A new Ophthalmosaurid Ichthyosaur From Jurassic British Columbia

An Upper Jurassic ichthyosaur (Ichthyosauria: Ophthalmosauridae) from the Bowser Basin, British Columbia

Authors:

Sissons et al

Abstract:

Although the Jurassic was a period of high diversity in ichthyosaurs, only a small number of specimens have been recorded from Canada to date. We describe here a new occurrence of an ophthalmosaurid ichthyosaur from a shallow marine depositional environment within the Bowser Basin of northern British Columbia. Based on vertebral diameters and the size of the humerus, the ichthyosaur was relatively large compared to other contemporaneous forms, yet possessed teeth that were small for its body size. As well, the height to length ratio of the preserved vertebrae suggests it may have had a more elongate, less regionalized body shape. Although indeterminate at a generic level, the presence of Late Jurassic ichthyosaurs in nearshore waters of northwestern North America further demonstrates their cosmopolitan distribution.

Paleoecological Study of the Burgess Shale Tulip Beds is Recommended

TAPHONOMY AND DEPOSITIONAL SETTING OF THE BURGESS SHALE TULIP BEDS, MOUNT STEPHEN, BRITISH COLUMBIA

Authors:

O'Brien et al

Abstract:

Burgess Shale–type deposits represent exceptional preservational windows for examining the biodiversity and ecological structure of some of the earliest metazoan communities that evolved during the Cambrian Explosion. While much attention has been paid to the original Burgess Shale locality, the Walcott Quarry on Fossil Ridge, temporal and regional variations of the depositional environment of the Burgess Shale biota as a whole are still poorly understood. Here we present the first comprehensive taphonomic and sedimentological study of the Tulip Beds on Mount Stephen (Campsite Cliff Shale Member, Burgess Shale Formation), based on a time-averaged assemblage of nearly 10,000 specimens. The taphonomic characteristics—size sorting, resistance to decay, and potential flow alignment—and mode of deposition of this assemblage are compared specifically to those of the nearby and stratigraphically younger Walcott Quarry assemblage. Like other Burgess Shale–type deposits, the Tulip Beds consist of millimeter-laminated, event-derived claystone, but lack the thicker claystone layers and prominent carbonate interbeds that occur in the Walcott Quarry. These differences suggest a depositional environment lower in energy and possibly more distal to the Cathedral Escarpment. Overall, taphonomic analyses suggest no significant decay biases, transport, or sorting of the assemblage, and most specimens, benthic taxa in particular, appear to have been buried close to their living environments. Single bedding planes with large accumulations dominated by a single taxon, e.g., isolated claws of Anomalocaris, suggest short time-averaged assemblages with limited background sedimentation. Overall the Tulip Beds locality is environmentally and taphonomically comparable to the Walcott Quarry and biotic variations between the two sites are likely to be primary in nature, thus paving the way for more detailed paleoecological investigations in the future.

Hedgehog, Tapir Relatives Found in Eocene Paleogene British Columbia

The Earth has experienced many dramatic changes in climate since the dinosaurs went extinct 66 million years ago. One of the warmest periods was the early Eocene Epoch, 50 to 53 million years ago. During this interval, North American mammal communities were quite distinct from those of today. This is illustrated by a study published in the latest issue of the Journal of Vertebrate Paleontology that describes an ancient hedgehog and tapir that lived in what is now Driftwood Canyon Provincial Park, British Columbia, some 52 million years ago.

"Within Canada, the only other fossil localities yielding mammals of similar age are from the Arctic, so these fossils from British Columbia help fill a significant geographic gap," said Dr. Natalia Rybczynski of the Canadian Museum of Nature, a co-author of the study. Other fossils of this age come from Wyoming and Colorado, some 2,700 miles to the south of the Arctic site of Ellesmere Island.

The ancient hedgehog is a species hitherto unknown to science. It is named Silvacola acares, which means "tiny forest dweller," since this minute hedgehog likely had a body length of only 2 to 2.5". The delicate fossil jaw of Silvacola was not freed from the surrounding rock as is typical for fossils. Rather, it was scanned with an industrial, high resolution CT (computed tomography) scanner at Penn State University so it could be studied without risking damage to its tiny teeth. Modern hedgehogs and their relatives are restricted to Europe, Asia, and Africa.

The other mammal discovered at the site, Heptodon, is an ancient relative of modern tapirs, which resemble small rhinos with no horns and a short, mobile, trunk or proboscis.

"Heptodon was about half the size of today's tapirs, and it lacked the short trunk that occurs on later species and their living cousins. Based upon its teeth, it was probably a leaf-eater, which fits nicely with the rainforest environment indicated by the fossil plants at Driftwood Canyon," said Dr. Jaelyn Eberle of the University of Colorado, lead author of the study.

Most of the fossil-bearing rocks at Driftwood Canyon formed on the bottom of an ancient lake and are well-known for their exceptionally well-preserved leaves, insects, and fishes. But no fossils of mammals had ever before been identified at the site. The fieldwork that resulted in these discovered was supported by Natural Sciences and Engineering Research Council of Canada.

"The discovery in northern British Columbia of an early cousin to tapirs is intriguing because today's tapirs live in the tropics. Its occurrence, alongside a diversity of fossil plants that indicates a rainforest, supports an idea put forward by others that tapirs and their extinct kin are good indicators of dense forests and high precipitation," said Eberle.

Fossil plants from the site indicate the area seldom experienced freezing temperatures and probably had a climate similar to that of Portland, Oregon, located roughly 700 miles to the south.

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