Despite its appearance, the new arachnid is not a direct ancestor of modern day spiders.Named Chimerarachne yingi, the animal resembles a spider in having fangs, male pedipalps, four walking legs and silk-producing spinnerets at its rear.However, it also bears a long flagellum or tail. No living spider has a tail, although some relatives of spiders, the vinegaroons, do have an anal flagellum.Four specimens of Chimerarachne yingi were found, and all are tiny, about 2.5 mm body length, excluding the nearly 3-mm-long tail.
“Any sort of flagelliform appendage tends to be like an antenna,” said Dr. Paul Selden, a researcher in the Paleontological Institute and the Department of Geology at the University of Kansas.“It’s for sensing the environment. Animals that have a long whippy tail tend to have it for sensory purposes.”The find confirms a prediction made a few years ago by Dr. Selden and colleagues when they described a similar tailed arachnid, which resembled a spider but lacked spinnerets. These animals, from the much older Devonian (about 380 million years ago) and Permian (about 290 million years ago) periods, formed the basis of a new arachnid order, the Uraraneida, which lies along the line to modern spiders.“The ones we recognized previously were different in that they had a tail but don’t have the spinnerets,” Dr. Selden said.“That’s why the new one is really interesting, apart from the fact that it’s much younger — it seems to be an intermediate form.”“In our analysis, it comes out sort of in between the older one that hadn’t developed the spinneret and modern spider that has lost the tail.”Chimerarachne yingi lies one step closer to modern spiders on account of its possession of spinning organs.