Abgeschickt von Allart am 05 Maerz, 2004 um 12:33:07
Hello Andreas, Brigitte,
I've been looking at your photographs and I think that the Leonaspis that you display are Kettneraspis. There seem to be some difficulties concerning Leonaspis. Adrain & Ramskold (1997) consider Leonaspis as a polyphyletic group. It is divided into Leonaspis, Kettneraspis and Adrain & Ramskold have added Edgecombeaspis in 1997 which is derived from Kettneraspis. Concerning differences between Leonaspis and Kettneraspis, the pygidial spines are a way to distinguish both genera. Leonaspis has 4 small spines between 2 long spines, while Kettneraspis has 2 small spines between 2 long spines.
Combined with my work on several cranidia and a cephalothorax of a Leonaspis-like species wearing an occipital spine, there are some comments. There are "Leonaspis" from Morocco that wear a spine on the occipital lobe but these seem to be much more robust and larger than what we see in our region. I have seen quite a few and mostly they appeared to be Kettneraspis. I am not sure about my own specimens because I have no pygidium saved with them. I do have a cephalothorax that is with certainty a Leonaspis or Kettneraspis. There are differences in the cranidium as well between both genera and they are described in the paper by Adrain & Ramskold, which I am trying to get somewhere. There is also a paper by Ramskold & Chatterton in which the polyphyletic group of Leonaspis is revised but I do not know about its contents and if it is earlier or later than the Adrain & Ramskold paper.
Allart