Leonard V. Hills

Morphometry of the teeth of western North American tyrannosaurids and its applicability to quantitative classification

Gross tooth morphology and serration morphology were examined to determine a quantifiable method for classifying tyrannosaurid tooth crowns from western North America. From the examination of teeth in jaws, tyrannosaurid teeth could be qualitatively assigned to one of five types based on the cross−sectional shape of the base of the tooth and charac− teristics of the mesial carina. A principal component analysis (PCA) revealed that much of the variance in tooth shape was a result of isometry, but some gross morphological variables exhibited strong positive allometry. Non−size associated fac− tors were also important in determining tooth shape, particularly when data on denticle dimensions were considered in the analysis. While PCA identified important factors in variation, PCA ordination plots did not cluster the teeth into distinct, separate groupings based on taxon or bone of origin. The group classification functions determined by discriminant anal− ysis, though not universally successful for classifying unidentified isolated teeth of all tyrannosaurids, do identify bone of origin of adult Albertosaurus, Daspletosaurus, and Gorgosaurus teeth at a statistically acceptable level.

Normal and pathological eggshells of Spheroolithus albertensis, oosp. nov., from the Oldman Formation (Judith River Group, late Campanian), southern Alberta

ABSTRACT Eggshell fragments collected from the Oldman Formation, southern Alberta, are described as Spheroolithus albertensis, oosp. nov. This oospecies exhibits a spheroolithid microstructure, sagenotuberculate outer surface ornamentation, and a shell thickness of 0.98–1.22 mm. A multilayering pathology of S. albertensis suggests that the egg laying taxon had a reptilian-like reproductive system.

Late Pleistocene Western Camel (Camelops Hesternus) Hunting in Southwestern Canada

Abstract Late Pleistocene large mammal extinctions in North America have been attributed to a number of factors or combination of factors, primarily climate change and human hunting, but the relative roles of these factors remain much debated. Clo-vis-period hunters exploited species such as mammoth, but many now extinct species such as camels were seemingly not hunted. Archaeological evidence from the Wally’s Beach site in southern Canada, including stone tools and butchered bone, provide the first evidence that Clovis people hunted North American camels. Archaeologists generally dismiss human hunting as a significant contributor to Pleistocene extinctions in North America, but Wally’s Beach demonstrates that human hunting was more inclusive than assumed and we must continue to consider hunting as a factor in Pleistocene extinctions.

New radiocarbon dates for Columbian mammoth and Mexican horse from southern Alberta and the Lateglacial regional fauna

Abstract New radiocarbon dates on Columbian mammoth ( Mammuthus columbi ) and Mexican horse ( Equus conversidens ) specimens from southern Alberta are 10,930±100 BP and 10,870±45 years BP, respectively—older than originally thought. These specimens are reviewed in the light of 10 other sites in southern Alberta that have yielded large mammal remains radiocarbon dated to about 11,000 BP. Thus, the regional fauna includes at least 11 mammalian species. This fauna was not restricted to the foothills, but extended well onto the plains and may prove useful in correlating foothills terraces with those of the plains.

Post-glacial vegetation history of the Mission Mountains, Montana

A pollen record from Rock Lake in the Mission Mountains, northwestern Montana reveals a four-zone sequence reflecting Holocene vegetation change. Chronologic control is provided by two well-known tephras, Glacier Peak (11 200 yr B.P.) and Mazama (6800 yr B.P.). The presence of Glacier Peak tephra above the basal inorganic sediments indicates deglaciation prior to 11 200 yr B.P. Colonizing vegetation (Zone I) after the fall of Glacier Peak tephra was dominated byArtemisia (sage) andAlnus (alder). The presence ofAbies needles,Picea needles, and oneTaxus needle in the core demonstrates that these taxa were at Rock Lake at the time Zone II sediments were deposited. The increase inPinus,Picea, andAbies pollen in Zone II (10 850-4750 yr B.P.) suggests warmer and drier conditions prevailed, and may record the Hypsithermal. The pervasiveness ofPicea andAbies pollen in Pollen Zone III (4750-3350 yr B.P.) suggests the emergence of the modern subalpine forest. Pollen Zone IV (3350 yr B.P.-present) is characterized by relatively little change in the pollen assemblages. One noted change, however, is the increase of Cyperaceae (sedge), which may indicate an expansion of shore-line around the lake, possibly reflecting increased precipitation.

Holocene migration of lodgepole pine (Pinus contorta var. latifolia) in southern Yukon, Canada

A palynological reconstruction (n = 25 profiles) suggests that the northern extent of lodgepole pine (Pinus contorta var. latifolia Engelmann ex S. Watson) occurred between 59° and 60°N latitude in northwest North America from 10,000 to 7000 calendar years before present (cal. yr BP) prior to entering Yukon. Although specific migration pathways could not be resolved with the available palynological data, mountains along the southern edge of Yukon appear to have diverted lodgepole pine migration through the Carcross and Frances Lake areas in southwest and southeast Yukon, respectively. Migration in the southwest (70 m/yr) was likely confined to lower elevations of the Yukon and Teslin river valleys, with lodgepole pine reaching 61°N ~2000 cal. yr BP. Along the eastern route, migration was channeled through a 15–20 km wide pass in a 200 km mountainous front. After breaching the Liard drainage divide north of Frances Lake ~4000 cal. yr BP, migration progressed northwest (160–220 m/yr) along the Tintina Trench. Lodgepole pine was estimated to have reached its near present-day northern limit (~63°N) ~1790 cal. yr BP, which is ~1290 years earlier than previously thought. This difference in arrival dates is due the use of a >5% rather than a >15% pine pollen content threshold, which appears to correspond with >1% pine tree cover in the landscape. Climatic cooling after 1000 cal. yr BP that caused a population decline at higher elevations is hypothesized to explain the present-day sparse and disjunct distribution of pine across Yukon north of 61°N.

Megaspores from the Upper Cretaceous (Campanian) Horseshoe Canyon Formation of south-central Alberta, Canada, with a review of the genera Costatheca and Spermatites

Eighty-nine samples from three boreholes penetrating the Horseshoe Canyon Formation (Late Campanian) in south-central Alberta (Canada) were investigated for megaspore content. The samples were found to contain 49 species belonging to the genera Azolla, Bacutriletes, Costatheca, Dictyothylakos, Echitriletes, Erlansonisporites, Ghoshispora, Glomerisporites, Minerisporites, Molaspora, Monophyllosporites, Paxillitriletes, Spermatites, Striatriletes and Trileites, including one new species of Spermatites (S. reticulatus). Deposits representing low-lying coastal plains with widespread peat swamps, meandering channels and back swamp environments yielded the highest numbers of megaspores. An analysis of characteristics of the 22 species of Costatheca and 18 species and one subspecies of Spermatites leads to the proposal of a system of shape classes. Dichotomous keys to species were prepared. The geographical and stratigraphical distributions of the genera were also reviewed to elucidate their potential use in biostratigraphic and palaeoecological studies.