Description
Pikaia is a primitive creature without a well defined head It is less than 2 inches (5 centimetres) long. It swam in the mid-Cambrian seas, and is closely related to the ancestor of all backboned animals (vertebrates), from fish to amphibians, reptiles, and birds to mammals. Pikaia is one of the most interesting of the multitude animal fossils found in the famous Burgess Shale in the mountains of British Columbia, Canada. When alive, Pikaia was a sideways-flattened, leaf-shaped animal. It swam by throwing its body into a series of S-shaped, zig-zag curves, similar to movement of snakes. Fish inherited the same swimming movement, but they generally have stiffer backbones. Pikaia had a pair of large head tentacles and a series of short appendages, which may be linked to gill slits, on either side of its head. In these ways, it differs from the living lancelet. Pikaia's anatomy is still not fully known and palaeontologists are still researching its details.
This primitive marine creature shows the essential prerequisites for backboned animals. The flattened body is divided into pairs of segmented muscle blocks, seen as faint vertical lines. The muscles lie on either side of a flexible rod which runs from the tip of the head to the tip of the tail.
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