Jere H. Lipps

Biotic Interactions in Benthic Foraminifera

Foraminif era have a long geologic record, extending back perhaps to the Cambrian, and they are both abundant and diverse during most of the Phanerozoic. Over 40,000 species now have been described, of which approximately 4000 are living today (Tappan, 1971). They occur in all modern marine communities, and have also been found living in brackish and fresh water (Arnal, 1958; Boltovskoy and Lena, 1971; Resig, 1974). Foraminifera are especially diverse and abundant in deep-sea, coral reef, and many soft-bottom, shallow-water habitats (Hessler, 1974; Smith et al., 1978; Thiel, 1975; Murray, 1973; Wefer and Lutze, 1976), making them one of the most important animal groups on earth. Yet little is known about their interactions with other organisms, although much has been published on their distributional patterns. Successful use of foraminifera in paleobiology and paleoenvironmental interpretations requires more detailed ecologic knowledge (Lipps, 1981).

Life Below the Ross Ice Shelf, Antarctica

Samples and observations under 420 meters of ice and 430 kilometers from the open sea on the Ross Ice Shelf at a water depth of 597 meters revealed an unusual assemblage of benthic organisms. Scavenging amphipods, an isopod, and fish were present but a living infauna was absent. The observations may be accounted for by sampling or spatial bias, or by extremely low or fluctuating trophic resources.

Phylogeny of Opisthokonta and the evolution of multicellularity and complexity in Fungi and Metazoa

While early eukaryotic life must have been unicellular, multicellular lifeforms evolved multiple times from protistan ancestors in diverse eukaryotic lineages. The origins of multicellularity are of special interest because they require evolutionary transitions towards increased levels of complexity. We have generated new sequence data from the nuclear large subunit ribosomal DNA gene (LSU rDNA) and the SSU rDNA gene of several unicellular opisthokont protists - a nucleariid amoeba (Nuclearia simplex) and four choanoflagellates (Codosiga gracilis, Choanoeca perplexa, Proterospongia choanojuncta and Stephanoeca diplocostata) to provide the basis for re-examining relationships among several unicellular lineages and their multicellular relatives (animals and fungi). Our data indicate that: (1) choanoflagellates are a monophyletic rather than a paraphyletic assemblage that independently gave rise to animals and fungi as suggested by some authors and (2) the nucleariid filose amoebae are the likely sister group to Fungi. We also review published information regarding the origin of multicellularity in the opisthokonts.

Trophic model for the adaptive radiations and extinctions of pelagic marine mammals

Pelagic marine mammals (cetaceans and pinnipeds) generally invaded the seas rapidly in response to new ecologic opportunities. After cetaceans initially appeared and radi- ated in the Eocene, they declined in the Oligocene, but radiated into many new adaptive types in the Miocene. Pinnipeds apparently evolved in the earliest Miocene, rapidly radiating into many adaptive types. We propose that the radiations, and declines, of species were rcsponses to the availability of trophic resources in oceanic environments. These trophic resources are closely related to upwelling processes in the oceans. We suggest that increased upwelling intensity, due to climatic or tectonic events, permitted the initial invasions and radiations and that decreased intensity caused cetacean extinctions in the Oligocene.

Foraminiferal ecology and paleoecology

Perhaps no fossil group is used as much as foraminifera for paleoecologic inference, both in academia and industry. Since the late 1960s, new concepts and much additional data have appeared that make it difficult for the casual worker not immediately concerned with foraminiferal ecology and paleoecology to stay abreast of the latest developments. In these notes, the authors summarize much of that information, or provide reference to more detailed sources. They also attempt to point out problems and other methods of dealing with them. Most paleoecologic work with foraminifera in the past has relied on direct comparison of fossil assemblages with the most similar modern assemblages, and inferring then that the environments were similar also. The method is used widely in scientific studies and in industrial applications. The result is based on the single hypothesis that the fossils are environmentally analogous to their modern counterparts. These notes present a number of alternative working hypotheses, and in some cases, examine the data to attempt of disprove them.

Miocene Glaciomarine Sediments from Beneath the Southern Ross Ice Shelf, Antarctica

Glaciomarine sediments with middle Miocene microfaunal assemblages are exposed at the sea floor below the southern Ross Ice Shelf. Plio-Pleistocene sediments are not present. Post-Miocene glacial sediments may have been deposited but removed by relatively recent ice shelf grounding. A meager Recent microfauna is present in some core tops.

Ice diatom floras, Arthur Harbor, Antarctica

SummarySea-ice microflora was collected from December 1971 to November 1972 from a variety of types of sea ice in the vicinity of Arthur Harbor, Anvers Island, Antarctic Peninsula. Sixty-seven identifiable species of diatoms, one silicoflagellate and several archaeomonads were recoverd from the ice. Of these, only 24 diatoms and the archaeomonads were considered to be truly cryophilic based on their occurrence and abundance. Qmode factor analysis revealed that four factors (species occurrences) account for 89% of the data. In a general way, these four factors are related to ice type-shore ice protected from turbulence, grounded pack ice, slush ice and sea ice. Shannon-Wiener species diversity functions range from 0.000 (monospecific) to 3.0515 (dominance divided among 9 species). Diversity also appeared to be related to ice type-protected shore ice was low, sea ice was intermediate, and grounded pack, exposed shore ice and slush were higherst. Short-term varibility in physical/biotic environment may control species diversity. Sea-ice assemblages may be useful in paleoclimatic interpretations of past ice distributions.

Origin of a widespread marine bonebed deposited during the middle Miocene Climatic Optimum

Bonebeds are vertebrate bioclast concentrations in beds that are local to basinal in extent. The middle Miocene Sharktooth Hill bonebed in the southeastern San Joaquin Basin of California is among the largest of such deposits, exposed over 15 km and containing a rich assemblage of marine vertebrates, with a mean density of ~200 specimens/m 2 . It ranks among the most widespread and richest bonebeds known, yet its genesis is poorly understood. Hypotheses for its origin and formation include mass death from shark predation, volcanic or red tide poisoning, accumulation from a calving ground for marine mammals, and condensed accumulation over a long period of time. Based on multiple kinds of evidence, we conclude that the bonebed formed over a protracted time interval of little to no net clastic sedimentation, coincident with a significant transgressive-regressive cycle between 16 and 15 Ma ago, during the middle Miocene Climatic Optimum (MMCO). Geochronological constraints bracket the duration of bonebed formation to no longer than 700 ka, indicating that time averaging is a critical consideration for paleoecological analyses of North Pacific Ocean biotic richness during the MMCO.

Modern mucociliary creeping trails and the bodyplans of Neoproterozoic trace-makers

Abstract The bulk of Neoproterozoic trace fossils can be interpreted as horizontal creeping trails produced by minute vermiform organisms moving on or just beneath the seafloor or under algal mats. We have investigated the formation of trails by living cnidarians and platyhelminths that creep by cilia on mucus ribbons. These relatively simple metazoans produce trails that are similar in size and morphology to some Neoproterozoic traces, owing to the entrainment of sediment within their mucus trails. Thus a mucociliary locomotory system provides sufficient means to form some types of Neoproterozoic traces. It follows that the body architectures of the Neoproterozoic trace-makers may have been quite simple, though complex bodyplans are, of course, not ruled out. Thus, the use of Neoproterozoic trace fossils to constrain the time of origin of bilaterians or of any crown-group bilaterian taxon remains questionable.

Distribution and ecology of fishes of the Antarctic Peninsula

Fishes were collected from twenty-two sites off the Antarctic Peninsula from 620 S to 690 S latitude in 1975. Specimens of thirty-three species representing seven families were taken. Species associations change with latitude, depth, season and substrate. The Peninsula does appear to be a zone of range overlap between the Patagonian fauna and that of the Antarctic continent. Of the thirty-three species collected, approximately one fourth represent range extensions or are newly described or previously undescribed. Based on the infor- mation reported here, and since fishes have been collected from relatively few sites, the taxonomy of many fish groups is poorly known, and habitat preferences of most fishes are unknown, we suggest that division of the Antarctic into various zoogeographic zones based on fish is not yet possible.