AMPHIBIOUS MOSASAURS?

[darren.naish@port.ac.uk]

In response to a report on Sunday's UK dinosaur meeting (I got to 
pick up most of new Battat series - stunning!), Dan Varner wrote..

>  "somewhat amphibious" ?! Mosasaurs were totally aquatic and a stranding
> would be as lethal to them as it is to a whale. Perhaps it would take
> longer to asphyxiate, but there would certainly be no hope of escape 
> using paddles or serpentine movements. The anatomical configuration 
> is just not there. But, more to the point, Jackson's post behooves me 
> to ask a question here. Is there any shred of evidence for this kelp 
> forest model of Cretaceous seas?

In reply, John Jackson wrote...

> These are very good questions you ask, Varner, and I'm glad you 
> asked them... and I'm sure Naish will be only too pleased to provide 
> you with some answers!

I certainly did *not* say that mosasaurs were amphibious. I said that 
their (often) elongate and flexible bodies would be better suited for 
locomotion and ambush predation in cluttered, three-dimensional 
marine environments, such as around reefs or in seaweed forests. 
Mosasaur experts will know that this certainly does not go for all 
mosasaurs: they were diverse, with a number of different body shapes.

As for the kelp forest thing, this is something I admittedly took 
some liberty with. It's actually a kind of Bakkerian idea - in his 
1992 paper on plesiosaur extinction cycles, he talks about black 
shales being evidence of massive organic content in the 
mid-continental seas, and then correlates the abundance of mosasaurs 
with this environment. Daryl Domning, the world sirenian authority 
who's published lots of papers on the apparent coevolution of 
herbivorous sirenians and desmostylians with kelps and their 
relatives, cites some palaeobotanical work indicating that kelpy 
plants were certainly present in the Mesozoic. The 'choked seaway' 
hypothesis made its artistic debut with Greg Paul's restoration of a 
late Cretaceous mid-continental seaway community (we have a copy up 
on our office wall). I've recently been discussing the idea with 
Mike Everhart: it's controversial, and it has its pros and cons:
something I wanted to discuss, but didn't have time for (I tried to 
cover way too much stuff). 

(This also explains why I never finished explaining why basilosaurs 
were _not_ _Lobodon_-style filter feeders. Answer is: their 
multicusped cheek teeth bear the kind of wear that marine tetrapods 
only get from biting big, bony prey (cf. Mike Taylor's 1992 
rhomaleosaur description) - krill-eating lobodont seals and basal 
toothed mysticetes (_Llanocetus_, 'aetiocetids') do not have this 
wear (this all based on Ken Carpenter's recent work on the _Dorudon_ 
skull)).

So, apologies, the choked seaway hypothesis is controversial and not 
accepted by all. I'd be interested to hear your thoughts Dan.

BTW, I haven't received John's email which started this thread. Can 
someone fwd me a copy?

"Arr, squiddy"

DARREN NAISH
darren.naish@port.ac.uk