|BACK TO INDEX||(page 1 of 1, 2, 3)|
|(click on a section of the picture to view a detailed image)|
|Figs. 1-3. Squalodon atlanticus Leidy.|
1) Portion of the right side of a jaw containing three teeth. Shiloh, N. J. Acad. Nat. Sci., Phila.
2,3) Teeth from Miocene of Maryland " labelled "Basilosaurus atlanticus. Acad. Nat. Sci., Phila.
|Figs. 4, 5. Squalodon protervus Cope.|
4) Tooth. Charles County near the Patuxent River. Acad. Nat. Sci., Phila.
5) Another tooth from the same locality and collection.
|Fig. 6. Priscodelphinus gabbi Cope.|
|6) Lumbar vertebra, lower view. Charles County near the Patuxent River. Acad. Nat. Sci., Phila.|
|Figs. 7, 8. Priscodelphinus ruschenbergeri Cope.|
7) Lumbar vertebra, lower view. Charles County. Acad. Nat. Sci., Phila.
8) Caudal vertebra, lower view. Charles County near the Patuxent River. Acad. Nat. Sci., Phila.
The order CETACEA exhibits within itself
forms of the widest divergence. Conforming in general to the fish-like form
of body, the members show variations in size between Balaenoptera sibbaldii,
85 to 90 feet long, and Platanista about 4 feet; in dentition from the
carnivorous form of Orca to the baleen plates of the Right Whale or the
almost toothless Monodon. The superficial fish-like characters of the
body are generally regarded as degenerative adaptations to the aquatic habitat.
The almost total loss of the hair, the equally complete loss of the hind limbs,
the flipper-form of the fore limbs and the development of hyperphalanges; the
position of the external nostrils on the upper part of the skull; all these
are found in general in animals originally terrestrial in habit, that have become
aquatic. To these characters should be added the broad, flat tail developed
in the horizontal instead of the vertical direction and devoid of bony support.
The following features of the skull have been mentioned by Beddard1 as characteristic of the CETACEA:
" The separation of the two parietals by the intervention of the supra-occipital, or their concealment by its overlapping.
" The overlapping of the muzzle generally by the premaxillae.
" The loose attachment between the various bones surrounding or connected with the organ of hearing.
" The absence or feeble development of the coronary process of the lower jaw."
The scattered locations and the fragmentary condition of the material described in the following pages rendered impossible a complete revision of the forms. All that has been attempted is to place the known material in the most available form.
The classification of the CETACEA is in a very unsettled condition so that no one scheme can be said to be the correct one. The scheme here given follows that of Flower and Lydekker.2
Animals most nearly approaching the land-living
ancestors of the group; the skull elongate with well-developed nasal bones and
the teeth differentiated into an anterior, incisor series and a posterior, molar
series. These teeth, especially the molars, are extended in the antero-posterior
direction and have tuberculated cutting edges; the anterior series is single-rooted
and the posterior two-rooted. The body was elongated and adapted to an aquatic
life but the attachment of the ribs, the structure of the palatal region and
other portions of the body are very seal-like in their relations.
There is but a single family, the ZEUGLODONTIDAE, which is confined to the Eocene formations. In the United States they are most abundantly found in the deposits of Alabama, Louisiana, and Mississippi.
Forms in which the skull has lost many of the
typical mammalian features retained in the previous suborder, especially in
the facial region; the external nares have retreated until they are simple openings
on the top of the head, descending almost vertically through the skull just
anterior to the front wall of the brain case. The retreat of the nares has driven
the nasal bones back until they are mere nodules in the posterior wall of the
upper portion of the nares. The nose is extended into a rostrum that may reach
great length and slender proportions; the teeth are variable, in some forms
they are quite similar to those of the preceding suborder, in others they are
simple and conical; either present in large number or reduced to a single tooth
in each half of the mandible. The vertebrae in the neck are, in the most highly
developed of the forms, ankylosed together in a short mass of bone, this leaves
the animal with no apparent neck; in other forms the cervical vertebrae are
all separate and the head and body are separated by a well-defined constriction.
All forms show a distortion of the anterior portion of the skull, which in some
reaches a high degree. The suborder has four families: SQUALODONTIDAE,
PLATANISTIDAE, DELPHINIDAE, and PHYSETERIDAE.
Following is a scheme given by Cope3 for the determination of the various families:
I. Teeth of two types, one and two-rooted.
Neck longer; teeth in both jaws .......................... Squalodontidae.
II. Teeth uniformly one-rooted.
a. Ribs nearly all two-headed.
Teeth in both jaws; neck generally longer ............. Platanistidae.
Teeth in lower jaw only; neck short ..................... Physeteridae.
aa. Four or five anterior ribs only two-headed.
Teeth in both jaws; neck short ............................. Delphinidae.
In the same article he speaks of the characters
here selected to designate the different families. He says: "All the above
characters are those of divergence from the principal mammalian stem, and have
relations to the conditions of aquatic life. Thus the posterior position of
the nostrils permits inspiration without the elevation of the muzzle above water
level, which is rendered difficult, if not impossible in the most specialized
types, by reason of the extreme flatness and inflexibility of the cervical vertebrae.
The absence of teeth is appropriate to the habits of the types which lack them."
(The confinement of the diet of the mysticoceti to soft bodied animals.) "The
disarticulation and the disappearance of the heads of the ribs in the mysticoceti
is appropriate to the support which all the viscera derive from the fluid medium
in which these large animals live." Again, "The line of the successional
modification of the CETACEA is found in the changes in (1) the shape
of the skull; (2) the extinction of the dentition; (3) the shortening of the
cervical vertebrae; and (4) in the separation of the ribs from articulation
with the vertebral centra. The modification of the shape of the skull is related
to the gradual transfer of the external nostrils to more and more posterior
This family is peculiar in its group in that it possesses teeth of two kind as in the ARCHEOCETI; the anterior teeth are simple and conical while the posterior or molar teeth are more complex and are two-rooted (there are teeth in the premaxillary). The skull, however, presents the characters of the ODONTOCETI. There are no living members of this family.
Macrophoca atlanticus Leidy, 1856, Proc. Acad. Nat. Sci. Phila., vol. viii, p. 220.
Squalodon atlanticus Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, pp. 132, 144, 151, 153.
Squalodon atlanticus Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. vii, p. 416, pl. xxviii, figs. 4-7; pl. xxx, fig. 18.
Basilosaurus (?) atlanticus Cope, n. n.
Description. The original specimens
described as M. atlanticus consisted of three molar teeth from Cumberland
County, New Jersey. They were described as follows by Leidy in 1856: "Crowns
of the molar teeth broader than the length; laterally compressed conical; the
anterior and posterior borders acute, the former with a series of two, and the
latter with four conical tubercles having denticulated borders; inner and outer
surfaces exceedingly roughened, especially toward the base, by longitudinally
acute and broken ridges. Root composed of an antero-posterior pair of fangs
confluent half their length.
"Length of largest tooth 2.25 inches; length of crown 10 lines, breadth 12 lines."
Cope in 1867 described a second specimen from Charles County, Maryland. "At least four of the most posterior molars were inserted in oblique alveolae, overlapping by their anterior fang the inner face of the posterior fang of the tooth in front, anterior to these the alveolae are less oblique, and separated by spaces. The palatal face is moderately convex, while the external surface is divided into two plane faces by an angulated line, which is strong posteriorly, vanishing anteriorly." The fragments are said to indicate a cranium about 30 inches long. The teeth "are longitudinally wrinkled and present a thick anterior and posterior cutting edge. The serrulations stand from behind, 3-2, 2-2, 3-2, 3-2, the anterior two of the last being very weak. The cutting edge of all these is serrulate. Not only in the number of the crests, but in the more elevated conic apex, do these teeth differ from those of S. holmesii."
A specimen in the Museum of the Philadelphia Academy of Sciences bears the name Basilosaurus atlanticus and purports to come from the Miocene of Maryland. No trace can be found of any description of such a species of Basilosaurus nor does the genus Basilosaurus occur in the Miocene. The label is by Cope and it is probable that it was intended for Squalodon atlanticus. The strong resemblance of the specimens to the teeth of the latter genus bears out this supposition.
Occurrence.Calvert formation. 4 Charles County near the Patuxent river.
Collections.The type specimen is in the Museum of the Philadelphia Academy of Natural Sciences.
Description. In 1867 Cope gave the following description of this species: "This species is represented in the collection by a single canine tooth, which presents the usual small crown and broad fang of the CETACEA. The fang is, however, shorter than in the 'Colophonodon and Stenodon,' and, with the crown very much compressed in one plane. A shallow groove extends on each side of it to the narrowed and flattened truncate base. The tooth is widest at the middle of the fang; the crown is rapidly acuminate, narrow lenticular in section, and furnished with a rather thickened postero-internal cutting edge. The anterior or external aspect is worn away by the attrition of a corresponding tooth, but was obtuse, and furnished with a longitudinal ridge on each side at the base of the crown. The surface of the enamel is rugose, more minutely on one side than on the other. The tooth is considerably curved. While the enamel is polished the fang is roughened and opaque.
Cynorca proterva Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, pp. 144, 152.
Cynorca proterva Cope, 1868, Proc. Acad. Nat. Sci. Phila., vol. xx, p. 185.
Squalodon protervus Cope, 1867, Proc. Acad. Nat. Sci. Phila., vol. xix, p. 151.
Squalodon protervus Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. vii, pp. 384-423, pl. xxviii, figs. 18-19.
Total length on middle 1 in. ........ 10.5 lines (48 mm.)
Length of crown ........................ [not given in text]
Width at base of crown ............. 4.5 lines (9 mm.)
Width at middle of fang ............. 5.25 lines (10.5 mm.)"
Occurrence. Calvert formation. Charles
County, near the Patuxent river.
Collection. Philadelphia Academy of Natural Sciences.
The teeth are undifferentiated, conical and single-toothed; the pre-maxillary is without teeth; the nose is extended into a long and slender rostrum and in the lower jaw the symphysis is very long. Zittel says that it is at least half as long as the jaw. The cervical vertebrae are all separate and the ribs, except the most posterior, are two-headed. Noteworthy living members of this group are Platanista of the Ganges which is entirely fluvatile in its habits, never going into salt water, and Pontoporia of the South American coast which is found near the mouth of the La Plata river but has never been found in the fresh water of the river. This last form serves as a connecting link in habits between the PLATANISTIDAE and the succeeding family which is confined to salt water. Most of the fossil forms of ODONTOCETI described from Maryland belong to the PLATANISTIDAE.
Cope has given the following scheme 5 for the determination of the genera of the family PLATANISTIDAE:
I. Teeth with roots extended transversely.
Teeth with lateral basal lobes; lumbar diapophyses wide.......Inia.
II. Teeth with cylindrical roots.
a. Caudal vertebrae plano-convex.
No caudal diapophyses ..................................................Cetophis.
aa. Caudal vertebrae plane.
b. Lumbar diapophyses spiniform.
Lumbar and caudal vertebrae slender .............................Zarhachis.
Lumbar and caudal vertebrae short ................................Ixacanthus.
bb. Lumbar diapophyses wide, flat.
Muzzle elongate, slender; cervical vertebrae long............Priscodelphinus.
Muzzle slender, cervical vertebrae, shorter ....................Pontoporia.
III. Teeth with longitudinally flattened roots.
Teeth in entire length of maxillary bone;
symphysis connate .....................................................Stenodelphis.
Teeth in all the jaws; symphysis not connate; an erect osseus
crest on posterior part of the maxillary ........................Platanista.
Teeth at the base of the maxillary only; muzzle produced into
a subcylindrical beak ..................................................Rhabdosteus.
IV. No teeth; an alveolar groove; muzzle depressed, elongate.....Agabelus.
The genus Lophocetus is not included in this scheme and it seems impossible to insert it as only the skull is known. Certainly it belongs in the second section; "forms with cylindrically rooted teeth."
Delphinapterus gabbi Cope, 1868, Proc. Acad. Nat. Sci. Phila., vol. xx, p. 191.
Tretosphys gabbi Cope, 1868, Proc. Acad. Nat. Sci. Phila., vol. xx, p. 191.
Tretosphys gabbi Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, pp. 7, 8.
Tretosphys gabbi Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol. vii, p. 434.
Priscodelphinus gabbi Cope, 1890, Amer. Nat., vol. xxiv, p. 615.
Description. Described from a single caudal vertebra. "It has pertained to a species of not more than half the length of T. grandaevus, and is less strongly constricted everywhere and especially below. In a caudal of near the same position, the ridges and chevron articular surfaces are much more elevated, especially those on the anterior part of the centrum. They embrace a very deep groove in this, a shallow one in the T. gabbi. An additional longitudinal ridge on each side the inferiors in front is wanting in T. gabbi. Both have a delicate one above the diapophyses in front, the T. grandaevus behind also. There is no posterior zygapophysis in the T. gabbi. The caudal of the latter is also relatively shorter.
Length centrum ..........................2 in. (50 mm.)
Depth articular face anterior........1 in., 5.7 lines (11.4 mm.)
Width articular face anterior,.......1 in., 7 lines (14 mm.)"
Occurrence. Calvert formation. Charles
County, near the Patuxent river.
Collection. The type specimen is in the Museum of the Academy of Natural Sciences of Philadelphia. It bears the label "Tretosphys gabbi Cope (Delphinapterus, Cope, type). Caudal vertebra, E. D. Cope, Charles Co., Md."
Delphinapterus ruschenbergeri Cope, 1868, Proc. Acad. Nat. Sci. Phila., vol. xx,
Tretosphys ruschenbergeri Cope, 1869, Proc. Acad. Nat. Sci. Phila., vol. xxi, pp. 7-9.
Tretosphys ruschenbergeri Leidy, 1869, Jour. Acad. Nat. Sci. Phila., 2nd ser., vol.
vii, p. 434 (mention only).
Priscodelphinus ruschenbergeri Cope, 1890, Amer. Nat., vol. xxiv, p. 615.
Description. This species was about
the size of Ixacanthus stenus. "They (the vertebrae) are also of
a slender form, more so than in any species of the last genus (Zarhachis).
What distinguishes it generically, is that instead of the slender diapophyses
of the caudal it has the broad ones of the true Dolphins, though broader even
than is usual in these, and it is perforated a little on one side of the middle
by the foramen seen among the whales and dolphins generally.
"Articular faces transversely oval; centrum slightly constricted with an obtuse keel along the median line. The two inferior keels of the caudal vanish on the middle part of the centrum.
Length of centrum ................... 1 in. 9 lines (68 mm.)
Height of centrum .............................. 10.3 lines (20.6 mm.)
Width of centrum .............................. 12.5 lines (25 mm.)
Width neural canal .............................. 5.2 lines (10.4 mm.)
Width basis diapophysis lumbar ......... 10.5 lines (21 mm.)
Width basis diapophysis caudal .......... 10 lines (20 mm.)"
The type specimen consists of two vertebrae,
a lumbar and a caudal vertebra.
Occurrence. Calvert formation. Charles County near the Patuxent river.
Collection. Philadelphia Academy of Natural Sciences.
(these web pages were prepared by R. D. Conkwright)