In the seventies , when researchers first examined the bizarre half - billion - yr - old fogey of a worm - like brute with a double row of rachis on its back and several pairs of legs that cease with claws , they could n’t make heads or tails of it . But now , this puzzling marine worm namedHallucigeniahas lastly showed its face ( in the fogy phonograph recording ) . The finding are published inNaturethis workweek .
The tubular body ofHallucigenia sparsaranges from 10 to 50 millimeter in length . It ’s a penis of the wildly diverse group of animals called ecdysozoans that are unite by one thing : They molt . This includes the familiar bug , spider , millipede and crustaceans , as well as roundworms , velvet worm , and tardigrade ( the water system bear ) . Just last yr , a near examination of their claws revealed thatHallucigeniaisan ancestor of advanced - day velvet worms . These are tropical legged worms that fire jets of slime at their prey .
However , features of its straits were still unsung until now . University of Cambridge ’s Martin SmithandJean - Bernard Caron from the University of Torontoused negatron microscopy to examine more than 165Hallucigeniaspecimens unearth from the 508 - million - year - old sediment of the Burgess Shale in Canada ’s Yoho National Park back in the 1990s . Some of these fossils come up accomplished with a pair of childlike eyes that sat above a halo of tooth .
Hallucigenia sparsa from the Burgess Shale . The fossil is 15 mm foresighted . Jean - Bernard Caron
“ A big balloon - similar orb at one goal of the specimen was in the beginning thought to be the chief , but we can now demonstrate that this actually was n’t part of the body at all , but a moody stain representing decay fluids or gut content that oozed out as the animate being was flattened during burial , ” Smith says in astatement . Once they figured this out , they dug forth the deposit covering the head . “ When we put the fossils in the negatron microscope , we were initially hoping that we might find eyes,”Caron adds , “ and were amaze when we also recover the teeth smiling back at us ! ”
Hallucigenia ’s head was small and elongate and sat at the end of a thin neck . The ring of tooth surrounding its rima oris likely help to generate sucking to pull food for thought into its pharynx , which was also lined with home plate and circular tooth . This foregut armor believably kept the food for thought from slipping out as it sucked . There were also three pairs of tentacles along its neck .
“ We previously thought that neither velvet worms nor their root had teeth,”Caron says . “ ButHallucigeniatells us that actually , velvet worm ascendant had them , and living forms just lost their tooth over meter . ” This mouth resemble those of roundworms as well as the usual ancestor of arthropods . Previous molecular workplace had already aggroup arthropod and tinea into Ecdysozoa , and this is finally being reassert by structural grounds .
