizon and locality: Linton, Ohio, Coal Measures. This amphibian is represented by the same portions of the skeleton as the preceding species, furnishing a good basis for comparison. It is very well preserved, displaying the characters, especially of the hind foot, which is almost entirely represented. Several features distinguish it from the I. ohiensis, one of which is of more than usual value if correctly indicated by the fossil. There are 10 vertebrÆ from the anterior end to the sacrum preserved in place, and none of them supports a rib, nor are there any ribs visible anywhere on the block of shale. I suspect that they exist on more anterior vertebrÆ, or may have been displaced to a more anterior position than they normally occupy. The abdominal chevrons are more anterior in position than are those of the I. ohiensis. The hind legs are longer than in that species; in this one the femur equals 7.5 vertebral centra in length. The external digit, on the other hand, while bearing 5 phalanges, is distinctly shorter. The fibular tarsal is of a transverse oval, not quadrate, form. The dorsal centra are shorter and deeper than long; the neural arches are elevated, with short but distinct zygapophyses, and a flat, subquadrate, superiorly truncate, neural spine. They bear short, vertically compressed diapophyses near the base of the arches. The neural spines of the caudal vertebrÆ become rapidly more slender, and also diminish in length, while the zygapophyses are continued to the fifteenth vertebra. The chevron bones are slender, and inclose a moderate hÆmal opening. MOODIE 1. Photograph of the type specimen of Pelion lyelli Wyman, from the Ohio Coal Measures. Supposed to represent the ancestral form of the Salientia. × 2. Original in American Museum of Natural History. 2. Scales of Cercariomorphus parvisquamis Cope, a microsaur from the Ohio Coal Measures. × 10. Original in American Museum of Natural History. 3. Type specimen of Cercariomorphus parvisquamis Cope, from the Ohio Coal Measures. Original in American Museum of Natural History. × 0.75. The femur is gradually expanded to the extremities. Proximally there is a trochanteric ala, besides the obtuse head. Distally the condyles are well distinguished, the external or fibular being truncate. The fibula is less than three-fifths the length of the femur, and is expanded at both extremities. Two proximal tarsals are distinct; the one next the fibula is larger than the other and transverse suboval in form. It has a median dividing ridge as though composed of fibulare and intermedium coÖssified. The tibiale is subtriangular. There are five distinct phalangeal tarsals. The toes are, in the order of their lengths, beginning with the shortest, 1-2-5-3-4. Their phalanges (including metatarsals) are, in the proper order, commencing with the hallux, 3-3-4-5?-5, the distal end of the fourth finger being lost. These bones are rather stout, and the unguals are simply conic. The form of the foot is short and wide. The number of the phalanges is nearly similar to that found in Amphibamus grandiceps, excepting that in that species the fifth digit has but 4. They are more numerous on most of the digits in Sauropleura digitata. Cope (Trans. Am. Phil. Soc., XVI, 289, fig. 1, 1888) contributed the following note on Ichthycanthus platypus: "A reËxamination of the type specimen of this species from the Coal Measures of Ohio, preserved in the Museum of Columbia College, New York, enables me to refer this species to the Rachitomi. The neural spines are distinct, showing that it belongs, probably, to the EryopidÆ. As the skull is not preserved, I can not determine the genus positively, but refer it for the present to Eryops. I append a figure of the posterior foot, which displays the characters of the tarsus of this group for the first time. The number of tarsals is as in a Theromorph reptile, except that two elements represent the cuboid bone as in the reptile, Stereosternum tumidum Cope; giving five elements in the distal tarsal row. There is but one centrale and no intermedium. Two fragments of caudal vertebrÆ adhere to the specimen."
The writer has had the privilege of restudying this interesting specimen and has already (484) described the foot and tarsus, as follows: The only known specimen of this anomalous amphibian is incomplete, representing the posterior half of the skeleton, and an abundance of ventral scutellÆ or calcified myocommata. The block of coal containing these interesting remains is from Linton, Ohio, and is preserved in the geological collections of Columbia University, from which institution Professor Grabau very courteously forwarded it for study. Ichthycanthus platypus was described by Cope from the Linton, Ohio, Coal Measures, locating it doubtfully in the Permian genus Eryops on account of the unusual condition of the tarsus and reconsidering a former decision in favor of a Coal Measures genus Ichthycanthus. In this disposition of the species into the Permian genus he is followed by Hay (317); but Baur (28) regarded the form as a member of the Coal Measures genus Ichthycanthus, after commenting on the later definition by Cope. The type of the genus, Ichthycanthus, to which Cope first allied the species under consideration, is I. ohiensis, a supposed amphibian from the Coal Measures of Linton, Ohio, founded on incomplete material. The form combines in an unusual and remarkable degree reptilian and amphibian characteristics. The leg bones, pelvis, and tarsus are all strikingly reptilian, but the phalanges in the arrangement of elements are so typically amphibian that if we had no other means of diagnosis we would incline to locate this Coal Measures species among the Amphibia. The leg (plate 23, fig. 1) recalls in its structure that of another Coal Measures species, Eosauravus copei Williston, which is, however, clearly a reptile. While there is a general degree of similarity between the foot structure of Eosauravus copei and Ichthycanthus platypus, yet there are very great differences in the phalangeal formula and the arrangement of the tarsal elements. These differences are clear and indicate a separation of the two species into distinct classes. The phalangeal formula in the Eosauravus, 2-3-4-5-4, is typically reptilian; while in the Ichthycanthus, 2-2-3-3-3, it is amphibian. The tarsus of the Ichthycanthus is amphibian in the presence of an intermedium, but this is very small and the remaining tarsal structures have nothing which might not be found in an early reptile. There may be a single or even two centralia in the reptilian tarsus among the early forms. The amphibian nature of the species having thus been established, it remains to give a detailed account of its skeletal anatomy, with comparative references to such other ancient forms as are available. Little can be said of the vertebral column, since only the molds of a few vertebrÆ remain, and these are so obscured by a closely adherent pellicle of carbonaceous material that their form can not be distinctly discerned. They are high, with relatively broad neural spines. There are no ribs preserved. The pelvis is obscured, but it is possible to determine the presence of an elongate ilium and an ischium. The leg of the left side is the best preserved of all the elements, and it is to this that our attention will be confined. The opposite leg is not so complete, yet all the long bones and a part of the tarsus are preserved with sufficient clearness to corroborate the findings of the left side. The femur, as has been stated, is reptilian in appearance. This is due to the well-rounded articular surfaces, as though the endochondrium were well developed, and to the large development of the greater and lesser trochanters, which are quite prominent, though these are distorted and depressed in fossilization. The bone is stout and well built and its form suggests an active habit of life. The tibia and fibula are separate, and do not otherwise have sufficiently noteworthy characters to call for a special description in this place, except to note an unusual anterior crest on the tibia. To the lower ends of these bones articulate the first row of tarsal elements, the tibiale, intermedium, and fibulare. The tarsus is composed of 9 elements arranged in 3 rows. The proximal row is composed of the tibiale, the intermedium, and the fibulare. On the edge of the tibiale there lies a portion of one of the caudal vertebrÆ, so that the form of this tarsal element is slightly obscured. The intermedium is a small, rounded element lying between the larger elements. The fibulare is rectangular and projects a considerable distance out from the tibia, but articulates directly with the large lateral distal tarsal. The centrale is triangular in form and is opposed directly by the tibiale and tarsalia 1 to 3. The phalanges are robust in appearance. The entire foot gives one the impression of a very broad structure. The ungual phalanges were apparently bluntly clawed. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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