mega orcas revisited

[Colin Mchenry <s172579@student.uq.edu.au>]

Greatings to all

I'm back after a winter of good field trips and complete chaos as they 
refurbish  ( = destroy and then rebuild) our building.  Collected a bit 
of Kronosaurus whilst out West - a bit a belly with some elasmosaur 
vertebrae and gastroliths inside it - and we also came across a nice 
elasmosaur (nearly all there apart from the head, unfortunately).

Anyway, I meant to add something to the posting Dazzer put up a few 
months ago on Mega-Orcas (13th June, I think), so here it is.

This (Northern) summer the BMNH put back on display their Mesozoic marine 
reptiles, after the specimens spent 7 years at the Doctors' (so to 
speak).  Of special interest (to me at least) are the various Jurassic 
pliosaurs included within this display, and I look forward to seeing them 
more closely next year.  Rhomaleosaurus (which includes the 
'gracile' R.megacephalus and the more 'robust' R.zetlandicus, the latter 
was described my Mike Taylor (now at Edinburugh)) is from the Lower 
Jurassic.  The Upper Jurassic forms include the smaller  (relatively - 
about 5 metres long?) Peloneustes and Simolestes (whose mandibles are 
very differently shaped, perhaps idicating specialised piscivore and 
molluscivore 
respectively?), the medium sized Pliosaurus (includes 3 species - 
P.brachydeirus, P.brachyspondylus, and P.andrewsi), and the giant 
Liopleurodon (L.ferox, L.pachydeirus, and L. macromerus).  Exactly how 
all these ulta-predators were making a living (in the same communities?) 
is a question worthy of an enterprising Ph.D...

The last major review of these beasts was done by the late great Bev 
Halstead/Tarlo, in 1960 (L.B. Tarlo, Bull. Brit. Mus. (nat Hist.), Geol., 
4 (5) 147-189), and little has been done since.  In that review he 
describes L.macromerus as belonging to the genus Stretosaurus, a genus he 
erected in 1959, noting "The pectoral girdle of this animal is so unusual 
that a new generic name is considered necessary for its reception" 
(Tarlo, L.B. Palaeontology, 2, 39-55).  For a while Stretosaurus got into 
the books as a huge cousin of Liopleurodon, bigger perhaps than 
Kronosaurus (there are tales of a 3 metre mandible, which would certainly 
qualify it for contention), but in 1975 a new Liopleurodon was found 
which made him realise that what he had thought was the pectoral girdle in 
Stretosaurus was in fact the pelvic girdle, and he thus put S. macromerus 
into Liopleurodon (an easy mistake to make, given the scrappiness of the 
larger pliosaur specimens) (Halstead, L.B., 1989, J. Geol. Soc., Lond., 
146, 37-40).

After 1975 there was a rush on re-interpretations of  plesiosaurian 
swimming and feeding, and in 1992 Mike Taylor published his description 
of the head of Rhomealosaurus zetlandicus (Phil. Trans. R. Soc. Lond., 
ser. B, 335, 247-280).  Mike and Arthur Cruickshank have since done some 
more work on pliosaurs, including a description of well developed 
underwater olfaction...!  Last year (just befor I left the U.K. to come 
here for the kronosaurs) there was a large (complete?) pliosaur found in 
clay near Westbury, and I think Glenn Stores (now at Cincinati) has got 
his hands on it.  A species of Pliosaurus, I think.

There were supposed to be some biggy's in N. America as well, during the 
Cretaceous this time.  When he was setting  the stage for Kronosaurus in 
1930, Heber Longman mentions Megalneusaurus rex (as an inferior, of 
course), but I've heard very little of it.  Do our American cousins know 
anything of this beast?

Down here in the South Kronosaurus rules the roost, with a number of 
specimens from Queensland (one of which can be seen at Harvard - but it 
doesn't really look like that), and some from Columbia.  Oliver Hampe has 
described the S. American ones as K. boyacensis (Courier Forsch.-Inst. 
Senckenberg, 145: 1-32  - I'll read it as soon as I get it translated!), 
and I would like to get a look at them.  The ones over here are K. 
queenslandicus.  Other Australian pliosaurs include Eric the opalised 
pliosaur (yet more antipodean pythonisms), a specimen found in fresh 
water deposits whose name escapes me, and another (smaller) beast from 
the same rocks as Kronosaurus, but which has a huge neck, larger 
forelimbs than hind, and a fish eating skull that looks just like that of 
the fresh water croc which we get here (yet to be named - the pliosaur, 
that is, not the croc).

Darren, I'd say that all the plesiosaurs ingested (hard volcanic) stones 
for ballast - they are present in at least one Kronosaurus specimen, and 
quite a few of the Woolungasurus specimens (the local elasmosaur) in the 
Queensland Museum.

Enough for now.

Colin McHenry

P.A. Swamps
Vert. Palaeo. Lab.
Dept. Zool
U.Q.
Oz