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Re: "Cetiformes" and Dinosauriformes

Nick,
Most of Class Scorpionea are the several Orders of eurypterids (sea scorpions), which have a history of being classified with horseshoe crabs (Class Xiphosurea). Only one Order (Scorpionida) was removed from Class Arachnidea, so dumping eurypterids in an expanded arachnid class would obscure their distinctiveness and just exacerbate the problem of an already unbalanced chelicerate classification. Class Scorpionea should have been formed a long time ago for a number of other reasons as well (such as showing that scorpions invaded land separately from the true arachnids).
By the way, for those who think I cry "possible convergence" too often, note that this is one of those cases in which I did the opposite---I resisted the arguments of a majority who continued to insist that the similarities between scorpions and sea scorpions was just due to convergence. If there is any convergence going on it is between scorpions and true arachnids due to adaptations to living on land.
-------Ken
******************************************* 
From: NJPharris@aol.com
To: kinman@hotmail.com, dinosaur@usc.edu
Subject: Re: "Cetiformes" and Dinosauriformes
Date: Mon, 24 Sep 2001 18:04:13 EDT

In a message dated 9/24/01 12:50:49 AM Eastern Daylight Time,
kinman@hotmail.com writes:

>      When I told people I was going to take scorpions out of Class
>  Arachnidea, some people thought my new Class Scorpionea was a little
wacky.
>
>  But several years later fossil evidence showed that scorpions and
>  eurypterids do share a key synapomorphy to the exclusion of other
arachnids
>  (my Class Arachnidea).

Um, well, that shows that scorpions and eurypterids should be classed
together, but why should they be a separate "class", rather than a
subdivision of Arachnida?

--Nick P. 


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