120 
GEOFFREY J. WITTEN AND A. JOHN COVENTRY 
Pogona species. Badham (1976) reported that 
the venter of P. vitticeps was “rarely patterned 
except in juveniles”. This colour pattern in the 
Big Desert animals is therefore interpreted as a 
neotenic character. 
Sexual dimorphism 
There is little size difference between the sexes 
(Table 1). Males are a little larger than females, 
significantly so in the non-Victorian specimens 
(P = 0.011). Limb and tail lengths are relatively 
greater in males, as noted by Badham (1976), 
and the head of males is relatively wider. 
In Big Desert animals the tympanum alters in 
shape from almost circular in hatchlings to oval 
in adults. This change is much more pronounced 
in females and may be used with reasonable 
reliability to sex adults. This dimorphism is less 
pronounced in other P. vitticeps populations and 
is not apparent in P. barbata. 
DISCUSSION 
The broad head of P. vitticeps is a characteristic 
difference from other species of Pogona (Bad¬ 
ham 1976). and the Big Desert population shares 
this character. In all head measurements, the cal¬ 
culated juvenile figures (X45, Table 2) for the 
Big Desert population are higher than those for 
other populations, but at adult size (XI50, Table 
2) the differences are negligible. This result is 
surprising because allometric coefficients are 
usually more labile than juvenile proportions 
(Witten 1985), and we can think of no adaptive 
explanation for it. It is possibly an artifactual 
result arising from earlier maturation in the Big 
Desert population. 
The differences in scale and pore counts are of 
a magnitude to be expected from different pop¬ 
ulations of a single species. Although some dif¬ 
ferences exist, such as a lower number of scales 
from rostral to interparietal and a higher num¬ 
ber of femoral pores in the Big Desert popula¬ 
tion, these are not great and fall far short of 
reasonable diagnostic characters. 
The taxonomic status of the population from 
the Big Desert should remain unchanged. There 
is no evidence from any character examined 
which would support the erection of a new taxon 
to accommodate the population. Accordingly, it 
should be recognised as a population of P. vitti¬ 
ceps which fails to achieve large size. We have no 
evidence indicating whether the reduced size of 
the species in the Victorian mallee is genetic or 
phenotypic. 
REFERENCES 
Badham, J. A., 1976. The Amphibolurus barbatuss pe- 
cies-group (Lacertilia: Agamidae). Australian 
Journal of Zoology 24: 423-443. 
Witten, G. J., 1985. Relative growth in Australian 
agamid lizards: adaptation and evolution. Aus¬ 
tralian Journal of Zoology 33: 349-362. 
APPENDIX 
Specimens examined 
All specimens are housed in the Museum of Vic¬ 
toria (NMV) or the Australian Museum (AM). 
Big Desert P. vitticeps. NMV: D18220, D52637 
D52690, D52742, D53482, D53827, D53836.' 
D53853, D53907, D53925, D54051, D54070- 
1, D54123, D54131-2, D54144, D54557 
D54749, D54754, D54759-60, D54789-90, 
D55036, D55064, D55251, D55305, D55583 
D56741, D58501. D58548, D58555, D59448, 
D59818. 
Sunset Country P. vitticeps. NMV: D699-700. 
D11753-4, D15379, D15382, D47858, 
D58472, D58477, D60324-5, D60609. 
D60694-5, D60708, D60741, D60760. 
D60762-3, D60768-9, D60778, D60785. 
D60826-8, D60841, D60854. 
Other P. vitticeps. NMV: R4547-8, R13781-2. 
D1123, D3072, D8970, D12164. D14181, 
D41501-2, D52088-9, D58570. AM: R13904- 
5, R15295. R17122-3, R21077, R47319. 
R107398, R107406, R107409-10, R107444. 
(Field tags) 11252, 1 1350, 11358-9. 
P. vitticeps not used in analysis. NMV: R4S55, 
D648, Dill, D787, D970. D103E DI036, 
D7871. 
P. barbata. NMV: D137, D151, D723, D744. 
D896, D966, D1345, D7934, D8038, D14034. 
D14036. D14679, D14699. D48900, D57127. 
AM: R17904, R20987, R21578, R25789, 
R107397, R107399-405, R107407-8. 
R107411-3, (Field tags) 11347-9, 11360. 
