Roland A. Gangloff

THEROPOD TEETH FROM THE PRINCE CREEK FORMATION (CRETACEOUS) OF NORTHERN ALASKA, WITH SPECULATIONS ON ARCTIC DINOSAUR PALEOECOLOGY

Abstract Theropod teeth are taxonomically diagnostic components of dinosaur assemblages. Seventy teeth have been recovered from six different localities in the Kogosukruk Tongue of the Prince Creek Formation (Upper Cretaceous) of the North Slope of Alaska. This assemblage of teeth shows slightly less diversity compared to well documented assemblages of teeth from the slightly older Judith River Formation of south-central Montana, the Aguja Formation of west Texas, and the Hell Creek Formation of eastern Montana. In addition, in contrast to the Judith River Formation assemblage of teeth in south-central Montana, the teeth assigned to Troodon dominated the Alaskan assemblage. The dominance of Troodon is attributed to adaptation by this theropod to low light conditions while over-wintering at a high paleolatitude.

Tabulaconus handfield; microstructure and its implication in the taxonomy of primitive corals

Numerous specimens of Tabulaconus Handfield, 1969, have been collected in carbonate buildups within the Adams Argillite (Early Cambrian, Tatonduk area, Alaska). The wall structure of this form has been investigated, along with contemporaneous archaeocyaths and algae, through the use of polished ultra-thin sections (2–3 μm thick) and scanning electron microscopy. The results of this microstructural comparison indicate that despite diagenetic alteration Tabulaconus has a skeleton that is unlike any presently known and is quite distinct from associated algae or archaeocyaths. It is more elaborate than that found in the archaeocyaths but has not reached the stage of complexity seen in the primitive coral Cothonion Jell and Jell, 1976. The presence of some elongated units may represent an initial step towards the fibrous skeleton typical of Paleozoic corals. This study shows that even though diagenesis alters the original microstructure of calcareous skeletons, the resultant fabrics and detailed structures can be useful in systematic descriptions. Tabulaconus is removed from the Gastroconidae Kordae due to the presence of rudimentary septa and constitution of the tabularium. A number of species assigned to the genus Bacatocyathus Vologdin and included within the Archaeocyatha appear to be examples of Tabulaconus or very close relatives. An emended description of Tabulaconus kordae , the type species, is proposed.

Contribution of isotopic biogeochemistry (13C, 15N, 18O) to the paleoecology of mammoths (mammuthus primigenius)

Carbon isotopic abundances in Alaskan, Albertan and Russian mammoths indicate a diet of C3‐plants. The relatively high nitrogen isotopic abundances suggest arid conditions in Alberta and Alaska during the last ice age, and similar conditions in Russia. Nitrogen isotopic abundances are higher in mammoths relative to coeval herbivores, which may be due to differences in protein content of their diet. Oxygen isotopic abundances are similar in mammoths and in modern mammals from the same areas. The characteristic isotopic signature of mammoth ivory allows distinction from elephant or marine mammal ivory.

THE FIRST PACHYCEPHALOSAURINE (DINOSAURIA) FROM THE PALEO-ARCTIC OF ALASKA AND ITS PALEOGEOGRAPHIC IMPLICATIONS

The last 15 years of field work along the beaches and bluffs of the Colville River, on Alaskas Arctic Coastal Plain, have produced a diverse record of high-latitude dinosaurs. Seven families and eight genera are documented with several other families and genera possibly being represented by less diagnostic remains and only a few scattered elements (Table 1; Nelms, 1989; Gangloff, 1994, 1998; Fiorillo et al., 1999; Fiorillo and Gangloff, 2000, 2001). Virtually all of the common major groups of theropods and ornithopods typical of the Late Cretaceous of northern North America are present. Most of the skeletal remains are found in rocks assigned to the Prince Creek Formation of the Colville Group (Detterman et al., 1963, 1975; Phillips, 1990). The diversity of the dinosaur record in Alaska has been significantly increased with the discovery of abundant tracks and trackways along the North Slope and Arctic Coastal Plain over the last six years. The majority of the ichnofossil record is contained in various terrestrial coal-bearing rocks assigned to the Early Cretaceous Nanushuk Group (Ahlbrandt et al., 1979). The dinosaur biozone spans the upper part of the Nanushuk group and all of the Colville Group, ranging from the mid to Late Cretaceous (Albian to Maastrichtian; Mull, 1985). The already diverse and abundant record of dinosaur skeletal fossils was increased by the discovery in 1999 of the first evidence of pachycephalosaurs from this region (Fig. 1). This taxon is now represented by a nearly complete left squamosal and the contiguous, posterior, basal part of the dome. The highly thickened bone with characteristic prismatic internal structure accompanied by the distinctive ornamentation diagnostic of this group allows for an unequivocal identification to the subfamily level. The specimen (UAM # AK-493-V-001, Fig. 2.2) is most of the left …

An Early Late Cretaceous Dinosaur Tracksite in Central Yukon Territory, Canada

Dinosaur tracks were first reported from the coal-bearing clastic sequences of the Ross River Block in 1999 by members of a University of Alaska Museum field party, and track sites were confirmed by a joint Alaska-Yukon team in 2000. This fault-bounded sedimentary block is 3 kilometers west of Ross River, in the Yukon Territory. The discovery was followed by two years of field mapping and collection. This research has resulted in the documentation of 251 individual tracks at two separate but stratigraphically related sites, as well as a short (four-footprint) trackway at one of the sites. Six ichnogenera were identified. Ornithomimipus, Amblydactylus, and Gypsichnites were recognized at one site. At a stratigraphically higher site, four ichnogenera were documented including Tetrapodosaurus, Irenesauripus, Amblydactylus, and Columbosauripus. This ichno-assemblage is compared with those of Aptian to Cenomanian age from Alberta, British Columbia, and Alaska. The discovery of unequivocal dinosaur evidence in ...

Edmontonia Sp., The First Record of an Ankylosaur from Alaska

A partial skull of the nodosaurid ankylosaur Edmontonia was recovered from Late Cretaceous marine claystones and siltstones assigned to the upper part of the Matanuska Formation by Grantz (1961) and Jones (1963). These fine-grained sediments often contain calcareous concretions and locally abundant shell prisms of Inoceramus. The skull appears to have weathered out of one of these concretions. This is con-