VENOMOUS & SEPTIC BITES

[darren.naish@port.ac.uk]

Special thanks to Darren Tanke for his highly informative email on 
septic bites in theropods etc. As Darren emphasises, I think we 
should all be careful to distinguish between venomous bites and 
septic bites. Graeme has now kindly provided the source for the 
printed speculation that _Neovenator_ may, perhaps like many other 
theropods, have possessed a septic bite. Therefore, though the 
suggestion was not included in the original paper (Hutt et al. 1996), 
it _has_ been attibuted to one of the authors of this paper. Thus 
Graeme should not have gotten any of the blame.. apologies if it 
seemed that way Graeme.

A concern I have about speculations on the behaviour of animals 
(incl. theropods) with septic bites is that many people are now 
assuming that these animals specifically killed THANKS TO their 
septic bites. Even in _Varanus komodoensis_, the importance of 'death 
by infection' behaviour is controversial and, judging by field 
observations made by Auffenberg and others, certainly not the usual 
method of killing used by the lizards. Raking wounds caused by teeth 
and claws, partial disembowelment, 'hamstringing', and exsanguination 
and concomitant shock all seem more normally employed by Komodo 
monitors, and certainly the effects are more immediate. 

In a related email, Dan Varner, the dean of contemporary mosasaur 
restoration, wrote..

>  My question is about the Gland of Gabe, which I have been told is the poison
> gland in the lower jaw of the varanoid Helodermids like the Gila 
> Monster. Could this have been present in mosasaurs? Could it have 
> been present in archosaurs?

To inject or otherwise conduct venom into the tissues of a bitten 
animal (either prey or an aggressor or perceived threat), animals 
generally need hollowed syringe-like teeth, as in viperid and elapid 
snakes, or teeth with base-to-tip grooves. The absence (to my 
knowledge!) of such modified teeth in mosasaurs strongly indicates 
that they could not / did not conduct venom. However, tooth 
base-to-tip grooves have now been reported in a number of basal 
archosauriform teeth - most notably in _Uatchitodon_ (as described by 
Hans Sues in _JVP_) and strongly indicate a venomous bite in 
these animals. A few more venomous archosauriforms are in press at 
the present time. 

Incidentally, an obscure speculation that _Iguanodon_ may have had a 
poisonous gland at the base of its thumb spike, and hence may have 
injected venom into predators with this weapon (Tweedie 1977) is 
effectively disproven by the absence of any similar structures (viz., 
base-to-tip grooves or hollowed out body with hollow tip) in the 
iguanodont thumb spike.

While on the subject, Tweedie's (1977) book also includes another 
bizarre idea: that, because there were (according to Tweedie) almost
immobile and highly vulnerable to predators when on the ground, 
azhdarchid pterosaurs must have had some form of chemical repellant 
with which to protect themselves. _Quetzalcoatlus_ was therefore 
visualized as a gigantic pterosaurian skunk. The full ref for this 
wonderful book is..

TWEEDIE, MICHAEL 1977. _The World of the Dinosaurs_. Weidenfeld & 
Nicolson (London), pp. 143.

To return to the injection of venom during biting, there is a 
disclaimer in that not all venomous biters do have hollow-tipped or 
groove-bearing teeth. Certain soricids (shrews) (and other 
insectivores*) are now known to possess true venom glands in the 
mouth, but they are only able to transfer the venom to the tissues of 
the prey during violent chewing: they literally have to invade the 
prey's tissues so that venom will be chewn into the wound. The 
evolution of this behaviour might be explained by the fact that some 
of the shrews that practise it the most, notable _Neomys_, the water 
shrews, catch and then immobilize prey that are nearly as large / as 
large as they are, i.e. frogs. 

Bakker's speculations about the presence of venomous bites in 
theropods can be found in..

BAKKER, R.T. 1993. Bakker's Field Guide to Jurassic Park Dinosaurs. 
_Earth_ 2 (5), pp. 33-43.

Writing about the theropod _Procompsognathus_, Bakker says..
 "In Jurassic Park, compys have poisonous saliva, used to 
numb the face, hands and feet of prey. This is plausible: some dino 
descendants (birds) have nerve toxins today, and a narcotizing 
bite has evolved in many other species, such as toads." (Bakker 
1993, p. 33)

This ignores the fact that only ONE bird is known to have nerve 
toxins, and that species with narcotising bites - toads, snakes, 
lizards - all reveal clear dental/osteological features indicating 
that they do. No theropod does.

Also of incidental interest is that fact that in the same article, 
Bakker suggests that, because hadrosaurs appear defenceless in the 
face of tyrannosaurian predators, they quite probably possessed some 
defensive capability we do not yet know of - perhaps they secreted 
noxious chemicals, he suggests. I will not comment on this, but I'm 
almost certain that it inspired the behaviour of a _Parasaurolophus_ 
in a 2000 A.D. comic series. The story was about a girl who lived 
together with a tyrannosaur, a dromaeosaur, a parasaurolophus, and a 
giant dimorphodontid pterosaur. The _Parasaurolophus_ was able to use 
a 'psycho-chamaeleon' skill, and become invisible to predators, 
psychically blending into the surrounding vegetation! 

*The name Insectivora has arguably won out over Lipotyphla.

"If you don't say what you know, no one will know what you know, you 
know"

DARREN NAISH
darren.naish@port.ac.uk