Giant crocodiles once roamed northeastern British Columbia. A recent article in Historical Biology presents the first detailed fossil footprints ever reported for giant crocodiles. The sites come from the Peace District of northeastern British Columbia, north of Tumbler Ridge.
Trail fossils include traces of swimming, made when crocodiles scraped the muddy bottoms of lakes and river canals with their claws. Some of these swimming tracks showed remarkable detail, including the parallel streaks representing scale patterns on the crocodile legs.
While the Tumbler Ridge area has become well known for its dinosaur footprints, there is something special about crocodiles. Unlike the dinosaurs, they survived, and still have not changed substantially since the Mesozoic.
In 2020, a crane company donated time and staff to retrieve four large squares containing some of the finest examples of these tracks and trails. They were taken to the Tumbler Ridge Museum, where they are safely stored and will be incorporated into future exhibits.
Ancient giants
The traces and traces we examined are in the age range of 95-97 million years from the Cretaceous period. The pieces included hookworms, ornithopods and turtles.
The size of crocodiles can be estimated from the distance between their nail prints. We used this distance to calculate a total body length of about nine meters, and possibly up to 12 meters. This was confirmed by our identification of a 75 cm long partial route, which allowed a similar length estimate of close to nine meters.
An example of giant crocodile swimming tracks created by a crocodile claw scratching the bottom of a river canal, showing scale streaks. Credit: C. Helm, Author provided
A crocodile of this huge size would weigh about five tons and would probably be a top predator. By comparison, the record length of living crocodiles today is about six meters.
Gigantism in crocodiles has been reported several times in fossils. In North America, the oldest fossil body of giant crocodiles is that of Deinosuchus, about 82 million years old, estimated to be eight to 12 meters long. Deinosuchus has been recorded by the United States and Mexico, but never by Canada.
The large swimming trails north of the Tumbler Ridge may represent a precursor to Deinosuchus, which lived at least 13 million years before the previously reported first appearance of giant crocodiles in North America.
Monitoring environmental changes
The environment consisted of a low delta plain with shallow lakes, river channels and wetlands with vegetation, located about 100 km inland from the coastline of the Western Inland Sea that connected the Gulf of Mexico with the Arctic Ocean.
3D photogrammetry image showing a route made by a young ankylosaurus to the left and right a hybrid between a crocodile route and a swimming trail. the horizontal and vertical scales are in meters. Credit: C.Helm, Author provided
It was possible to document multiple episodes of flooding and emergence, which determined if and when the animals were walking or swimming. This helped to explain the variety of traces and traces found.
These findings follow the discovery of 112-million-year-old swimming tracks made by much smaller crocodiles (between one and two meters long) at the UNESCO Tumbler Ridge World Geopark. Our acquaintance with the nature of the extremely well-preserved trails near the Tumbler ridge led immediately to the first identification of crocodile tracks swimming in Africa.
The coexistence of footprints created by walking anchovies and crocodiles swimming on a single surface was fascinating and unprecedented in fossils. One of the ankylosaurus routes is the smallest that has been described so far from the area. They were pieces only 10 cm wide, which were obviously made by a minor.
Ancient crocodiles walked on two legs like dinosaurs Provided by The Conversation
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Reference: Traces of giant prehistoric crocodiles discovered in northern British Columbia (2022, April 1) recovered on April 1, 2022 by
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