Genus Sarotrocercus

Is a genus of small animals discovered on the Burgess Shale. They have a segmented body with nine segments and as such they are classified as a an arthropod.they also have two big stalked eyes and 20 comb like appendages on their underside which i can only assume were for swimming (kind of like a horseshoe crab not not the same). as you might of guessed from the picture the animal swam upside down, and were one of the few Burgess Shale animals that swam freely. 

Phylogeny

Animalia-Arthropoda-incertae sedis (meaning uncertain placement)-Sarotrocercus-obilta

source

The Sarotrocercus (1981)

Phylum : Arthropoda
Class : incertae sedis
Genus : Sarotrocercus
Species : S. oblita

  • Middle Cambrian (550 Ma)
  • 4 cm long (size)
  • Canada (map)

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 (one pair) and the body segments (nine pairs).

This small animal was a creature that swam freely on its back, moving perhaps through movements of the gills and the action of its the 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.

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