The Coal Measures Amphibia of North AmericaMoodie, Roy Lee
Science
The Coal Measures Amphibia of North America
Moodie, Roy Lee
Amphibians, Fossil -- North America; Paleontology -- Carboniferous; Paleontology -- North America
There remain only a few indefinite impressions of the cervical vertebræ.
The union of the skull with the vertebral column is obscured and lost.
Impressions of the dorsal vertebræ are well preserved, and wax molds
made from these show the structure of the dorsal vertebræ surprisingly
well. They are long and cylindrical, with the median portions slightly
constricted by a deep pit on each side of the low neural ridge, which
takes the form observed in _Thyrsidium_, _Molgophis_, _Phlegethontia_,
_Dolichosoma_ (fig. 8) and other genera. The vertebræ are strongly
amphicœlous and the notochord was probably persistent. The sides of the
vertebræ are smooth.
The ribs are all intercentral in position; the anterior ones very broad
near the base, recalling the broadly expanded ribs described by Schwarz
(540) for _Scincosaurus_, _Ptyonius_, _Thyrsidium_, and other genera.
Posteriorly the ribs become slender and cylindrical. They are all rather
long and distinctly curved, with probably a cartilaginous tip.
There is preserved a single element of the right side of the pectoral
girdle. This is, I think, the coracoid, an element which has hitherto
escaped observation among the American Microsauria. It is long and
spatulate at both ends, with the median portion apparently almost
cylindrical, not unlike that described by Credner (181) for the coracoid
of _Branchiosaurus_, save that the lower end of the branchiosaurian
coracoid is acuminate. In the present form it is spatulate. Its
relations with the other elements of the pectoral girdle have never been
satisfactorily determined.
The fore limbs are both partially preserved. The humerus of the right
side is complete. It is greatly elongated for a microsaurian. The form
of the element is not unlike that of a lizard, with the lower end of the
bone spatulate and endochondrium well developed. Very little difference
can be seen between the form of the arm bones, which represent the radius
and ulna. They are both elongated, with constricted median portion and
expanded truncate ends. The carpus is unossified and the cartilage has
left no trace of the elements.
The right hand has two metacarpals preserved, which are fully half as long
as the radius and ulna. They are separated some little distance from the
ends of these elements, though this may be due to post-mortem shifting.
The carpus may, however, have been broad. On the left side are preserved
portions of the humerus, radius, ulna, and 3 metacarpals, lying close to
the vertebral column. The carpal space is not so large on the left as on
the right. The ventral armature is well preserved in a narrow patch about
an inch in length. The chevron-shaped rods are quite large, there being 2
of them in 1 mm.
Measurements.
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