Somewhere between the iron maiden andPinhead , you ’ll regain a misunderstood insect namedHallucigenia . For decennary , researchers could n’t make chief or tails ( literally ) of these off-the-wall - search fossils , calling it an “ evolutionary misfit ” because they could n’t be neatly linked to modern animals . But now , this legged worm has finally witness its post in the evolutionary tree of lifetime – as ancestors to advanced - day velvet worms , harmonize toworkpublished inNaturethis week .
Between five and 35 millimeters long , Hallucigenialived on the sea floor around 505 million years ago during the Welsh Explosion – a outburst in biodiversity when most major animal groups first appeared in the fossil record . It has seven or eight pairs of leg that end in claw . Their fossils were first name in the 1970s , but former interpretations placed it rearward and upside - down : The row of spines on its back were think to be its legs , which themselves were intend to be tentacles along its back , and its head was false for its stern . Thisview was overturnedand the office put in their right situation in the 1990s .
In hunting of “ smoking throttle ” characteristics linking this eccentric worm with modern animal , Martin SmithandJavier Ortega - Hernández from University of Cambridgeexamined the brass ofHallucigenia sparsaclaws in fossils uncovered from the Burgess Shale in Canada ’s Rocky Mountains .
“ It ’s often guess that modernistic fauna groups arose fully work during the Cambrian Explosion , ” Smith tell in anews release . “ But phylogenesis is a gradual process : today ’s complex anatomies emerge step by step , one feature of speech at a time . By decode ‘ in - between ’ fogy likeHallucigenia , we can determine how different animate being groups built up their modern body plans . ”
After magnifying the claw 1,000 times , the duo discovered an significant connection to modern velvet worms , also known as onychophorans . These legged worm survive in tropical rainforests andfire jets of slime at their prey . layer of cuticle ( interchangeable to our fingernail ) are nestled one inside another – like an onion or a Russian nesting chick – in bothHallucigeniaclaws and the velvet worm ’s nipper and jaws , where they are basically leg qualify for chewing .
“ Because it did have onion - layer claws , Hallucigeniawas not an evolutionary dead end,”Smith writes in The Conversation . “ Rather , it represents an early pit stop on the elbow room to the velvet worm body plan , which uprise gradually over time . ”
In this unexampled home tree , velvet worms andHallucigeniaare distant cousins separated by half a billion old age , with other legged insect ( forebode lobopodians ) belong elsewhere . “ It turns our current savvy of the evolutionary tree of arthropod – the radical including spider , insect and crustaceans – upside down,”Ortega - Hernandez articulate . “ Most cistron - based studies suggest that arthropod and velvet louse are close related to to each other ; however , our results show that arthropod are really closer to water bears , or tardigrades , a group of intrepid microscopic animals best known for being able to survive the vacancy of space and sub - zero temperatures – leaving velvet worms as aloof cousin-german . ”
Images : Elyssa Rider viaScienceDaily(top ) , M. R. Smith / Smithsonian Institute via CambridgeCC BY - NC - SA 3.0(middle )
