Shark Week!

Shark Week's coming to the CFDC! For those of you who haven't gotten your fill of sharks from Discovery Channel's Shark Week, we're staging our own six-day event, complete with a new exhibit, shark activities for kids during Dino Day Camp, and special digs for shark fossils. We've been pretty busy setting everything up, and the final display is going to look pretty awesome; there's preserved sharks from the University of Manitoba, a microscope set up with slides of shark skin, and a giant fossilized Cretoxyrhina shark that comprises three huge field jackets.
Cretoxyrhina vertebra with the
jaws of a baby Great White.

Because of the emphasis on sharks, I thought I'd do a little feature on the ones that we find around Morden, kind of like the one I wrote about mosasaurs a few weeks ago. We get four different kinds of shark here, all of which lived during the Late Cretaceous and went extinct millions of years ago. Since sharks are cartilaginous, their skeletons don't fossilize very easily (cartilage is the soft tissue that your nose and ears are made out of); usually, we'll only find their teeth, which are much harder and more durable.

I'm not so sure about this...
Cretoxyrhina is our most awesome shark, topping out at 24 feet (similar to Great Whites) and possessing a dominant spot in Western Interior Seaway ecology. Its size enabled it to confidently challenge and defeat plesiosaurs, small and mid-size mosasaurs, and every other kind of fish that lived at the time, and its teeth are large and smooth, helping it to slice straight through bone and cause catastrophic injury to its prey. Despite its effectiveness in combat, however, it eventually lost the fight for top spot in the food chain to bigger mosasaur genera like Tylosaurus and went extinct about 80 million years ago. As such, we only find Cretoxyrhina in older shale layers where mosasaurs are very uncommon. Fortunately, it tends to fossilize extremely well in those layers relative to other prehistoric sharks, with a number of nicely articulated (meaning that much of the skeleton is still in one piece) specimens having been discovered in North America, including some at the CFDC.

Squalicorax is our most common shark in terms of the number of teeth we find; at about 10 to 16 feet long, it was lower down on the food chain than mosasaurs, plesiosaurs, and the biggest of fish, and as such, it likely engaged in a lot of scavenging activity in addition to the normal predation on smaller marine creatures that people expect from the well-known sharks of today. This versatility combined with a smaller food requirement made it a better survivor than Cretoxyrhina, living until the end of the Cretaceous period when the dinosaurs finally went extinct. For whatever reason, Squalicorax is the only local shark that has serrated teeth, which would have been useful for peeling flesh off of bones.

We also get sharks called Cretolamna and Archaeolamna around Morden, but they're very rare and there isn't much known about our local species. They were likely a little smaller than Squalicorax, but didn't possess the more effective serrated teeth. Worldwide, the Cretolamna genus is known to have survived the mass extinction 65 million years ago, living for about another eight million years in North America and 25 million years around the north-western regions of Africa before going extinct, while Archaeolamna probably died out with the dinosaurs and marine reptiles.

Sharks as a group survived the end of the Cretaceous and, being efficient and sophisticated hunters, are the preeminent marine creatures in many ocean habitats today. This week coming up, we're going to have all our best shark material on display, so be sure to come see it! Everything will be taken down after August 17 to be put away for next year.

Matt Remple
Field Tech