Tuatara: Volume 18, Issue 1, July 1970
The Identity of the Pliocene Seal from Cape Kidnappers, New Zealand, Previously Known as Arctocephalus caninus
The Identity of the Pliocene Seal from Cape Kidnappers, New Zealand, Previously Known as Arctocephalus caninus
Pinniped skull remains from Cape Kidnappers, New Zealand were described by Berry (1928) as a new species of fossil Arctocephalus - A. caninus. In later years Berry himself appreciated the generic differences of Arctocephalus, Neophoca and Phocarctos and thought that as his specimen is considered to be the oldest fossil seal known from New Zealand it merited reassessment in the light of modern knowledge. This he did in a series of uncompleted papers and manuscripts that were still unpublished at his death in 1962. The second author has seen and examined the type specimen of A. caninus in the Dominion Museum, Wellington, (DM 532) and subsequently through the courtesy of the New Zealand Geological Survey, had access to Dr. Berry's manuscripts, and feels that our independently reached conclusions should be amalgamated.
The remains consist, (Plate 1) as Berry has already detailed them, of an incomplete left mandible with post canines 3, 4, and 5 still in position, but with the anterior part of the horizontal ramus broken in front of the level of pc 3, and the coronoid process and condyle abraded; the anterior portion of the left maxilla with the canine and post canines 1 and 2 in position; and nine separate teeth, one of which is the lower canine, and the others can almost certainly be given their correct positions in the jaws.
The bones were found about 1922 by the late Mr W. D. Southcott of Hastings. ‘Dr. Berry later went to great trouble to localise the point of collection and decided it was from the Opoitian sandstones immediately below the Black Reef Limestone, between Clifton and Cape Kidnappers, Hawke's Bay. It remains the geologically oldest fossil seal known from New Zealand’ (Fleming 1968). The Opoitian sandstones are considered to be Pliocene (Fleming 1962).
Much of the manuscripts are taken up with very detailed descriptions of the teeth, but it is considered that these were adequately noted in the original paper. Berry does however compare his fossil with the skull of a young female Phocarctos found in Maori middens in the sandy dunes at Ocean Beach, a few miles south of Cape Kidnappers. The Ocean Beach skull although from a female is of the same degree of maturity as the fossil, and is in all respects very similar. It is in fact only in the details of the cusping of the post canines that Berry considers that the fossil differs enough from the Ocean Beach specimen and other available specimens of Phocarctos to be recognised as a new species. The characters he used are:
1. |
Upper pc 1 and 2 lack prominent accessory cusps — whereas in Phocarctos these are always present. |
2. |
Upper pc 5 has a more prominent and sharper anterior accessory cusp than in Phocarctos, but is otherwise similar. |
3. |
Lower pc 1 and 2 have smaller anterior accessory cusps than in Phocarctos. |
4. |
Lower pc 3 has a posterior accessory cusp which is missing in Phocarctos. |
5. |
Lower pc 3, 4 and 5 — the anterior accessory cusp is larger than in Phocarctos and is directed more horizontally forwards. |
The accessory cusps on otariid post canines show a high degree of variability in detail and from inspection of a reasonable number of Phocarctos post canines it is felt that characters 2, 3 and 5 above come within the range of variability and are not useful as characters on which to recognise a new species. Similarly (character 1) the degree of prominence of anterior accessory cusps varies considerably and their complete absence occurs not infrequently. From the photograph (Plate 3) it can be seen that the posterior accessory cusp on lower pc 3 of the fossil is extremely small. Phocarctos usually has the posterior surface of this tooth, and also that of pc 4, without any accessory cusps, but occasionally such a small cusp does occur. A similar very small one is present on pc 4 of a single skull (1843.11.25.2) in the British Museum (Natural History) collection, so though it may occur only seldom, such a cusp may presumably also occur on pc 3. Plate 3 also illustrates the close similarity in shape between a recent Phocarctos jaw (DM 1359) and the Cape Kidnappers jaw.
It is thus felt that such a very variable character as the cusping detail is not sufficient to distinguish this fossil from modern specimens of Phocarctos hookeri and it is therefore suggested that Berry's name of Arctocephalus caninus be put in the synonymy of Phocarctos hookeri.
page 17The present distribution of Phocarctos is on the Auckland Islands, Campbell Island and on the Snares, where the animals are to be found all the year round. As stragglers they reach Macquarie Island, Stewart Island and have been recorded as far north as Kaikoura, north of Christchurch (Mr. L. D. Bowring, Kaikoura, pers. comm.). But apparently as recently as 1863 these sealions used to breed on the west coast of the South Island, though during the next thirty years they became much rarer on the New Zealand mainland, and even on Stewart Island in 1874 had not been seen for some time, though their tracks through the bush were visible. (Thomson 1921).
Both the Ocean Beach and Cape Kidnappers specimens are from young animals, so either Phocarctos bred at least as far north as Hawke Bay, or close enough so that the young animals could swim there. The apparently very recent withdrawal of resident Phocarctos from the New Zealand mainland to the more distant islands, and the presence of both the Ocean Beach specimens and the Pliocene fossil from the same area suggest that the general distribution of Phocarctos was once considerably wider than it is now.
Summary
Arctocephalus caninus from Pliocene sandstone, Cape Kidnappers, Hawke Bay. New Zealand was described by Berry in 1928. The page 18 result of Dr. Berry's unpublished manuscripts are here combined with the independent conclusions of the second author. Comparison of the Pliocene fossil with a skull of Phocarctos hookeri from a Maori midden and also with recent specimens of P. hookeri indicate that this is the correct identification of the Cape Kidnappers fossil, thus extending the known range of Phocarctos.
References
Berry, J. A., 1928. A new species of fossil Arctocephalus from Cape Kidnappers. Trans. N.Z. Inst. 59: 208-211.
Fleming, C. A., 1962. New Zealand Biogeography. A paleontologist's approach. Tuatara 10(2): 53-108.
——, 1968. New Zealand fossil seals, in: Notes from the N.Z. Geol. Survey 5. N.Z. J. Geol. Geophys. 11: 1184-1187.
Thomson, G. M., 1921. Wildlife in New Zealand. Part 1. Mammalia. N.Z. Board of Science and Art. Manual No. 2.
* Deceased
** Department of Zoology, University of New South Wales.