Spartobranchus tenuis is an extinct species of acorn worms (Enteropneusta). It existed in the

Middle Cambrian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ...

(505 million years ago). Petrified mark animals were found in British Columbia, Canada in the

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...

formation. It is similar to the modern representatives of the family

Harrimaniidae Harrimaniidae is a basal family of acorn worms. A taxonomic revision was undertaken in 2010, and a number of new genera and species found in the Eastern Pacific were described. In this family the development is direct without tornaria larva, and ...

, distinguished by branching fiber tubes. It is a believed predecessor of

Pterobranchia Pterobranchia is a class of small worm-shaped animals. They belong to the Hemichordata, and live in secreted tubes on the ocean floor. Pterobranchia feed by filtering plankton out of the water with the help of cilia attached to tentacles. ...

, but this species is intermediate between these two classes. Studies show that these tubes were lost in the line leading to modern acorn worm, but remained in the extinct graptolites and saving still perystozyabernyh.

Description

Detailed analysis shows that ''Spartobranchus tenuis'' had a flexible body consisting of short proboscis, collar and narrow elongated stem that ended in a bulbous structure that may have served as an anchor. The most complete specimens reached long, with proboscis of about half a centimeter in length.

References

* Jean-Bernard Caron, Simon Conway Morris & Christopher B. Cameron
Tubicolous enteropneusts from the Cambrian period
Nature 495, 503–506 (28 March 2013) doi:10.1038/nature12017

External links

{{Taxonbar, from=Q25435098 Hemichordates Cambrian animals Cambrian genus extinctions