Mosasaur predation on a nautiloid from the Maastrichtian Pierre Shale,Central Colorado,Western Interior Basin,United States

Mosasaurs were common predators on the ammonites that inhabited the upper water column of the Late Cretaceous Western Interior epicontinental seaway of North America. Mosasaurs developed predictable behaviour patterns for feeding on ammonite prey. There are no previous reports of mosasaur predation on the much less common Cretaceous nautiloids, possibly because of the prey's predominantly deep, epibenthic habitat, as deduced from modern Nautilus life habits. A single specimen of the highly inflated nautiloid, Eutrephoceras dekayi (Conrad), prey to a small adult mosasaur, likely Platycarpus, Prognathodon or Mosasaurus, is reported herein from the Pierre Shale of Colorado in the Early Maastrichtian biozone of Baculitesgrandis transitional to the biozone of B. clinolobatus. The nautiloid was killed in the same manner as described previously for discoid ammonites (Placenticeras, Sphenodiscus) from coeval strata in the USA and Canada.     

The cephalopod macrosystem: A historical review, the present state of knowledge, and unsolved problems: 2. Classification of nautiloid cephalopods

Major classifications of nautiloid cephalopods are critically reviewed. It is suggested that this cephalopod group is subdivided into 5 subclasses and 17 orders: Ellesmeroceratoidea (including the orders Plectronocerida, Protactinocerida, Yanhecerida, and Ellesmerocerida), Endoceratoidea (including the orders Endocerida and Intejocerida), Actinoceratoidea (including the order Actinocerida), Nautiloidea (with the orders Basslerocerida, Tarphycerida, Lituitida, Discosorida, Oncocerida, and Nautilida), and Orthoceratoidea (including the orders Orthocerida, Ascocerida, Dissidocerida, and Bajkalocerida). The above orders are briefly described.     

Siphuncular structure in the orders Tarphycerida and Barrandeocerida (Cephalopoda: Nautiloidea)

Abstract: The siphuncular structure is described in two Silurian taxa, Boionautilus tyrannus and Cumingsoceras complanatus, currently placed in the Tarpycerida. Tarphycerids have the Nautilus type of connecting ring that is composed of an outer, thick, spherulitic‐prismatic layer and an inner glycoprotein layer, the latter was destroyed by diagenesis. However, both Silurian specimens have the connecting ring of the calcified‐perforate type, previously known to occur in orthocerids, actinocerids, plectronocerids and now also in barrandeocerids. In this type, the inner layer of the connecting ring is calcified and perforated by pore canals. Boionautilus and Cumingsoceras are therefore classified with barrandeocerids and not with tarphycerids.     

西藏申扎地区奥陶纪鹦鹉螺类化石的新材料

塔尔玛桥东-扎扛一带是近年发现的藏北地区第二个有可靠生物化石依据的奥陶系出露区。描述的鹦鹉螺化石是该区鹦鹉螺化石的一小部分,包括1新属、2新种和1未定种,分别是Taermaocerasgen.nov.,Taer-maocerasregularegen.etsp.nov.,Taermaocerasovatumgen.etsp.nov.及Taermaocearssp.。     

NAUTILOIDS WITH MULTIPLE PAIRED MUSCLE SCARS FROM LOWER–MIDDLE ORDOVICIAN OF BALTOSCANDIA

Abstract:  The number, outline and arrangement of muscle scars on the internal mould of the body chamber of five species of Early and Middle Ordovician nautiloids from Baltoscandia are described. The ellesmeroceratids Oelandoceras haelluddenense Foerste and Pictetoceras oliviae King have 9–10 pairs of muscle scars. The oncoceratid Phtanoncoceras ellipticum (Lossen), and Botellusoceras torpense gen. et sp. nov., order and family indeterminate, have eight and nine pairs of muscle scars, respectively. The tarphycerid Estonioceras imperfectum (Quenstedt) has four pairs of muscle scars.