Gale A. Bishop

A NEW MIDDLE EOCENE PROTOCETID WHALE (MAMMALIA: CETACEA: ARCHAEOCETI) AND ASSOCIATED BIOTA FROM GEORGIA

A shallow-marine fossil biota was recovered from the Blue Bluff unit (formerly part of the McBean Formation) in the Upper Coastal Plain of eastern Georgia. Biochronologically significant mollusks (e.g., Turritella nasuta, Cubitostrea sellaeformis, Pteropsella lapidosa) and calcareous nannoplankton (e.g., Chiasmolithus solitus, Reticulofenestra umbilica, Cribocentrum reticulatum) indicate a latest Lutetian-earliest Bartonian age, or about 40 to 41 Ma. Georgiacetus vogtlensis new genus and species is described from a well-preserved, partial skeleton. Georgiacetus is the oldest known whale with a true pterygoid sinus fossa in its basicranium and a pelvis that did not articulate directly with the sacral vertebrae, two features whose acquisitions were important steps toward adaptation to a fully marine existence. The posterior four cheek teeth of G. vogtlensis form a series of carnassial-like shearing blades. These teeth also bear small, blunt accessory cusps, which are regarded as being homologous with the larger, sharper accessory cusps

EARLY CRETACEOUS ARTHROPODS FROM THE TLAYUA FORMATION AT TEPEXI DE RODRIGUEZ, PUEBLA, MEXICO

The arthropod macrofauna from the Middle Member of the lithographic limestones of the Tlayda Formation, in quarries at Tepexi, Mexico, is comprised of marine and nonmarine components. Marine taxa include a new species of flabelliferid isopod, a new genus and species of an anomuran, and a new genus and species of a brachyuran crab. Remains of an arachnid and an odonate nymph represent nonmarine constituents. Previous paleoenvironmental interpretations of a restricted lagoon, with periodic episodes of marine and freshwater influences are consistent with the nature of the arthropod fauna. Isopod remains, represented only by corpses, that resemble moder ectoparasites of fishes suggest that they are directly associated with the abundant fish remains found in the quarries, either as ectoparasites that released their hosts before they died or possibly as scavengers that fed on fish remains. The next most abundant arthropods are the crabs, most of which are corpses, suggesting that this group lived in or very near to the depositional site of the Tlayia Formation. Based upon the new fossil material, the stratigraphic range for the Aeglidae has been extended to span Albian to Holocene time. Extant representatives of this family inhabit fresh water environments of South America.

A NEW CRAB, ZYGASTROCARCINUS CARDSMITHI (CRUSTACEA, DECAPODA), FROM THE LOWER PIERRE SHALE, SOUTHEASTERN MONTANA

The third species belonging to Zygastrocarcinus from the Cretaceous of the Western Interior is represented by a single carapace collected from below the Groat Sandstone Bed, Gammon Ferruginous Member, Pierre Shale of Carter County, Montana. Comparison of Zygastrocarcinus cardsmithi n. sp. with the other North American congeners, Z. mendryki (Bishop, 1982) and Z. griesi Bishop, 1983, and with the Pacific Slope species Z. richardsoni (Woodward, 1896) suggests early separation of the Pacific Slope and Western Interior lineage having Z. cardsmithi as a possible ancestor to Z. mendryki and Z. griesi.

Pierre Feces: A Scatological Study of the Dakoticancer Assemblage, Pierre Shale (Upper Cretaceous) of South Dakota

ABSTRACT An integral part of the fossil crab assemblage described as the Dakoticancer Assemblage consists of fossil fecal material. Large coprolites (about 10 mm in diameter) are represented by (1) hemicylindrical feces which usually contain fish remains and (2) cone-shaped spiraled coprolites which contain no hard remains. Small coprolites (1.0 mm diameter and smaller), called fecal pellets, are ubiquitous and occur as ovoids, rods, and tapes. The ovoids are all prolate with some being smooth-surfaced and variable in size and others having undulatory surfaces. Rod-shaped pellets occur as small, smooth-surfaced and large, longitudinally striated cylinders. Tape-like castings of round or rectangular cross-section are uncommon. The small coprolites are found in and around crabs and molluscs preserved as apatite concretions. The pellets are often found along trails associated with open burrows; one of which preserves the impression of a segmented burrower. The large coprolites are interpreted to be the decayed remains of the feces of a vertebrate predator which preyed principally on fish. The fecal pellets are interpreted as the feces of deposit-feeding organisms which burrowed through the decaying, sediment-filled corpses of crabs and molluscs. The enrichment of the area of the corpses in phosphates may have been instrumental in the formation of the apatite concretions which preserve the Dakoticancer Assemblage.