TUSK SHELL: OYSTER BAY FORMATION

The lovely large creamy tusk shell, Dentalium sp., you see here is in the collections of John Fam, Vice-Chair, Vancouver Paleontological Society.  

This particular scaphopod, or Tusk Shell, is one of many species of molluscs helping to untangle the complex geology of Vancouver Island. He hails from Early Paleocene - Early Eocene, Oyster Bay Formation, Appian Way Beds, near Cambell River, Vancouver Island, British Columbia, Canada. 

This area was mapped by the Geological Survey of Canada and initially included as part of the Cretaceous Nanaimo group. 

It was extensive collecting by members of the Vancouver Island Palaeontological Society that led to a revision of the geology of this area. Many of the fossils found in more recent years are a match for those found in the early Cenozoic of western North America, including the beautiful marine community captured in the block you see here.

Tusk shells are members of a class of shelled marine mollusc with a global distribution. Shells of species within this class range from about 0.5 to 15 cm in length. This fellow is 8 cm end to end, so near smack dab in the centre of his cohort.

The Scaphopoda get their nickname "tusk shells" because their shells are conical and slightly curved to the dorsal side, making the shells look like tiny tusks (picture a walrus or mammoth tusk in your mind’s eye). The scientific name Scaphopoda means "shovel foot," a term that refers to the "head" of the animal, which lacks eyes and is used for burrowing in marine sediments.

The most distinctive feature of scaphopods, however, and one that differentiates them from most molluscs, is the duo openings on their tubular shells. Most molluscs are open at just one end.

We could call scaphopods the great deniers. They live their adult lives with their heads literally buried in the sand. A tiny bit of their posterior end sticks up into the seawater for water exchange. Water is circulated around the mantle cavity by the action of numerous cilia.

When the available dissolved oxygen runs low for this fellow he ejects water from the top end of his shell by contraction of his "foot."