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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.

My first words this evening must of necessity be directed to the Paleontological Society and its selection committee for choosing me to receive this prestigious medal. I am profoundly grateful and deeply honored. I assure you that this award is one I shall treasure for the rest of my days and, although I have every intention of continuing my work in paleontology, I see it as a crowning tribute to a career that already has brought me boundless joy, pleasure, and satisfaction. On occasions such as this it is only natural to reflect on one’s career, to recall its high points, and to remember those who helped advance it through selfless gifts of time and knowledge, far exceeding that to be expected of any teacher or mentor. In my case, such reflection takes me back many years, to my initial ventures in paleontological research as a University of Michigan graduate student. There I first described a new Ordovician trilobite under the watchful eye of Professor Erwin Stumm and, based on that, published …

Deltaplax new genus, Deltaplax burdicki new species, and Deltaplax dellangeloi new species (Mollusca, Polyplacophora, Neoloricata, Multiplacophora) from the Mississippian Lower Buffalo Wallow Group (Chesterian) of Indiana, USA are described. the new genus is established by one partially articulated and one associated specimen with marginal fringes of two types of large spines, bilaterally symmetrical head and tail valves, and fifteen medial valves arranged in three longitudinal columns similar to those described previously for other multiplacophorans. the two specimens represent separate species differentiated by morphologies of the auxiliary valves, one type of spine, and subtrapezoidal versus triangular tail valves. the tail valve of the articulated specimen also had sutural laminae that projected under the preceding intermediate valve. the presence of sutural laminae allows for placement of multiplacophorans in Subclass Neoloricata of Class Polyplacophora. the head, intermediate, and tail valves are mucronate with comarginal growth lines and ridged insertion plates that probably inserted into soft tissue comparable to the girdle of modern polyplacophorans. the new specimens also indicate one left-handed, one auxiliary, and one right-handed valve in multiplacophorans was equivalent to a single bilaterally-symmetrical intermediate valve of extant polyplacophorans. However, multiplacophoran head valves have plates that project from the lower layer at the lateral margins and articulate with the first intermediate valves that overlap the head and second intermediate valves. These features have not been observed in more typical neoloricates, fossil or modern. Pending systematic revision of the class, Multiplacophora thus is retained as a separate order distinguished by the unique shared characters.

Giant Middle Coniacian to Lower Campanian Platyceramus Seitz is among the largest Cretaceous bivalves, commonly reaching an axial length of over 1 m, and occasionally over 2–3 m in size. The genus is characterized by its large size, very low convexity, normal inflation limited mostly to the umbonal area, and flattened flanks. It is especially common in moderately deep calcareous shale facies, as well as in chalks and limestones of the Niobrara Formation and equivalents. Preferred facies contain abundant pyrite, elevated total organic carbon (TOC), and very low biotic diversity. The genus maintains its giant size in these facies, and becomes more abundant. It clearly prefers dysoxic facies. As such, it probably is chemosymbiotic; photosymbiosis is almost ruled out because of inferred water depths of 200–350 m. It is also found more sparsely, and of smaller size, in oxygenated facies, including shoreface sandstone. The study area contains over 81 giant-sized Platyceramus platinus (Logan, 1898) on a single bedding plane; there are very few small ones. This allows spacing, orientation, and size analysis to be performed on an adult population.