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Introduction Any news of new dinosaur remains draws a lot of attention. Dinosaurs have been extinct for 65 million years, yet they capture the imagination of children and adults alike. Until recently, palaeontologists thought that dinosaur remains in British Columbia were uncommon. Several new fossil finds demonstrate how wrong they were. Dinosaur footprints and trackways prove to be our best evidence of dinosaurs in this province (see the following links to other reports on dinosaur trackways in the Living Landscapes programme).
During the summer of 2004, researchers with the Geological Survey of Canada, Ministry of Energy and Mines, and Simon Fraser University discovered the first evidence of dinosaur trackways in a fossilized streambed which drained into the Pacific Ocean. These trackway sites represent the western-most physical evidence for dinosaurs so far identified and provide a rare glimpse into a Jurassic-Cretaceous community of the west-coast of North America. The Discovery Palaeontological field trips in northern British Columbia tend to be concentrated in July or August when weather is the most predictable and warm. The remoteness of many fossil localities in the north is frustrating, and necessitates the use of helicopters to get from place to place. While helicopter rides are fun, they also are expensive and limit the amount of fossils that can be collected per visit. The fossils mentioned in this report were discovered in mid-August 2004, during routine geological mapping in the central part of the Bowser Basin, and fortunately, the rocks containing fossils were small enough that they could be extracted and transported easily. The field team included Mike Boddy (Ministry of Energy and Mines), Dr. Carol Evenchick (Geological Survey of Canada), Dr. Peter Mustard (Simon Fraser University), and Darrell Adzich - the helicopter pilot. Between them, they collected dinosaur footprints, a single trackway (with four individual foot prints), fragments of bone, two turtles, an assortment of petrified wood, some unusual items which were thought to be fish, and some clams from two fossiliferous sections of rock outcrop. Dr. Richard Hebda and Dr. Kendrick Marr of the Royal BC Museum returned to one of the sites in the summer of 2005 and recovered more footprints, and many plant fossils. Most of the bones collected (during the initial visit to the area) are dark and freshly exposed. However, weathered bone also exposed on some rocks shows a characteristic pale grey-blue colour. The trackways were well-preserved and had not been exposed for long. Some plants, the unusual unidentified items, and the vertebrate remains (two turtles, assorted bones, and dinosaur tracks) were wrapped and shipped to the Royal BC Museum to be added to the museum collection. The clams went to The University of Calgary for detailed study. The Geological Setting The Bowser Basin, a large sedimentary basin, occupied lowlands and offshore marine environments of the west coast of ancient North America. Sediments from eroding highlands in the northeast, settled in low-gradient streams, and in coastal and offshore environments. The animal and plant remains that settled to the bottom of slow-flowing, silt-laden streams and offshore marine environments were buried and eventually turned to rock. Rocks in the 60,000 square kilometer Bowser Basin and adjoining Sustut Basin preserve a 5,000 metre thick sequence of sediment. The Geological Survey of Canada and the BC Ministry of Energy and Mines have been exploring the Bowser Basin for oil and gas. The exact time period represented by Bowser Basin rocks is not settled, but the rocks containing the fossils (detailed below) either are latest Jurassic or earliest Cretaceous in age (approximately 145 to 125 million years old) and are difficult to date more accurately. The fossil-bearing rocks are part of the Skelhorne, and Groundhog-Gunanoot assemblages of the Bowser Lake Group. The Skelhorne Assemblage was preserved in deltaic environments preserved as thinly layered siltstones, sandstones and conglomerates. These rocks contain many plant and marine fossils, including silicified logs, bivalves (including oysters), cephalopods such as belemnites and ammonites, and ichnofossils (trace fossils). The Groundhog-Gunanoot assemblage is preserved in sandstone, siltstone, calcareous and carbonaceous mudstones, thin beds of conglomerate, and coal, deposited in a low gradient deltaic environment; plant fossils are common, including tree stumps up to 1 metre in diameter still in place, but marine fossils are rare. The footprints occur in fine-grained sandstones and siltstones that were deposited in a stream or a river delta. Ripple marks formed where waves and river currents disturbed sand in shallow water. Several of the rocks with trackways show such ripple marks, indicating that these dinosaurs walked in shallow coastal, deltaic, or riverine environments. The footprints are not deep even though some are made by animals comparable in size to modern ostriches, so the silty, sandy mud must have been firm and not sloppy. Hard-packed silty substrate occurs in areas where flowing water winnows away mud and finer silt, leaving only coarser, well-packed material. While ripple marks can be made in sandy wind-blown environments, the presence of clams and turtles in the same rock suggests that we are dealing with an aquatic nearshore environment, not arid habitat. Whether or not the preserved environment was within tidal influence of the ancient coastline cannot be determined without more study. Millions of years of geological activity solidified the sediments to rock, and these rocks were thrust upward during the growth of the west coast mountain ranges. Today, the preserved environments are found on separate mountains, one near the confluence of the Nass River and Panorama Creek, and the other near Tumeka Lake. The exact location of the fossiliferous outcrop will not be detailed here to minimize the risk of unauthorized fossil collection. Only small sections of rock outcrop are exposed at each site, so without excavation, the amount of fossil material to be collected is limited. Notwithstanding this limitation, the exposed rock shows great promise, and more work is needed to document what else is present. For more information on the Bowser Lake Basin, see: http://www.bowserbasin.com/
Dinosaur Remains Hollywood movies portray dinosaur fossils as perfectly articulated skeletons. Unfortunately, a complete body fossil of a large animal is rare and most fossil finds consist of isolated teeth, bones, and if you are extremely lucky, a few bones in articulation. Dinosaurs also leave trace fossils, such as coprolites (palaeo-poop), skin impressions, and tooth marks on bones where flesh-eating dinosaurs stripped meat from scavenged carcasses; the most common traces left by dinosaurs are footprints. The only undisputed dinosaur remains found in the Bowser Basin consist of trackways left by theropods. Theropods (the name literally means "beast-foot") are the carnivorous dinosaurs such as Tyrannosaurus, Allosaurus, and Albertosaurus. Their trackways reveal what scientists call a digitigrade stance (i.e. they walk on toes (digits) rather than the heel of the foot). Three large toes radiate forward, and a smaller fourth toe is positioned farther back on the foot. Normally it does not contribute to a footprint. The trackways from the Bowser Basin outcrop are not as well-defined as tracks left at other track sites, but show the characteristic three-toed foot-print, impressions of toe pads, and in some cases, the tips of the claws leave a well-defined mark. Modern-day emus, cassowaries, and oystercatchers leave trackways that look much like those of theropod dinosaurs. Unlike cats, most did not retract their claws and so claw tips often left a mark in mud or sand. Certain theropods such as Velociraptor and Troodon differ slightly, in that they raise the inner toe on each foot, and would leave only a two-toed print. The footprint left by modern ostriches is superficially similar to what could be expected from Velociraptor and Troodon, but evolved for efficient locomotion not retraction of an existing toe.
In British Columbia, we have dinosaur trackways from as early as the Jurassic-Cretaceous boundary (about 145 million years ago, in the Mist Mountain Formation/Minnes Group - a "group" is a collection of related rock formations) to as late as the Campanian-Maastrichtian of the Late Cretaceous (between 83-65 million years ago, in the Wapiti Formation). The fossil record of dinosaur trackways and those of other vertebrates is quite good but not well-studied in British Columbia. The best areas for tracks so far are in the northeast (e.g. Peace River and Tumbler Ridge areas) and in the southeast. The fact that most of the identified trackway sites are located in the eastern half of the province is due to the history of exploration for road construction, mining, and forestry, and not because of the distribution fossil-bearing rock. No doubt there are many more remote, naturally exposed sites that await discovery. Tracks help determine what types of animals were present in the area, especially when there are no skeletal remains preserved. Tracks of several types of dinosaurs have been found in BC including those of a wide range of theropods, ornithopods ("duck-billed dinosaurs"), and ankylosaurs. While localities such as those near the Tumbler Ridge area show well-preserved footprints and higher species diversity, the Bowser Basin trace-fossils show the first evidence of dinosaurs on Pacific coast of this province. A footprint of a large theropod from southeastern BC dating to the Jurassic/Cretaceous boundary (about 145 million years ago) measures almost one metre in length. It represents one of the largest theropod tracks known and likely came from an animal that rivaled Tyrannosaurus Rex in size - but lived about 75 million years earlier. The location of this large footprint is kept secret until it can be studied properly - and to protect the site from private collectors and fossil dealers. Birds, crocodiles, turtles and other small reptiles also left footprints preserved in British Columbia's sedimentary rocks, but these do not receive the same attention as dinosaur trace fossils. Some rocks at the sample sites contained a jumble of large bones packed together. In one case, the exposed rock was too large to carry back in a helicopter, so only a small sub-sample of this rock was collected. The rest of the large block containing the jumbled bones still is on site, and so can be recovered in the future to complement the material already in hand. None of the bone fragments recovered on the first trip to the area showed any obvious structure to indicate whether they represent a dinosaur or a large "non-dinosaurian reptile" (e.g., crocodilian, turtle, mosasaur, or plesiosaur). Hopefully with future exploration of the outcrop, bones with diagnostic crests, processes, joint sockets, and recognizable foramina (openings for nerves and blood vessels) will be found and give us an idea of what groups of reptiles are represented.
Turtle Shells The discovery of turtles was a big surprise, because well-preserved turtles are rare. The larger of the two specimens, is nearly complete. The shell appears intact but part of the carapace has weathered away. Toes, the tail, and the neck are visible along the edges of the rock, but the head is missing. Recent CT scans of this large turtle show evidence of limbs within the shell, but the density of the surrounding rock limited the clarity of the resulting images. The second turtle found, is far smaller and its shell superficially looks like that of a modern soft-shelled turtle (Family Trionychidae). This smaller shell is poorly preserved, and only the inside of the carapace is exposed. Fine parallel ridges indicate the position where vertebrae were attached and show where the spinal chord passed along the shell. Dr. Don Brinkman at the Royal Tyrrell Museum of Palaeontology has determined that this smaller turtle is not a softshell turtle as initially suggested, and also that it is not a juvenile of the larger turtle from the same site. Both of these turtles are being studied at the Tyrrell Museum, but will be returned to the Royal BC Museum once they are prepared and described. Initial impressions are that both turtles represent new species, but their relationships to known fossil turtles cannot be determined until they are fully prepared.
Invertebrates Some of the items recovered were thought to represent articulated scales of an aspidorhynchid fish (Family Aspidorhynchidae, imagine long, slender, armoured fishes superficially resembling modern needlefishes [Family Belonidae]). Close examination revealed a pattern of fine ridges almost exactly as you would find in a worn section of modern cuttlebone. If this specimen is indeed from a cuttlefish, then it suggests that the area was an estuarine environment influenced by tidal currents. All clam fossils also recovered were sent directly to the University of Calgary for study. Plants Wood chunks also were recovered with the animal remains. The fragments collected to date show fine details of the internal structure and the ends of each fragment are not worn smooth, so had not been transported far in water prior to burial. While the geologists who first visited the site noted the presence of stems and other plant remains, they concentrated their efforts on animal remains and so many plant specimens, and perhaps new species await discovery. In 2005, the field team collected fossilized wood fragments, cycad leaves, and fern fronds, several kinds of ginkgo leaves, and many other plant fossils that have yet to be identified. These fossils are catalogued in the palaeontology collection at the Royal BC Museum. Many of the rocks show jumbled masses of leaves. Such accumulations occur in lagoons and swamps of deltas, much as you could find in the Fraser River Delta today. So far no flowering plant remains have been identified, confirming that the fossiliferous deposits likely are no younger than Early Cretaceous.
Conclusion Presently, the material from the Bowser Basin is sufficiently interesting to warrant additional exploration of the area. Bones from large vertebrates, trackways, clams, plant fragments, and some problematic remains (cuttlefish?), all combined to give us a unique window into this mid-to late Mesozoic community of animals and plants. Acknowledgments Special thanks to Mike Boddy (Ministry of Energy and Mines), Dr. Carol Evenchick (Geological Survey of Canada), Dr. Peter Mustard (Simon Fraser University), Darrell Adzich, Dr. Richard Hebda, Royal British Columbia Museum, Victoria, and Dr. Kendrick Marr, Royal British Columbia Museum, Victoria, for specimen collection, and input on the preparation of this document. Dr. Richard Hebda reviewed an early version of this report. References Evenchick, C.A. and D.J. Thorkelson. 2005.
Osadetz, K.G., C.A. Evenchick, F. Ferri, L.D. Stasiuk, and N.S.F. Wilson. 2003.
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