THE MICROSAURIAN FAMILY MOLGOPHIDÆ, FROM THE COAL MEASURES OF OHIO AND
MAZON CREEK, ILLINOIS.
=Family MOLGOPHIDÆ Cope, 1875.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 157, 1875.
Cope, Bull. U. S. Nat. Mus., No. 1, p. II, 1875.
Type of family: _Molgophis_.
Body long, serpentine, a few species apparently limbless, ribless, and
with abdominal armature lacking. Vertebræ elongate, neural and hæmal
spines short or absent. Ribs long, heavy, and broad. The vertebræ
seem to bear the characteristic marks of the family. One species has
the skeleton reduced to a lanceolate skull and a string of about 50
slender vertebræ, all the rest of the skeleton being absent. The
family is very poorly known, but was apparently of wide distribution
in North America and confined to this continent. The representatives
of the group are known from Iowa, Illinois, and Ohio.
Four genera are assigned to the family, but future discoveries will
undoubtedly demand revision of the present classification. The genera
are _Molgophis_, _Pleuroptyx_, _Phlegethontia_, and _Erpetobrachium_.
The distinguishing characters of these genera are apparent from the
descriptions of the various forms. The skeletons of the species are too
incompletely known to allow the establishment of a tabular key to the
genera.
=Genus MOLGOPHIS Cope, 1868.=
Cope, Proc. Phila. Acad. Nat. Sci., p. 220, 1868.
Cope, Trans. Amer. Phil. Soc., XIV, p. 20, 1869.
Cope, Geol. Surv. Ohio, II, pt. II, p. 368, 1875.
Cope, Trans. Amer. Phil. Soc., XV, p. 263, 1874.
Type: _Molgophis macrurus_ Cope.
Cope (123) gives the following:
"The characters of this genus are: body long, serpentine, without
dermal armature, so far as known; vertebræ long and broad, with very
prominent zygapophyses and moderate neural spines; ribs large, curved.
No limbs or cranium can be ascribed to the type of the genus. The ribs
are long, and though the head is not bifurcate, there appears to be
both tubercle and head on the dilated extremity. Where crushed they
display a large median vacuity.
"This genus differs from Ophiderpeton Huxley (334) in the characters
of the dorsal vertebræ, which, in their projecting zygapophyses,
resemble those of Amphiuma. The lack of ventral armature distinguishes
it from _Œstocephalus_, while its well-developed ribs separate it from
_Phlegethontia_."
=Molgophis macrurus Cope.=
Cope, Proc. Phila. Acad. Nat. Sci., p. 220, 1868.
Wyman, Am. Jour. Sci. and Arts, p. II, fig. 1, 1858 (refers to a
batrachian reptile).
Cope. Trans. Amer. Phil. Soc., XIV, p. 20, 1869.
Cope, Trans. Amer. Phil. Soc., XV, p. 263, 1874.
Cope, Geol. Surv. Ohio, II, pt. II, p. 368, pl. xliii, fig. 1, 1875.
Type: Specimen No. 8617 G, American Museum of Natural History, collection
of Dr. J. S. Newberry.
Horizon and locality: Linton, Ohio, Coal Measures.
This species is established by remains of 2 individuals, one embracing
16 and the other 14 vertebræ, with ribs. The neural arches, viewed from
above, have a =V=-shaped outline posteriorly, from the fact that
the broad zygapophyses meet on the median line and spread out distally
over the broad anterior ones adjoining. The latter appear to be somewhat
concave and to border the former exteriorly as well as inferiorly. The
base of the neural spine extends to the posterior emargination, but not
quite to the anterior. The breadth of the dorsal vertebræ above is equal
from the emargination behind to the anterior margin of the anterior
zygapophyses.
The ribs are long for an amphibian, but not long for a reptile. They are
well curved, chiefly near the proximal extremity. The longest found,
measured by a cord, equals two and two-fifths vertebræ. These vertebræ,
measured along the median line above, equal 11 lines; one of these is 3.6
lines in width above. This animal has been, like _Amphiuma_, a snake-like
amphibian, but was probably still larger. How near the affinities to
this genus may be can not now be determined, owing to the want of many
important parts of the skeleton, but it differs in the important feature
of large, well-developed ribs. The size of the vertebræ would indicate a
body of the size of the common rattlesnake (_Crotalus horridus_) and too
large for _Brachydectes newberryi_, which is only known from jaws.
[Illustration: Fig. 32.--Drawing from Cope's figure of _Molgophis
brevicostatus_ Cope, × 0.5]
=Molgophis brevicostatus Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 369, pl. xliv, fig. 1, 1875.
Moodie, Proc. U. S. Nat. Mus., 37, p. 27, 1909.
Type: Specimen No. 8341 G, Amer. Mus. of Nat. History.
Horizon and locality: Linton, Ohio, Coal Measures.
Represented by portions of the vertebral column of several individuals.
One of these includes 9 pairs of ribs, with vertebræ, and another 13
pairs. The vertebræ are subquadrate in section, and the concavity of
the two articular faces is not deep. They support strong lateral ridges
separated by deep concavities. The heads of the ribs are somewhat
contracted, and the shafts present outward a tubercular angle at a
distance of one-fourth the length from the head. The remaining part
of the shaft is stout, nearly straight, and gradually contracts to an
obtuse extremity. It possesses a narrow medullary cavity. In none of the
specimens is there any trace of abdominal armature, but abundant remains
of the contents of the abdominal cavity, in proper position, are preserved
on the blocks. This species is more massive than Molgophis macrurus, and
the ribs are shorter, thicker, and less curved.
Ventral scutellæ are present in one specimen of this species. There are
a number of specimens. They have the following numbers at the American
Museum: 158, 1100 G, no number, 8341 G (type), no number, 8466 G; and 4477
in the U. S. National Museum.
Measurements of Type Specimen of Molgophis brevicostatus Cope.
mm.
Length of 7 vertebræ 105
Length of 1 centrum 16
Diameter of same vertically 11
Length of a rib on a curve 24
Greatest thickness of same 2.5
=Molgophis wheatleyi Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, pp. 369, 370, pl. xlv, fig. 1,
1875.
Cope, Trans Am. Phil. Soc., XV, p. 263, 1874.
Type: Specimen No. 1101 G, American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
A critical study of the type specimen of this species does not reveal
anything essentially different from the description of Cope. The following
is taken from his report (123):
"Established on a specimen which exhibits about twenty-five vertebræ
with ribs, and the posterior portion of the cranium. No traces of
abdominal scales or rods, thoracic shields, or limbs are visible. By
such negative characters it is referable to the genus _Molgophis_,
although the definition of this genus is incomplete. The present
batrachian may, indeed, be ultimately found to be an _Ophiderpeton_,
to which it also bears some resemblance.
"The specimen is that of an animal of very much smaller size than the
_M. macrurus_. The vertebræ are of moderate length, with a low neural
spine, and centrum angular at the sides and truncate at the articular
extremities when in place. The ribs are rather short, slightly curved,
apparently hollow and intercentral in position. Although the vertebral
centra are ossified, the elements of the cranium have a larval
appearance. These consist of two parallel bony plates, which resemble
the fronto-parietal bones of the frog; they are slightly separated
from each other, but do not inclose a fontanelle. A wedge-shaped bone
extends from the outside of the front of each of these, acuminate
behind, and widening anteriorly in the position of a postfrontal bone.
In front of the posterior border of each parietal, on its outer side,
a bony enlargement arises which contracts outward and forward into a
narrow element which curves forward beneath the postfrontal. These
look like an anteriorly directed quadrate with articular bone, such
as seen in the larvæ and some adults of existing batrachians. These
determinations will require confirmation from additional material.
In the meantime it is evident that the present specimen can not be
referred to any of the other species herein described. The elements of
the cranium are entirely smooth with no sign of sculpture, and in this
respect the present species is unlike any of the other known from the
Carboniferous."
The vertebræ are not so clearly marked as one is led to believe from
Cope's figure.
Measurements of the Type of Molgophis wheatleyi Cope.
mm.
Length of entire specimen 63
Length of portion of skull preserved 9
Posterior width of same 8.5
Length of a vertebra 1.5
Width of a vertebra 1.5
Length of a posterior rib 5
Width of rib 5
The species is dedicated to Charles M. Wheatley, of Phœnixville,
Pennsylvania, one of the original investigators of the Linton deposits. It
is a part of the Newberry Collection.
Additional material of this species is represented by specimens Nos. 7
and 8699 G of the American Museum of Natural History. They are both very
unsatisfactory. They consist of molds of the vertebral column, with in
one case an enlargement at one end which may represent the head, and if
such, the specimen probably represents a distinct species. The impression,
No. 7, contains molds of about 30 vertebræ which are very similar in
form to those exhibited by the type of the species. To the vertebræ
are articulated short, curved ribs of a slender nature. The vertebræ
themselves are short and somewhat constricted in the middle.
The other impression, 8699 G, contains impressions of about 20 vertebræ,
apparently immature, though one can not be entirely sure as to the
nature of the structures. They are covered over with a thin layer of
carbonaceous material which is impossible to remove satisfactorily. The
two specimens remind one of what Huxley has written in regard to the forms
of Microsauria (334) from Kilkenny, Ireland.
Measurements of Nos. 7 and 8699 G (Molgophis wheatleyi).
mm.
Length of No. 7 87
Length of head mold 18
Posterior width of head 6
Length of vertebra 2
Length of rib 3
Length of specimen No. 8699 G 53
=Genus ERPETOBRACHIUM Moodie, 1912.=
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, p. 353, 1912.
Type: _Erpetobrachium mazonensis_ Moodie.
The generic characters are apparent in the greatly elongated fore limb,
in the exceptionally broad scapula, the long radius and ulna, which
slightly exceed the humerus in length, a character hitherto unknown among
Carboniferous Amphibia.
=Erpetobrachium mazonensis Moodie.=
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, pp. 353-354, pl. 2, fig. 2;
pl. 8, fig. 3, 1912.
Type: Specimen No. 799 (222), Yale University Museum.
Horizon and locality: Mazon Creek shales, near Morris, Illinois.
The scapula of the present form is exceptional in its shape. It resembles
an asymmetrical pyramid, the anterior side of the lower edge of the bone
being contracted so that the anterior edge of the element is arcuate. Its
top is very thin and possibly terminated in a broad cartilage. The lower
end is thick and heavy and the articular surface is, apparently, well
formed, though somewhat obscured.
The element identified as a clavicle is lying on its edge and has the
proportions of the clavicle of _Mazonerpeton costatum_. The exterior
edge is somewhat rounded and small. A portion of another element which I
suppose to represent the coracoid lies alongside the humerus, although its
form is quite obscured. (Plate 3, fig. 3.)
The humerus has a remarkably well-formed head. In perfection of formation
it corresponds well with that of the higher reptiles. This surface can
even be divided into an anterior and a posterior articulation. The element
projects posteriorly for the distance of 1 mm. from the surface of the
shaft. The shaft immediately below the head is somewhat flattened and has
an ovoid section. Further on it becomes flattened, a part of which is
probably due to pressure during fossilization.
The elements of the forearm are both preserved and are approximately equal
in size. They are remarkable in that they exceed the humerus in length,
although they are not so heavy as that element. They are greatly elongate
and slender, with the middle of the shaft only moderately contracted. The
articular surfaces are well formed and both bones were hollow, as was
also, apparently, the humerus. The ulna may be represented by the most
posterior of the two elements, though the relations of the elements may
have been reversed (fig. 15, D).
The base of the left wing of an orthopterous insect possibly allied to
_Paolia gurleyi_ Scudder lies between the radius and ulna. The nodule also
contains impressions of plants, a portion of a frond of a _Neuropteris_
and the impression of one of the Cordaites. Lying next the radius is a
slender elongate element which may be a rib or a portion of a metacarpal.
If a rib, it indicates that the animal belongs among the Branchiosauria.
The fragment is only half as long as the radius and is entirely too
obscure to base any conclusions. The other characters of the specimen
point quite strongly to its microsaurian affinities.
The structure of the articular surfaces of the limb bones alone would
indicate the microsaurian relationship of _Erpetobrachium_. It may be
provisionally associated in the family Molgophidæ with such forms as
_Molgophis brevicostatus_ Cope, _Molgophis_ (_Pleuroptyx_) _clavatus_
Cope, and _Molgophis macrurus_ Cope from the Coal Measures of Linton, Ohio.
Measurements of the Type.
mm.
Length of scapula 14
Distal width 6
Proximal diameter 3
Length of clavicle (?) 24
Length of humerus 25
Length of ulna 24
Proximal width 4
Diameter of shaft 2
Distal width 3
Length of radius 25
Proximal width 4
Diameter of shaft 3
Width of distal end 4
=Genus PLEUROPTYX Cope, 1875.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 370, pl. xlii, fig. 1; pl.
xliv, fig. 2, 1875.
Cope, Proc. Phila. Acad. Nat. Sci., p. 16, 1875.
Moodie, Proc. U. S. Nat. Mus., 37, p. 27, 1909.
Type: _Pleuroptyx clavatus_ Cope.
The specimens on which the species of this genus repose do not exhibit
crania. The 5, probably 6, specimens which represent them offer various
views of the vertebral column, and in none is there any trace of ventral
or thoracic armature. Limbs can be ascribed to them with probability only.
The vertebræ are of moderate length, with well-developed zygapophyses, and
a short and not very elevated neural spine in the dorsal region, which
is not sculptured in any way. The generic character is seen in the ribs.
These are rather short and very stout and support an ala on the posterior
or convex border, which expands downwards, and then suddenly contracts to
the shaft. The extremity of the latter is broad and truncate, and includes
a medullary cavity, which is only partially fitted with cancellated tissue.
=Pleuroptyx clavatus Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 370, pl. xlii, fig. 1; pl.
xliv, fig. 2, 1875.
Cope, Proc. Phila. Acad. Nat. Sci., p. 16. 1875.
Moodie, Proc. U. S. Nat. Mus., 37, p. 27, 1909.
Type: Specimen No. 8617 G, American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
The general appearance of the species of Pleuroptyx is that of the
Molgophis, so far as known, but nothing resembling the peculiar structure
of the ribs is seen in any other. There is no assurance that the genus is
distinct from Molgophis.
Parts of two individuals express the typical characters of this species,
while a third only differs in being considerably smaller. A fourth may
very probably be referred here, and another, bearing several elements of a
leg, should be most likely associated with the last mentioned.
The ribs are considerably narrowed near the head, and appear to possess
a low tubercular process some distance below it. The shaft is curved
throughout; the laminar expansion is quite thin; while the distal end is
expanded and concave, perhaps for the attachment of cartilage, although no
trace of this remains on the shale. The neural spines have short bases,
oblique anterior and nearly straight posterior borders, with obtuse
extremity. I perceive no essential difference in the smaller specimen,
which is one-third less than the types.
The limb is appropriate in its proportions to the present species, and may
be described in this place. The first segment is one-third longer than
the second, and has a transversely expanded head. The shaft is stout, the
distal extremity not expanded and concave. The second segment is stout,
more expanded proximally than distally, the proximal end truncate and
slightly concave. A bone, much displaced, lies near it, and is probably
ulna or radius; it is as stout as the first, the end not expanded. Of
metatarsals there are 2, three-fifths the length of the second bone of the
leg, and of phalanges 2, of 2 digits each. The proximal are three-fourths
the length of the metatarsals, and indicate elongate toes. The obverse of
the specimen is preserved, and contains no additional toes or phalanges.
[Illustration: Fig. 33.--Forelimb of a member of the Molgophidæ, possibly
Pleuroptyx clavatus Cope. × 0.75.]
Measurements of the Type of Pleuroptyx clavatus Cope.
mm.
Length of vertebral centrum 14
Depth of a vertebral centrum 9
Depth of entire vertebra 22
Length of neural spine 8
Height of a neural spine 6
Length of a rib on the curve 42
Width of a rib at ala 9
Width of a rib at extremity 5
Length of first segment of leg 38
Length of second segment of leg 24
Length of metapodial bone 10
Length of first phalanx 7
Hitherto only two portions of the dorsal series and a left limb have been
assigned to this species. The present specimen (No. 4479, U. S. Nat. Mus.)
thus proves of interest in determining that the creature was long-tailed,
like _Œstocephalus_, _Ptyonius_, and _Phlegethontia_, but unlike the first
two genera the neural and hæmal spines are not elongate nor marked with
radiating lines. The neural spines are indistinct and if developed at all
were very low and short.
The centra are short, cylindrical, and thick. They gradually decrease
in size to where they are lost, since the portion preserved does not
represent the entire length of the tail. There may have been 15 more
vertebræ distally and 5 more proximally, thus making about 75 caudal
vertebræ, as Woodward (630) has determined obtains in _Ceraterpeton
galvani_ Huxley.
The ribs are continuous throughout the length of the tail preserved and
have precisely the same structure as is found in the dorsal region with
the possible exception that the posterior alar expansion is not so well
developed in the caudal ribs. The ribs are decidedly fan-shaped and
articulate by a single head with a short transverse process. They are
distinctly curved like all microsaurian ribs.
Measurements of Specimen of Pleuroptyx clavatus Cope.
(No. 4509, U. S. National Museum, Linton, Ohio, Coal Measures.)
mm.
Length of tail as preserved 105
Length of anterior vertebra 1.5
Diameter of anterior vertebra 1
Length of rib 5
Width of rib 1
The above-described specimen represents what I suppose to be the posterior
part of the body of _Pleuroptyx clavatus_ Cope. The characters of the ribs
and vertebræ are the same. The fragment is interesting, since it gives
an insight into the form of the body, which was slender, conforming thus
to other long-tailed microsaurs. Length of specimen, 65 mm.; width of
specimen, 30 mm.
There is still a third example of this species among the collections
belonging to the National Museum (No. 4484). The specimen includes a badly
crushed posterior portion of a skull and a series of about 16 crushed
vertebræ, with several pairs of ribs and ventral scutes.
Very little can be said of the skull save that the maxilla of the right
side was long and bore from 15 to 20 teeth, of which 9 are preserved more
or less completely. The mandible is likewise crushed and one can not
determine its elements. Portions of 2 or 3 teeth are preserved. The form
of the mandible is long and slender.
The ventral scutes are of the pectoral region. They are long, slender, and
thread-like. They are not closely packed, but I count 12 in a distance of
a millimeter.
So far as can be determined the vertebræ are the same as has been
described for other specimens. They are short and heavy. The ribs show,
for the most part, the same characters as the type specimen.
Measurements of Third Specimen (No. 4484, U. S. Nat. Mus.).
mm.
Length of specimen 60
Length of preserved portion of skull 15
Length of tooth 25
Posterior width of mandible 3
Length of anterior Vertebra 2
Length of rib 4
Width of rib 1
=Genus PHLEGETHONTIA Cope, 1871.=
Cope, Proc. Am. Phil. Soc., p. 177, 1871.
Cope, Geol. Surv. Ohio, II, pt. II, p. 366, 1875.
Type: _Phlegethontia linearis_ Cope.
This is one of the most interesting genera of the present series. It
rests chiefly on a single specimen of one species, which is not perfect,
but which displays the following characters: Head elongate-triangular;
body and tail extremely elongate, the dorsal vertebræ without ribs, and
the caudals without dilated spines; no ventral armature nor limbs. As a
great portion of the length is presented, and no ventral rods or scales
are visible, and as this character is confirmed by a second specimen, it
probably belongs to the genus. The pectoral shields are also wanting in
the specimen, but as there is a considerable vacuity behind the skull of
the specimen, it may be that these were lost with other parts. Chevron
bones are not observable on the caudal vertebræ. This form is a true
amphibian snake.
=Phlegethontia linearis Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 367, pl. xliii, fig. 2, 1875.
Type: Specimen in the American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
In the only specimen the dorsal vertebræ are much involved anteriorly,
so that the length is not readily ascertained. There is an outline of
a triangular object which may represent the skull of this specimen,
although it is so far removed from the vertebræ that there is some doubt
as to whether it belongs with the vertebræ or not. Indeed, there is even
doubt whether it is a skull. The vertebræ have longitudinal diapophysial
keels, and have a zigzag interlocking of neural arches. The latter are
distinctly turned outward. The vertebræ are very numerous, and the tail
very attenuated. The number preserved is about 60. The total length of
the coils unwound is about 295 mm., or 11 coils in 8 lines; but there are
interruptions not measured and confusions not unraveled.
This is the most elongate and slender of all the species of the
Carboniferous Amphibia. The vertebræ are apparently ribless and there are
no evidences of limbs or pectoral plates. It may be said that the body
consists entirely of skull and vertebræ.
Measurements of the Type of Phlegethontia linearis Cope.
Entire length of skull (?) 18 mm.
Width of same 8 mm.
Length of vertebral column as preserved 295 mm.
Length of single vertebra 2.50 mm.
Height of vertebra 1.50 mm.
Estimated length of body 15 in.
No. 8370 G, American Museum of Natural History, shows a few vertebræ.
=Phlegethontia serpens Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, p. 367, pl. 32, fig. 2, 1875.
Type: Specimen No. 1102 G, American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
This amphibian is much larger than the last, approaching nearly in its
dimensions the _Molgophis macrurus_. It is represented by a series of 22
vertebræ, which, like those of _Phlegethontia linearis_, are devoid of
ribs, abdominal armature, dilated neural spines, etc. The series when
complete must have been very long, as there is little difference in size
between the first and the last of the 22. They are marginate fore and
aft, and much contracted medially, owing to the transverse expanse of
the diapophyses. There may be, indeed, a diapophysial element beneath
these, but, if so, the two are indistinguishable. They are connected by
longitudinal impressions, indicating the existence of the tendinous bands
in the longitudinal muscles seen in _Amphiuma_, or the osseous spicules
seen in the same situation in birds. The neural spines, as indicated by
their narrow bases, occupy the length of the neural arch, and remind one
of _Amphiuma_. Width of one of the vertebræ, 3 lines.