As I’ve said, the latest issue of Science is chock-full of great articles on speciation and evolution. In one of them, Gabriele Kühl, Derek Briggs, and Jes Rust describe a new 390-million-year-old fossil from the Hunsrück Slate beds in Germany. This species, named Schinderhannes bartelsi, has what is called a “great appendage” in front of the mouth, consisting of two large protrusions, each of which has spines as well as leglike filaments on it. (This appendage was probably a device to grab prey and convey them to the radial mouth behind.) It also has two “winglike” protrusions that were used for locomotion, and a tail spike. The reconstruction by Elke Groening is below:
This weird animal is similar to Anomalocaris, one of the mysteries of the Burgess Shale fauna (see Steve Gould’s Wonderful Life for an overview): both have the “great appendage”. The new fossil, however, is 100 million years younger than those of the Burgess Shale. Kühl et al.’s work shows, however, that the “great appendage” animals were “paraphyletic” (that is, they don’t form a group of species more closely related to each other than to any other species), and that Schinderhannes bartelsi is actually an arthropod more closely related to the chelicerates, the group including horseshoe crabs and scorpions. Indeed, the front claws of scorpions and horseshoe crabs are probably derived from this great appendage.
More than 99% of all species that existed over life’s history are thought to have gone extinct without leaving descendants, and fewer than 1% of these are known as fossils. How many weird and wonderful species like this will never be known to science? A sad sidelight on this is that the Hunsrück Slate beds have since been closed, so there is no chance to see what other fossils lie in this amazing formation.
Gabriele Kühl, D. E. G. Briggs, and J. Rust. 2009. A great-appendage arthropod with a radial mouth from the Lower Devonian Hunsrück Slate, Germany. Science 323:771-773.