Sarotrocercus


Sarotrocercus is a small Cambrian organism known from Burgess shale-type localities, reaching a centimetre or two in length. It was pelagic and swam on its back. It may lie in the arthropod crown group, and a recent study has revised some points of its original description.

Morphology

It had a head shield followed by a body of nine segments and a caudal tip featuring a series of spines on the end. A pair of big eyes at the end of stalks emerged from the front of the shield. The head bore a pair of sturdy appendages that ended in a bidentate segment. Ten pairs of appendages with an elongated structure of comb-shaped, probably gill branches, are attached to the at the head segment and the body segments.

Ecology

This small animal was a creature that swam freely on its back, moving perhaps through movements of the gills and the action of its long tail tuft. The Burgess Shale contains few swimming organisms; the submarine landslides that buried organisms mainly smothered benthic and nektobenthic organisms. Organisms living in the water column above this habitat were able to escape and above the 'danger zone' and are therefore much rarer. Among these are the notable Amiskwia, Nectocaris and Anomalocaris.