BIG DEAD FISH etc

[darren.naish@port.ac.uk]

Good to see Colin back on the list. Am pushed for time but 
some quick comments on some things discussed/mentioned 
in his email...

_Leedsichthys_: the osteology, affinities etc of this fish are 
currently being reviewed by Jeff Liston (Hunterian 
Museum). I don't know what I'm allowed to say but Jeff has 
gone through all of the NHM material and obviously is 
doing lots with Meg, the Hunterian's specimen. I got the full 
run-down from Martill a few weeks ago and loads of new 
stuff is coming out of this. It looks like Dave was right 
about the size: _L. problematicus_ is indeed in the 15-20 m 
bracket. Incidentally a new specimen was discovered last 
year in Peterborough. We are excavating it this summer. 
Incidentally, there is a second species of _Leedsichthys_ 
(_L. notocetus_) from Chile.

The 'Sikanni ichthyosaur' (Manabe and Nicholls, in press I 
believe) is not a shastasaur (neither in the traditional sense 
nor in the sense of it being a cymbospondylid or basal 
merriamosaurian) according to Makoto Manabe. The photos 
and reconstructions do indicate that it was not unlike 
_Cymbospondylus_, _Phantomosaurus_ etc in proportions. 

Giant pliosaurs (again): Martill and I recently borrowed the 
giant vertebrae from Peterborough and have been describing 
them. Based on comparisons with near-complete skeletons, 
we estimate they belonged to an animal 15-17 m long. Dino 
Frey and Marie-Celine Buchy have just submitted an MS on 
a similar-sized pliosaur from Mexico. Both of these animals 
appear to be pliosaurids s. s. (ie. sensu O'Keefe).

Size of giant rhinos - _Paraceratherium_ (correct name for 
_Baluchitherium_, _Indricotherium_ etc according to Lucas 
and Schoch) is no way 30 tons. 10-16 tons is more like it.
See Fortelius, M. & Kappelman, J. 1993. The largest land 
mammal ever imagined. _Zool. J. Linn. Soc._ 107, 85-101. 
Also estimates by Greg Paul in various of his papers.

Terrestrial locomotion of giant seals and plesiosaurs: this is 
very much on my mind at the moment as Dave and I 
actually had a huge row about it the other day (plus Stig and 
I have recently been working on monachine pinnipeds and 
thus have been looking at _Mirounga_ and kin quite a bit). 

>Maybe< if _Mirounga_ wasn't around we might doubt it's 
ability to move on land, but not necessarily. Unlike 
plesiosaurs, elephant seals still have an intact sacrum and 
sacroiliac contact, and also flexible, distally well-muscled 
forelimbs with a mobile elbow and foldable fingers. I think 
the conclusion from a fossil one would be: it probably could 
move on land, but it would have been one hell of an effort. 
This is not different from what some people say about 
plesiosaurs, even though plesiosaurs lack such features and 
are arguably more committed to an aquatic lifestyle. 

And given that harem-based polygany, marked sexual size 
dimorphism, terrestrial moulting and terrestrial pupping are 
all ubiquitous throughout pinnipeds, the hypothetical 
absence of monachines or even all phocids from the extant 
fauna would not stop us from thinking that _Mirounga_ 
could move on land in an imaginary world where this 
animal was only known as a fossil (BTW, it's been 
suggested that pinnipeds cannot become fully aquatic 
because of the above constraints).

Self-beaching in cetaceans: best known for killer whales, 
but not unique to this species - there is one population of 
_Tursiops_ that also self-beaches and belugas are known to 
stay motionless in water less than 30 cm deep after 
intentional and unintentional stranding. _Inia_ is 
anecdotally reported with the ability to cross emergent sand 
bars.

Laying eggs in water: Colin points out that some snake-
necked turtles do this. Apparently laying shelled eggs in 
water is not such a problem as traditionally thought. A 
must-read on this is... Skulan, J. 2000. Has the importance 
of the amniote egg been overstated? _Zool. J. Linn. Soc._ 
130, 235-261.

Finally, Colin, I would have loved to do a presentation with 
you at SVPCA 2002. Sadly the deadline for submissions 
was some weeks ago.

Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth
Burnaby Building
Burnaby Road                           email: 
darren.naish@port.ac.uk
Portsmouth UK                          tel: 023 92846045                   
PO1 3QL                                www.palaeobiology.co.uk