Michael Ayress

A taxonomic and distributional survey of marine benthonic Ostracoda off Kerguelen and Heard Islands, South Indian Ocean

From an examination of 34 grab and dredge samples ranging from 110 m to 3584 m water depth, collected during Eltanin cruise 47 across the Kerguelen Plateau, 26 shallow-water and 35 deep-sea benthonic ostracod species have been identified. Systematic notes and illustrations of the common and some of the rare species are presented. Two new species are described: Philoneptunus cassidyi n. sp. and Taracythere abyssora n. sp. Comparisons made with the Atlantic and SW Pacific Oceans and circum-Antarctic regions indicate that the fauna comprises dominantly cosmopolitan deep-sea species while most of the other species have close affinities with the SW Pacific. In the Kerguelen material, seven distinct depth assemblages appear to correspond well with differing watermasses and there is evidence that the relatively shallow position of Antarctic Intermediate Water permits elevation of the upper depth limits of some deep-sea species. Some species have developed ornament of fine reticulation, features not previously seen in those species outside the Kerguelen region.

Aratrocypris, an enigmatic new cyprid ostracod from the Tertiary of D.S.D.P. sites in the S.W. Pacific

The new cyprid genus, Aratrocypris, based on four species ranging in age from Upper Palaeocene to Recent, is described. One species is left in open nomenclature and three, A.rectoporrecta (the type species), A.vaccamaris and A.praealta are described as new. The genus bears a unique plough-like structure anteroventrally and the possible function of this and the palaeoecology of the animal are discussed in detail. It is suggested that the plough-like structure, in association with other carapace structures such as the posterior position of the adductor muscle scars and the hinge, together with the strong degree of anterodorsal overlap, are indicators of a feeding mode associated with forward movement through the sediment. However, it is also possible that the animal was a filter feeder living within the sediment at a steep angle to the sea floor with the anteroventral structure protruded beyond the sediment water interface.

Two unusual new species of the ostracod genus Cytheropteron from the Late Cainozoic of the deep sea

Two new deep sea species of the genus Cytheropteron (C. branchium and C. pherozigzag spp. nov) are described. Both species occur in abyssal and bathyal Pliocene to Quaternary environments in the S. W. Pacific; the latter species has also been recovered from abyssal palaeodepths in the N.E. Atlantic and E. Indian Ocean in the Late Quaternary. Both species are unusual in possessing shallow yet prominent slit-like structures below and posteroventral to the alar process. Such structures are unknown in other species of the genus; their possible function is discussed.

New bythocytherid andcytherurid ostracode species from the deep-sea, Australia, with enigmatic dorsal expansion

Abstract Six new species of deep-sea cytheracean Ostracoda are described from the southwestern Pacific and eastern IndianOceans. The new species are Abyssobythere inequivalva, Cytheropteron anisovalva, C. dorsocorrugatum, C. lumalatum, C. parapulcinella and C. lobatulum . These species possess a hollow expansion of the shell above the hinge, forming a linear keel in all except in the latter species which has a laterally drooping dorsal lobe. We observe in some species that there is internal communication between the dorsal keel space and the interior of the duplicature. This suggests that the space has a particular function; various possible advantages inherent in the possession of such structures, including controlled buoyancy, are discussed.

Glyphidocythere, a new deep marine, paradoxostomatid (Ostracoda) from the Quaternary and Recent of the Indo-Pacific

Chapman’s (1910) Pseudocythere funafutiensis from 1924m off Funafuti, western Pacific is redescribed and illustrated together with additional Pleistocene and Recent material from the Coral and Tasman seas. A new paradoxostomatid genus, Glyphidocythere, is described to accommodate it and two other species yet to be formally described from the Banda Sea, eastern Indonesia. The genus is apparently restricted to the marine slope environment of low (less than 20°) southern latitudes. In the Coral and Tasman seas G. funafutiensis occurs within a narrow bathyal depth range (955m to 1754m) coincident with the Antarctic Intermediate Water.

A new record of Aratrocypris Whatley et al., 1985, Ostracoda, from the Lower Cretaceous of the North Sea: a range extension for the genus

During analyses of ditch cuttings samples from wells 34/10-53A and 35/9-F-1H drilled by Statoil ASA in the North Viking Graben, North Sea, 16 specimens pertaining to Aratrocypris were found. One specimen was found at 1260 m (depth below KB) in 35/9- F-1H within an interval of Lower Paleocene claystones, and based on its white chalky preservation characteristics is considered reworked from Maastrichtian chalk. The remaining 15 specimens were found among ostracod-rich microfossil assemblages of Early Cretaceous age in a sample at 4190 m of 34/10-53A, and at 2166 m of 35/9-F-1H. Although these samples contain numerous ostracods, the occurrence at such a low stratigraphical level was unexpected since Aratrocypris , hitherto, has not been found older than Coniacian/Santonian. Their preservation condition as orange-stained opaque carapaces is the same as that of the remainder of the assemblage found at that level in the Lower Cretaceous. For this reason the possibility of it being caved from higher levels of the well is ruled out. The find, therefore, represents the earliest record of the genus, and is important also when considering its early zoogeographical distribution. Ostracods occur in well 35/9-F-1H at two levels: Lower Paleocene and Lower Barremian–Lower Hauterivian. Each assemblage has a very different style of preservation which allows them to be easily separated. Ostracod assemblages of the younger level are white, translucent carapaces, a preservational style consistent with the abundant foraminifera …