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Five species of bivalves and two species of gastropods are described from late Selandian to earliest Thanetian wood-fall communities from the Katsuhira Formation in Urahoro Town, eastern Hokkaido, northern Japan. Three bivalves and two gastropods are new to science:Thyasira(Thyasira)oliveriAmano and Jenkins, new species,Astarte(Astarte)paleocenicaAmano and Jenkins, new species,Poromya katsuhiraensisAmano and Jenkins, new species,Neverita majimaiAmano and Jenkins, new species, andBiplica paleocenicaAmano and Jenkins, new species.Poromya katsuhiraensisn. sp. andNeverita majimain. sp. are the earliest records of their genus.Astarte paleocenican. sp. is the last species before the genus disappeared from the northern Pacific region during the Eocene, only to reappear with the opening of the Bering Strait during the latest Miocene. Moreover, two bivalve species and one gastropod genus are Cretaceous relict forms:Propeamussium yubarense(Yabe and Nagao, 1928),Myrtea ezoensis(Nagao, 1938), andBiplicaPopenoe, 1957. These species and other relict protobranch bivalves had wide geographical ranges in the deep sea during the Cretaceous, which helped them to survive the end-Cretaceous mass extinction. The chemosynthesis-based speciesBathyacmaea? sp.,Myrtea ezoensis, andThyasira oliverin. sp. were recovered, but small bathymodioline mussels have not been found. This confirms that the small deep-sea mussels did not appear in the wood-fall communities at least by the earliest Thanetian.UUID:http://zoobank.org/125bd4ab-b172-43d9-80b9-57b75a805150

Twenty species of Pectinoidea (12 Propeamussiidae, three Cyclochlamydidae, five Pectinidae) are herein listed. Six new species of Pectinoidea (three Propeamussiidae, three Cyclochlamydidae) are from littoral and bathyal depths of the western and southwestern Pacific, sampled by various expeditions and cruises to Papua New Guinea and the South China Sea, viz. Propeamussium regillum n. sp. from the bathyal Bismarck and Solomon Seas, Parvamussium minusculum n. sp. from the lower bathyal South China Sea, Cyclopecten inoculatus n. sp. from the bathyal Bismarck Sea, Cyclochlamys corrugata n. sp., Cyclochlamys barbatula n. sp. and Micropecten reticulatus n. sp. from shallow coastal waters of Papua New Guinea. Fourteen species of Pectinoidea (nine Propeamussiidae, five Pectinidae) are new records for the Bismarck Sea (five), for the Solomon Sea (four), and for the South China Sea (seven).

Twenty-five species of Pectinoidea (24 Propeamussiidae, 1 Cyclochlamydidae) are herein listed from the Mozambique Channel, northwestern and southern Madagascar, and northeastern South Africa. New species: Propeamussium rosadoi, Parvamussium catillus, Parvamussium kilburni, Parvamussium puillandrei, Parvamussium strongae, Cyclopecten cassiculus, Cyclopecten kantori, Cyclochlamys bacachorda. New synonym: Amussium sewelli Knudsen, 1967 = Propeamussium watsoni (E.A. Smith, 1885). New records for the Mozambique Channel and northwestern Madagascar: Propeamussium andamanicum, Propeamussium arabicum, Propeamussium caducum, Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium torresi, Parvamussium vesiculatum, Cyclopecten kapalae, Similipecten eous. New records for southern Madagascar: Propeamussium jeffreysii, Propeamussium sibogai, Propeamussium watsoni, Parvamussium formosum, Parvamussium scitulum, Parvamussium thyrideum, Par...

Carnivory is unusual among bivalve molluscs and is limited to a few families in the distantly related orders Pectinida, Mytilida and Anomalodesmata. Despite the significance of dietary shifts in the evolution of the bivalves, the anatomy of the alimentary system, and of the gastric chamber in particular, has been described in detail for only a few carnivorous species. Here we describe the anatomy of the gastric chamber in a pectinid, Propeamussium jeffreysii, and an anomalodesmatan, Bathyneaera demistriata, expanding the known morphological disparity of the alimentary system in both groups. We found the stomachs of both to be modified to varying degrees for a carnivorous habit, with thickened, muscular walls, extensive cuticular linings, and reduced sorting areas and gastric chamber compartments (i.e. the dorsal hood, the left pouch and the food-sorting caecum). Despite some superficial similarity, each retains distinct hallmarks of their ancestry among filter-feeding relatives, allowing precise homology assessment of individual characters to differentiate between them. In addition, we found that the gastric chamber of P. jeffreysii represents an intermediate morphology between previously described P. lucidum and filter-feeding pectinids. Consequently, variation in the anatomy of the gastric chamber in Pectinida parallels a previously identified trend towards greater specialization for carnivory in the Anomalodesmata. Our results indicate that the current classification scheme of stomach types does not reflect phylogenetic affinity across the Bivalvia and highlight the need for accurate homology assessment of individual characters of the gastric chamber for inferring evolutionary relationships.

This paper addresses the systematics of Pectinoidea collected in the northeast Atlantic on the Lusitanian seamounts, on Galicia Bank, and on the Meteor group seamounts. There are 21 species recorded, of which three (Parvamussium intuslaevis, Cyclopecten cincinnatus, Cyclopecten vimineus from the Meteor group seamounts) are described as new. A lectotype is designated for Propeamussium lucidum (Jeffreys in Thomson, 1873). Cyclopecten antiquatus (Philippi, 1844) is for the first time recorded alive at 805–1160 m on the Meteor group and Galicia seamounts, and distinguished from the Mediterranean–eastern Atlantic species C. hoskynsi (Forbes, 1844). Bathypecten Schein‐Fatton, 1985, is placed in synonymy of Catillopecten Iredale, 1939, and the relevant North Atlantic species accordingly named Catillopecten eucymatus (Dall, 1898) (comb. nov.). The character regarding the development of internal ribs, traditionally considered to diagnose Parvamussium and Cyclopecten, is here shown to conflict with characters of th...

A correlation of bivalve biostratigraphic units recognized in different regions around the Pacific is attempted. Thesame bivalve groups and frequently the same genera are used in both northern and southern regions, involving monotaceans and pectinaceans for the Lower Jurassic and inoceramids for the Middle Jurassic. Five Lower Jurassic assemblage zones have been recognized in Argentina. A Meleagrinella faunule is found in Toarcian-Aalenian deposits and a Propeamussium andium Assemblage Zone spans the lowest Bajocian. One faunule and four assemblage zones are proposed for the Bajocian-Callovian of Argentina based on the distribution of inoceramid faunas: Retroceramus cf. inconditus faunule; Parainoceramus? westermanni, R. marwicki, R. patagonicus and R. stehni Assemblage Zones. All of them are accurately calibrated against the local ammonite zonation. Relation of these bivalve assemblages with Northeast and Far-East Russia bivalve zonations shows approximately equivalent distributions in time for similar groups, though most South American assemblages consistently seem to be somewhat younger than their Boreal counterparts. The comparison shows that direct correlation between bivalve zones is possible, especially between relatively close regions. Furthermore, knowledge obtained from Andean faunas can be applied to adjust the age of local units based on bivalves, such as the New Zealand stages.

Propeamussium(Parvamussium)holzensen. sp. andPropeamussium(Parvamussium)robinsonensen. sp. are described from the Upper Cretaceous Holz Shale Member of the Ladd Formation, Santa Ana Mountains, southern California. These species occur withBostrychoceras elongatum(Whiteaves),Glyptoxoceras subcompressum(Forbes), andInoceramus orientalus(Sokolow), which are indicative of a late medial Santonian age (Bostrychoceras elongatumBiochron).Propeamussium(Parvamussium)cowperi(Waring), from the Campanian Chatsworth Formation of the Simi Hills, southern California, is also redescribed and reillustrated for comparative purposes.

Stratigraphic and paleontologic data on the Pleistocene marine transgressions make it possible to establish biogeographic regions and subregions in the late glacial (interstadial), ultimate, and penultimate interglacial stages. Morphologic stability of species suggests that the ecology was unchanged, and that the zoogeographical units established recently by Z. A. Filatova can be used for reconstruction. In nearshore zones of Mindel-Riss sea basins (Stor, Holstein, North, Kolvin-Padymey, Sanchugovka, Pinakul seas), the northern limit of the Atlantic middle boreal subregion was near Denmark, the high boreal subregion was in the eastern part of the "Pechora Land," and the low arctic boundary was on the right tributaries of the Yenisey River. The Pacific boreal region extended to the west coast of Bering Strait. Open shelves were inhabited by low arctic mollusks on the western side of Eurasia; east from the Kanin Peninsula there lived high arctic species now distributed in the Eurasian marine province (fauna with Propeamussium groenlandicum, Bathyarca, and Cuspidaria). In the Riss-Wurm (Eem, Boreal, Kazantzevo, Val'katlen) seas, the boundaries of the Atlantic middle boreal and high boreal subregions were in the North Dvina River basin and on the Pyasina River, respectively. The Atlantic low arctic subregion was connected with the Pacific. A province with a Portlandia fauna was present in the eastern Baltic. In the Bolling-Allerod stage, middle boreal mollusks were distributed as far north as Bergen; high boreal mollusks reached Tromso and the Danish Straits. Pacific low arctic species were displaced to 175°W long. The Mindel, Riss, and Wurm seas were inhabited by arctic mollusks along the entire coast. End_of_Article - Last_Page 2510