THE MICROSAURIAN FAMILY UROCORDYLIDÆ, FROM THE COAL MEASURES OF OHIO.
=Family UROCORDYLIDÆ Lydekker, 1890.=
Lydekker, Cat. Fossil Reptilia and Amphibia, pt. IV, p. 196, 1890.
Moodie, Bull. Am. Mus. Nat. Hist., XXVI, art. XXV, p. 357, 1909.
Type of the family: _Urocordylus wandesfordii_ Huxley.
Locality and horizon: Coal Measures of Kilkenny, Ireland.
Stout and long-tailed forms, with the tabulare cornua frequently much
produced and pitted cranial bones; lateral lines well-developed;
palate with teeth on palatines, vomers, premaxillæ, and maxillæ, the
two latter elements bearing conical teeth and the others bearing
short, stumpy cones, at least in one species; pineal foramen well
forward; nostrils and orbits in the anterior part of skull; scapula
peculiarly curved and pointed; other pectoral elements sculptured;
neural spines and chevrons of caudal vertebræ much dilated at their
extremities, and pectinated; no caudal ribs; vertebræ in one genus
apparently capped with a sculptured plate as in _Zatrachys_; tail very
long and tapering to a point, 50 to So caudal vertebræ; dorsal region
short; limbs well developed, with clawed digits; carpus and tarsus
cartilaginous; endochondrium well formed.
There are 4 genera which constitute this family: _Urocordylus_, from
the Coal Measures of Ireland; _Ceraterpeton_, from the Coal Measures of
Ireland and England; _Diceratosaurus_, from the Coal Measures of Linton,
Ohio; Eoserpeton, from the Coal Measures of Linton, Ohio.
These may be distinguished by the following characters:
I. Skull triangular, truncated behind, with rounded muzzle
and aborted tabulare cornua, neural spines of caudal
vertebræ long, slender, and expanded in a fan-like
manner; tail with about 80 vertebræ; ventral scutes
oat-like _Urocordylus._
II. Skull parabolic and of great width, with short cornua
projecting from the supratemporal; tabulare cornua
nearly twice as long; neural spines of caudal vertebræ
low and wide; ventral scutes oblong; caudal vertebræ
about 50 _Ceraterpeton._
III. Skull broad with obtuse snout, tabulare cornua absent,
large, pointed posterior expansions from supratemporal,
posterior table within the cornua truncate; vertebræ
with an apical sculptured plate; caudal vertebræ
numerous, over 75; ventral scutellæ bristle-like,
arranged _en chevron_ _Diceratosaurus._
IV. Skull a broad oval, with large posterior projecting
supratemporal horns, posterior table of skull
between cornua truncate without the small lateral
projection from the supratemporal, orbits a long oval,
ribs long, curved and slender, tail unknown, possibly
shorter than in other members of the family; it is
restored as short in Journal of Geology, XVII, p. 77,
fig. 20, 1909, but this is uncertain; the skull has
all the characters of the family _Eoserpeton._
The relationships of the family are not far to seek. They fall in
immediately with the Amphibamidæ and Hylonomidæ in being among the most
reptile-like of the Paleozoic Amphibia. The group is, however, distinctly
amphibian in the possession of 4 fingers, with the usual microsaurian
phalangeal formula.
=Genus DICERATOSAURUS Jaekel, 1903.=
Jaekel, Neues Jahrbuch f. Mineral., Geol. u. Paleon., Bd. 1, p. 112,
1903.
Moodie, Jour. Geol., XVII, pp. 63-69, figs. 13-15, 1909.
Type: _Diceratosaurus punctolineatus_ Jaekel.
Orbits in the anterior two-thirds of the axial skull length, nostrils
near to the anterior end of the skull; pineal foramen in the center
of the skull roof; skull provided with tabulate cornua and a broad
backwardly directed process; quadrate angle does not project on the
border of the skull; sculpture of the cranial elements impressed as
radial grooves; 12 presacral vertebræ, 1 sacral with expanded neural
spine which is sculptured at the top, with simple long, apparently
separately ossified transverse processes; extremities small; foot with
5 digits; phalangeal formula 2-3-3-4-3.
The most important differences between _Diceratosaurus_ and
_Ceraterpeton_, the most nearly allied genus, is (in _Diceratosaurus_)
in the more anterior position and small size of the orbits, the backward
extension of the quadrate region, and the dorsal expansion of the
vertebral spines. A further, and more important, difference between the
genera is in the location of the backwardly directed processes from the
skull. In Ceraterpeton they project backward from and are a portion of the
tabulare element, while in Diceratosaurus the projection consists almost
entirely of squamosal and supratemporal.
=Diceratosaurus punctolineatus Cope.=
Cope, Proc. Phila. Acad. Nat. Sci., 1875, p. 16.
Cope, Geol. Surv. Ohio, II, pt. II, p. 372, pl. xli, fig. 4, 1875.
Moodie, Bull. Am. Mus. Nat. Hist., XXVI, art. XXV, p. 356, pl. lxv,
1909.
Type: Specimen No. 8606, American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
The species was first described by Cope as _Ceraterpeton punctolineatum_
(122). It was redescribed on more abundant material (plate 19) by Jaekel
(347), and the following is taken from the discussions of these two
authors, checked by my own observations on the type specimen. This shows
a portion of the skull, consisting of the squamosal and supratemporal
with a projecting, convergent horn. The sculpturing on the skull is
similar to that on the pectoral plates, of which there are three preserved
(plate 14, fig. 4). The bones of the fore limbs are stout and short. The
ribs are only slightly curved. The character of the vertebræ can not be
ascertained. The sculpturing of the bones consists of radiating ridges,
grooves, and pittings.
Jaekel (347) described from the museum collection at Berlin 3 specimens of
this species, among which were 2 skulls. There were associated with these
remains some pectoral plates and limb bones with a nearly complete series
of vertebræ. A modified translation of Jaekel's description follows:
The skull of the largest specimen has, including the horns, a length of 35
mm. and a width of 30 mm. on the occipital border. From the anterior end
to the posterior border of the skull (exclusive of the horns) there is a
length of 25 mm. The pineal foramen lies about midway of this length. The
orbits are rather large, almost circular, and lie about midway between the
pineal foramen and the anterior border of the skull. The nostrils, which
lie anterior to the orbits, are a rather oblique oval and narrowed on the
lateral ends. The distance between them is about the same as that between
the orbits, which measures 7 mm.
[Illustration: MOODIE PLATE 16
1. Type specimen of _Diceratosaurus punctolineatus_ Cope, from
Linton, Ohio, beds. × 1. Drawn from photograph. _cl_=clavicle;
_h_=humerus; _ic_=interclavicle; _mc_=metacarpals;
_r-u_=radius-ulna; _rb_=rib; _sc_=scapula; _sq_=squamosal;
_vs_=ventral scutellæ.
2. Skull of _Sauropleura longidentata_, Moodie, from the Coal
Measures of Linton, Ohio. × 1. Drawn from photograph.
_fr_=frontal; _m_=maxilla; _n_=nasal; _or_=orbit; _par_=parietal;
_pp_=postparietal; _tab_=tabulare.
3. Mandible of _Sauropleura longidentata_, Moodie, from Coal
Measures of Linton, Ohio. × 1.5. Drawn from photograph.
4. Type specimen of _Sauropleura enchodus_ Cope, from the Coal
Measures of Linton, Ohio. × 1.
5. Additional specimen of _Diceratosaurus punctolineatus_ Cope, from
the Coal Measures of Linton Ohio. × 1. _f_=femur; _il_=ilium;
_mc_=metacarpal; _mt_=metatarsal; _ph_=phalanx; _r_=radius;
_t_=tibia.
]
The skull roof is sculptured with pits much like those of _Archegosaurus_.
The larger the bones, the rougher the sculpture. The bones of the middle
of the skull (that is, the parietals, frontals, premaxillæ, nasals, and
postparietals) are of the normal form and only show an unusual difference
in that they are large in the inverse order. The pineal foramen lies in
the anterior third of the parietals; that is the primitive condition
which occurs in the young forms of the Branchiosauridæ. The nostrils are
inclosed by the premaxillæ in front, in the median line by the nasals and
laterally by the maxillæ. The jugals, by their backward prolongation,
form, behind the maxillæ, the border of the skull, and only attain to some
size on the upper side of the cranium.
Jaekel's "perisquamosal" (see plate 15), which is of a doubtful nature, is
not indicated in the type specimen nor in the specimens of the other two
species (462) assigned to this genus. In _D. robustus_ and _D. lævis_ the
"perisquamosal" region is easily separable into its component elements.
The sutures between the elements may have been indistinct in his specimen,
but it is hardly conceivable that a union of the skull bones would occur
in one species and not in another of the same genus. Jaekel's suggestion
(347) that "Etwas mehr Wahrscheinlichkeit möchte ich der Vorstellung
beimessen, dass diese Ausbreitungen zum Schutz freier Kiemen dienten, wie
sie z. B. bei den Perennibranchiaten als baumförmige Organe weit am Halse
herausragen" can hardly find acceptance with students of the Paleozoic
Amphibia, since there is not the slightest evidence that the Microsauria
ever possessed external gills and considerable presumptive evidence that
they did not. His comparison of the "perisquamosal" to the "Kiemendeckel"
of the fishes is also very unhappy on morphological grounds, since the
elements of his "perisquamosal" form constituent parts of the skull roof,
which the operculum never does.
The palate of the skull (plate 15, fig. 2) has been determined by removing
the skull bones of one specimen. Anteriorly the premaxillæ and maxillæ
are clearly recognizable as large dentiferous elements. The premaxillæ
have 4 to 7 teeth, the short maxilla has 3 to 4. All the teeth are of
nearly equal size. Smaller teeth seem to be indicated by impressions found
between the larger ones. The vomers, which are tolerably large, unite with
the premaxillæ behind and inclose at least half of the palatine foramen on
the inner side. They are furnished with small teeth, which in the anterior
part are very irregularly placed, but they are more regular posteriorly.
The palatines and transverse bones are questionably identified. They
seem to lie posterior and lateral to the vomers, but the sutures are
indistinct. The large parasphenoid seems well displayed and is more or
less heart-shaped. There would seem to be a slight indication of double
occipital condyles. The pterygoids are broad plates which inclose the
parasphenoid and form the lateral boundary of the palate. The cotyli are
very indistinct, but appear as elongate grooves.
The pectoral girdle (plate 15, fig. 3) consists, apparently, of seven
elements, three paired and one unpaired. The unpaired element (the
interclavicle) is truncate posteriorly and acuminate in front, with its
surface radially grooved and the anterior borders beveled for articulation
with the clavicles. The clavicles are triangular, as is usual with the
Microsauria. They are sculptured with radiate grooves and ridges, with
decided inosculations at the ossific center. The coracoids have only
part of their surface ornamented; most of their surface is smooth for
articulation with the interclavicle and scapula. A long spine projects
from the inner surface of the coracoid. A pair of small elements lie one
on either side of the clavicles and Jaekel (347) interprets them as the
cleithra. If they are cleithra they are unique among the Microsauria.
The pectoral girdle does not, however, indicate that _Diceratosaurus_ is
"unique among all known quadrupeds."
Jaekel regards the limb which is preserved with the material as an arm
(plate 15, fig. 4), but there is no reason stated for his conclusion. It
has all of the characters of the leg and may be regarded as such. Only
a part of the lower end of the femur is preserved. The tibia and fibula
are preserved as separate rod-like elements with one of the bones longer
and larger, probably the tibia. There are 5 toes which have the customary
phalangeal formula for a microsaurian foot of 2-3-3-4(?)-3. The tarsals
are unossified.
The vertebræ (plate 15) were perforated for the notochord, and are
hour-glass-shaped, with the neural arch thickened to support a heavy
spine which bore a sculptured plate. These apical plates occur in the
dorsal region, but diminish toward the caudal vertebræ. The number of the
vertebræ in the dorsal region is very small and in the tail very large.
There are possibly 2 vertebræ in the cervical, 11 in the dorsal series;
the thirteenth carries the pelvis. There are over 100 vertebræ in the tail.
The ribs have an expanded head and the transverse processes of the
vertebræ are long.
The following account is based on the writer's study of the type specimen
and he is able to add several points of interest to a knowledge of the
anatomy of the type of this interesting microsaurian.
The type specimen consists of 11 consecutive vertebræ with a portion of
the skull, the greater portion of the pectoral girdle, parts of both
fore limbs, ribs, and ventral scutellæ (plate 14, fig. 4). The species
is represented in the collection by yet another specimen, on which Cope
based his _Tuditanus mordax_ (plate 22, fig. 5), of which he himself says:
"Further examination of the specimen on which the latter (_T. mordax_)
was founded leads to the belief that it is an imperfect cranium of
_Ceraterpeton (Diceratosaurus) punctolineatum_ Cope." The plates referred
to are rather to be regarded as elements of the pectoral girdle and I
believe they represent the clavicle and a portion of the interclavicle.
The skull of the present species is fully described by Jaekel. The
type specimen does not offer any evidence in support of Jaekel's
"perisquamosal," but rather tends to the idea that he is incorrect in his
assumption of the fusion of these elements of the skull. The direction
taken by the ridges and grooves on the elements preserved indicate a
separation between the supratemporal and the squamosal. I do not find
that the grooves have the tendency to arise from a common center of
ossification in the squamosal, as suggested in the figures of Jaekel.
The horn which projects backward from the squamosal is rather large and
heavy for the size of the skull, and after curving slightly inward ends
in a blunt point and not sharply, as Jaekel figures in his specimens. The
vertebral column is indistinctly preserved and I have nothing to add to
Jaekel's account given above.
In the structure of the pectoral girdle my results are greatly at variance
with those of Jaekel. I do not find the remarkable elements which Jaekel
has figured (347) in his specimens. On the other hand, I find a normal
microsaurian pectoral arch (464), such as has been described for numerous
other forms. There are present, distinctly preserved in the type specimen,
the scapulæ, the clavicles, and the interclavicle, with the possibility
of the coracoid. The peculiar element referred to by Cope as resembling a
"lacertilian pubis" is without doubt the left scapula of the animal (plate
16, fig. 1). Its form compares very favorably with that of _Ceraterpeton_
as figured by Woodward (630). The coracoid may be represented by the
fragment which lies close to the scapula. The sculptured element lying
next to the supratemporal horn of the skull is the right clavicle
preserved bottom side up. Of the other two sculptured elements, one is the
interclavicle, only a portion of which is preserved. The left clavicle
lies beside it. The clavicles in this species have a tendency to assume
the triangular shape so common in other species of Microsauria, and the
interclavicle, so far as can be determined, was shield-shaped. The upper
surfaces of the pectoral elements are marked by grooves for the attachment
of the pectoral muscles.
[Illustration: Fig. 24.
A. Skull of _Diceratosaurus lævis_ Moodie, from the Linton Coal
Measures. × 1. _f_, frontal; _j_, jugal; _mx_, maxilla; _n_,
nasal; _or_, orbit; _par_, parietal; _pof_, postfrontal; _po_,
postorbital; _pf_, prefrontal; _pp_, postparietal; _sq_,
squamosal; _spt_, supratemporal; _qj_, quadratojugal; _pmx_,
premaxilla; _tab_, tabulare.
B. Reconstruction of skull outlines of _Diceratosaurus robustus_
Moodie, from the Coal Measures of Ohio. × 0.75. _fr_, frontal;
_f_, jugal; _or_, orbit; _par_, parietal; _pof_, postfrontal;
_po_, postorbital; _pp_, postparietal; _qj_, quadratojugal;
_spt_, supratemporal; _tab_, tabulare.
]
The ventral scutellation is present in a small patch (plate 16, fig. 1)
near the horn of the skull. The scutæ are oat-shaped and take the usual
form. The ribs are not long, are rather stout, and beyond the proximal
curve are nearly straight to the obtuse tips. The heads of the ribs are so
obscure that it is impossible to determine whether they were two-headed
or not. They are expanded proximally and there is a slight tendency to a
division of the head.
Portions of both fore limbs are preserved. The right limb possesses the
humerus, separate radius and ulna, and 2 metacarpals. The other possesses
only the radius, 3 metacarpals, and a portion of a phalanx. The humerus is
a very stout bone and at once recalls that of _Amblyrhynchus_. The ends
are expanded and there are roughnesses on the bone for the attachment of
muscles. The radius and ulna are subequal in size. They are both expanded
more proximally than distally. The carpus was cartilaginous. An additional
specimen of this species is figured on plate 16, fig. 5. This adds to our
knowledge of the pelvis especially.
Measurements of the Type.
mm.
Length of entire specimen 80
Length of tabulate horn of skull 20
Width at base 4
Width at tip 2.5
Length of right humerus 16
Width at middle of shaft 3
Width at proximal end 5
Width at distal end 5.5
Length of radius 9
Length of ulna 9
Width of radius at proximal end 2.5
Width at middle 1.5
Width at distal end 2
Width of various portions of
ulna same as radius.
Length of the only phalanx preserved 5
Length of vertebra 5
Width of vertebra 4
Length of longest rib 17
Width of rib at widest part 1.5
Width of clavicle 18
Length of clavicle 20
Length of interclavicle 25
Width of interclavicle 16
Length of single side of chevron scute 7
Width of same .25
The specimen (No. 2566, Am. Mus. Nat. Hist.) on which Cope based his
_Tuditanus mordax_ is composed of two plates of the above-described
species.
=Diceratosaurus lævis Moodie.=
Moodie, Jour. Geol., XVII, No. 1, p. 63, figs. 13, 14, 1909.
Type: Specimen No. 102 (8680 G), American Museum of Natural History, where
it forms part of the Newberry collection.
Horizon and locality: Linton, Ohio, Coal Measures.
The species is represented by an almost complete skull, which had been
identified previously by Cope as _Tuditanus radiatus_. The specimen
consists of the impressions of the bones of the cranial roof, the bones
themselves having disappeared. It is not probable that the dorsum of the
skull was smooth. The details in the structure of the skull have been
ascertained quite definitely. There can be no doubt that the arrangement
of the elements is accurate, as shown in figure 24 A. The supratemporal,
as in _Erpetosaurus tabulatus_ Cope, is excluded from the parietal.
The form of the skull at once recalls that of the species _D.
punctolineatus_, as figured by Jaekel (see plate 15). The orbits are
located in nearly the same region of the skull and the sutures separating
the cranial elements are quite similar in the anterior portions. The
species _D. lævis_ is based on the divergent character of the horn-like
protuberances which project from the squamosals. The horns of _D.
punctolineatus_ are convergent. The present skull is also smaller and the
parietals in _D. lævis_ are much larger than in the type species. In the
type species, also, the pineal foramen is located well forward in the
parietal, while in the present form the foramen is located well posterior.
The skull is almost rectangular. The nostrils are elongate ovals. The
orbits are circular and the distance between them is equal to two-thirds
of the dimensions of the orbit. They are located well forward in the skull
and are bounded laterally by the maxillaries. The nostrils have much the
same character as in the type form, being broadly oval.
The premaxillæ are elongate transversely, being about twice as long as
wide. They are identical in shape and relations with the same elements
in _D. punctolineatus_ Cope. The nasal is nearly square and forms
the interior boundary of the nostril. The frontal is elongate in the
median length of the skull and it is acuminate posteriorly, where the
acumination is inclosed by the parietal and postfrontal. The parietals are
by far the largest elements in the cranium. They form together an oval
which is elongate in the longitudinal diameter of the skull. They inclose
between them, in the median suture, the small pineal foramen. They are
acuminate in front, with a broad truncate posterior base, where they are
bounded by the postparietals. The postparietal is nearly square, being
somewhat wider than long. It joins the tabulare and the parietal. The
tabulare is elongate in the long diameter of the skull. It ends anteriorly
in a point which is inserted between the postorbital and the parietal, and
bears a short protuberance posteriorly, much as does the same element in
the type species.
There are four elements which take part in the formation of the posterior
border of the skull. These are the postparietal, the tabulare, the
squamosal, and the supratemporal. It is very unusual for the supratemporal
to reach the posterior edge of the cranium. The pref rental lies anterior
to the orbit, of which it forms the anterior border. The lacrimal has not
been detected, although Jaekel (347) has indicated it in his drawings
of the skull of the type species. The maxilla is elongate and forms the
lateral border of the skull. No teeth have been detected, although they
were doubtless the same as Jaekel has figured in _D. punctolineatus_.
The jugal is an elongate element joining the maxilla posteriorly. Jaekel
included this element in his "perisquamosal," but the sutures are clearly
evident in the present specimen and there is no evidence of a structure at
all similar to a "perisquamosal." The postorbital is fully as large as the
jugal which it joins, forming a part of the posterior border of the orbit
and ending posteriorly in a point which is inclosed by the tabulare and
the squamosal. The postfrontal with the foregoing element forms the entire
posterior border of the orbit and it likewise ends in a point inclosed
by the parietal and the postorbital. The quadratojugal has much the same
shape and relations as in _D. punctolineatus_, although it is located
further back. The squamosal is also elongate, as are most of the posterior
cranial elements, and it also has an acumination which is directed forward
and is inclosed by the postorbital and jugal. The anterior suture of this
element is rather indistinct, but it is, I believe, as represented (fig.
24). The element is elongate and is prolonged posteriorly to form the
horn, which ends in a blunt point and is not sharp, as in the type species.
Jaekel (347) regards the species _Diceratosaurus punctolineatus_ Cope
as being unparalleled among known vertebrates in the possession of a
"perisquamosal" element. In closely allied species the "perisquamosal" is
easily separated into its component elements, and the morphology of the
present skull would throw considerable doubt on Jaekel's interpretation
of the skull of the type species. Another specimen, described below as
another species of this genus, shows no evidence of this fusion. So far as
I can learn, there have been no cases of true fusion of cranial elements
correctly reported, unless it be that which possibly exists between the
two frontals in the skull of _Diplocaulus_. It was on the basis of such
fusions that Maggi (397) proposed to derive the interparietals of the
primates from the tabulare of the stegocephalians.
The posterior outline of the skull in the present specimen is not well
preserved and the outline as given may be slightly inaccurate. The
indentation figured by Jaekel in the posterior border of the skull of the
type form is not present in the species under discussion.
Measurements of the Type Skull of Diceratosaurus lævis Moodie.
mm.
Length of skull along median suture 37
Length from muzzle to tip of horn 50
Width between tips of horns, estimated 40
Width of orbit 7
Length of orbit 10
Width of skull across the orbits 30
Interorbital width 6
Length of nostril opening 2
Width of nostril 1
Diameter of the pineal foramen - 1
=Diceratosaurus robustus Moodie.=
Moodie, Jour. Geol., XVII, No. 1, p. 67, fig. 15, 1909.
Moodie, Bull. Am. Mus. Nat. Hist., XXVI, art. XXV, p. 355, pl. lxiii,
fig. 2, 1909.
Type: Specimen No. 8611 G, American Museum of Natural History.
Horizon and locality: Linton, Ohio, Coal Measures.
The present species is indicated by the left portion of a cranium
representing a large individual. The characters of the skull are so
clearly marked that it seems worthy of description. The presence of horns
as given in the restoration of the skull (fig. 24, B) is based on the
analogy with the other two species of this genus, in both of which horns
are present. The generic determination of the species is based on the
large size of the postorbital, which is essentially characteristic of the
other species of _Diceratosaurus_.
The characters which distinguish the species from others of the genus are
the large postorbitals and the small parietals, which are excluded from
union with the postfrontals on account of the large size of the frontal.
In the other two known species the frontal is small and the parietal comes
forward to join the postfrontal. The present species exhibits a skull
which is nearly twice as large as that of _D. lævis_ and nearly three
times the size of the skull of _D. punctolineatus_.
The portion of the skull preserved shows the cranium to have had a rather
acuminate snout, not blunt as in the type species. The orbit is an
elongate oval, although it has the same relative position in the skull
as in the other species. The nostril is indicated by an oval depression
near the anterior edge of the skull. The frontals, as indicated by the
sutures present on the portion of the skull which is preserved, are fully
as long as the parietals. Whether they were as wide as is represented is
uncertain. The postfrontals are very small bones, the sutures of which are
somewhat uncertain, although they can not be far from what is represented
(fig. 24, B). The postorbital is large and elongate, and is distinctive of
this species on account of its unusual size, although it does not attain
the same proportions as in other members of the genus. The parietals are
elongate and narrow. The pineal foramen is represented by its lateral
edge and its position is about midway of the longitudinal diameter of
the parietals. The narrow postparietal is represented by its anterior
border; as restored (fig. 24, B) it may be too long. The tabulare, also,
is represented by an anterior portion and it shows this element to have
the position and form which is typical of the form _Diceratosaurus lævis_.
Such other of the cranial elements as are indicated are based on the
relations discovered in _D. lævis_.
The heavy line on the left of the drawing (fig. 24, B) represents the
outline of the preserved portion. The skull, as restored, may be a little
too long, and the shape of the horns is conjectural. In the orbit there
are preserved 2 misplaced teeth showing longitudinal fluting. The longest
tooth is about 3 mm.
Measurements of the Type Skull of Diceratosaurus robustus Moodie.
mm.
Median length of skull, estimated 67
Posterior width of skull, estimated 78
Length of orbit 18
Width of orbit 12
Length of longest tooth 3
Width of same tooth at base 1.5
Length of postorbital 27
Width of postorbital 14
=Genus EOSERPETON Moodie, 1909.=
Moodie, Jour. Geol., XVII, pp. 76-79, fig. 20, 1909.
Moodie, Bull. Am. Mus. Nat. Hist., XXVI, p. 355, pl. lxiii, fig. 1,
1909.
Type: _Eoserpeton tenuicorne_ Cope.
The genus was proposed for the reception of a single species originally
referred by Cope to _Ceraterpeton_ (_C. tenuicorne_). The species can
not be placed in the genus Ceraterpeton on account of the form and
structure of the skull, which varies widely from that of the type species,
Ceraterpeton galvani Huxley, from the Kilkenny Coal Measures of Ireland.
The most important character in which the present species differs from _C.
galvani_ is the peculiar form taken by the squamosal and by the position
of the "horn." These characters will be evident on referring to figure
25. No undoubted remains of _Ceraterpeton_ have been found outside the
British Isles. Fritsch referred (251) a species, previously described as
_Scincosaurus crassus_, to this genus, but Andrews (8), Jaekel (347) and
Woodward (630) all unite in placing the species in the genus where it was
formerly described. Jaekel even says that the Scincosaurus has no horns,
so far as he can determine. Cope referred 3 species (123) from the Linton
Coal Measures of Ohio to the genus _Ceraterpeton_, but it has been shown
elsewhere (347) that no one of them belongs in the genus, nor in fact do
they all belong in one genus.
=Eoserpeton tenuicorne Cope.=
Cope, Geol. Surv. Ohio, II, pt. II, pp. 372-373, pl. xlii, fig. 2,
1875.
Cope, Proc. Am. Phil. Soc., XXII, p. 407, 1885.
Cope, Proc. Am. Phil. Soc., XXXVI, p. 85, pl. iii, fig. 2, 1897.
Moodie, Proc. U. S. Nat. Mus., vol. 37, p. 23, 1909.
Type: Specimen in the American Museum of Natural History. There are also
specimens Nos. 4472 and 4473 in the U. S. National Museum.
Locality and horizon: Linton, Ohio, Coal Measures.
The species was founded on a complete skull preserved on obverse sides
of a block of coal. Cope (123, pl. XLII, fig. 2) figured this skull. The
figure is poorly executed and does not do justice to the specimen, which
is really well preserved. In general the skull is oval, with the orbits
located well towards the acuminate snout. The interorbital space is equal
to twice the width of the orbit. The pineal foramen lies near the center
of the skull. The quadrate angles are drawn out into slender acuminate,
longitudinally striate horns, processes from the squamosal. The "horn"
arises from an expanded base, which is a portion of the cranial element
at the postero-lateral angle of the skull. This character is taken as
the distinctive one of the genus. It is possessed by no other form of
Carboniferous air-breathing vertebrate, in association with the other
characters of the form.
Measurements of the Type of Eoserpeton tenuicorne.
mm.
Median length of skull 26
Width across squamosal enlargement 30
Width across base of horns 25
Length from muzzle to tip of horn 40
Length of horn 10
Width of horn at base 4
Length of orbit 4
Width of orbit 3
Interorbital span 6
Nos. 4472 and 4473, U. S. National Museum, from Linton, Ohio, Coal
Measures.
mm.
Median length of skull 16
Maximum width of skull 20
Length of horn from base 7
Length of orbit 3
Interorbital width 3.5
Length of vertebral column to sacrum 33
Length of femur 5.5
Length of tibia and fibula 3
Length of second digit (incomplete) 7
Length of metatarsal 1.5
Length of clavicle 6
Width of clavicle 3.5
[Illustration: Fig. 25. Restoration of skeleton of _Eoserpeton tenuicorne_
Cope. × 1 .5.
Skull: _pmx_, premaxilla; _n_, nasal; _fr_, frontal; _par_, parietal;
_pf_, prefrontal; _mx_, maxilla; _pof_, postfrontal; _po_,
postorbital; pp, postparietal; _j_, jugal; _qj_, quadratojugal;
_spt_, supratemporal; _sq_, squamosal; _tab_, tabulare.
Skeleton: _ic_, interclavicle; _cl_, clavicle; _sc_, scapula; _h_,
humerus; _r_, radius; _u_, ulna; _c_, carpus; _sr_, sacral rib
(uncertain?); _il_, ilium; _f_, femur; _fb_, fibula; _t_, tibia;
_ts_, tarsus.
]
The boundaries of the premaxillæ are indefinite, but what remains of
the sutures indicates that the elements were small. No teeth have been
detected. The nasal is likewise not clearly defined, but the frontal
is an elongate element which occupies the space between the orbits and
joins the parietal posteriorly. The parietals form a large oval space, so
characteristic of many of the Carboniferous Microsauria, in the anterior
third of which occurs the median parietal foramen. The postparietal is
almost square, and forms part of the posterior boundary of the skull.
The tabulare has the usual position and relations. The prefrontal is
ill defined. The postfrontal is small and forms a slender rod on the
postero-inner boundary of the orbit. The postorbital is small and its
bounding suture with the postfrontal is indefinite. The jugal is only
partially represented in the specimen, and that part forms the outer
boundary of the orbit. The maxillary sutures are not defined. There are
no evidences of teeth, since the skull is compressed dorso-ventrally. The
quadratojugal is, apparently, a larger element than usual, with the visual
relations. The supratemporal lies in great part in front of the squamosal,
but still has the normal relations of that element. The squamosal is the
characteristic feature of the skull. It is very tumid at its base and
projects into a long, slender, acuminate horn, the tumid portion being
ornamented by radiating striæ.
Another specimen of this species presents the greater part of the
skeleton. However, very little can be added to our knowledge of the skull
structure. It is barely possible that the second specimen may be distinct
from the type. The horns are curved inward, but otherwise there is little
or no difference. One of the most interesting and important features
of the complete specimen is the unusual preservation of a leg, with
impressions of 15 or more vertebra;, and traces of curved ribs which are
intercentral in position.
The femur is slender and expanded at the ends, with the articular surfaces
well formed. The tibia and fibula are mere rods of bone, although the
tibia has slightly expanded extremities. There is no osseous tarsus.
There are 5 digits in the foot; the second one is entire and contains 4
phalanges; the other digits are incomplete. The foot is remarkably long
and slender, and is fully as long as the tarsal space plus the tibia, with
the terminal phalanx clawed.
There are impressions of 2 oval and elongate clavicles in the pectoral
region. The outer end is not expanded as is usual, and the surface is
ornamented with grooves and ridges which radiate from a common center.
The entire remains measure scarcely 3 inches in length and it is to be
doubted if the creature attained a length of more than 4 inches. It is
probably a young form, but there are no evidences of external gills. The
chevron armature is but poorly preserved, but so far as can be determined
it is not different from that of other Microsauria, such as _Amphibamus_.
[Illustration: MOODIE PLATE 17
Type of _Saurerpeton latithorax_ Cope. × 1.5. Original in U. S. National
Museum.]