Chapter XVIII

THE MICROSAURIAN FAMILY NYRANIIDÆ, FROM THE COAL MEASURES OF OHIO.

=Family NYRANIIDÆ Lydekker, 1890.=

Lydekker, Cat. Fossil Reptilia and Amphibia, p. 166, 1890.

Skull with the palatines situated near the middle line, internally to
the vomers and pterygoids, and the palatine vacuities small and placed
far back. Vertebræ (_Ichthyerpeton_) discoidal. Teeth less complex
than in the Anthracosauridæ. A ventral armor present and the entire
body covered with small cycloid imbriated scales.

The type genus of this family was placed by Fritsch (251) with the Archegosauridæ, although its resemblance to _Anthracosaurus_ was pointed out; it was subsequently made the type of a family by Lydekker (393) in 1890, and placed next the Archegosauridæ. Known from the Coal Measures of Bohemia, Ireland, and Ohio.

Two genera from North America, _Ichthyerpeton_ and _Cercariomorphis_, are assigned tentatively to this family, both known from the Coal Measures (462) of Linton, Ohio, and both with the body completely scaled. The distinguishing characters are found chiefly in the shape and arrangement of the scales, the structure, form, and size of the body, all of which are given full treatment in the discussion below.

=Genus ICHTHYERPETON Huxley, 1866.=

Huxley, Trans. Roy. Irish Acad., XXIV, p. 195, pl. xxiii, fig. 1;
Scientific Memoirs, III, p. 195, pl. 23, fig. 1, 1866.

The genus was founded by Huxley (334) for the reception of the species _Ichthyerpeton bradleyæ_ from the Kilkenny Coal Measures of Ireland. The remains of the type specimen represent "the hinder moiety of the trunk, with the greater part of the tail, of an animal whose scaly integument and laterally compressed, fin-like tail might easily lead one to take it for a fish, were not its true position among higher vertebrata settled at once by the digitate hind limb; while its alliance with the labyrinthodonts is indicated by the delicate spicular ossicles, which form a rudimentary dermal shield along the belly." (Huxley.)

=Ichthyerpeton squamosum Moodie.=

Moodie, Jour. Geol., XVII, No. 1, p. 69, 1909.

Moodie, Proc. U. S. Nat. Mus., 37, p. 24, 1909.

Type: Specimens Nos. 4476 and 4459, U. S. National Museum.

Locality and horizon: Linton, Ohio, Coal Measures.

The present species is based on well-preserved remains from the Linton, Ohio, beds. There are two specimens of the species preserved on blocks of coal and together they represent the greater part of the length of the animal. The species is located in the genus Ichthyerpeton, which was founded by Huxley (334, p. 351) on remains from the Coal Measures of Ireland, on account of the character of the dermal covering, which consists of small scales such as Huxley described in the form from Ireland. The specific characters of this form are the small size of the rounded scales, the attenuated tail, the apparent absence of limbs, the character of the ventral scutellation, and the slightly curved condition of the ribs.

It is estimated, from the portions preserved, that the animal attained a length of not less than 3 feet and its body was long and slender. It may have had an appearance similar to the modern caudate genus _Siren_, though there were doubtless 4 limbs present instead of 2. The slenderness of the body is at variance with the condition found in the type species _Ichthyerpeton bradleyæ_ Huxley, in which the trunk was rather stoutly built. The character of the anterior portion of the body in the present species can not be determined and the skull is wanting. There are no evidences of anterior limbs, although the ventral scutellation preserved would seem to include the pectoral region. No pectoral shields are preserved, nor are there any traces of pelvic girdle or limbs.

The preserved portions on one block include nearly the entire tail and the posterior region of the body, and on the other block the dorsal region of the body and the anterior portion of the tail, so that the two specimens supplement each other in an interesting manner. There are impressions of several vertebræ preserved. They are much the same in character as Huxley has described for the type species (_I. bradleyæ_). They are short and thick and were probably amphicœlous. There are likewise preserved the remains of rather slender recurved ribs mingled in with the remains of the ventral scutellation and distinguished from the elements of the abdominal shield by their size and curvature. They are, apparently, single-headed, but the character of their articulation can not be determined. The ventral scutellation consists of fine continuous rods arranged in the regular chevron pattern. They do not seem to be divided into oat-shaped scutes, as is the case with the form described by Huxley. The ventral rods are closely packed for a distance of more than 6 inches, but as they are scattered their exact arrangement can not be determined. They seem to have extended to the cloacal region, but there are no evidences of the specialized clasping organs such as Fritsch (251) has described in the ventral scutellæ of _Ophiderpeton_. The scales, which are well preserved on the tail, may have covered the entire body, since there are many scattered scales in the dorsal region of one of the specimens. They are slightly oval, tuberculate, and measure scarcely 1 mm. in their longest diameter. They show but slight evidences of having been imbricated, though it is likewise possible that they were simply inclosed within the integument, and somewhat separated from one another. The most posterior part of the tail preserved seems to indicate that the tip was attenuated. It was probably flattened from side to side. We may thus regard _Ichthyerpeton squamosum_ as an elongate aquatic animal with a long, flattened tail, and since there were possibly no limbs or very small ones, it would be an animal highly adapted for life in the water. The present species is of interest because it represents an additional discovery of the scaled Amphibia in North America. The species previously known from the Linton, Ohio, deposits is _Cercariomorphus parvisquamis_ Cope. Dermal scales have also been observed in specimens of _Amphibamus grandiceps_ Cope and _Micrerpeton caudatum_ Moodie (462, 478) from the Mazon Creek, Illinois, beds, and Sir William Dawson (208) described scales accompanying several forms from the Joggins deposits of western Nova Scotia.

1. Mandible of _Micrerpeton deani_ Moodie, from the Linton. Ohio,
Coal Measures. Original in American Museum of Natural History,
No. 2934. × 0.6.

2. Portion of the skull of _Micrerpeton deani_ Moodie, possibly of
the same individual as the mandible. From the Linton, Ohio, Coal
Measures. Original in American Museum of Natural History, No.
3535 G. × 0.4.

3. Type of _Cercariomorphus parvisquamis_ Cope, from the Linton,
Ohio, Coal Measures. Original in American Museum of Natural
History. × 1.

4. An additional specimen of _Cercariomorphus parvisquamis_ Cope,
from the Linton, Ohio, Coal Measures. Original in American Museum
of Natural History. × 1.

5. Skull of _Sauropleura scutellata_ Newberry. From the Coal
Measures of Ohio. × 1.

6. Tooth of _Mastodonsaurus_ sp. indet. of the Carboniferous of
Kansas. Original in University of Kansas Museum. × 1.

7. Tooth of _Mastodonsaurus giganteus_ Jaeger, from the Triassic of
Germany. Introduced for comparison with the tooth from the Kansas
Carboniferous. × 1.

]

Measurements of the Types of Ichthyerpeton squamosum Moodie.

Length of animal as estimated from two impressions 3 ft.
Length of longest impression 21 in.
Length of specimen containing tail impression 9 in.
Width of tail impression: Maximum 50 mm.
Minimum 6 mm.
Width of a single scale 1 mm.
Distance from base of tail to tip 125 mm.
Length of specimen as preserved 225 mm.
Width of chevron rod space 30 mm.
Length of rib 25 mm.
8 chevrons in a distance of 3 mm.

=Genus CERCARIOMORPHUS Cope.=

Cope, Proc. Amer. Phil. Soc., 1885, p. 405.

Type: _Cercariomorphus parvisquamis_ Cope.

The type specimen of this genus is supplemented by a portion of the body of another specimen which adds a little to our knowledge of the animal's form, but nothing as to structure. Cope's original description is as follows:

"Represented by a fusiform body which terminates in a long, slender,
cylindrical tail, and which is covered with small subquadrate scales
quincuncially arranged. No fins or limbs are preserved, and the form
of the head can not be made out. Probably a portion of the skull
is preserved. There are some scattered bodies in the body portion,
which look like deeply concave vertebræ with the zygapophyses of
batrachians. There are some linear impressions at one point, which
resemble the bristle-like rods on many Stegocephali. They are so few
as to be of little importance. The scales are like those of fishes.
There are traces of segmentation in the axis of the long tail.

"The position of this curious form is quite uncertain. It is quite
different from anything observed hitherto in the American Coal
Measures."

=Cercariomorphus parvisquamis Cope.=

Cope, Proc. Amer. Phil. Soc., 1885, p. 405.

Moodie, Science, n.s., XLI, No. 1056, p. 463, 1915.

Type: Specimen No. 2560, Newberry Collection, American Museum of Natural History.

Horizon and locality: Discovered by Samuel Huston at the Linton, Ohio, Coal Mines. (Plate 21, figs. 3, 4; 24, figs. 2, 3.)

The scales (Plate 24, fig. 2) in their present condition are entirely smooth. At a distance of 20 mm. from the base of the tail they are in 20 longitudinal series. At that point the transverse diameter of the body is 140 mm. The outline contracts rather abruptly to the tail, of which 66 mm. are preserved. The surface of the tail is obscured by a thin layer of carbonaceous matter not sufficiently thick to obscure scales, which are evident at distances of 16 mm., 43 mm., and 52 mm. from the tip. The scales on the tail are smaller than those on the body and are without markings of any kind. The anterior half of the body is depressed and distorted, but the remainder is well preserved and shows a fairly good outline of an apparently limbless body.

An additional specimen (No. 8683 G, of the Newberry Collection, American Museum of Natural History) reveals no new facts as to structure, but serves to show that the body of the animal was long and slender (plate 21, fig. 4). The portion studied comes undoubtedly from the middle of the body. No limb elements are preserved. The scales are somewhat larger, especially toward the sides of the body, than in the type. The fragment measures 70 mm. in length by 18 mm. and 26 mm. in width. One of the largest scales measures 1 mm. in diameter.

Measurements of Type.

mm. Length of entire remains 180 Greatest width 22 Greatest width of
undisturbed portion 15 Length of an individual scale .75