Crocodile Fossils
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Figs. 1, 2. Thecachampsa (?) sericodon Cope. | ||
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1) Tooth. Charles County near the Patuxent River. Acad. Nat. Sci., Phila. 2) Tooth. Same locality and collection. |
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| Figs, 3-5. Thecachampsa (?) sicaria Cope. | |||
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3) Crown of a tooth. (After Cope.) 4) Portion of lower jaw. (After Cope.) 5) Another view of the same. (After Cope.) |
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| Figs. 6a, 6b. Thecachampsa (?) contusor Cope. | |||
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6a) Lateral view of tooth. Charles County near the Patuxent River. 6b) Basal view of the same specimen. |
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| Figs. 7-9. Thecachampsa (?) antiqua (Leidy). | |||
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7) Tooth. " High cliffs of the Potomac River, 40 miles above the mouth of the river in Westmoreland County, Virginia." Acad. Nat. Sci., Phila. 8) Another tooth from the same locality and collection. 9) Another tooth from the same locality and collection. |
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Class REPTILIA
Order CROCODILIA.
Suborder EUSUCHIA.
Family CROCODILIDAE.
Thecachampsa, Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, p. 143.
Thecachampsa, Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 11.
Thecachampsa, Cope, 1882, Amer. Nat., vol. xvi, p. 988.
In the original description the form is separated
from Crocodilus by "the entire hollowness of the external stratum
of the crowns of the teeth, and their composition of closely adherent concentric
cones. These internal cones, which number at least three, may be homologous
with the included crowns of the successional teeth of other Crocodilia, but
they must be regarded as functional in a physiological sense, since they compose
the bulk of the crown of the tooth within."
In 1869 Cope says: "Further investigation
shows that this genus is gavial-like, and that the peculiarity which characterizes
its dentition also belongs to Plerodon Meyer, of the European Miocene."
In 1882 he says, under the head Crocodilus:
"A peculiarity of the composition of the crowns of some of the species
has been noticed, on account of which I proposed a genus Thecachampsa.
In this type the crown is composed of concentric hollow cones, one within the
other. I have not been able to separate the crowns of the recent crocodiles
into such bodies, and they are generally too thin to display more than a few
such layers, were they so separable. This character was first observed in some
species of the Atlantic Coast, e. g., C. antiquus Leidy, and C. squankensis
Marsh; and the two Eastern Miocene species, C. sericodon Cope (type of
Thecachampsa) and C. sicaria Cope."
Later, about 1895, Cope was again of the opinion
that the genus Thecachampsa should stand. In consultation with Dr. W.
B. Clark in regard to the preparation of the latter's Bulletin on the Eocene
deposits of the Middle Atlantic States he was, according to Dr. Clark, "distinctly
of mind that the genus should be called Thecachampsa instead of Crocodilus"
In the same article in which T. sicaria
was described, Cope gave the following synopsis of the species of Thecachampsa:
" Crowns of teeth not compressed, with short
cutting edges ........................ T. antiquus
(C.
antiquus L.)
Crowns cylindric, curved, with long and delicate
cutting edges .................... T. sericodon.
Crowns compressed, with very long crenulate cutting
edges, on a marginal
base ................................................................................................... T. sicaria."
Thecachampsa (?) sericodon Cope.
Thecachampsa ? sericodon Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, p. 143.
Thecachampsa sericodon Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 12.
Thecachampsa sericodon Cope, 1869, Amer. Nat., vol. iii, p. 91.
Thecachampsa sericodon Cope, 1871, Trans. Amer. Philos. Soc., vol. xiv, p. 64, pl. v,
figs. 7 and 8. (Pp. 1-104 appeared in 1869.)
Thecachampsa sericodon Cope, 1875, Proc. Amer. Philos. Soc., vol. xiv, p. 363.
Thecachampsa (Crocodilus) sericodon Cope, 1882, Amer. Nat., vol. xvi, p. 984.
Thecachampsa sericodon (?) Case, 1901, Md. Geol. Survey, Eocene, p. 95, pl. x, fig. 3.
Description.— This species
was based "on a number of specimens of elongate conic crowns, which resemble
to a considerable extent those of Crocodilus antiquus Leidy, of the same
epoch. They differ from T. contusor in their more compressed and elongate
form, the presence of a subacute ridge on each side, the apical three-fifths
of the crown, the absence of the lateral grooves, and the chevron sculpture.
They are, on the contrary, minutely striate, and possess a silky lustre.
"Length of the medium specimen 16.5 lines (23
mm.); base of the crown 9 lines (18 mm.)."
Occurrence.— Calvert formation. Charles
County near the Patuxent river.
Collections.— The type specimens,
two teeth, are in the museum of the Academy of Natural Sciences of Philadelphia.
Thecachampsa (?) sicaria Cope.
Thecachampsa sicaria Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 12.
Thecachampsa sicaria Cope, 1869, Amer. Nat., vol. iii, p. 91.
Thecachampsa sicaria Cope, 1871, Trans. Amer. Philos. Soc., vol. xiv, pp. 63, 64, pl.
v, figs. 6, 6a, 6b. (Pp. 1-104 appeared in 1869.)
Thecachampsa (Crocodilus) sicaria Cope, 1882, Amer. Nat., vol. xvi, p. 984.
Description.— Described from teeth
"with much compressed crowns of the tooth with prominent cutting edges."
The specimens were loaned to Cope by Mr. P. T. Tyson, the State Geologist of
Maryland.
Occurrence.— St. Mary's (?) formation.
"Near the mouth of the Patuxent River."
Collection.— Not known.
Thecachampsa (?) contusor Cope.
Thecachampsa contusor Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, p. 143.
Thecachampsa contusor Case, 1901, Md. Geol. Survey, p. 96, pl. x, fig. 4.
Crocodylus antiquus Hay, 1902, Bull. 179, U. S. Geol. Survey, p. 512. (In part.)
Description.— This species is of
very doubtful value, it probably belongs with Th. antiqua. It was described
from a single tooth, "remarkable for its short conic form. The basis is
circular, and its diameter is three-fifth the length of the tooth. The apex
is rather acute and circular in section, it is directed to one side, and the
tooth is slightly flattened on the inside of the curve. This face is bounded
by a low obtuse ridge on each side, for the basal two-thirds of the crown, which
are not distinguishable from a series of ridges which mark, at a distance of
a line, the basal three-fifths of the crown; they are less distinct on the convex
aspect, and are separated by concave surfaces. Instead of the cutting ridges
of Crocodilus, the apex is provided with a narrow flattened plane on
each side. The surface of this portion and of much of the convex face, is marked
by a minute decussation or chevroned sculpture.
"Vertical length 14.5 lines (29 mm.);
diameter of the base of the crown 8.5 lines (17 mm.)."
Cope says in Trans. Amer Philos. Soc., vol. xiv,
1871, p. 64: "The peculiar form of the tooth on which T. contusor
was based is due, I find, to attrition and partial destruction of the enamel."
Occurrence.— Calvert formation. Charles
County near the Patuxent river.
Collection.— Formerly in the Philadelphia
Academy of Natural Sciences.
Thecachampsa (?) antiqua (Leidy).
Crocodilus antiquus Leidy, 1851, Proc. Acad. Nat. Sci. Phila., vol. v, p. 307.
Crocodilus antiquus Leidy, 1852, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. ii, pp.
135-138, pl. xvi, figs. 1-5.
Crocodilus antiquus Emmons, 1858, Rept. N. Car. Geol. Survey, p. 215, fig. 35b.
Thecachampsa contusor Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, p. 143.
Thecachampsa antiqua Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, p. 12.
Thecachampsa antiqua Cope, 1869, Trans. Amer. Philos. Soc., vol. xiv, p. 64, fig. 16.
Thecachampsa (Crocodilus) antiqua Cope, 1882, Amer. Nat., vol. xvi, p. 983.
Crocodylus antiquus Hay, 1902, Bull. 179, U.S. Geol. Survey, p. 512. (In part.)
Description.— The description given
by Leidy is as follows: "One of the teeth, represented in Fig. 1, Plate
XVI, is a little less in breadth than the first anterior inferior tooth of the
adult Crocodilus biporcatus. In the specimen the lower part of the fang
has been broken away, but the tooth appears to have been as long, or nearly
so, as that referred to of C. biporcatus. It is slightly less curved
than that of the latter, and the crown, though as long, is much less robust,
more slender, less curved, and more pointed at the summit. The enamel is more
finely and sharply striated and at the apex of the crown is not so rugous, and
its lateral carinated ridges are not so elevated and extend but a relatively
short distance below the point of the tooth; upon one side disappearing entirely
nine lines from the commencement, and on the other after five lines only. The
fang is simply cylindrical and invested by a thin lamina of osteo-dentine continuous
with the basal edge of the enamel. The large conoidal pulp cavity of the tooth
extends to within eight lines of the summit of the crown. Within this cavity,
in the specimen which was not at all worn off from use, was already formed a
young tooth, represented in Fig. 2, closely corresponding in form with the half
inch of the summit of that which ensheathed it, a circumstance, however, which
is the ordinary one in the living species of Crocodile.
"The second specimen of the teeth, represented
in Fig. 3, consists of a crown only, which is as long as that of the former
tooth but slightly more slender, and the enamel is a little smoother, and its
ridges, though not so elevated, are longer.
"The color of the dentinal substance and
osteo-dentine of the teeth is umbreous brown or chocolate; the enamel is lighter
colored, glistening, and delicately undulating and interruptedly striate.
Measurements. First specimen:
Thickness of the broken edge of the pulp cavity,
three inches below the summit of the crown. 1.25 lines (3 mm.)
Probable length of the tooth in its perfect condition,
if the parietes of the pulp cavity decreased in
thickness at the same rate as a
corresponding tooth of Crocodilus biporcatus ......... 5 inches (125 mm.)
Length of crown laterally ................................................ 1.5 inches (37 mm.)
Lateral diameter of base of crown...................................10 lines (20 mm.)
Transverse diameter of base of crown ............................ 9.25 lines (18 mm.)
Lateral diameter of fang ............................................... 12 lines (24 mm.)
Transverse diameter of fang ......................................... 10.5 lines (21 mm.)
Second specimen: Length of crown laterally ................ 1.5 inches (37 mm.)
Lateral diameter at base of crown ................................... 9 lines (18 mm.)
"Dr. Wyman 1
has described and figured the crown of a tooth of a Crocodile from the Miocene,
at Richmond, Virginia, which corresponds to the above descriptions, and probably
belong to the same species.
"In relation to the specimens of the concavo-convex
vertebrae, their size indicates a species of crocodile probably no less than
eighteen feet in length.
"One of the specimens represented in Fig.
4, I judge to be an anterior dorsal, probably the second; the other is a posterior
dorsal, or a lumbar vertebra.
"In the former, the spinous process excepting its base, the transverse processes, the articular or oblique processes excepting part of the right anterior and left posterior, and right anterior margin of the body, with the corresponding lateral tubercle, are broken away. In form and general proportions, it bears a great resemblance to the corresponding vertebra of the Crocodilus gangeticus, and the most striking difference is observable in the spinal canal, which in the former is cordifonn or trilateral with rounded angles and the apex downwards, while in the latter it is reversed. Judging from its base, the inferior spinous process has been relatively thicker and not so broad as in Crocodilus gangeticus or Alligator lucius. The junction of the body with the neural arch is still indicated by suture in the specimen. The posterior convex head of the body is hemispherical. The lateral tubercle for the head of the lob is formed upon a relatively broad base.
Measurements. Length of the body from the bottom of the concavity
to the summit of the convexity........................... 3 inches (75 mm.)
Length laterally, exclusive of the convexity................. 3 inches (75 mm.)
Depth of concavity .................................................. 10 lines (20 mm.)
Vertical diameter of concave extremity has been
about ................................................................ 3 inches (75 mm.)
Transverse diameter of concave extremity................... 3 inches (75 mm.)
Vertical diameter of convexity at base......................... 2 inches (54 mm.)
Transverse diameter of convexity at base.................... 2.5 inches (62 mm.)
Transverse diameter of body at middle from one
suture to the other ............................................. 3 inches (75 mm.)
Antero-posterior breadth of base of
spinous process .............................................. 22 lines (44 mm.)
Vertical diameter of spinal foramen ............................14 lines (28 mm.)
Transverse diameter of spinal foramen......................... 1 inch (25 mm.)
"The other vertebra, represented in Fig. 5, consists of the body only with the abutments of the neural arch and a small portion of the right anterior articular process. It is more compressed at the sides than in Crocodilus gangeticus, and therefore appears relatively deeper and narrower.
Length of the body from the bottom of the
concavity to the summit of the convexity ............ 3.25 inches (81 mm.)
Length laterally, exclusive of the convexity, has
been about ...................................................... 3.25 inches (81 mm.)
Vertical diameter of convexity has been about........... 3 inches (75 mm.)
Transverse diameter of convexity has been about...... 3 inches (75 mm.)
Transverse diameter of body at middle from one
lateral suture to the other ................................. 2.25 inches (56 mm.)
"The fragment of rib consists of the vertebral
third of one of the posterior ribs. It is thick and strong in accordance with
the size of the animal, but presents nothing peculiar.
"The ungual phalanx appears, so far as I
can ascertain from comparison with those of Alligator lucius, to be the
first of the thumb. It is of large size and very robust. Its base is trilateral
with rounded angles, and presents a transverse concave articulating surface.
The depressions for the lateral ligaments just above the condyles are remarkably
deep. Just postero-superiorly to one of the depressions is an oval tubercle
for tendinous attachment.
Length of phalanx ..................................................... 2.25 inches (56 mm.)
Greatest breadth at base ......................................... 15 lines (30 mm.)
Greatest depth of base ............................................ 13 lines (26 mm.)
Breadth of condyles ................................................ 10.5 lines (21 mm.)
"For the species to which the fragments
of the skeleton described belonged, I propose the name Crocodilus antiquus."
Occurrence. — Chesapeake group. High
Cliffs of the Potomac river, 40 miles above the mouth of the river in Westmoreland
County, Virginia.
Collection. — The specimens consist
of two teeth, two vertebrae, a fragment of a rib and an ungual phalanx. They
are in the Museum of the Academy of Natural Sciences of Philadelphia.
1 Amer. Jour. Sci., ser. ii, vol. x, 1850, p. 233, figs. 8a and 8b.
updated
3/2/05
(these web pages were prepared by R. D. Conkwright)