Fossil worm adds head to its spiny appearance

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Whether it’s upside down or right side up, Hallucigenia sparsa looks like it wriggled right out of a nightmare. And giving the wormlike creepy-crawly a head hasn’t helped.

An analysis of 508-million-year-old H. sparsa fossils from the Burgess Shale in Canada revealed that the 10- to 50-millimeter-long critter had a small pair of simple eyes set atop a narrow head. Below the head was a long neck that protruded from a tubular body sporting 10 sets of dangly appendages and seven pairs of spines. Platelike structures surrounded  H. sparsa ’smouth opening and tiny teeth lined part of its gut, researchers report  June 24 in Nature .

Those toothy features are similar to some seen in present-day tardigrades, or water bears (SN: 7/26/14, p. 4), hinting at the evolution of such gnarly mouthparts. 

WRIGGLE IT  H. sparsa rolled along on its 20 legs and may have reared up on its hind ones, as in this illustrated video. Credit: Lars Fields