Specimens of the large, shallow-marine, volutid gastropod Volutoderma Gabb, 1877, herein recognized only from strata of Late Cretaceous (Coniacian through early Maastrichtian) age in British ...Columbia, Washington, California, and Baja California have commonly been identified as Volutoderma averillii (Gabb, 1864). This review of available specimens assigns them to two genera: Volutoderma and Longoconcha Stephenson, 1941. Twelve species, nine of them new, comprise three morphologic lineages of Volutoderma, i.e., 1) "Typical" includes V. querna n. sp., V. averillii (Gabb), V. blakei n. sp., V. jalama n. sp., V. perissa n. sp., and possibly Volutoderma? n. sp.; 2) "Angelica" includes V. angelica n. sp., V. elderi n. sp., and V. ynezae n. sp.; and 3) "Magna" includes V. santana Packard, V. magna Packard, and perhaps V.? antherena n. sp. A new species of Longoconcha, L. eumeka, is the first Pacific Slope record of this genus, which has a Gulf Coast and Tethyan Old World distribution. A smaller volutid, Retipirula Dall, 1907 is endemic to the study area and was formerly known only from its type species R. crassitesta (Gabb, 1869) of Paleocene age. Two new Retipirula are reported: R. calidula of latest Maastrichtian age and R. pinguis of Paleocene age. Only the Volutoderma lineage containing V. averillii has been found north of San Francisco. Recovery of rudist bivalves from formations yielding Volutoderma suggests that these volutes were warm-temperate to subtropical gastropods. Co-occurrences of these gastropods and rudistids may aid in placing the warm-temperate/subtropical boundary during the Late Cretaceous.
: Opines constitute a small subfamily of Mesozoic astartid bivalves that lived mostly in the Tethys Sea region. They first appeared in western Europe during the Middle Triassic, became most ...widespread during the Jurassic and had their first undoubted appearance in the New World during the Late Jurassic. Their Pacific slope of North America record is studied in detail for the first time. The earliest of the Pacific slope opines is Opis californica Stanton of Early Cretaceous (Hauterivian or Barremian) age. The other six opine species in the study area are of Late Cretaceous age (collectively Middle Turonian – early Late Maastrichtian), have hinges bearing two strong cardinal teeth in each valve, and are placed in the new subgenus Hesperopsis, which is the first astartid to have a partially internal ligament. These six species comprise two morphological lineages inferred to have evolved from O. (H.) popenoei sp. nov. The ‘holzana’ lineage includes O. (H.) holzana sp. nov. and O. (H.) rosarioensis Anderson and Hanna. The ‘anae’ lineage includes O. (H.) anae sp. nov., O. (H.) vancouverensis Whiteaves and O. (H.) triangulata (Cooper). Hesperopis lived in warm temperate waters in offshore shelfal areas. It had a vertical commissure and probably lived as an edgewise recliner. Through time, the species of both lineages became larger and either broader or more elongate. Neither Opis shastalis Anderson, of Aptian age, nor Opis virginalis Waring, of late Palaeocene age, are opines. A junior secondary homonym of Opis trigonalis (Sowerby) was detected and is renamed here as Opis tamurai nom nov.
Fossilized argonaut egg cases have been recovered from marine siltstones of the late Miocene exposed around margins of the Los Angeles Basin, California. Low radial ribs on the thin, keelless, ...planispirally coiled egg cases suggest referring them to Mizuhobaris lepta new species. Occurrence of these egg cases in fine-grained Monterey Formation sediments with mesopelagic fish fossils, nannofossils, and Foraminifera indicate deposition in middle-to-upper bathyal depths. Argonaut egg cases have been described from Tertiary strata in Japan, New Zealand, Sumatra, and Europe, but this is the first report of fossilized argonaut egg cases from the Western Hemisphere. Secretion of egg cases by argonauts probably developed during the Paleogene as a solution to problems of spawning encountered by octopi as they acquired an epipelagic, open-ocean habitat. Shape and sculpture of the egg cases represent responses to hydrodynamics rather than an inheritance from or copying of ectocochliate cephalopods. The cases may provide the eggs with protection from ultraviolet radiation present in the argonauts' near-surface habitat.
Two new genera and three new species of shallow-marine, warm-water gastropods are reported from outcrops of various Cretaceous formations between British Columbia and Baja California. The potamidid ...Cedrosia pacifica new genus and species is from Turonian strata on Cedros Island, west coast of Baja California, Mexico. It is the earliest potamidid known from the rock record of the Pacific Slope. Alamirifica corona new genus and species, whose suprageneric relationships are uncertain, is from Turonian strata in southern California. The holotype has a round and rimmed aperture most similar to the photine buccinid Neoteron Pilsbry and Lowe, 1932. The holotype also has a pyramidal spire most similar to some fossil cerithioideans traditionally placed in the potamidid Pyrazus Montfort, 1810, but the type species of Pyrazus does not have a pyramidal spire. Future work might reveal that Alamirifica belongs to a new family. Four other Pacific Slope species are tentatively assigned to Alamirifica: the Aptian A.? harrissi (Allison, 1955); the Coniacian A.? ursa new species; the late Coniacian to early Campanian A.? harveyi (Whiteaves, 1903); and the poorly preserved Turonian Alamirifica? sp. As presently known, Cedrosia and Alamirifica were endemic to the study area, but they strongly resemble some Old World Tethyan gastropods. The distribution of A.? harveyi lends support to a relatively northern site of deposition for the Nanaimo Group.
The Pacific Slope of North America's paleontologic record of Paosia, a nearshore-marine, pseudomelaniid gastropod primarily associated with the Old World Cretaceous Tethyan realm, is established for ...the first time. Former workers have almost universally referred to this genus by its junior synonym name TrajanellaPopovici-Hatzeg, 1899. Six species, including Paosia pentzensis new species, are recognized, and all are from siliciclastic facies. Their documentable geologic range is late early Albian to early Campanian. Four of the five previously named species were misallocated to genus Acteonina and one was placed in genus “Trajanella.” Paosia originated in western Europe and in the Caucasus Mountains region during the latest Jurassic (Tithonian). It arrived in the study area, possibly in the Aptian, but certainly by the late early Albian and, most likely, by way of Japan and the north Pacific gyre. Worldwide, the genus had its peak diversity during the Albian and Cenomanian. The only other Western Hemisphere records of Paosia are a species from the Campanian of Jamaica and a possible species from the Coniacian of Texas. Paosia had a preference for tropical waters, but its presence in the study area indicates that it could live in temperate-tropical transition areas. Most of the Pacific Slope of North America species are represented by a few specimens, but when plentiful, they display variability in overall shape between juvenile and adults, with the last whorl of the adults becoming more cylindrical with growth. Paosia kollmannii new name is proposed for the homonym Trajanella acuminataKollmann, 1979.
Three new genera and six new species of shallow-marine gastropods are named from Upper Cretaceous strata found mainly in California. The trochids Cidarina cretacea new species and Cidarina beta new ...species, the ficid Bulbificopsis garza new genus and new species, and the cancellariid Mataxa arida new species are from the Maastrichtian part of the Moreno Formation of north-central California. This is the earliest record of Cidarina, whose previous chronologic range was middle Eocene to Recent. Bulbificopsis is the first record of a Cretaceous ficid from the Pacific slope of North America, and Mataxa was previously known only from Upper Cretaceous strata in the southeastern United States and northeastern Brazil. The buccinid Eripachya jalama new species and the fasciolariid Calkota daileyi new genus and new species are from the lower upper Campanian Jalama Formation in southern California. Calkota is also recognized herein as occurring in upper Maastrichtian strata of North Dakota and South Dakota. The new melongenid genus, Pentzia, established for Fulgur hilgardiWhite, 1889, is from Campanian strata throughout California; middle Campanian strata on Sucia Island, Washington; and upper Campanian to lower Maastrichtian strata in northern Baja California, Mexico.
Two new genera and ten new species of shallow-marine, warm-water gastropods are reported from several Upper Cretaceous formations found between British Columbia and southern California. The buccinid ...Zaglenum new genus is represented by two new species and the turbinellid Fimbrivasum new genus is represented by three new species. The nododelphinulid Trochacanthus pacificus new species is the first record of this genus in the Western Hemisphere, and the procerthiid Nudivagus? califus new species could be the first record of this genus on the Pacific slope of North America. The xenophorid Xenophora (Endoptygma) hermax new species is only the second known Cretaceous species of this genus on the Pacific slope of North America, and this species establishes that Endoptygma Gabb, 1877, is a valid taxon. The neritid Otostoma sharonae new species is only the fourth known Cretaceous species of this genus on the Pacific slope of North America. The ringiculid Ringicula? (Ringiculopsis?) hesperiae new species is the first Campanian record of this genus on the Pacific slope of North America and the first recognition of this subgenus in this area.
Two new genera and ten new species of shallow-marine, warm-water gastropods are reported from several Upper Cretaceous formations found between British Columbia and southern California. The buccinid ...Zaglenum new genus is represented by two new species and the turbinellid Fimbrivasum new genus is represented by three new species. The nododelphinulid Trochacanthus pacificus new species is the first record of this genus in the Western Hemisphere, and the procerthiid Nudivagus? califus new species could be the first record of this genus on the Pacific slope of North America. The xenophorid Xenophora (Endoptygma) hermax new species is only the second known Cretaceous species of this genus on the Pacific slope of North America, and this species establishes that EndoptygmaGabb, 1877, is a valid taxon. The neritid Otostoma sharonae new species is only the fourth known Cretaceous species of this genus on the Pacific slope of North America. The ringiculid Ringicula? (Ringiculopsis?) hesperiae new species is the first Campanian record of this genus on the Pacific slope of North America and the first recognition of this subgenus in this area.
Four new molluscan species, a bivalve and three gastropods, are named from shallow-marine, lower Upper Cretaceous (Cenomanian Stage) strata in Oregon. The laternulid bivalve Cercomya (Cercomya) ...hesperia new species is from the Bernard Formation in east-central Oregon and from the Osburger Gulch Sandstone Member of the Hornbrook Formation in southwest Oregon. It is the first Cenomanian record of this genus. The iteriid gastropods, Vernedia pacifica new species and Sogdianella oregonensis new species, are from unnamed Cenomanian strata in east-central Oregon and represent the first records of these genera in western North America. The actaeonellid gastropod Trochactaeon (Neocylindrites) allisoni new species from these same deposits represents the first record of this genus in Oregon. The new species of Cercomya sensu stricto, Vernedia, and Neocylindrites are very similar to western European species, and the new species of Sogdianella is most similar to a Peruvian species.
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