united states national museum bulletin 247

Growth apparently continues at a decreasing rate while the intercartilaginous plates persist between the vertebra's center and its own. For example, the lumbar vertebrae of the large cetothereus described in this study have tall, broad neural spines and broad, elongate transverse processes. Erosion or weathering has removed the original external bony surface of the squamosal bones and their zygomatic processes and the surface at the back of the parietal bones.

For more than half the length of the rostrum, the sides are nearly parallel proximally and then become rather strongly curved distally. Anterior to the anterior extension of the vomer, each premaxillary curves downward and inward to meet its. Vomer posteriorly and premaxillaris anteriorly contribute to the floor and sides of the longitudinal rostral groove.

Each premaxilla reaches its maximum width (105 mm.) at the level of the anterior edges of the maxillae and projects forward 140 mm. The orbital rim of the frontal supraorbital process is quite thin and arched.

A NEW WHALEBONE WHALE

UNITED STATES NATIONAL MUSEUM BULLETIN 247 greater length being in the anteroposterior direction. In

10 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 ankylosed in front with the bcisisphenoid, the Une of contact

A NEW WHALEBONE WHALE 11 External to the anterior process of the periotic, the ventral

The involucrum (Fig. 4b) reaches its greatest width posteriorly, especially at the last third of its length, and then narrows sharply towards the anterior emargination. The posterior peduncle of the tympanic bulla, before breaking off, was fused with the inner end of another broad ridge parallel to the anterior margin of the ventral side of the posterior process. The outer denser part of the periotis is wedged in a deep cavity, which is partly occupied by the anterior process and is for the greater part hidden by the overhanging inner edge of the squamosal; but it is compressed from side to side.

Viewed from the ventral side, the cerebral profile of the parscochlear-isinuous and the posterior face are abruptly truncated above the overall large fenestra rotunda. The fossa for the stapedial muscle is rugose, wider than long and extends downward on the inner face of the. Overall level concavity (pi. 16, fig. 2) for receiving the head of the malleus which is located next to and outside the epitympanic opening of the aquaeductus Fallopii.

Anterior to this face, the base of the anterior thin) aedicle of the tympanic bulla is fused with the anterior process.

A NEW WHALEBONE WHALE 15 The fossa incudis may be described as a small pit located on

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16 UNITED STATES NATIONAL MUSEUM BULLETIN 2 47 the apex the posterior edge of the coronoid process becomes

A NEW WHALEBONE WHALE 17

18 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 Atlas: Except for a portion of the neural spine the atlas

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On the dorsal and ventral levels of the centrum, the anteroposterior ridges are low and broad and separate opposite depressed areas. The edges of the anterior and posterior planes of the center project beyond and over-. The sixth cervical feature characterized in part by changing the direction of its transverse processes is the upper process instead of being directed outwards in line with the transverse axis of the center somewhat forward as well as outward at least projected at the base; the ventral process was rather slender at the base and directed more downward than outward. .

The anteroposteriorly compressed athinlamina, which originates at the anterolateral border of the centrum but is dorsally fused to the base of the pedicle of the neural arch, supports the superior transverse processes. The anterior face of the centrum is depressed, shallowly concave, its raised lips projecting beyond and overhanging the lateral faces. the lateral depressions are wider and more conspicuously developed on the ventral face than on the dorsal face. The median anteroposterior ridge on the ventral face is distinctly more prominent than the corresponding ridge on the dorsal face.

The wide dorsoventrally expanded lamina supporting the upper transverse process is significantly larger than the corresponding structure in the sixth cervical in accordance with the dimensions of this process, its posterior surface passing inconspicuously into that of the neural arch.

22 UNITED STATES NATIONAL MUSEUM BULLETIN 247 Dorsal vertebrae. — All of the epiphyses on the nine

24 UNITED STATES NATIONAL MUSEUM BULLETIN 247 has slightly increased its anteroposterior diameter (73.5

26 UNITED STATES NATIONAL MUSEUM BULLETIN 2 47 PART 1

28 TJNITED STATES NATIONAL MUSEUM BULLETIN 2 47

30 XJNITED STATES NATIONAL MUSEUM BULLETIN 247

32 UNITED STATES NATIONAL MUSEUM BULLETIN 2 47 than the posterior. The pedicles of the neural arch do not

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The distance between the ends of the transverse processes of the dorsal side of the metapophysis to the ventral side. tive lumbar region and also protrudes beyond the anterior end of the sixth and the posterior end of the tenth lumbar region. the center of the sixth, seventh, eighth and ninth lumbar segments is completely ankylosed on the left side due to the bony bridge. USNM 23056) with a completely ankylosedepiphysis has similarly elongated transverse processes, a tall neural spine, thin laminae-like metapophyses (directed more strongly upward), and a rather tall neural canal (60 mm). Five caudal vertebrae (USNM 23059) found associated with the atlas, three dorsal, one lumbar, and other skeletal elements of Pelocetus provide minimal information about the caudal series.

Anterior Caudal: In view of the development of the posterior haemal tubercles (hemapophyses), the posterior widening of the centrum and the large thickened metapophyses, the largest caudal vertebra (USNM 23059) is considered the third or fourth in the caudal series. The anterior caudal of these Calvert setoteres is usually characterized by an enlargement of the posterior end of the centrum, due to the development of the posterior haemal tubercles. Themetapophyses are markedly thickened, bent upwards and outwards, projecting no further than the level of the front of the centrum and thus not clasping the base of the neural spine of the preceding tail.

Anteroposterior diameter of centrum Transverse diameter of centrum anterior Vertical diameter of centrum anterior Tip of neural spine to ventral surface of centrum Least anteroposterior diameter of pedicle.

A NEW WHALEBONE WHALE 35 The neural spine presumably was rather short, judging

36 UNITED STATES NATIONAL MUSEUM BULLETIN 247

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The stem is thickest below the head and is markedly flattened inwards towards the distal end. A wrinkled area (Fig. 22a) on the outside of the shaft between the head and the ulnar facet may indicate the position of origin of the short head of the triceps. At the lower or distal end (Fig. 22c) of the transversely flattened stem, the ulnar facet is slightly narrower than the radial facet, more concave, saddle-shaped, and extended upward at the back of the stem distally.

The radius (fig. 23a) is a rather long, stout, slightly curved and transversely flattened bone, measuring about 15% inches (398 mm.) in length. The distal limb (fig. 23c) of the shaft of both radii is rough and deeply pitted, indicating the presence of a cartilaginous cap or epiphysis.

40 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 radial facet (radial margin) to the distal end the shaft

44 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7

BIBLIOGRAPHY

A NEW WHALEBONE WHALE 45 RjDEWOOD, W. G

The Miocene Calvert Sperm Whale

INCREDIBLE SORT OF REMODELING of the skull led to the separation of the phytheroid stock from other odontocetes which, with the exception of the ziphioids, appear to have followed a more conventional line of development in cranial architecture. On the skulls of two lower Miocene genera {Diaphorocetus and Idiorophus), the fat pad, or reservoir for spermaceti, spread backwards behind the nasal passages and the resulting adaptation of the skull bones involved formed a supracranial basin. The "dishing-in" of the roof of the braincase is . attributable at least in part to the pressure of this developing spermaceti reservoir.

The associated changes of the relative proportions and relationships of the dorsal skull bones included the depression of the frontal bones along the median longitudinal line, the posterior enlargement or widening of the inverted right premaxillary, the crest-like height of the maxillary lateral, the loss or marked reduction of the and the nasal level other against the frontal behind the strongly enlarged left nasal passage, and the marked widening of the rostrum proximally. Other genera show a tendency for the teeth to be loosely implanted in large alveoli, while the intervening septa decrease in thickness and finally disappear, leaving an open alveolar gutter in the maxillary {Aulophyseter). The type Balaenodonphysaloides Owen consists of a portion of the root of a tooth from the Red Crag of Felixstowe, Suffolk, England.

However, the tooth type is significantly larger and structurally different from Orycterocetus teeth. The teeth of the two types of Hoplocetus crassidens (types) are characterized by an enlarged or bulging root from a proportionally small crown from a neck-like constriction. Abel (1905, p. 53) rejects the validity of the stated generic characters of Hoplocetus, but nevertheless places it in.

The teeth of Scaldicetus caretti, in addition to their larger size, are characterized by very thick and rough apical enamel, anastomosing ridges but generally directed towards the apex of the crown with numerous connecting or interlacing lines; invisible constriction of the root at the base of the crown. As the aforementioned extinct physeteroids may have had no bearing on the general distribution of the Calvert Miocene sperm whale, their status is not further considered. Dentine core of thin teeth often curved with funnel-like open pulp cavity; fine ring lines of.

48 UNITED STATES NATIONAL MUSEUM BULLETIN 2 47 growth and longitudinal fluting characterize the dentine

THE SPERM WHALE ORYCTEROCETUS 49

THE SPERM WHALE OEYCTEROCETUS 51 The opposite premaxillaries of all known fossil and recent

52 UNITED STATES NATIONAL MUSEUM BULLETIN 24 7 of the anterior end of the vomer. As will be observed from

THE SPEKM WHALE ORYCTEROCETUS 53 margin of the exoccipital from the hinder end of the

56 UNITED STATES NATIONAL MUSEUM BULLETIN 247 presphenoid is lodged. The vomer contributes a portion

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58 UNITED STATES NATIONAL MUSEUM BULLETIN 247 Teeth

THE SPERM WHALE ORYCTEROCETTJS 59

60 UNITED STATES NATIONAL MUSEUM BULLETIN 247 large excavated fossa for the stapedial muscle. This

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THE SPERM WHALE ORYCTEEOCETUS 61

62 UNITED STATES NATIONAL MUSEUM BULLETIN 247 Measurements (in mm.) of the right tympanic bulla of

THE SPERM WHALE ORYCTEKOCETTJS 63

S. GOVERNMENT PRINTING OFFICE: 1965

S. National Museum Bulletin 247, Plate 1

10 Cervical Vertebrae, USNM 11976, Pelocetus calvertensis

S. National Museum

S. National Museum Bulletin 247, Plate