Geology and Geography

The podotrematous crab family Dakoticancridae includes four genera, Dakoticancer Rathbun, Tetracarcinus Weller, Avitelmessus Rathbun, and Seorsus Bishop, all known solely from the Late Cretaceous of North America. Lathelicocarcinus Bishop, originally referred to the family, must be reassigned. Fine details of anatomy, preserved on specimens of D. overanus Rathbun and A. grapsoideus Rathbun, permit description of genital openings and interpretation of functional morphology of appendages. Although one species, D. australis Rathbun, has been found associated with burrow structures, all were probably vagrant epifaunal animals on fine-to medium-grained siliciclastic substrata. Food was probably obtained by generalized low-level predation and scavenging. Results of a cladistic analysis are consistent with the stratigraphic data suggesting that T. subquadrata Weller is nearest the rootstock of the family and that other taxa within the family are derived from it.

aBStRaCt We describe a small crab inside the phragmocone of a heteromorph cephalopod Baculites sp. smooth from the Gammon Ferruginous member (lower Campanian) of the pierre Shale in Butte County, South Dakota. The crab Ferricorda kimberlyae (Bishop, 1987) is well preserved with its carapace and pereiopods parallel to and between two septa of the phragmocone. Because of its superb preservation, the specimen is unlikely to have been washed into the phragmocone. The crab probably retreated into the phragmocone chamber to avoid predation or to molt and was subsequently buried by an influx of rapid sedimentation. This is the first instance of inquilinism by a crab in a heteromorph ammonite. Despite the rarity of such fossils, the occurrence of crabs inside ammonite shells was probably not uncommon on sea floors during the mesozoic. morphological details of the specimen reveal that Ferricorda is a dynomenid crab.

A new species of homolid crab, Zygastrocarcinus tricki sp. nov., is reported from the Late Cretaceous (middle Campanian, Baculites scotti Zone) of the Pierre Shale Formation (Baculite Mesa, Pueblo County, Colorado). This nearly complete homolid, hereto described is the sixth species assigned to the genus and extends our knowledge along with the geographical range and geological age of this taxon.

The fossil crab Propinnotheroides orangeburgensis is described from the Eocene Santee Limestone in Orangeburg County, South Carolina. The specimens, two nearly complete carapaces preserved in lithi ed coquina, add signi cant detail to our knowledge of the Eocene decapod faunas inhabiting the offshore bryozoan bioherms on the southeastern coast of North America. The coquinoid limestone facies of the Santee Limestone and Ocala and Castle Hayne Limestone represent shallow offshore bioherms and patch reefs deposited on the upper shelf of the ancient continental shelf. The bryozoan bioherms and patch reefs provided a nutrient-rich environment in which fostered the development of a distinctive Eocene reef fauna, including a diverse decapod fauna. RESUMEN El cangrejo fósil Propinnotheroides orangeburgensis nuevo género, nueva especie, es descrito para el Eoceno de la Caliza Santee en el Condado de Orangeburg, Carolina del Sur. Los especímenes, dos caparazones casi completos preservados en coquina liti cada, añaden detalles signi cativos a nuestro conocimiento de las faunas eocénicas de decápodos que habitaron los biohermas de briozoarios en plataforma interna del sureste de la costa norteamericana. Las facies de caliza coquinoide de la Caliza Santee y de la Caliza Ocala y Castle Hayne representan biohermas y parches arrecifales depositados en la parte superior de la antigua plataforma continental. Los biohermas de briozoarios y parches arrecifales proveían un ambiente rico en nutrientes en el que se desarrolló una fauna arrecifal peculiar, incluyendo una diversa fauna de decápodos.

Fourteen species of decapods crustaceans are described from a single locality near Mexia, Texas, where Paleocene sediments of the Mexia Clay Member of the Wills Point Formation crop out. The species are represented by Hoploparia sp., Linuparus wilcoxensis Rathbun, 1935, an unnamed paguroid, Kierionopsis nodosa Davidson, 1966, Pithonoton cardwelli new species, Caloxanthus sp., Macroacaena johnsoni (Rathbun, 1935), new combination, Raninoides bournei (Rathbun, 1928), R. treldenaesensis (Collins and Jakobsen, 2003), Prehepatus sp., Tehuacana americana (Rathbun, 1935), new combination, Costacopluma texana new species, Paraverrucoides alabamensis (Rathbun, 1935) and Viapinnixa mexiaensis new species. Morphological details unknown for previously described species are included. New systematic placements are offered based on recent research. Intraspecifi c morphological variation is documented for the goneplacoid crab Tehuacana americana. Costacopluma texana is the second Paleogene species of that genus in southeastern USA, and because of its abundance represents the most completely described species for the genus. This fauna represents one of the most diverse assemblages of Paleocene crustacean decapods. RESUMEN Se describen catorce especies de crustáceos decápodos colectados en una sola localidad cercana a Mexia, Texas, en donde afl oran sedimentos del Miembro Arcilloso Mexia de la Formación Wills Point. Las especies están representadas por Hoploparia sp., Linuparus wilcoxensis Rathbun, 1935, un paguroideo indeterminado, Kierionopsis nodosa Davidson, 1966, Pithonoton cardwelli especie nueva, Caloxanthus sp., Macroacaena johnsoni (Rathbun, 1935), combinación nueva, Raninoides bournei (Rathbun, 1928), R. treldenaesensis (Collins y Jakobsen, 2003), Prehepatus sp., Tehuacana americana (Rathbun, 1935) combinación nueva, Costacopluma texana especie nueva, Paraverrucoides alabamensis (Rathbun, 1935) y Viapinnixa mexiaensis especie nueva. Se incluyen detalles morfológicos, no descritos para especies previamente reportadas. Se ofrece una sistemática actualizada, basada en investigaciones recientes.

Ekalakia lambcrti n. gen., n. sp. is represented by two specimens from eastern. Montana. Both were collected f r om the P i e r r e Shale of Late Cretaceous (Campanian or M a a s t r i c h t i a n ) age. This taxon enlarges our knowledge of the Mesozoic Dromioidea.

Four specimens of Sodakus tatankayotankaensis n. gen., n. sp., and 12 specimens oiRan-inella oaheensis n. sp. collected from the Mobridge Member of the Pierre Shale (Maastrichtian) in South Dakota are described and compared with allied forms. The specimens form part of the Da-koticancer Assemblage.

Over 1,300 fossil decapods have been collected from the Upper Cretaceous Coon Creek Formation in Union County, Mississippi. The fauna is dominated by Dakoticancer australis Rathbun, 1935 (raised from subspecies rank) (49%), with smaller proportions of numerous other taxa: Protocallianassa mortoni (Pilsbry, 1901) (26.9%); Hoploparia tennesseensis Rathbun, 1926 {10.1%); Linuparus canadensis (Whiteaves, 1885) (4.7%); Tetracarcinus subquadrata Weller, 1905 (2.8%); Notopocorystes testacea (Rathbun, 1926) (2.7%); Paguristes whitteni, new species (2.8%); Raninella tridens Roberts, 1962 (0.8%); Eryma flecta Rathbun, 1926 (0.3%), and Cristipluma mississippiensis, new species (0.1%). Paguristes whitteni, new species, is represented by an enigmatic series of 30 claws. Cristipluma mississippiensis, new species,is based on a single specimen. Its scarcity in the shallow water Coon Creek fauna attests to
the probability of Cristipluma already at that time inhabiting deep wa

A new species of galathid crab, Eomunidopsis cobbani, occurs in the Larimer and Richard Sandstones (Pierre Shale) of Larimer County, Colorado. This new species extends the stratigraphic range of the genus in North America from latest Albian or earliest Cenomanian and Recent into the latest Campanian or earliest Maastrichtian and expands the paleogeographic range from the Gulf Coastal Plain into the Western Interior of the United States. The species is described from 48 specimens and occurs with Homolopsisl sp., a diverse molluscan fauna, and fossil wood
fragments. Eomunidopsis cobbani and Homolopsis sp. form a third possible decapod assemblage, the Galathea Assemblage, described from the Western Interior of the United States.

"Four hundred twenty-five fossil decapods, preserved in apatite concretions, were col- lected from the Early Campanian Gammon Ferruginous Member of the Pierre Shale in Butte County, South Dakota. The fauna, confined to a 4.3 meter interval of rock and mapped over eight square kilometers, is dominated by the mud shrimp Protocallianassa russelli n. sp. (74.5% of decapod fauna), the crab Necrocarcinus davisi n. sp. (14.6%), and the lobster Hoploparia mickelsoni n. sp. (9.5%), but includes four other crabs: Dioratiopus hearttailensis n. sp. (1.2%), Raninella oaheensis Bishop, 1978 (0.5%), Xanthosia elegans occidentalis n. sp. (0.5%), and Rugafarius fred- richi n. gen., n. sp. (0.2%). This group of decapods is considered to be an assemblage, the Proto- callianassa-Necrocarcinus-Hoploparia Assemblage, because of similarities to the Dakoticancer Assemblage in faunal characteristics, mode of preservation, and geographic and stratigraphic dis- tribution. This assemblage predates the migration of Dakoticancer overarms Rathbun into the Western Interior and the consequent development of the Z)aA:o?zcancer Assemblage, which contains descendents of taxa in the Protocallianassa-Necrocarcinus-Hoploparia Assemblage, repeatedly present in the Upper Pierre Shale."

The Carolinian Ghost Shrimp (Callichirus major Say 1818) inhabits the open sandy beaches of the Sea Islands of Georgia. Burrows of this fossorial
thalassinidean are distributed along the foreshore fromjust above mid-tide level to the shallow subtidal, forming a narrow band of high-density
burrow apertures called the burrow strand. Burrow distribution along North Beach was investigated by random quadrat sampling every 7.5 m from high-tide line to low-tide line for 4 km along transects spaced 100 m apart. The burrow strand has a steep shoreward (and a gentler seaward) gradient and exhibits variable densities along its length, peaking at approximately 15 burrows/M2. The Georgian Ghost Shrimp (Callianassa biformis Biffar 1970) inhabits sheltered, rippled, muddy-sand tidal flats in the lower foreshore, usually bordering sounds between the Sea Islands on the Georgia coast. Burrows are distributed as a burrow strand parallel to the shore, but are somewhat more diffuse than those of the Carolinian Ghost Shrimp and reach much higher maximum densities (up to 483 burrows/M2). In unstable substrates burrow density of the Carolinian Ghost Shrimp is highly
variable and generally reduced. Relict marsh muds, appearing along the lower beach of the erosive front of St. Catherines Island, prevent colonization of such areas by this animal. Burrow distribution is controlled shoreward by length of exposure, seaward by predation, and laterally by substrate grain size and stability. Use of Ghost Shrimp burrows in interpretation of the geologic record should be done with great caution because a broad spectrum of burrow morphologies can be produced by a
single species and many species produce similar burrows.

ABSTRACT—The third species belonging to Zygastrocarcinns 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 possibleancestor to Z. mendryki and Z. griesi