Vancouver Island Cretaceous Fossils: A clam, a shark tooth, and an ammonite.
Driving from Comox to Campbell River along the new Inland Island Highway, you see frequent outcroppings of sedimentary rock where the highway has cut into the ground and exposed the rock underneath. This rock, which is part of the Nanaimo Group stretching from Nanaimo and the Gulf Islands in the South to Campbell River in the North, is composed largely of shale and sandstone that was deposited during the Upper Cretaceous. It is rich in fossils that tell a story of warm shallow seas that existed some 65-90 million years ago during the age when Tyrannosauridae ruled on land.
But you won't find T-rex or its cousins in these fossil beds because T-rex, like all dinosaurs, was terrestrial. There were no marine dinosaurs. But that doesn't mean that these seas were not without their monsters as well. Giant marine reptiles roamed the Cretaceous seas in search of fish, ammonites, and other marine creatures to feed on. On Vancouver Island, an elasmosaur was discovered on the banks of the Puntledge River in 1988. This marine reptile, which has a cast on display in the Courtenay Museum, is a long-necked plesiosaur with two sets of paddle-like fins. Since then several other partial fossilized skeletons of elasmosaurs have been found in Cretacous shales on Vancouver Island.
Mosasaurs were another group of large marine reptiles that hunted these seas. Mosasaurs resembled giant crocodilian lizards. Incomplete remains from several mosasaurs have been found on Vancouver Island. And they left more than just bones as evidence of their presence. Large ammonites have been unearthed with the unmistakable bite marks of a mosasaur left on their shells. While it is highly unlikely that you will encounter the remains of one of these marine predators, you will, with a little effort, be able to uncover a great deal about the world in which they lived.
Their world was a marine environment, abundant in life, some of which is familiar today and some of which is alien and bizarre. To begin with, Crustaceans scurried across the ocean floor as they do today. The spiny lobster, Linuparus vancouverensis is a common find in flat cigar-shaped concretions that weather out of the shale. At Shelter Point near Campbell River, hundreds of crabs have been found of a species that is found nowhere else in the world. Claws from ghost shrimp are everywhere preserved in shale, but, unfortunately, only their claws. Their softer bodies and carapace failed to survive the ages.
And like modern oceans, Cretaceous seas were packed with bivalves. These bivalves ranged in size from the tiny clam in the photo above to the gigantic Inoceramus vancouverensis. Inoceramus is one of the most common fossils you will find. Unfortunately, because of its great size--sometimes over a meter across--you rarely find complete specimens. Instead, you find fragments that appear as veins of calcite crystals up to a centimeter thick arranged in a palisade. Few collectors hunt these fossils, but they do serve as an important marker. Although Inoceramids were around before the Cretaceous, they flourished worldwide in the Cretaceous so if you find this characteristic vein, you know you are probably in Cretaceous. Some Inoceramid bivalves were particularly intricate. Bivalves of the Sphenoceramus genus, for example, had elaborate frilly shells. Many species of Sphenoceramus are found on Vancouver Island.
Other thick-shelled common bivalves that are well preserved include the Glycymerita veatchii and Idonearca truncate. With its strong radiating grooves, G.veatchii has a superficial resemblance to modern cockles. I. truncate looks somewhat like an elephant's trunk when viewed in profile.
Inoceramus and Idonearca along with all bivalves belong to a group of soft-bodied animals called molluscs. Elasmosaurs and mosasaurs may have been terrifying in comparison, but, in terms of numbers and biomass, the Cretaceous seas belonged to molluscs. Gastropods, distant cousins of the bivalves, are well represented, with snails such as Capulus corrugatus and Longoconcha navarroensis commonly found on Vancouver Island. Another gastropod Tessarolax distorta, a bizarre snail with 5 spindles protruding from its back, looks like a snail carrying a sea star. It is somewhat common, especially on the Trent River.
Among the molluscs, there is one group of shelled animals that is prized among collectors worldwide: the ammonites. Fortunately, Vancouver Island Cretaceous shale is abundant in these distant relatives of the nautilus. The Cretaceous was the last great age of the ammonites. But before they disappeared into extinction at the end of the Cretaceous, nature tried one last experiment in evolutionary design: She unravelled the ammonites. Continued . . .
Vancouver Island Cretaceous | Evolution with aTwist | The Where and How