PDF (Lo-Res) - Smithsonian Institution Libraries

56 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
radiocarpalis (not so in Pelagodroma). Humeri of P. grallaria
are longer, and the tuberculum dorsale is broader, not as raised
above the margo caudalis, and not as elongate distally as those
of P. marina. In F. grallaria the tuberculum ventrale is as high
as wide rather than higher than wide as in P. marina. On the
cranial surface, the sulcus at the base of the crista deltopectoralis
is shallower than in P. marina. The sulcus ligamentis transversus
ends ventrally beside a shallow sulcus on the ventral
margin of the crista bicipitalis in F. grallaria, but not in P. marina,
where there is no shallow sulcus.
Oceanites sp.
A few bones of a very small storm-petrel are smaller than
those found in any genus except Oceanites. Comparisons were
made with Grey-backed Storm-petrels {Oceanites nereis) and
Wilson's Storm-petrels {O oceanicus). The few measurements
available suggest O nereis is smaller, but although lengths of
the tarsometatarsi overlap {O. nereis, mean=33.47 mm,
range=31.1-34.6 mm, n=4; O oceanicus, mean=35.21 mm,
range=33.0-37.2 mm, n=5), those of the ulnae do not {O.
nereis, mean= 17.67 mm, range= 16.7-18.4 mm, «=4; O oceanicus,
mean= 19.73 mm, range= 19.1-20.4 mm, n-5). Ulnae
of two of the fossil specimens are 18.1 mm and 18.7 mm long,
suggesting that they may belong to the smaller taxon. Oceanites
oceanicus is regularly seen offshore, and a specimen of O
o. parvus was collected ashore on Amsterdam (Roux and Martinez,
1987). In 1995 a small colony of O. oceanicus was found
breeding on St. Paul (Micol, 1995). Because the specimens of
O. oceanicus measured were mainly from Heard Island, they
may be bigger than birds breeding on more northern islands
(see discussion in Marchant and Higgins, 1990), so it is possible
that O oceanicus from the Amsterdam group could be similar
in size to O nereis. The fossils are referred only to Oceanites
sp.
Pelecanoides urinatrix
Bones of a diving-petrel are present in many sites. At
present, two diving-petrels are found in the Indian Ocean. The
smaller South Georgian Diving-petrel {Pelecanoides georgicus)
breeds on subantarctic islands, and the larger Common
Diving-petrel (P. urinatrix) has a more widespread distribution,
between 35°S and 55°S (Marchant and Higgins, 1990).
Both exhibit size variation that is to some extent clinal, with
southern populations being larger (Marchant and Higgins,
1990), but this is not the case in New Zealand (Appendix 7).
The fossils, particularly the ulnae and carpometacarpi, are
larger than bones of P georgicus from Heard Island, smaller
than bones of P. urinatrix exsul from both Auckland and Heard
islands, and smaller than bones of P. u. urinatrix from beaches
around Cook Strait in New Zealand (Appendix 7). They are,
however, similar in size to P. u. chathamensis from Southeast
Island in the Chatham Group, and so they are referred to P. uri­
natrix. There are two records of P. urinatrix from Amsterdam
(Roux and Martinez, 1987; Micol and Jouventin, 1995).
Catharacta skua
Skua bones were recovered from several sites, but most were
in poor condition. They are much smaller than those of the
Subantarctic (Brown or Southern Great) Skua {Catharacta
skua lonnbergi) from the New Zealand subantarctic islands and
are bigger than than those of the Antarctic Skua (C. maccormicki)
(Appendix 8). The carpometacarpus is longer than the
tarsometatarsus in C. maccormicki, in contrast to C. skua lonnbergi,
in which the opposite is true. Unfortunately, none of the
fossils were complete enough to use this feature. The Tristan
Skua (C. skua hamiltoni), however, for which no comparative
material was available, is smaller than C. skua lonnbergi and
breeds on Gough Island and in small numbers on Amsterdam
(Micol, 1995). Because the fossils are markedly smaller than
bones of C. skua lonnbergi but are bigger than bones of C.
maccormicki, it seems probable that the Amsterdam skua fossils
are referable to C. skua hamiltoni.
Anas marecula
The bones of a small duck found in the collection were obviously
missed when duck material was extracted for the study
that resulted in the description of a new species, Anas marecula,
by Olson and Jouvenin (1996) (see Table 1). The series they
analyzed, now in the USNM, was composed of at least 33 individuals.
Those listed herein are almost certainly parts of the
same individuals.
Discussion
COMPOSITION OF THE FOSSIL FAUNA
We consider some records based on fossils from Amsterdam
Island to be of questionable validity; these are as follows:
1. Wandering Albatross {Diomedea exulans). The record
of this species is of bones of a single individual identified by
Jouanin and Paulian (1960) before D. amsterdamensis was described,
and which Jouventin et al. (1989) reported to be of
similar size to the bones they referred to D. amsterdamensis.
2. Kermadec Petrel {Pterodroma neglecta). Jouanin and
Paulian (1960) identified this species from a few bones that
were smaller than those herein described of Pterodroma macroptera
and bigger than those of P. mollis. The given lengths
for the bones are in the size range of P. baraui and P. arminjoniana.
Pterodroma baraui was only described in 1964, and neither
of these two species was compared to the fossils. Pending
reexamination of the bones, the record of P. neglecta from Amsterdam
is suspect.
3. Broad-billed Prion {Pachyptila vittata). Jouanin and
Paulian (1960) identified the prion bones they had as this species
and thought it probable that they were of the subspecies P.