SINK OR SWIM!!
Imagine a dinosaur being swept far out to sea. It might seem like a crazy idea, but it appears that such an event happened in many places. The story however becomes even more amazing when we learn that these victims were unusually heavy creatures for their size, the kind that would be expected to sink like a stone once they were in water over their heads. To some, the story may not come as a complete surprise however. Way back in the dark ages, for example in the spring of 1995, an item appeared in Dialogue. In part, it ran as follows……
“Sometimes it takes a youngster to come up with an interesting question. The occasion was a lecture on dinosaurs, presented in Edmonton’s Provincial Museum on December 11, 1990. Following the main address by Dr. Phillip Currie of the Royal Tyrrell Museum, an excited group of boy scouts was asking most of the questions. “Is it fun to look for fossils?” “How many dinosaurs has Dr. Currie found?” “What is the biggest fossil found in Alberta?” … Dr. Currie patiently fielded all the queries. Then one young boy asked “Did dinosaurs swim?” As Dr. Currie answered the question, it became evident that this really was an interesting topic.
Dr. Currie remarked that little is actually known about dinosaur habits. There are some tantalizing hints however concerning ankylosaurs or armoured dinosaurs. These remarkable animals were built something like tanks. Their hides were decorated, and weighted down by row upon row of bony knobs and spikes. In Alberta, the vast majority of articulated ankylosaur skeletons are found upside down. They lie on their backs with feet projecting upward. Most experts, Dr. Currie included, suspect that these animals foolishly ventured into water over their heads. Unfortunately, as their bodies were top heavy, these animals tipped over, sank and drowned.
One wonders if the ankylosaurs voluntarily entered deep water, or if a flash flood overtook the victims. Evidences of similar sad events are widely dispersed. American palaeontologist Dr. Robert Bakker, in his 1986 book The Dinosaur Heresies (William Morrow and Company, Inc. New York), discussed several occurrences of armour-plated nodosaurs (ankylosaur relatives) found upside down in marine sediments. He asks the rhetorical question whether these dinosaurs foolishly went swimming or whether their carcasses were merely washed out to sea. He concludes: “The problem of oceangoing nodosaurs is especially perplexing because the Como carcass, upside down at the bottom of the Benton Sea, is not an isolated instance. Nodosaur carcasses lying on their backs cropped up in marine beds in Kansas in 1909 and several times since in similar sedimentary circumstances.” (p. 40)”
As in the Dialogue excerpt above, so it was that the discovery of an ankylosaur skeleton, north of Fort McMurray, Alberta, on Monday March 21, 2011, should not have come as a total surprise. Here was another terrestrial (land loving) dinosaur found, presumably upside down, in marine sediments. But the site was 150 km from the nearest land based artifacts. This creature did not just step into water over his head! There were some other remarkable features to this case too. This specimen was found in sediments quite a lot lower down in the rock layers than most ankylosaurs. Also this big and no doubt heavy specimen (5 m long and a very solid 2 m wide) was beautifully preserved in its original three dimensional shape.
In general, ankylosaur fossils are rare. Yet here was an almost complete specimen, not squashed as most dinosaurs are, but shaped as in life, displaying its short but powerful legs, its wide body protected by heavy armour, and its tail supplied with a heavy club at the tip.
The creatures found in the sediments of the Alberta oilsands, north of Fort McMurray, typically include clams, and beautiful ammonites (like squid but with shells), and large swimming reptiles like plesiosaurs and ichthyosaurs. But now here we have a rare skeleton of a terrestrial dinosaur. Moreover these dinosaurs, though rare, are known for being found in sediments which include marine creatures. What kind of flooding, one wonders, would sweep these creatures off their feet and wash them far out to sea? How fast were those water currents moving to carry these heavy creatures along and then dump them in a permanently entombing slurry of sediments? On the topic Robert Bakker himself remarked: “Most fossil bones owe their preservation to quick burial by sediment right after the death of their owner …. Big bones, such as those of dinosaurs, required big floods of mud to cover them…” (p. 44 and 45)
So the events of March 2011 near Fort McMurray give us lots to think about. Consider the rushing waters carrying dinosaurs and sediment. Think about what kind of flood (perhaps like a tsunami?) that event must have involved. How far did that flooding extend? Most of the other ankylosaurs in the province of Alberta are found much farther south near Drumheller and beyond. Yet most of them were also overcome by deep water. And just to put things in some sort of context – a similar nodosaurid ankylosaur has been found in similar marine sediments on James Ross Island, in Antartica!! I, for one, am certainly happy there are no similar disasters in the world today.
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