Topography and topology of the teleost telencephalon: a paradox resolved

Analysis of vasculature in the telencephalic pallium of a teleost allows th e considerable depth of the sulcus externus, which lies at the lateral exte nt of the ependymal attachment, to be appreciated. The depth of this sulcus is compelling evidence for a simple eversion process tan outfolding of the pallia[ wall of each hemisphere) during telencephalic development in all r ay-finned fishes that is not complicated in teleosts by secondary migration of pallial cell groups. A simple eversion process is known to occur in som e ray-finned fishes with relatively simple telencephalic cytoarchitecture b ut has been disputed in teleosts based on the pattern of olfactory tract pr ojections. A resolution to the conflicting hypotheses of pallial relationsh ips across ray-finned fishes and in comparison with other craniate radiatio ns is presented here, based on a re-examination of hodological and histoche mical data mandated by this sulcal anatomy. (C) 2000 Published by Elsevier Science ireland Ltd.