ELEPHANT-EATING & BIPEDAL LIZARDS

["Darren Naish" <dwn194@soton.ac.uk>]

Bipedality in lizards... Matt Wedel wrote..

> I've known about the basilisk and the Australian frilled lizard being 
> able to do the emergency biped thing for a while, but I could have 
> sworn that not too long ago I saw a post about a Central American 
> lizard that is really, truly, honest-to-goodness habitually bipedal.  
> If I remember right, the lizard in question had either just been 
> discovered, or just been discovered to be a biped.

A great many lizards (generally those with elongate caudofemoralis muscles and
a non-autotomous tail) are facultative bipeds - the best known include the
Basilisks (_Basiliscus_) [the creatures some of you have been referring to as
'Jesus Christ lizards' - this name due to their ability to dash across the
surface film of water by way of unusual pocketed pedal scales on long toes] of
South America and some of the Aussie dragons. 

One of the dragons (this is the popular name given to agamids and is
increasingly used in technical herp publications), the Frilly/Frilled lizard
(_Chlamydosaurus kingii_), is now known to be a true biped. This is big news to
most people: Since when?, they ask.

The problem comes from observing _Chlamydosaurus_ when behaving naturally, as,
until 1992, all observations on locomotion in this lizard consisted of people
grabbing it by the tail and then seeing how fast it would run when released.
Herpetologists Shine and Lambeck (1992) filmed Frilly lizards with hidden
cameras, and were thus able to observe them naturally for the first time. Some
similar (or the same? I dunno) footage was included on a documentary about
Kakadu - I've seen this (in 1996) but don't have a copy or a citation - and,
sure enough, this shows the animals prancing around on their hind legs,
forelimbs held down against the thorax. They can stand and walk (with an odd,
hoppy gait) bipedally - I've seen it with my own eyes. However, they don't seem
to do it for too long, as they regularly hop onto tree trunks and hang there,
clinging in a vertical posture. It has been suggested that bipedality and trunk-
clinging in this species are correlated.

I see discussions about Komodo monitors have resurfaced. Last time this happened
it went on for ages and Mickey told people to cut it out. After all, monitors
aren't dinosaurs. So I'll be brief.

Komodo monitors (a bit of a misnomer, as Komodo is only a tiny part of their
range) feed on introduced animals, particularly goats and deer. They commonly
attack people (especially kids) and have killed several. BUT - few people seem
to realise, if the monitors subsist on mammals introduced by people, what were
they eating before people came along? There are a few cryptic references here
and there to a population of pygmy stegodonts that also lived on Flores, Komodo
etc. in Pleistocene times - and I think I recall a proper paper in the Athlon
volume honouring L.S. Russell. So this solves the problem - these giant monitors
evolved to eat pygmy elephants! 

Problem: where are these elephants now? As was the case with Pleistocene island
faunas around the world, I always assumed that the invasion of humans in early
Recent times was the cause of pygmy stegodont extinction. But in a 1995 book
called _Nightmares of Nature_ (I forget the author), it is suggested that the
monitors themselves ate the stegodonts into extinction. This kind of thing is
ecologically improbable but, hey, perhaps it's not impossible. After all,
monitors are too cool and perhaps they haven't learnt about resource management.

In a kind of ironic way, it may therefore have been to the monitors advantage
that people invaded these islands and bought mammals from elsewhere with them. 
There are a million and one other fascinating facets to Komodo monitor biology,
behaviour and ecology, but, hey, this is dino-l not herp-l. Whoops, I forgot.

"Nothing was wasted. Only the whale."

"This is the only part of the buffalo we don't use. We don't know what it is."

DARREN NAISH B.Sc.