New guide to mosasaurs

[bh480@scn.org]

From: Ben Creisler bh480@scn.org
Subject: New Guide to Mosasaurs

Jeff Poling has just posted my long-delayed guide to 
mosasaur names at http://www.dinosauria.com/dml/dmlf.htm. 
Many thanks, Jeff! This guide is a follow-up to my guide 
to the Plesiosauria posted last year, and any comments or 
corrections would be very welcome. Still to come is a 
similar guide to the Ichthyosauria, though I'm tempted to 
wait for Motani and McGowan to publish their 
Ichthyopterygia volume of Handbuch der Palaeoherpetologie 
before posting anything of my own. There are some major 
controversies swirling around ichthyosaur taxonomy at the 
moment that I certainly have no expertise to takes side 
concerning. (I mean, how can some researchers 
classify "Ichthyosaurus" acutirostris as a species of 
Stenopterygius while others classify it in 
Temnodontosaurus--two genera that are pretty far apart by 
anybody's reckoning. And then there are the omphalosaurs 
and the species of Mixosaurus that may or may be distinct 
genera...) 

A couple of comments about the mosasaur guide:

Liodon Agassiz 1846, not "Leidon" Owen 1841
Lingham-Soliar had a paper in 1993 in Modern Geology 
arguing that Leiodon Owen is a distinct and definable 
genus. All find and good--except that the valid name for 
the taxon is Liodon Agassiz, 1846. Leiodon is preoccupied 
by a fish (Leiodon Swainson, 1839) so Owen's spelling is 
out. Agassiz "corrected" Owen's latinization of Greek ei 
to i (a la deinos to dino- in Dinosauria), and it counts 
as a valid replacement name.

Nuchal Fringe--the Frill is Gone?
Lingham-Soliar had another paper Modern Geology in 1991 in 
which he traced the supposed nuchal fringe or dorsal crest 
often added to mosasaurs to a paper by Williston in which 
he mistook tracheal rings for a frill along the neck and 
back of a specimen of Platecarpus. Osborn endorsed the 
idea in his memoir about Tylosaurus, instructing Charles 
R. Knight to paint Tylosaurus with a dorsal fringe, much 
to the delight of later artists, who found the feature a 
great temptation to artistic license.  However, Williston 
later realized his error and printed a short retraction in 
1902. This correction has forgotten and overlooked, and as 
far as I can determine, there is NO preserved fossil 
evidence for a frill along the neck or back of mosasaurs. 
All fine and good EXCEPT that Lingham-Soliar restored 
Mosasaurus with some kind of low crocodile-like dermal 
frill along its back in his recent 1999 article in Science 
Spectra! Now I'm confused. What's the story? The frill is 
gone...or not?  

Also, I can find no record of fossils showing that 
Clidastes had an extra soft-tissue sea-snake-like 
expansion of the enlarged flattened bones at the end of it 
tail, as commonly depicted.