THE AMERICAN COAL MEASURES BRANCHIOSAURIDÆ.
Definition Op the Family Branchiosauridæ Fritsch, 1879. Coal Measures and
Permian Op North America and Europe.
Fritsch, Fauna der Gaskohle, Bd. I, p. 69, fig. 30, 1879.
Lydekker, Cat. Fossil Reptilia and Amphibia, pt. IV, p. 210, 1890
(Protritonidæ;).
Stegocephalic, salamander-like animals, with broad, anteriorly truncate
skull. Teeth smooth with large pulp-cavity. The parasphenoid narrowed
anteriorly, posteriorly expanded to a shield-shaped plate. Vertebra;
with the notochord persistent and intravertebrally expanded. Pelvis well
developed, the ilium and ischium osseous with large cartilaginous margins,
the pubis unknown, possibly hyaline cartilage. Ribs short, straight,
present on almost all vertebræ. Skin with delicately ornamented scales.
Eyes with sclerotic plates. Palatal elements toothless or with small
tooth-like tubercles on pterygoids and palatines. Ventral armature on
throat, chest, and abdomen, extending on to the limbs, consisting of small
delicate scutellæ arranged in a chevron pattern.
The above definition is modified from Fritsch (Fauna der Gaskohle, Bd. I,
p. 69, 1879).
The North American species are: (?) _Sparodus_ sp. indet. Dawson,
_Micrerpeton caudatum_ Moodie, _Mazonerpeton longicaudatum_ Moodie,
_Mazonerpeton costatum_ Moodie, _Eumicrerpeton parvum_ Moodie.
=Genus MICRERPETON Moodie.=
Moodie, Jour. Geol., 17, p. 39, figs. 1 to 6, 1909.
Type _Micrerpeton caudatum_ Moodie.
The genus _Micrerpeton_, of which the single species is described below,
was the first evidence of the occurrence of the Branchiosauria in America.
There have been three other genera referred to the Branchiosauria from
North American deposits, but there is good evidence that none of them
belong there. The genus Amphibamus was originally referred to the
_Xenorhachia_ by Cope (105, pp. 134-137) on account of the supposed
cartilaginous condition of the vertebræ and the absence of ribs. Later
he abandoned this order and placed the form in the Branchiosauria, where
it was retained by Zittel (642). Recently Hay has shown (316), and I am
able to corroborate his statement, that ribs are present in the species,
and that they are long and curved, not at all like the short ribs of
the true Branchiosauria. These long, curved ribs undoubtedly exclude
_Amphibamus_ from the Branchiosauria and indicate its close affinities
with the Microsauria. The genus _Pelion_ has also been referred to this
order on purely negative evidence (642, p. 375). This genus is excluded
from the Branchiosauria by the well-ossified condition of the limb bones,
in which the endochondral ossification is seen to be well developed, a
condition not found, so far, among the true Branchiosauria. The form of
the head and the elongate hind limb would also tend to exclude the genus
from the Branchiosauria. In the Branchiosauria the fore limb is usually
larger than the hind limb, the reverse of which is the case in _Pelion_.
The genus _Sparodus_, as it occurs in North America, is uncertain. It is
indicated by remains which are almost impossible of determination.
The genus _Micrerpeton_ may be distinguished from other known
Branchiosauria by the large size and anterior position of the orbits,
absence of a posterior table to the skull, the short, heavy limb bones,
the slender ilium, and the expanded, elongate, and laterally compressed
tail. The genus may be defined as follows: Small forms, the known
representative attaining a length of less than 2 inches; head broad and
short; sclerotic plates present; interorbital space less than the least
diameter of the orbit; occiput concave; pineal foramen in the line which
cuts the posterior edge of the orbits; teeth small, pleurodont denticles;
presacral vertebræ 20 or 21, of which probably 5 are cervical; 1 sacral;
ribs short, straight, and heavy, central; scapula ovoid; limbs stumpy and
heavy, fore limb exceeding the hind in size; endochondral ossifications
distinctly absent; tail long, expanded, and flattened, probably provided
with a thin expanded membrane; body covered with minute, ovoid or rounded
scales which are ornamented with concentric lines; color markings
vertical to the long axis of the body and abundantly present on the tail;
lateral-line organs represented by the dorsal and median lateral lines
on the tail, the sensory pits probably occurring in specialized darkened
scales. Coal Measures of Mazon Creek shales near Morris, Grundy County,
Illinois.
=Micrerpeton caudatum Moodie.=
Moodie, Jour. Geol., 17, p. 39, figs. 1-6, 1909.
Type: Specimen No. 12,313, Walker Museum, University of Chicago.
Horizon and locality: Mazon Creek shales, near Morris, Illinois.
The species is represented by very complete remains (plate 2), which are
preserved on opposite halves of a nodule. The specimen was collected many
years ago by Mr. W. F. E. Gurley at Mazon Creek, but it has never before
been studied, although Dr. Newberry examined it and said in a note that
Professor Cope should see it. Unfortunately Cope did not see it and it
lay unknown for more than a quarter of a century. I am indebted to Dr.
Stuart Weller for calling my attention to the specimen, as well as for the
privilege of describing it.
The specimen is exceptionally perfect (plate 25, fig. 4). Nearly all the
skeletal elements are present, and the general contour of the body, the
character of the dermal covering, the color-markings, the lateral-line
system, and many other features of interest have been detected. Such
completeness of preservation is very uncommon even among the remains
obtained from this locality. In this case the entire form was preserved,
but the collector, in cracking the nodule, lost the chips containing the
feet, so that only portions of the limbs remain. It is thus impossible to
determine the phalangeal formula, but the feet were probably like those
of _Branchiosaurus amblystomus_ Credner, as given by Credner, to which
species the present form is closely allied and indeed must be placed in
the same family with _Branchiosaurus_, _Pelosaurus_, and _Melanerpeton_.
[Illustration: MOODIE PLATE 2
Drawing × 3.5. of type specimen of _Micrerpeton caudatum_ Moodie, from the
Coal Measures of Mazon Creek, Illinois, showing skeletal elements, form
of head and tail, the lateral-line sense-organs, banded color-markings,
and ventral scutellæ. On the edges of the tail impression are indications
that in life the tail had a thin fold of skin above and below the fleshy
portion, much as in the larvæ of _Amblystoma_ at the present day.]
The remains here described represent a small, salamander-like form, and
they are among the earliest geological evidence of the group, which,
without doubt, gave rise to the modern salamanders. The parts preserved
in the specimen are: the complete outline of the head with most of the
cranial elements clearly distinguishable, as well as the black pigment
of the choroid; the entire vertebral column, including pits in the tail
region, where the vertebræ were without doubt entirely cartilaginous;
parts of the pectoral girdle; the ilium; the left humerus; the ventral
scutellation; the ribs of one side of the body and indications of ribs on
the other; portions of both hind limbs; and a complete impression of the
fleshy tail. On this impression of the tail are preserved small, horny
scales, transverse color-markings, and the distinct impressions of the
lateral-line system.
The bones of _Micrerpeton caudatum_, as in so many of the fossils from
this locality, have been replaced by a white, friable mineral which is
probably kaolin. The animal is preserved on its back and it is thus
illustrated from the ventral side. The entire length of the animal is only
49 mm., of which the tail occupies nearly half.
[Illustration: Fig. 13. Restoration of _Micrerpeton caudatum_, a
branchiosaur from the Coal Measures of Illinois. × 2.]
The head has much the same shape as in the species of Branchiosaurus
described and figured by Fritsch (251), Credner (181), and Thevenin (568).
The eyes occupy relatively the same position as in that genus. The orbits
are very large and broadly oval. Within the borders of the rim the stone
is blackened as though by the black pigment of the iris, such as Cope has
described in _Amphibamus_. Under a rather high power of magnification
the cranial bones are seen to be represented by mere flakes of white
mineral matter. The sutures separating the cranial elements are distinctly
preserved on the main half of the nodule.
The openings of the skull are five the two orbits, the two minute
nostrils, and the pineal foramen. A median suture separates the skull
into halves and the pineal foramen lies slightly anterior to the
posterior third of its length. The boundaries of the premaxillæ are not
distinct, but they are very small elements and form the inner border of
the nostrils, which are clearly indicated by bosses of stone. The nasal
element is nearly square and lies anterior to the frontal, which it
borders broadly. The parietal is about the same size as the frontal and it
apparently forms a portion of the inner border of the orbit, although this
is not assured. The parietal is elongate and unites posteriorly with the
postparietal. The postparietal, with the tabulare and the squamosal, form
the posterior boundary of the skull, and they are hence not unlike the
same elements in other Stegocephala. The pref rental forms the anterior
border of the orbit. The lacrimal has not been detected. The maxilla
is elongate and forms the antero-lateral border of the skull. The jugal
forms an important element in the lateral border of the cranium and joins
the quadratojugal posteriorly. The postfrontal is triangular and with the
postorbital forms the posterior border of the orbit. Both of the elements
are acuminate posteriorly, although the suture between them is indistinct,
and they inclose between their posterior acuminations an anterior
projection of the supratemporal. The squamosal has the usual relations and
borders the supratemporal laterally. The latter element forms the quadrate
angle of the cranium.
The entire length of the vertebral column is preserved, although
the nature and structure of its elements can not be determined. The
impressions of a few of the vertebræ show that some of the centra were
amphicœlous, but other than this nothing is definite. The cavities which
the centra occupied were filled by the white mineral matter and the force
of the blow which cracked the nodule destroyed the form of the mold. It is
possible that where the mineral matter has filled the cavities the centra
were osseous or partly cartilaginous, and where the cavities were unfilled
the centra were entirely cartilaginous. The length of the vertebral column
from the base of the skull to the last impression of a cartilaginous
centrum is 33 mm.
The number of centra between the sacral vertebra and the skull is 20 as
they are preserved, but there may have been one more, the atlas. Fritsch
has represented 21 in his restoration of _Branchiosaurus salamandroides_,
and this is a further indication of an affinity between the two genera,
although Credner has represented 26 presacral vertebra; in _Branchiosaurus
amblystomus_. The presacral vertebræ are thus seen to vary within narrow
limits, but the number of presacrals is near 20, and this may be taken
as typical. It is interesting to notice that in modern forms of the
salamanders the presacral vertebræ number about 20. There is but a single
sacral centrum in _Micrerpeton_. The sacral rib has not been detected, but
it is restored after the condition found in _Branchiosaurus_. The right
femur partially covers the sacral vertebra, and its structure can not be
determined. I count impressions of 17 caudal centra, of which at least
12 may have been partially ossified. In the cervical region there are
distinct impressions of transverse processes on at least 5 vertebræ, and
this number is assigned to the neck, although it is by no means certain
that this is the correct number. The neck was at least short, if we may
judge from the position of the remains of the pectoral girdle. No cervical
ribs are definitely determined. There is a short rib lying between the
fifth and sixth vertebræ, but to which it belongs is uncertain.
There are impressions of 10 ribs preserved on one side of the vertebral
column and one on the other side. They are short, straight, and heavy,
as are the same elements in _Branchiosaurus_. This character alone is
sufficient to place _Micrerpeton_ among the Branchiosauria, since no
such ribs are known in other groups of the extinct amphibians. The ribs
preserved lie next the seventh to the seventeenth vertebræ on the left
side, and there is one on the right side which may belong to either the
fifth or sixth vertebra. They are central in their attachment, and in this
they agree well with the mode of rib attachment in the modern salamanders.
All of the ribs are single-headed and are composed, for the most part,
of perichondral tissue. The position of the ribs in the matrix inclined
backwards, and, making a small angle with the vertebral column, is very
suggestive of the condition in _Branchiosaurus_.
The pectoral girdle is represented by three distinct elements of the left
side, which are identified as scapula, clavicle, and coracoid, following
the nomenclature given by Woodward (631), although Credner (186) would
name them otherwise. The scapula is represented by an ovoid fragment
lying next to the vertebral column. The clavicle was probably spatulate,
as in _Melanerpeton_, but the inner end of the element is not visible.
The coracoid is represented by its outer end only, and its inner pointed
extremity is not visible. The interclavicle has not been detected.
The humerus lies somewhat to one side of the pectoral girdle, as if
there had been a large amount of epiphyseal cartilage. Its position may
be due to post-mortem shifting, but there is little other evidence of
any movement after deposition. The humerus is a large, heavy bone in
comparison with the rest of the skeleton. It is expanded at each end, and
its ends show concavities, proving that the bone is formed principally
of perichondral tissue, as would be expected from such an early
Branchiosaurian. The endochondrium has not yet developed in this form,
which is evidently adult. There is no other element of the arm present.
There is but a single element of the pelvis preserved, a slender elongate
rod which is undoubtedly the ilium, since it has the usual position for
that element and is much too large for a sacral rib. It has much the same
shape as the ilium in the modern _Salamandra_, and is not expanded as is
the ilium of _Branchiosaurus_. This element, like the humerus, seems to
have been but a hollow cylinder of bone and undoubtedly had cartilaginous
ends, as in the ilium of the recent _Salamandra_. The two femora are
preserved nearly entire, the right one lying upon and partly obscuring the
sacral vertebra. The femur is much more slender than is the humerus, with
slightly expanded ends, and, like the humerus, shows the concavities at
the ends, indicative of the perichondral character of the tissue composing
it. There are two elements of the leg preserved more or less entire. The
larger bone may represent the tibia and the smaller the fibula. They both
present characters similar to those of the femur and humerus. They are
simple rods of bone tapering at the distal end. The feet have been lost,
though doubtless they were present at one time.
The ventral surface of the body, as in other members of the
Branchiosauria, was covered and protected by a series of small scutes
arranged in the regular chevron pattern. The form of the scutes and their
number can not be determined. The lines which represent them are, however,
distinct. Some of the scutes are missing and some of them are obscured
by lying over the vertebral column. They are all somewhat shifted to the
left. The lines are very small and close together. I count 16 of them
in a distance of 2 mm. In length the longest line preserved is a little
more than 4 mm., measuring from the point of the chevron. The lines
representing the scutes come to a point in a median ridge which is now
represented by a line. The dermal scutes on the abdomen were probably the
forerunners of the abdominal ribs of the reptiles (fig. 9).
The impression of the tail contains some of the most interesting features
in the entire specimen. Scattered over it and in places laid in mosaic
are impressions of small dermal scales, which may have covered the
entire body. In form the scales are ovoid, being half as wide as long,
and the markings on the scales partake of the nature of radiating lines,
much after the pattern of the sculpturing of the cranial bones in the
Microsauria. The scales are less than 0.5 mm. in diameter and their
character can only be ascertained under high magnification. Near the
middle of the tail there are preserved distinct transverse bands of
dark color, which are more or less evident throughout the entire tail
impression, but they are elsewhere not so distinct as in the central
region. The lines are evidently due to rows of pigmented scales, and in
all probability the animal's body was transversely striped.
The most interesting and important single structure discovered on the
specimen is the impression of the lateral-line system, which is clearly
evident as two dark lines on the impression of the fleshy part of the
tail. The sense-organs are represented by two longitudinal rows of
pigmented scales, one beginning at the tip of the tail, the other taking
its origin from the median line somewhat further forward. I am indebted to
Dr. Katashi Takahashi for calling my attention to the similarity of this
arrangement to that found in the recent _Necturus_. The arrangement and
disposition of the lines containing the sense-organs is practically the
same in the two forms. The median lateral-line takes its origin from the
extreme tip of the tail and is continued to the base, where the impression
is broken. The dorsal lateral-line has its origin rather abruptly from the
median lateral-line at a distance of 6 mm. from the tip of the tail. The
sense-organs were undoubtedly located beneath specialized pigmented scales
on the surface, and to this pigment is due the preservation of the lines.
The fact that the arrangement of the sense-organs of _Micrerpeton_
corresponds so exactly to the condition found in _Necturus_ is of
considerable interest. _Necturus_ alone among the modern tailed
Amphibia has the arrangement described for the lateral-line system of
_Micrerpeton_. All other forms of the Caudata, as also the larval forms
of the Salientia, have an arrangement of the lateral-line system which
is perfectly distinct from that found in Necturus, although the basis of
the same arrangement is found in all. In _Amblystoma_, for instance, the
median lateral-line is not present on the tail, and the dorsal line is
incompletely developed. The close similarity of the arrangement of the
systems of sense-organs in the two forms, _Micrerpeton_ and _Necturus_,
may be of genetic significance with regard to the latter form. The
lateral-line sense-organs are of a very fundamental significance, and
it is not at all improbable that the same arrangement of the lines has
existed from the Carboniferous period or earlier. We know that such
has been the case in a great many of the fishes. The ancestors of the
modern Caudata must have originated somewhere in the basal Carboniferous
or earlier periods, and, in the writer's opinion, the Branchiosauria
represent the ancestral group of the Caudata. This suggestion is by no
means new, since Baur and others have held the same view. This topic has
been discussed at length elsewhere (459) by the writer.
The relations of the form _Micrerpeton caudatum_ are readily determined.
The number of the presacral vertebræ, the form and position of the
ribs, the shape of the skull, the arrangement of the cranial elements,
the structure of the pectoral girdle and the character of the ventral
armature all clearly bespeak a close relationship with _Branchiosaurus_,
_Melanerpeton_, _Pelosaurus_, and other European branchiosaurian forms
from the Upper Carboniferous and Lower Permian.
The above-described species, with others given below, is the earliest
geological evidence of the Branchiosauria, since the oldest European
forms are from the Stephanian (Upper Carboniferous), which probably lies
somewhat above the horizon of the Allegheny series of North America. The
presence of the Branchiosauria in America is of considerable interest in
the bearing it has on the distribution and migration of the Paleozoic
animals. Knowledge of how the group came to occur in such widely separated
localities in approximately contemporary geological strata is an unsolved
problem of paleontology. It is possible that the piscian ancestors of the
Amphibia migrated across or along the borders of the seas and began the
amphibian phase of development independently in the two continents. That
evolution should, in this case, have followed almost exactly parallel
lines seems incredible.
Measurements.
mm.
Length of entire animal 49
Length of head in median line 6.5
Width of head at posterior border 8
Length of orbit 2.5
Width of orbit 2
Interorbital space 2
Length of the vertebral column 33
Length of the vertebral centrum
in dorsal series 0.5
Length of trunk from base of
skull to sacrum 22
Length of rib 1.5
Length of scapula 3
Maximum width of clavicle 2
Length of humerus 2.5
Length of ilium 1.5
Length of femur 2
Length of tibia 1.5
Length of tail impression 21.5
Width of tail impression at base 4
=Genus EUMICRERPETON Moodie.=
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, p. 330, 1912.
Type: _Eumicrerpeton parvum_ Moodie.
The genus is established on three well-preserved specimens representing
nearly the entire anatomy. The generic characters are found in the very
broad posterior table of the skull, with its short length, reduction of
tympanic notch, and shortness of body. The body-length of _Eumicrerpeton_
(plate 5, fig. 1) is less proportionately than that of other closely
allied genera. Other generic characters are found in the sharp
postero-lateral angle of the skull, and it is to be distinguished from
_Micrerpeton_, especially, by the short, stumpy limb bones. The narrow,
elongate eye, placed close to the edge of the skull, is a character not
observed hitherto in the Branchiosauria. The genus is closely allied to
_Branchiosaurus_ of Europe.
=Eumicrerpeton parvum Moodie.=
Moodie, Proc. U. S. Nat. Mus., 40, p. 430, fig. 1, 1911.
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, pp. 331-336, pl. 3, figs. 3
and 4; pl. 4; pl. 5, fig. 1; pl. 6, figs. 1 and 2, 1912.
Moodie, Amer. Nat., 44, pp. 367-375, figs. 1-4, 1910.
Moodie, Science, n. s., XXXI, No. 789, p. 233.
Type: Specimen No. 803, Yale University Museum. Other specimens, No. 802,
Yale University Museum, and No. 4400, U. S. National Museum.
Horizon and locality: Mazon Creek shales, near Morris, Illinois.
The impression of the outline of the entire body is preserved (plate
3, figs. 1 and 2) in three specimens, and in all are found molds and
impressions of the alimentary canal, which, in one specimen (471), are
remarkably complete and instructive. The three specimens will be discussed
separately, since they show different features.
The impression of the larger animal (No. 803, Yale University Museum),
which is probably an adult, presents the following elements: the entire
skull, both humeri, impressions of posterior and anterior ventral
armature, portions of the alimentary canal, one femur, portions of a
fibula and tibia, and the entire impression of the tail, on which, as in
_Micrerpeton caudatum_, there occur two definite dark lines, one beginning
at the tip of the tail and running obliquely along the tail to where the
impression is broken at the anal region; the other beginning at a distance
of 4.5 mm. from the tip and running almost parallel with the median line.
These two lines undoubtedly represent the lateral-line system.
The skull is especially noted for its shortness and the great posterior
width, as well as for the almost entire absence of the tympanic notch.
The pineal foramen is located on a line with the posterior border of the
orbits. The eyes themselves are narrow and acuminate at each end, with a
pronounced convexity inwards and a flattening on the outer margin. They
are located on the very border of the skull, but relatively more posterior
than in _Micrerpeton_. No sclerotic plates are evident. The median suture
can be indistinctly observed running the entire length of the skull. The
sutures bounding the outside of the f rentals and the squamosals are
partially evident, but not satisfactorily preserved. The mandible is
represented by a mold which in wax impression shows short, stumpy teeth.
Posterior to the skull at a distance of a millimeter there are two sharp
impressions which may represent the anterior edges of the interclavicle
or they may be branchial elements. They are distinctly curved, however,
and probably represent portions of the interclavicle. A wax impression
does not show a discrete structure, but the boundaries of some larger
element. No other remains of the pectoral girdle can be discerned. The
humeri are short and relatively thick. Wax impressions show them to have
had truncate or slightly concave ends, thus indicating the absence or
slight development of the endochondrium. No other elements of the arm are
preserved.
The impression of an elongate femur and the heads of the tibia and fibula
of the left side are preserved.
The ventral armature is preserved in two small patches, and these show
the chevron-shaped rods to have been very fine much more delicate than in
_Micrerpeton_.
The body impression is very instructive and interesting, both in showing
the form of the body and because in it are preserved the larger portions
of the alimentary canal. The form of the body can best be discerned by
reference to the figures (plate 3, figs. 1 and 2; plate 5, fig. 1).
The portions of the alimentary canal preserved consist of the greater
portion of the stomach, three coils or loops of the small intestine, the
rectum, and a pit which undoubtedly represents the anal opening. The anus
is found at a distance of 16 mm. from the tip of the tail and is somewhat
removed from the body portion, as in modern salamanders. On each side of
the posterior end of the rectum there occur a pair of enlargements which
probably represent the oviducts at their posterior ends (fig. 15, C).
[Illustration: MOODIE PLATE 3
1. The larger specimen of _Eumicrerpeton parvum_ Moodie. × 1.
2. The smaller specimen of _Eumicrerpeton parvum_ Moodie. × 1.
3. Type specimen of _Erpetobrachium mazonensis_ Moodie. × 1.
4. Type specimen of _Erierpeton branchialis_ Moodie. × 1.
5 and 6. Type specimen of _Mazonerpeton longicaudatum_ Moodie. × 1.
7. A copy of Cope's drawing of the type specimen of _Amphibamus
grandiceps_ Cope. The original was destroyed by fire. × 3.
]
The tail impression is more acuminate than in _Micrerpeton_, but shows
the same structures as in that form, _i.e._, the lateral lines which have
already been mentioned. _Micrerpeton_ was a more rapid swimmer than the
present form on account of the greater development of the tail.
The second specimen of the species (No. 802, Yale Museum) shows much the
same character as the specimen already described, except that there are
impressions of small, blunt teeth on the mandible. The two humeri and the
femur of the left side are preserved and the interclavicle is represented
by an identical impression, as in the first-described specimen. The tail
impression, though similar in form, does not exhibit so much of the
structure of the lateral lines (fig. 15, B).
The matter of especial interest in connection with this second specimen
is the remarkably perfect preservation of the alimentary canal, which is
entire, except for the very anterior end of the œsophagus. The posterior
portion of the œsophagus, which measures 3.5 mm., is clearly preserved.
Its anterior end is thrown around posteriorly and indicates that this
end was loosened after death and became displaced before fossilization.
The length preserved may represent the entire œsophagus. The œsophagus
is constricted before it enters the stomach, which shows the usual
curvature found in modern salamanders. The stomach measures 6 mm. in
length by 2 mm. in breadth, and consists of a single enlargement as in
the modern _Amblystoma punctatum_. It increases in size somewhat toward
the pyloric end and then very gradually constricts to the pylorus. Three
divisions of the small intestine can be seen. The most anterior one,
corresponding to the duodenum, is segmented, as though the intestine had
been filled with food before interment. The remainder of the intestine,
corresponding to the ilium, is looped in the form of two figures =8= which
are superimposed, with the upper portions of the =8= at right angles to
each other. The rectum is clearly discernible, though its lower portion
is somewhat obscured by having the lower part of the upper loop of the
intestine lying over it. The anus lies at a distance of 1.5 mm. posterior
to the transverse line from, the upper end of the femur, and is quite well
back on the tail, as in modern salamanders. In this specimen also occur
two oval bodies which may be identified as the lower ends of the oviducts,
thus indicating, in all probability, that the animal was a female.
[Illustration: Fig. 14. Mazon Creek Amphibia.
A. Third specimen of _Eumicrerpeton parvum_ Moodie, which exhibits
the alimentary canal well preserved. × 2. Original in United
States National Museum. _a_, anus; _f_, femur; _h_, humerus;
_ic_, interclavicle; _in_, intestine; _m_, mandible; _or_, orbit;
_st_, stomach; _t_, tibia and fibula.
B. Type specimen of _Amphibamus thoracatus_ Moodie. Original in
United States National Museum. × 2 (For description see P. 132.)
]
A dissection of several species of modern caudates has resulted in
the discovery that the adult condition of the alimentary canal of all
the species dissected (_Amblystoma punctatum_, _Necturus maculosus_,
_Diemyctylits torosus_, _D. viridescens_, etc.) is much more complex than
that exhibited by the specimen under discussion. A very near approach to
the condition found in _Eumicrerpeton parvum_ is found in an immature
branchiate individual of _Diemyctylits torosus_, 56 mm. in length, from
a fresh-water pond on Mount Constitution, on Orcas Island, Puget Sound,
Washington.
The similarity of the intestinal structure is of considerable importance
to our understanding of the relationship existing between the
Carboniferous Branchiosauria and the modern Caudata, and only confirms
other arguments, offered in another place (459), concerning their
immediate relationship.
The branchiosaurian affinities of the present species are almost too
evident to need discussion. The entire structure is essentially similar to
that of other genera of the order.
The third specimen of this species (No. 4400 of the U. S. National Museum)
is almost as perfectly preserved as were the other two specimens. The
skull structure, the intermediate position of the pineal foramen, the
epiotic notch, and the shape of the skull are essentially similar to the
described specimens of the species. The present specimen is more developed
than the other two and probably represents an adult. The alimentary canal
is perfectly preserved.
It is nearly half again as long as the smallest of the above-described
specimens, and the skull is proportionately longer and wider. There is
preserved also an impression of the anterior ends of both clavicles. The
right humerus is imperfectly preserved, as is also the right femur and
tibia; other than these the fossil is merely an impression.
The skull is so similar to those described above that additional
description is unnecessary. The pineal foramen is quite large and lies
on a line which cuts the orbits into equal longitudinal parts. The
interorbital space is about equal to the long diameter of the orbit.
Traces of sclerotic plates are observed in the left orbit, but they are
quite imperfect.
The alimentary canal (fig. 14_a_) is unlike the previously described
structures, in that the intestine is longer and more convoluted. It
lies in five longitudinal folds and ends in an enlarged cloaca, near
which there are impressions of two glands, or the posterior ends of
the oviducts, as was suggested for the Yale specimens. The creatures
undoubtedly fed on small plants and animals much as do the recent
salamanders.
Measurements of Eumicrerpeton parvum Moodie.
No. 803 (222), Yale University Museum: mm.
Length of animal 37.5
Length of skull 4.5
Posterior width of skull at table 6
Long diameter of eye 1.75
Transverse diameter of eye 65
Length of left humerus 1.50
Number of ventral armature rods in 1 mm 10
Length of femur 1.75
Width across base of tail impression 3.5
Length of tail from base to tip 17
No. 802 (471) Yale University Museum: mm.
Length of animal 30
Length of skull 4
Posterior width of skull 5
Length of œsophagus 3.5
Length of stomach 6
Width of stomach 1.33
Estimated length of intestine 18
Width across base of tail impression 2.5
Length of tail from base to tip 7
No. 4400, U. S. National Museum: mm.
Length of entire animal 45
Length of skull 6
Width of skull 9
Transverse diameter of orbit 1.50
Long diameter of orbit 2.25
Interorbital space 2.50
Diameter of pineal foramen 50
Length of body from back of skull to pelvis 22
Greatest width of body 9
Length of tail 16
Width of tail at base 5
Length of humerus 3
Length of femur 2.50
Length of tibia (fibula?) 1.75
Length of stomach 3
Length of intestine (estimated) 5.6
Width of intestine 1
[Illustration: MOODIE PLATE 4
1 and 2. Vertebræ of _Spondylerpeton spinatum_ Moodie. × 1.
3. Type specimen of _Mazonerpeton costatum_ Moodie. × 1.
4. Type skeleton of Cephalerpeton ventriarmatum Moodie. × 0.9.
5 and 6. The halves of the nodule containing a practically complete
skeleton of Amphibians grandiceps Cope. × 1.
Originals of above figures in the Yale University Museum.
]
=Genus MAZONERPETON Moodie.=
Moodie, Kans. Univ. Sci. Bull., vol. VI, No. 2, p. 336, 1912.
Type: _M. longicaudatum_ Moodie.
The genus is distinguished from other known branchiosaurian genera by
the great length of the dorsal region, the elongate tail (plate 5, fig.
2), with its well-developed caudal ribs, the reduction of the tympanic
notch, the broad nature of the scapula, the elongate interclavicle, and
the slender ilium. The number of dorsal vertebræ is identical with that of
_Branchiosaurus_ of Saxony.
=Mazonerpeton longicaudatum Moodie.=
Kans. Univ. Sci. Bull., VI, No. 2, p. 337, pl. 3, figs. 1-2; pl. 7,
fig. 3; pl. 10. 1912.
Type: Specimen No. 795 (1234), Yale University Museum.
Horizon and locality: Mazon Creek shales, near Morris, Illinois. (Plate 3,
figs. 5 and 6.)
The remains consist of the following elements: an incomplete skull; nearly
the entire vertebral column, consisting of cervical, dorsal, sacral, and
caudal vertebræ, 36 in number; several ribs preserved on each side of
the vertebral column; a portion of the ventral armature; the scapulæ; a
clavicle; the interclavicle; both humeri; the radius and ulna of one side
and the ulna of the other; portions of both hands; the ilium of the right
side; both femora, and a partial impression of the left tibia.
The skull is, unfortunately, very poorly preserved. Enough remains,
however, to determine the essential characters. The skull bones, unlike
any other American branchiosaurian, have an ornamentation consisting of
sharp pits and elevations which in places have a quincuncial arrangement
and in others take the form of definite lines of pits or tubercles similar
to the condition found in many of the Microsauria. The orbits are large
and are situated back of the median transverse line of the skull. They
are almost circular in form and contain 6 elongated sclerotic plates very
closely arranged around the borders of the right orbit. The plates are
twice as long as wide. The interorbital width is 1.25 times the transverse
diameter of the orbit.
Not many of the sutures of the skull are discernible. Portions of
the frontals, the nasals, the prefrontals, the parietals, and the
supratemporals can be identified. Their arrangement is shown in figure
14_a_. There is a decided posterior table to the skull, with truncate
posterior border. The tympanic notch is shallow, with its outer border not
so well protected as in _Branchiosaurus_.
The cervical vertebræ are incomplete, but their number was 4 or 5, as in
_Micrerpeton_. The structure of the dorsal vertebræ is also uncertain,
although the shape can be discerned. The vertebræ are short and thick,
very unlike the long, cylindrical vertebræ of _Cephalerpeton_. The heavy
transverse process is quite evident on the best preserved vertebræ. This
process recalls that described by Credner for the Saxony Branchiosauria.
Several of the vertebræ show the articulation of the ribs with this
process. The ribs of the caudal region recall very strongly those of
_Branchiosaurus_. They are quite heavy in the anterior caudal region and
then diminish rather rapidly to the point where the tail is broken and
lost.
The ventral armature is represented by a patch of chevron rods 21 mm. in
length. The rods take a very peculiar form, being short crescentic bundles
of fine rods, hair-like in appearance. In one of these bundles I count 5
smaller rods. The bundles are arranged in rows similar to the pattern so
characteristic of the Carboniferous Amphibia, as described elsewhere. The
patch of ventral armature preserved belongs to the abdominal region. A
single row of the crescentic bundles measures 11 mm.
Both scapulæ are preserved in their entire form. They are quite different
from those of any other genus, being broadly crescentic with a posterior
concavity and an anterior protuberance. The anterior surface of both
scapulæ is obscured. Vascular foramina occur near the base of both
scapulæ; there being three of them in the right scapula, arranged in
the form of an isosceles triangle. The morphology of these foramina is
uncertain. They have never been observed among the Carboniferous Amphibia,
and, so far as I am aware, they are entirely unknown among higher
vertebrates.
The temnospondylous Amphibia of the Carboniferous and Permian possess, in
the coössified scapula-coracoid, three foramina, very similar to the ones
in the present form, but they are confined to the coracoidal region and,
in the Branchiosauria, as identified by Credner, the coracoid is a free
element, although I have never been sure of its identity among American
forms. Williston has called these foramina the glenoid, the supraglenoid,
and the supracoracoid foramina (Journal Geology, XVII, No. 7). They are
not, however, to be correlated with the three foramina above mentioned,
since in the Temnospondylia the foramina belong with the coracoid and not
with the scapula. The condition of the Temnospondylia occurs in the bony
fish _Xiphactinus audax_ Leidy, and an analogous condition obtains in the
reptiles, as in the Mosasaurs and Dinosaurs.
[Illustration: Fig. 14_a_. Skeleton of _Mazonerpeton longicaudatum_
Moodie. _c_, carpus; _cl_, clavicle; _cr_, caudal ribs; _cv_, caudal
vertebræ; _h_, humerus; _f_, femur; _or_, orbit; _r_, radius; _sp_,
sclerotic plates; _sc_, scapula; _u_, ulna: _vs_, ventral scutellæ. From
Mazon Creek. Original in Yale University Museum.]
Near the outer edge of the right scapula there is a large fragment
preserved, which, I think, must be the misplaced clavicle. It is obscurely
triangular or, more exactly, spatulate. The interclavicle is represented
by fragments only, and seems to have had a narrow form.
The humeri recall those of _Micrerpeton_. They are somewhat elongate
and apparently cylindrical in their normal condition, although somewhat
flattened in the fossil. The shaft is considerably constricted at the
middle and the ends are expanded, in which expansion the lower end
exceeds. The ends are abruptly truncate, indicating a small amount of
endochondral ossification or its entire absence.
The mesopodial elements, unlike what is described for _Cephalerpeton_,
are quite dissimilar in form, recalling the condition in _Mesosaurus
brasiliensis_ McGregor. The larger element is, apparently, the ulna.
It has the lower end greatly expanded and the shaft is curved outward,
resembling very much a reptilian ulna. The radius is much smaller than the
ulna, lacks the lower expansion, and is shorter by 1 mm.
The carpus is represented merely by a blank space, with evidences of
impressions of cartilage in the sandstone. The hand of the right side
contains 4 phalanges. There are 2 phalanges preserved in the first digit,
including a sharp-pointed terminal phalanx, and the second digit has only
the metacarpal. The third has the metacarpal and the first phalanx, which
does not differ in form, but only in size, from the metacarpal. The fourth
digit contains only the metacarpal. Of the left hand there are portions
of 3 digits preserved, including 3 metacarpals and a phalanx, which in
structure are not different from those of the right hand.
The ilium of the left side is preserved, apparently entire. It is elongate
and cylindrical, its upper end adjoining the twenty-eighth vertebra.
The head of the femur lies close to the lower end of the ilium, so that
that element must have been suspended in the flesh, much as in modern
salamanders. It could not have been of much use as a support for the
body. The form of the femur is not unlike that described for the humerus,
save that its lower end is smaller than the upper, while in the humerus
the extremities are of equal diameter. A portion of the right femur is
preserved, extending in an opposite direction to the left.
Measurements of the Type.
mm.
Length of entire specimen 64
Length of portion of skull preserved 6.5
Posterior width of same 7
Width across orbits 11
Long diameter of orbit 3
Transverse diameter of orbit 1.75
Interorbital width 4.75
Length of dorsal vertebræ 48
Length of caudal series 11
Length of anterior dorsal centrum 2
Length of anterior dorsal rib 4
Length of anterior caudal rib 1.75
Length of scapula 5
Greatest width of scapula 4.25
Probable length of interclavicle 6
Width of same 3
Length of clavicle 4.5
Width of same 1.5
Length of right humerus 6
Distal width of same 2
Length of ulna 3.25
Distal width of same 1
Length of radius 3
Width of carpal space 2
Length of metacarpal 1.74
Length of first phalanx 1.75
Length of distal phalanx of right hand .35
Number of chevron rods in 1 mm. 4
Length of ilium 2.25
Length of femur 4
Proximal width of femur 1.50
=Mazonerpeton costatum Moodie.=
Moodie, Kans. Univ. Sci. Bull., VI, No. 2, p. 341, pl. 2, fig. 3; pl.
8, fig. 4; pl. 9, fig. 2; pl. 10. 1912.
The remains on which the present species is based are inclosed in a much
fractured nodule. The parts of the animal which have been identified
are: a part of the skull and left mandible, two clavicles, a humerus,
impressions of several vertebræ, a portion of the dorsal region of the
body with several ribs, two portions of the caudal region with several
ribs and unidentified fragments. (Plate 4, fig. 3.)
The animal, from the shape and form of the ribs, is undoubtedly a
branchiosaurian, since short, heavy, straight ribs have not yet been
found to be associated with other than branchiosaurian structures. It
is placed in the genus Mazonerpeton on account of the structure of the
pectoral elements, the form of the humerus, and the length of the tail,
all of which agree in structure with _Mazonerpeton longicaudatum_. The
animal attained, perhaps, a length of 4.5 inches, while that of _M.
longicaudatum_ was about 3 inches. The tail in the present species is very
long and slender, more elongate than in any other known branchiosaurian.
[Illustration: Fig. 14_b_. Skeleton of _Mazonerpeton costatum_ Moodie. ×
1.5. Original in Yale University Museum, _dv_, dorsal vertebra; _ch_,
neutral spines; _cl_, clavicle; _cv_, caudal vertebræ; _f_, femur: _h_,
humerus; _m_, mandible; _rb_, rib; _sk_, skull; _v_, vertebræ.]
The part of the skull preserved is very unsatisfactory and, aside from the
fact that it seems to represent the under side of the left half of the
skull, little can be said. Three sutures can be observed, but what sutures
they are is undetermined. The left mandible lies crushed on the edge of
the skull and partially obscures what little there is of that structure.
The slightly curved impression, from which the bone has been either broken
or weathered, measures 13 mm. in length by 3 mm. in posterior diameter by
1 mm. in anterior diameter. These measurements show the element to have
been slender and pointed anteriorly.
Very little accurate information can be derived from the study of the
vertebral column of the specimen, nor can the dorsal vertebral formula
be made out, since only a portion of the length of that region is
preserved and only a few rather indefinite impressions can be discerned.
These impressions show the vertebræ to be short and higher than in most
Branchiosauria.
The caudal series is represented by two sections, one of which is,
apparently, from near the base of the tail, judging from the size of the
caudal ribs preserved; the other is from near the tip of the tail, and
shows the constituents to have been long and slender. Ribs are apparently
absent on this section. The position of the two caudal sections shows
that when the animal died it was coiled up much like a snake, so that in
the fractured nodule three sections of the body are visible. The tail was
probably half as long again as the body.
The ribs throughout the body are short, heavy, and straight, with, in
the dorsal series, a lateral and a distal expansion which is taken as a
distinctive specific character. Judging from imperfect impressions in
the dorsal series, the ribs were attached to a transverse process of the
centrum, thus agreeing with other branchiosaurians in this respect. The
ribs show a progressive decrease in length from the cervical region to the
point of their disappearance on the tail.
[Illustration: MOODIE PLATE 5
1. A reconstruction of the possible appearance in life of the Coal
Measures branchiosaurian, _Eumicrerpeton parvum_ Moodie, a
small, primitive salamander, less than 2 inches in length,
based on three specimens from the Mazon Creek Shales. The
lateral-line organs are represented as dark bands on the tail,
the sense-organs being, apparently, situated beneath specialized
pigmented scales, to which is due the preservation of the lines.
2. A restoration, natural size, of the branchiosaurian,
_Mazonerpeton_, based on two specimens. The form of the animal
is quite salamander-like. It is shown when about to feed on a
specimen of _Acanthotelson stimpsoni_, which is said to be a
brackish-water crustacean. The branchiosaur and crustacean may
possibly have inhabited the same body of water.
]
The pectoral girdle is represented by two elements, one of which is
certainly the right clavicle, and the other is possibly the left clavicle,
though its form is somewhat distorted by pressure. Both elements are in
the form of an elongate spatula with the dorsal surface greatly concave
and the inner end acuminate.
The right humerus is imperfectly preserved, though the impression allows
one to gain an exact idea of its form. It lies under the right clavicle.
Its ends are truncate with a contracted shaft and expanded extremities;
the bone was apparently hollow.
[Illustration: Fig. 15.
A. Impression of _Erierpeton branchialis_ Moodie. _bb_,
basibranchial; _hyp_, hypohyals; _m_, mandible; _d_, body
impression. × 3.
B. _Eumicrerpeton parvum_ Moodie. _a_, anus; _f_, femur; _h_,
humerus; _in_, intestine; _l_, liver; st, stomach; _r_, radius;
_u_, ulna. × 3.3.
C. Larger specimen of _Eumicrerpeton parvum_ Moodie. _a_, anus; _d_,
dorsal lateral-line; _h_, humerus; _in_, intestine; _ml_, median
lateral-line; _st_, stomach. × 2.6.
D. Skeleton of _Erpetobrachium mazonensis_ Moodie. _cl_, clavicle;
_h_, humerus; _r_, radius; _sc_, scapula; _u_, ulna. × 2.
E. Rib of _Mazonerpeton costatum_ Moodie. × 2.5. Originals in the
Yale University Museum.
]
In another nodule (No. 804, Yale Museum) there is a single bone preserved
which resembles, to a great extent, a rib of the present species (fig. 15,
E), although somewhat larger, and it has been provisionally identified as
such. The element is very slightly curved, but shows the expanded head of
the rib of this species.
Measurements of the Type of Mazonerpeton costatum Moodie.
No. 800 (777), Yale University Museum: mm.
Length of portion of skull preserved 14
Length of right clavicle 16
Width of right clavicle 4
Length of dorsal region represented 30
Length of cervical rib 8
Length of dorsal rib 6-5
Length of caudal rib 3
Length of caudal portion of body preserved 55
Length of mandible 15
Greatest width 6
Length of right humerus 10
Greatest width of humerus 2
No. 804 (332), Yale University Museum:
Length of rib 11
Width of head of rib 2
Diameter of shall 1
=Sparodus sp.= (?).
Dawson, Phil. Trans. Roy. Sue. London, pt. II, p. 643, pl. 40, figs.
52 to 56, 1882.
Dawson, Proc. and Trans. Roy. Soc. Canada, XII, p. 75. 195.
Type: Specimen in the Peter Redpath Museum of McGill University.
Horizon and locality: Coal formation at the South Joggins, Nova Scotia.
The material on which the above determination is based was collected in
1878 by Sir J. W. Dawson in the coal formation at the South Joggins,
Nova Scotia. Nothing has been collected since that date that would give
additional information as to the nature of the form represented. I give
here Dawson's description of the remains:
"In the coaly matter or mineral charcoal at the base of tree No. 10
appeared a few fragments of an animal which may possibly belong to the
above-named genus of Fritsch, though I am by no means certain of this
identification or of the real nature of the animal.
"The skull is represented by a fragment of a maxillary or intermaxillary
bone, with blunt conical teeth. It is smooth or marked merely with
microscopic dots. There is also a fragment which may be a palatal bone
studded with minute teeth.
"A few vertebræ associated with the above bones are long and narrow, with
large zygapophyses and long neural spines. Length of body (i.e., of the
vertebra) about 3 millimeters.
"With these remains are a few bony scales different from those of any
other species found in these trees, and more resembling scales of Ganoid
Fishes. They are somewhat rectangular in form, enameled on the surface and
beautifully sculptured with waving lines.
"In the same trunk were found some teeth and bones referable to
_Hylerpeton dawsoni_, and it is not impossible that the remains above
referred to may have belonged to some creature devoured by that animal,
and which would not otherwise have obtained admission to the interior of
an erect tree. The tree itself had been removed by the sea, all but a
little of the base, and this was in a very unsatisfactory state, so that
doubt might even exist as to the limit between the deposit in the interior
of the tree and that under its base."
[Illustration: Fig. 15_a_. Type material of _Sparodus_, consisting of
_a_, a tooth (× 25); _b_, four of the smaller teeth (in maxilla?) (× 25);
_c_, three bony scales (× 5); _d_, fragment of a limb bone (× 2); _e_, a
vertebra (× 2). (After Dawson.)]