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Re: Paleo Find of the Year 2001
> Every year I hold a vote for the most important paleontology find of the
> year. In my December newsletter and via a post to the Dinosaur Mailing
> List, I have called for nominations. The list of nominations is as
> The nominations are dinosaur-biased, and I realise that. However, these
> were the only nominations provided.
May I add another nomination?
John G. Maisey & M. Eric Anderson: A primitive chondrichthyan braincase from
the Early Devonian of South Africa, JVP 21(4), 702 -- 713 (December 2001)
This, the earliest known chondrichthyan braincase, has important
consequences for the systematics of Gnathostomata. It displays several
features that were so far considered synapomorphies of Osteichthyes (or they
+ Acanthodii). The list of osteichthyan synapomorphies already being eroded
by several basal actinopterygians and sarcopterygians (they all have
eyestalks, for example, like basal placoderms and chondrichthyans), only
three remain -- the presence of premaxilla, maxilla and cleithrum. As these
are dermal bones, their absence in chondrichthyans, which don't have any
dermal bones, could easily be secondary. Their absence in placoderms may or
may not be due to the usual homologization problems with placoderms.
From p. 712: "It is quite remarkable that, in the space of just two
years, fossils have been described that affect concepts and
characterizations of two major clades (the osteichthyans and
chondrichthyans) that originated in the 19th Century [sic]. The
morphological basis for osteichthyan monophyly is weakened by these
discoveries, but in reality it was never strong."
"From a developmental perspective, it may be much easier to lose new
characters than to gain (or regain) them."