ANTARUTIO BENTHOS
166
few recent examples to be brought forward. The small free-living hydroid, Boreohydra simplex recorded from muddy substrates in northern
Europe and South Georgia (Westblad, 1952) will surely be collected in
intermediate localities.
IX. ORIGINS OF THE ANTARCTIC BIOTA
Unfortunately the direct evidence for the origins of the Antarctic
fauna and flora is extremely poor for the Tertiary, which is the geological period from which evidence would be most useful. All other
evidence is indirect, being based either upon geological deductions
regarding climate, derived from many sources, or upon deductions based
on the present faunal and floral elements.
The earlier geological history of Antarctica probably bears little
relationship to the existing fauna. A rich Cretaceous marine fauna in
West Antarctica indicates an environment of temperate to cooltemperate climate. None of the Mollusca present appears to be related
to any of the present Antarctic fauna, although there are discernible
relationships with living forms from the Subantarctic and farther north.
Similarly the echinoderms represented in these beds no longer survive
in the Antarctic (Lambert, 1910). Lower Miocene beds from West
Antarctica contain fossil penguins and a " cool " molluscan fauna
(Adie, 1970). None of the Mollusca seems to be identical with existing
forms. Smith Woodward (1908) identified six teleost vertebrae centra
from the Tertiary of Seymour Island as belonging to Notothenia. The
Notothenioid fishes have thus been in the area for some 30 million years.
The echinoid genus Schixaster occurs in the Eocene of Snow Hill Island
(Lambert, 1910). Schixaster is closely related to the living Antarctic
schizasterid genera, Abatus, Amphipneustes and Tripylus. However,
the family Cassidulidae represented in the same beds no longer occurs
in Antarctic waters.
Discussing the geological history of the Cirripedia in the Antarctic,
Newman and Ross (1971) concluded that in spite of the extensive
Cretaceous and Tertiary faunas, no genera or species known as fossils
have survived except for the Pleistocene Bathylasma corolliforme.
Based on a study of palaeomagnetically dated deep-sea cores
spanning some four and a half million years, Hays (1970) presented an
extremely useful time scale for the last few million years. Present conditions result in a belt of terrigenous deposits around the Antarctic
Continent (and extending generally to the limit of pack ice) followed
by a beIt of diatom-radiolarian ooze (which extends as far north as the
Antarctic Convergence). These two zones have fluctuated northwards
repeatedly in the last 400 000 years, the ooze beginning to be deposited
A.Y.B.-lO
7
166
few recent examples to be brought forward. The small free-living hydroid, Boreohydra simplex recorded from muddy substrates in northern
Europe and South Georgia (Westblad, 1952) will surely be collected in
intermediate localities.
IX. ORIGINS OF THE ANTARCTIC BIOTA
Unfortunately the direct evidence for the origins of the Antarctic
fauna and flora is extremely poor for the Tertiary, which is the geological period from which evidence would be most useful. All other
evidence is indirect, being based either upon geological deductions
regarding climate, derived from many sources, or upon deductions based
on the present faunal and floral elements.
The earlier geological history of Antarctica probably bears little
relationship to the existing fauna. A rich Cretaceous marine fauna in
West Antarctica indicates an environment of temperate to cooltemperate climate. None of the Mollusca present appears to be related
to any of the present Antarctic fauna, although there are discernible
relationships with living forms from the Subantarctic and farther north.
Similarly the echinoderms represented in these beds no longer survive
in the Antarctic (Lambert, 1910). Lower Miocene beds from West
Antarctica contain fossil penguins and a " cool " molluscan fauna
(Adie, 1970). None of the Mollusca seems to be identical with existing
forms. Smith Woodward (1908) identified six teleost vertebrae centra
from the Tertiary of Seymour Island as belonging to Notothenia. The
Notothenioid fishes have thus been in the area for some 30 million years.
The echinoid genus Schixaster occurs in the Eocene of Snow Hill Island
(Lambert, 1910). Schixaster is closely related to the living Antarctic
schizasterid genera, Abatus, Amphipneustes and Tripylus. However,
the family Cassidulidae represented in the same beds no longer occurs
in Antarctic waters.
Discussing the geological history of the Cirripedia in the Antarctic,
Newman and Ross (1971) concluded that in spite of the extensive
Cretaceous and Tertiary faunas, no genera or species known as fossils
have survived except for the Pleistocene Bathylasma corolliforme.
Based on a study of palaeomagnetically dated deep-sea cores
spanning some four and a half million years, Hays (1970) presented an
extremely useful time scale for the last few million years. Present conditions result in a belt of terrigenous deposits around the Antarctic
Continent (and extending generally to the limit of pack ice) followed
by a beIt of diatom-radiolarian ooze (which extends as far north as the
Antarctic Convergence). These two zones have fluctuated northwards
repeatedly in the last 400 000 years, the ooze beginning to be deposited
A.Y.B.-lO
7