ANCIENT SPHENODONTS ON NZ

[darren.naish@port.ac.uk]

Derek Tearne has addressed some of the things I wrote about NZ and 
its fauna. 

WHY IS SPHENODON A NZ ENDEMIC, AND NOT AN INVADER
THAT CAME IN ON A RAFT?

I wrote..

>Sphenodonts are probably best interpreted as Mesozoic relicts, as 
are >>leopelmatid (=ascaphid) frogs.

And Derek said..

> I note you assume these were here all the time and yet you say:
> >NZ's hoplodactyline geckos probably have invaded NZ after its
> >separation - there is no evidence that hoplodactylines were living 
> >in the late Cretaceous -

This is because both sphenodontids and leiopelmatid frogs were 
definitely present in the late Cretaceous: that is, they were alive 
before NZ split off from the rest of Gondwana. Because frogs cannot 
raft, and because sphenodonts apparently had no where to raft _from_ 
(i.e. there are no post-Lower Cretaceous sphenodonts outside of NZ), 
I have to conclude that both groups were on NZ before it split off. 
To my knowledge, there is no reason to think that hoplodactyline 
geckos had evolved by the end of the Cretaceous. Yet by this time, NZ 
had split from Gondwana and was a separate landmass. The geckos 
therefore evolved _after_ NZ has split, and, as they seem to have 
originated somewhere in Australasia that is not NZ, they must have 
invaded NZ _after_ its separation.

> I was under the impression there was no record for the sphenodon 
> prior to the Holocene.  I would not tend to assume the absence of a
> particular creature from our fossil record to be much of an 
> indication of anything.  In the case of Sphenodon I guess its 
> nearest relatives were a considerable rafting distance, but then 
> they're much hardier beasts than geckos.

Indeed, the record for _Sphenodon_ on NZ goes back only about 1000 
years I think. Recent isotopic dating of Kiore teeth (_Rattus 
exulans_) by Richard Holdaway has shown that these rats (which are 
universally thought to have been carried around the Pacific by the 
Polynesians) have been on NZ since 2000 BP. Yet the earliest evidence 
for Maori on NZ dates to 800 BP. It is therefore conceivable that 
sphenodonts were introduced to NZ by humans.. but do you think this 
is likely? Sphenodonts are not known from anywhere in the west 
Pacific, so where could people have got them from? (yes, I am aware 
that certain mythical Welsh lizard-like animals have been likened to 
tuataras, but I do not deem them relevant here).

The primary reason for thinking that _Sphenodon_ is a relict, endemic 
to NZ, is that no other post-Cretaceous sphenodont is know from 
anywhere else in the world. The Cainozoic has a very rich small 
lepidosaur fossil record - there are abundant fossil lizards and 
snakes in Australia, the Americas, Europe and Asia (OK, so Africa 
ain't so hot..) - but in none of these places are there any things 
that look to be fossil sphenodonts. If _Sphenodon_ has rafted in from 
somewhere after NZ's separation, we would expect to find 
post-Cretaceous sphenodont fossils elsewhere in the world. This 
hasn't yet happened.

China and Mongolia has abundant Lower Cretaceous sphenodonts. If 
_Sphenodon_ were to have rafted into NZ after its separation in the 
late Cretaceous, then sphenodonts must have survived on mainland Asia 
to at least the end of the Cretaceous before _Sphenodon_ itself 
reached NZ. This seems unlikely given the rich Asian Upper Cretaceous 
and Cainozoic tetrapod record. 

> Incidentally, there was an article in New Zealand geographic a
> couple of years ago which featured a specimen of a giant gecko
> found in a French collection unlabelled but who's closest affinities
> were other New Zealand Geckos.  (I'm not implying that the specimen
> rafted to France).

You are referring to _Hoplodactylus delcourti_, a giant (37 cm SVL) 
hoplodactyline gecko described by Bauer and Russell in 1986. The only 
known complete specimen sat at the Musee d'Histoire Naturelle de 
Marseille for years (at least 117 of them actually). Unfortunately 
the specimen is lacking locality data, but the fact that it is a 
hoplodactyline strongly indicates that it came from the NZ area. 
Also, it seems to correspond with a large lizard from Maori folklore 
called the Kawekaweau. Bones that appear to be from this gecko were 
described in 1988 by Bauer and Russell: these bones were found at 
Otago.

No one doubts that _H. delcourti_ was taken from NZ to Marseille at 
some point in the recent past.

"Are you OK?"
"I just saw their destination"

DARREN NAISH
darren.naish@port.ac.uk