Re: Triassic mammal-like reptiles?

[K and T Dykes <ktdykes@arcor.de>]

<<Any chance the material was redeposited from a Triassic formation?  Are
there any Triassic units near the Australian locality or in its
subsurface?>>

The authors discussed such possibilities, Phil, and I think the paper's
hanging around on line: Thulborn T & Turner S (2003), The last dicynodont:
an Australian Cretaceous relict, Proceedings of the Royal Society B, 270,
p.985-993.  I don't seem to have saved a copy of the file, so I'll just have
to nip off and fetch the print...

Back again.  The relevant six fragments were found in 1914 in north-central
Queensland.  Somebody said they were very like stuff Broom was sweeping up
in Karoo, especially the dicynodonts.  They then hung around in the
Queensland Museum, as various other things occurred; a couple of world wars,
depressions, energy crises, cold wars, weddings and assorted other global
catastrophies.  A bit later (85 years or so) somebody noticed them lying
around, had a look and went golly gosh!

"Adherent matrix, a yellow-brownish mudstone, betrays their most likely
source as the Allaru Formation, a thick (ca. 250 m) succession of mudstones
and siltstones which outcrop exstensively in the region of Alderley..."
(reference number omitted, p.985).  And from a bit later on the same page:
"There are no outcrops of pre-Cretaceous rocks in the vicinity of
Alderley..."

On page 987 they pose the question: Is this a dicynodont?  Based on the
anatomy their answer is yes.  If the things had been found in suitable
Triassic strata, there'd be no reason for any doubt at all.

As this is unlikely sounding stuff, they begin addressing the age issues on
page 989.  Associated fossils include a bit of ?/Platypterygius/ ichthyosaur
(which doesn't mean much to me).  They mention the complete lack of
pre-Cretaceous rocks  in the area: "(ie. on the entire 1 : 250 000
geological map showing ALderley station..:"  The nearest Triassic exposures
are over 100km away.  There's one paragraph which summarises their case on
the age succinctly and clearly (same page):

"In short, we can find no reason to doubt that QMF15.990 originated from the
Rolling Downs Group.  It seems quite certainly to be Early Cretaceous in age
and was probably introduced into the marine environment by flood-waters that
also carried the carcases of sauropods, ankylosaurs and ornithopod dinosaurs
(Molnar 1991, 1996a,b)."

Although those dinos weren't furry, even I can  appreciate the age
implications of their presence.  The best explanation presently available is
that these fragments come from a Lower Cretaceous dicynodont.  While that
sounds outrageously unlikely, they couldn't come up with a more plausible
conclsion.  And the authors certainly appear to have tried all options.