RE: Coelacanth article in current NatGeo

["Choo, Brian" <bchoo@museum.vic.gov.au>]

The real question is why clade Teleostei is so successful (as they form the 
vast bulk of living actinopts) - other extant ray-fin lineages are relictual 
and haven't produced new genera since the early Paleogene. Teleosts seem to 
have two utterly unfair adaptive advantages over other fishies:

1) Mauthnerian system (greatly enlarged nerve cells in the medulla connected to 
elongated axons running down the spine) = superfast avoidance reactions when 
threatened.

2) Teleost jaw suspension (mobile maxilla & premaxilla) allowing the lips to 
protrude far in advance of the rest of the skull. A highly efficient means of 
feeding (greater reach/ suction draws food items into the mouth) but, more 
importantly, it is very easily reconfigured to tackle any sort of food item 
anywhere in the water column. Put a single species of teleost in an isolated 
lake, come back in a couple of 100k years and chances are it will have exploded 
into numerous novel forms, with the jaw modified into all sorts of odd 
configurations (as happened with cichlids the African rift lakes). Put a single 
species of lungfish in an isolated lake, wait around for the same amount of 
time and chances are you'll essentially have the same lungfish.

Cheers
Brian


________________________________________
From: owner-DINOSAUR@usc.edu [owner-DINOSAUR@usc.edu] On Behalf Of Augusto Haro 
[augustoharo@gmail.com]
Sent: Friday, 25 February 2011 5:00 AM
To: erikboehm07@yahoo.com
Cc: DML; david.marjanovic@gmx.at
Subject: Re: Coelacanth article in current NatGeo

I think Choo is right. Chondrichthyans also have fleshy fins, thus
suggesting fleshy fins came first. Thus, the reason by which fleshy
fins were good may reduce to the reason by which fins are good. Now,
it may be asked why ray fins are more adaptive, if they persisted
because of intrinsic adaptive superiority and not because of luck at
the mass extinction (or because of other improvement in
actinopterygians).


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