The Beaked Whales of the Family Ziphiidae / An Account of the Beaked Whales of the Family Ziphiidae in the Collection of the United States Museum... - Frederick W. True

The dimensions of the several skulls are as follows:

Dimensions of ten skulls of Ziphius cavirostris (including the types of Z. grebnitzkii Stejneger and Z. semijunctus Cope).

Column headings: A: 83991. Bering Island. grebnitzkii. B: 21248. Bering Island. grebnitzkii. C: 22874. Bering Island. grebnitzkii. D: 21246. Bering Island. grebnitzkii. E: 20993. Bering Island. Type grebnitzkii. F: 22069. Bering Island. grebnitzkii. G: 21245. Bering Island. grebnitzkii. H: 21975. Type semijunctus. I: 20971. Barnegat, N. J. Female, cavirostris. J: 49599. Newport, R. I. Male, cavirostris.

Measurements.	A	B	C	D	E	F	G	H	I	J
	mm.	mm.	mm.	mm.	mm.	mm.	mm.	mm.	mm.	mm.
Total length	900	877	^a807	850	963	882	855	797	945	915
Length of rostrum	491	480	^a397	470	550	480	476	463	550	514
Height from vertex to inferior border of pterygoids	433	450	...	...	515	471	481	349	440	465
Distance from tip of rostrum to posterior free margin of pterygoids (median)	664	670	...	...	735	682	673	614	735	726
Distance from the same to anterior end of nasals	617	621	^a538	600	690	623	589	590	708	676
Breadth between centers of orbits	495	513	^b499	488	563	^b486	492	393	476	530
Breadth between zygomatic processes	511	513	...	505	573	531	530	415	503	548
Breadth between temporal fossæ	270	309	325	300	349	317	311	242	302	313
Breadth of rostrum at base	319	331	345	324	380	337	320	249	307	337
Breadth of rostrum at middle	102	117	^b94±	107	120	109	112	83	112	113
Breadth of premaxillæ at same point	54	67	58	62	78	70	75	44	62	80
Depth of rostrum at middle	66	81	80	79	118	117	113	50	77	107
Breadth of premaxillæ in front of nares	176	177	184	205	221	230	219	128	176	234
Greatest breadth of anterior nares^c	74	77	77	90	98	103	108	70	76	112
Greatest length of temporal fossa	161	158	154	149	152	140	146	133	143	155
Greatest depth of temporal fossa	81	73	77	79	87	74	89	67	80	76
Length of orbit (ant.-post.)	131	133	132	130	137	126	117	113	134	132
Distance from anterior end of orbit to maxillary notch	78	92	82	70	83	89	85	61	82	99
Length of tympanic bulla	...	...	...	...	53	...	...	54	...	55
Breadth of tympanic bulla	...	...	...	...	24	...	...	37?	...	25
Length of mandible	...	769	...	...	...	...	...	679	...	842
Length of symphysis	...	170	...	...	...	184	...	149	...	176
Depth of mandible at coronoid	...	153	...	...	...	...	...	133	...	153

^a About 150 mm. lacking from end of beak. ^b A little abraded. ^c Taken on a level with the curve of the inner margin of the premaxillæ. Is only approximate.

SEX CHARACTERS.

It will be found from an examination of the foregoing descriptions that in those specimens in which the sex is known to be female, or is marked as such, the premaxillæ are comparatively narrow, the mesirostral ossification only slightly developed, the prenarial basin undeveloped, and the teeth quite slender, with a diameter of from 10 to 14 mm. As the teeth in some of them have closed roots there can be no doubt that they are adults. On the other hand, those skulls known or believed to be from adult males have the mesirostral ossification enormously developed, a deep prenarial basin, and fusiform teeth with closed roots and a diameter of from 25 to 30 mm. It appears to be a fact, therefore, that in the females the mesirostral ossification is never greatly developed at any age, that the teeth are never thick and fusiform, and that the prenarial region is never deeply concave. Immature individuals present, of course, the appearance of the females, except that the teeth are open at the root and that the mesirostral ossification is not developed at all. Conversely, the females, broadly speaking, always present characters of immaturity, but in adults the roots of the teeth are, of course, closed.

That these conclusions are correct is borne out by an examination of descriptions and figures of specimens from other parts of the world, for which purpose a few are available in the writings of New Zealand zoologists and others. Hector, for example, in 1873,[40] published a description and figures of a skull from the Chatham Islands which had a large mesirostral ossification, deep prenarial concavity, and large, thick teeth, having a diameter of 34 mm. This is the same combination of characters found in the Newport specimen, which is known to be a male, and the Bering Island skulls supposed to be those of males.[41]

In 1876,[42] Haast figured and described a female 26 feet long, and hence presumably adult, from Lyttleton Harbor, New Zealand, which had a small development only of the mesirostral ossification, a slight prenarial depression, and rather slender teeth with closed roots and a diameter of 19 mm. This combination of characters is found in the Barnegat skull, also known to be an adult female.

In the same paper Haast describes[43] and figures the skull of another female from Akaroa Harbor, New Zealand. This individual was larger than the last and was accompanied by a suckling calf. Hence, there can be no doubt that it was mature. The skull shows a moderate development of the mesirostral ossification, and slender cylindrical teeth with closed roots and a diameter of 16 mm.