Fossil Cetacea of New Zealand IV.—Notes on Some of the Bones of Kekenodon onamata Hector
[Read before the Otago Branch, September 8, 1936; received by the Editor, October 28, 1936; issued separately, June, 1937.]
In the year 1880 the late Sir James Hector described and figured the astonishingly large teeth of the extinct whale to which he gave the above name. He records “that they were obtained from the Upper Eocene strata at the Waitaki Valley in Otago” by A. McKay (1880), of the Geological Survey.
The “grinders,” probably molars, are 4 and 5 inches in length, though even these figures do not represent their entire length, as the ends of the roots are broken. They have the general form of crown found in Squalodonts, with the two fangs of the root united for most of their length, and for that reason Hector did not refer the whale to the genus Zeuglodon, but bestowed a new name on the fossil.
Kellogg (1923, p. 27) points out the strong resemblance of these teeth to those of Dorudon serratus, which implies a close relationship, and he adds “the character of the teeth places this primitive form with the Zeuglodonts and not with the Squalodonts, as supposed by Hall (1911). In addition to the teeth, Hector figured the tympanic and the periotic bones without, however, giving any description of them, and mentioned that other fragments of the skeleton had been collected by McKay at the same time and place.
By the courtesy of Dr. W. B. Oliver, the Director of the Dominion Museum, I have been enabled to examine these other bones, and it seems worth while to put on record the results of my study, incomplete though they are in some respects. Dr. Oliver also was good enough to have photographs and measurements made after I had commenced to study them, and I thank him for his readiness to comply with my various requests in respect of these and other specimens in his charge. It is quite clear from the size of the teeth that the skull must have been very large and heavy, but insufficient material was gathered, and this was so friable that it was difficult to remove it from the rock: and even some of the parts gathered by McKay suffered during the journey to Wellington so as to be useless for any accurate description. Hector indeed mentions fragments of a “massive solid jaw, one portion showing the posterior part of the ramus having a depth of 6–7 inches.”
On a later visit to the same area McKay (1881, p. 104) collected further material of four other individuals, which he labelled 126.96.36.199, and they still bear these figures, the original specimen being
Number 1. McKay states that “No. 3 proved to be a nearly entire skeleton about 23 feet long, but it sustained such damage during its carriage to Wellington that it is not now possible to put the parts together so as to form an entire skeleton.” A most unfortunate and disappointing affair; but in those days the modern method of treating fossils so that they will hold together had not been introduced. No. 4 comprised fragments of the skull, tympanic bone, but no teeth, both scapulas, sternum, numerous vertebrae including the atlas and axis, ribs, etc.” It is these bones that I propose to describe.
Reference must be made to the attempts of later geologists to discover more material at this classical spot. In 1903 Mr. A. Hamilton, accompanied by Professor Park, endeavoured to identify the precise locality at which McKay had made his collections in the hope that more of the remains of this interesting whale might be found. Hamilton (1903) believed that he had identified the spot, but adds "we were not able to find any bones or teeth of Kekenodon, which must have been obtained from the upper beds at this point before the recent erosion by the river.”
Park (1904, p. 511) includes among the fossils of Mount Brown beds at Kakanui relics of “Kekenodon” and at Maerewhenua (loc. cit., p. 522). The latter is evidently the specimen I described (1936) as Microcetus hectori (see also McKay, 1881, p. 104), which as I have recorded was labelled by Hector as “K. onamata.” Park also records the occurrence of Kekenodon at the original locality on the river Waitaki “about half a mile below the junction of the Wharekuri Stream, at which spot I made a large collection of fossils which included Kekenodon.” Unfortunately he does not state what bones were collected at any of these localities and it is not beyond question that some of them were those of Prosqualodon or Lophocephalus, which had not then been recorded as having been found in New Zealand.
In 1934 I heard that Dr. Marwick was intending to visit Kurow, and at my request he was good enough to spare time to examine the locality at Wharekuri, but was unsuccessful in finding any bones of the whale. He writes that “either the river was too high (at the time of his visit) or that the terrace gravels had slumped down over the spot” (letter). But these naturalists were uncertain as to the exact spot that McKay described, and each located the scene at a different place.
Description of Some of the Bones.
I proceed to give an account of the following bones—atlas, axis, thoracic vertebrae, ribs, sternum, scapula, and pelvis.
The atlas (labelled “2”) has been broken, but has been pieced together, and nothing seems to be missing. The neural arch presents a foramen in each side, immediately above and internal to the condylar facet, which transmits the first spinal nerve; as is the case in Zeuglodonts, as well as in modern Odontocetes, but which I have noted as being absent in Prosqualodon. The neural spine is as usual feeble, and the hypapophysis is absent; the transverse process is single, short and vertically extended.
|Greatest width over trans. proc.||23|
|Neural canal; vertical diameter||9|
|Neural arch; length of roof||5|
|length of floor||6|
|Prezygapophysis (condylar facet), horizontal width||6|
|Posterior zygapophysis, width||5.5|
|Transverse process, from inner surface of arch to tip||9|
|Transverse process, vertical height||5.5|
The axis (no. 2) is cracked and has been repaired, but a part is still missing from one side. The posterior end of the centrum has lost the epiphysis. The odontoid is but little prominent, its base is coextensive with the centrum, and the process projects as a low, rounded mound (much less pronounced than in Prosqualodon). The neural canal is transversely extended, being broader than high, as it is also in the following vertebrae. The neural spine is as usual compressed laterally and prolonged forwards above the arch of the atlas. There seems to have been both upper and lower transverse processes, quite short, but as both are broken it is impossible to ascertain whether they met to form the wall of a vertebraterial canal; they probably do, as such a condition exists in Zeuglodonts generally.
|Length of centrum plus odontoid||7|
|Centrum, height anterior face||8.5|
|Centrum, width anterior face||15.5|
|Neural canal; diameter||6|
|Neural canal, horizontal Centrum, posterior face, height||10|
|Centrum, posterior face, width||11|
The other vertebrae marked “2” are too much damaged to be measurable. One thoracic with an imperfect neural arch has a centrum of width 9 cm. and height 7.5; neural canal, width 5. On one side the two costal facets are recognisable.
Thoracic vertebrae. A block of stone numbered “4” contains a number of vertebrae pressed together, of which the one that is exposed is a thoracic; a second similar one is partly exposed, and four others deeper in the block have quite thin centra and are evidently cervicals (not “caudals” as McKay stated). These vertebrae are slightly displaced from their natural positions in relation to one another and present the edges of the centra. The second thoracic is twisted round as compared with the rest, so that its dorsal surface faces in a direction at right angles to that of the exposed one. Dr. Oliver was good enough to measure the thoracie vertebra. The neural canal has greater width than height, as is usual in this region of the column; the spine is relatively thin and is broken short,
about 5 mm. being lacking; the transverse process is missing from one side and is incomplete on the other side. It is comparatively stout and springs from the side of the neural arch.
|Neural spine (tip to inner surface of arch)||6.5|
|Transverse process, from inner surface of arch||14|
|height at base||5|
Humerus (of no. 2). A short bone measuring 11 cm. by 8 cm.; has a rounded “head” at one end and two convex condyles at the distal extremity separated by a slight furrow. One condyle measures 5 cm. across, the other 3.5 cm.
The scapula (no. 2) is embedded in plaster of Paris; it belongs to the right side and exhibits its outer face. The supra-scapular border, the margin of which is broken, forms a semicircle. The acromion, which is broken at the end, is of rather large size, but of the usual shape: it does not spring from the actual coracoid border, so that a small narrow prescapular fossa exists, whose extent is partly concealed by the plaster which covers its edge above the origin of the acromion. The coracoid process appears to be even less defined than in that whale, but it may be that the plaster conceals part of it. I did not wish to dig out the plaster, as the bones are so friable. A slight ridge extends from the base of the acromion along the surface of the blade reaching almost to the suprascapular border (broken). This is like the bladebone of Mystacocetes, but differs from modern Odontocetes.
|Total height from glenoid to middle of suprascapular border||26|
|Width at base||11.5|
|Width at free end||7|
|Glenoid width (ant. post.)||9|
|Distance from coracoid to origin of acromion||4.5|
Ribs. Eleven more or less imperfect ribs were arranged in the case in what is approximately their correct position, presumably so arranged by Hector. One of the longest measures 73 cm. in a straight line from head to end, and 95 cm. along the curve.
The sternum (of no. 4) has a squarish body, somewhat convex along its anterior margin, and is continued backwards as a broad process about half the width of the body. The side bears two pairs of pits for the articulation of ribs, one on the side of the “body,” the other at the side of the “process,” and the latter is smaller than the former. From the middle of the bone there rises a low rounded mound between the two costal facets; not very unlike the condition in Balaenids. The bone is thus thicker in its middle than on either side.
|Greatest width of “body”||7|
|Width of “process”||3.5|
|Thickness at middle||5|
|Thickness behind the mound||3.5|
The sternum of no. 2 is slightly smaller, the anterior margin is concave and the posterior “process” narrower.
Pelvis (no. 4). It is of interest to note that in these early whales the pelvis differs but little from that of modern representatives in that the three constituent bones are not defined. The pelvis of Kekenodon agrees closely with that of the Mystacocetes rather than with Odontocetes. It is a triradiate bone still resting on the matrix. One ray (which I will call A) is broad, flat and longer than the other two; it is splintered off the matrix at its extremity, but according to Oliver its impress is still recognisable. Of the others, one (B) is longer, narrow and cylindrical, its end is cracked and a short piece is lacking; the third ray (C) is shortest, rounded at tip and appears uninjured. A second pelvis (no. 2), though imperfect otherwise, has the long ray complete; hence we are able to state that about 2.5 cm. is missing from this ray in no. 4.
|Total length including impress of A to missing end of B||21|
|Width of A near end||5.8|
|Width of A about middle||5.2|
|Length from tip of A to opposite curved margin||15.5|
|Width of longer ray (B)||1.9|
|Width of shorter ray (C)||2.5|
|Length of shorter ray (C) to opposite margin (A to B)||10.5|
Flower, writing of the Sperm whale, says, “In all known toothed whales the sole rudiment of the pelvis is formed by a pair of bones (ossa ischia),” and in his Osteology (1876) states that bone ossifies
from a single centre, its identification with ischium depends on the fact that it serves for the attachment of certain muscles connected with the rudimentary femur. Beddard, on the other hand, following Delages, suggests that this single bone really represents the typical three bones of normal mammals united, for, he says, “there is a forward process suggesting the ilium, and a downward process, the pubis, and a slight hollow in the middle suggesting an acetabulum with which in Balaena mysticetus the rudimentary femur articulates.” The pelvis of Kekenodon certainly resembles that of the Mystacocetes in being three-rayed; ef. von Haast (1883), who figures the pelvis of Balaenoptera australis (-physalus. Linn.).
Locality: Wharekuri, in the Valley of the River Waitaki (Oligocene).
Beddard, F.E., The Book of Whales.
Benham, W. B., 1936. The Teeth of an Extinct Whale, Microcetus hectori Benham, Trans. Roy. Soc. N.Z., vol. 65, p. 239.
Flower, W., 1876. Osteology of the Mammalia, Macmillian.
— 1867. On the Osteology of the Cachalot or Sperm Whale (Physeter macrocephalus), Trans. Zool. Soc., vol. 6, p. 364.
Hall, T. S., 1911. On the Systematic Position of the Species of Squalodon and Zeuglodon described from Australia and New Zealand, Proc. Roy. Soc. Victoria (n.s.), vol. 23, p. 258.
Hamilton, A., 1903. Notes on a small Collection of Fossils, etc., Trans. N.Z. Inst., vol. 36, p. 465.
Hector, J., 1881. Notes on N.Z. Cetacea, Recent and Fossil, Trans. N.Z. Inst., vol. 13, p. 435.
Kellogg, R., 1923. Description of Two Squalodonts, etc., Proc. N.S. Nat. Muse., vol. 62, art. 16.
Mckay, A., 1881. Report of Geological Survey, p. 68.
Park, J., 1904. On the Marine Tertiaries of Otago and Canterbury, Trans. N.Z. Inst., vol. 37, p. 489.
Von Haast, J., 1883. Notes on a Skeleton of Balaenoptera austrails Desmulins, Proc. Zool. Soc., p. 592.
Fig. 1.—Photograph of atlas (× ¼), anterion view. n.sp. neural Spine.
Fig. 2.—Side view of the same (× ¼) showing the foramen for the spinal nerve.
Fig. 3.—Photograph of the axis, posterior end (× ¼), Ltr., lower transverse process; pt.zy., post-zygapophysis; u.tr., upper transverse process.
Fig. 4.—Side view of the Same, showing the rounded, wide, shallow odontoid process.
Fig. 5.—Photograph of a block containing several vertebrae. (× ⅙). (I owe these photographs to the courtesy of Dr. Oliver.)
Fig. 6.—The scapula. An outline, enlarged tracing from a photograph. The bone is mounted in plaster of paris. (× circa ¼).
Fig. 7.—The pelvis. An outline of enlarged tracing of a photograph. (× circa ½). A,B,C, the three rays.
Fig. 8.—The sternum, outline enlarged. Dorsal surface. (× circa ⅔). costal facets; m, marked convexity on dorsal surface.
Fig. 9.—Side view of the same. (× circa ⅔).