256 
Carpenter 
encounters, erects a large colorful flap of 
skin in the neck region. Directing this frill 
forward toward the adversary, it gapes, rises 
on its front legs, and sometimes lunging 
forward, creates a startling effect (Fig. 1). 
The toad-headed agamid {Phrynocephalus 
mystaceus) , a small agamid of Central Asia, 
erects lateral flaps in the neck region, while 
gaping toward its adversary. The bearded 
dragon (Amphibolurus barbatiLs) of Aus- 
tralia erects and laterally expands a ventral 
beard-like gular flap while gaping (Fig. 2). 
An iguanid with fixed ornamentation 
which enhances its threat posture is Corytho- 
phanes hernandezi of Central America. While 
it threatens with mouth agape, there are 
color changes which result in vivid pattern- 
ing that enhances its “aggressive appear- 
Figure 1. The threat posture of the adult male 
Frilled Lizard {Chlamydosaunis kingi — Agami- 
dae) of Australia. The accessory skin flaps are 
erected, the mouth is gaped as he rises high on 
all four legs and orients toward his adversary. 
He may rise on the hindlegs alone and sway back 
and forth. 
ance.” And at the same time it compresses 
its body, thus increasing its laterally viewed 
size (Fig. 3). Many other lizards will gape 
as a threat, but have no ornamentation to 
enhance this threat. The anguid lizard 
Abronia deppei lowers its head and presents 
the top of its head adorned with large armor- 
like scales to its adversary (Fig. 4). The gila 
Figure 3. The threat posture of the Helmeted 
Lizard (Corythophanes hemandezii — Iguanidae) 
from Mexico. Besides gaping, a very dark pattern 
of black appears on the dewlap, head, and shoulder 
region. 
Figure 2. The threat posture of the Bearded 
Dragon (Amphibolurus barbatus — Agamidae) of 
Australia. The gular area expands forward and 
laterally as the mouth is gaped and he orients 
toward his adversary. 
Figure 4. When threatening, Abronia deppei (An- 
guidae) lowers its head, which is provided dorsally 
with knobbed scales, and moves toward its ad- 
versary with mouth slightly agape. 
