70 
there may have been an increase in male counts. In several ground 
dwellers in dense vegetation, females have on average two more 
presacral vertebrae than males. Included here are the Psammodromus 
hispanicus group, Lacerta agilis, L. derjugini, L. praticola? and 
Adolfus alleni. Number of abdominal vertebrae appears also to be 
influenced by relative clutch mass (Bauwens, Barbadillo & Gonzalez, 
1997). 
Relative tail length 
Because caudal autotomy and partial regeneration are frequent, 
adequate data on the relative length of intact tails in adultlacertids are 
not easy to collect. In most adult lacertids, intact tails vary in length 
from about 1.7 to about 2.7 times the length of the head and body. 
However, they are often over three times as long in many Takydromus, 
Psammodromus algirus, Gastropholis, Philochortus neumanni and 
P. hardeggeri, Latastia longicaudata, Pseuderemias mucronata and 
P. striata. The longest tails occur in Takydromus sauteri, where they 
E.N. ARNOLD 
may be four times as long as the head and body, and in some T. 
sexlineatus, where the tail is five times as long. Tails are particularly 
short, being around 1.4 to 1.6 times the head plus body length, in 
Holaspis, Eremias argus, E. przewalskii, E. quadrifrons, Acantho- 
dactylus tristrami, A. robustus and Mesalina rubropunctata. In 
Meroles anchietae and Eremias arguta the figure falls to about 1. 
Very long and very short tails are both derived conditions within 
the Lacertidae that have arisen several times. Very long tails are 
frequent in forms that climb in vegetation matrixes, such as 
Takydromus, Gastropholis, Psammodromus algirus and perhaps the 
species of Philochortus mentioned. In at least the first two genera, 
the tail is used to maintain position among stems and twigs (Arnold, 
1989b, 1997) and, in general, appears to spread weight in flimsy 
vegetation. This occurs in some Takydromus, such as T. sexlineatus, 
when they run across the top of high grass, a situation where the tail 
may perhaps also contribute thrust through lateral sinusoidal mo- 
tion. In the two main clades of Takydromus (Arnold, 1997) there are 

Fig. 3 Limb proportions of lacertid lizards based on data in Table 1; sexes pooled. Vertical axis: FL/HL — Forelimb span/hindlimb span. Horizontal axis: 
HL/SV — Hindlimb span/snout-vent distance @ — More primitive ground dwellers; O — Ground dwellers of the clade consisting of Philochortus and its 
sister group; e — forms that regularly climb to some extent. Ground dwellers using dense vegetation (upper box), also included is Lacerta andreanszkyi 
which often occurs in the interstices of scree: A. Nucras lalandei, B. Lacerta vivipara, C. Lacerta andreanszkyi, D. Tropidosaura montana, E. Adolfus 
alleni, F. Lacerta agilis, G. Mesalina ercolinii and H. Takydromus amurensis. Ground dwelling forms of generally open situations (lower box): K. 
Psammodromus hispanicus, L. Eremias persica, M. Ichnotropis capensis, N. Philochortus intermedius, P. Latastia longicaudata, Q. Ophisops schluetert, 
R. Pedioplanis lineoocellata, S. Acanthodactylus schmidti, T Acanthodactylus scutellatus, U. Heliobolus lugubris, V. Meroles reticulatus, W. Meroles 
ctenodactylus, X. Meroles anchietae, Y. Pseuderemias mucronata, Z. Mesalina balfouri. Ground dwellers that probably fall between the above two 
situations: I. Nucras boulengeri, J. Mesalina species A, SW Arabia (Arnold, 1986b). Forms known to climb on continuous surfaces and in vegetation 
matrixes; overall, q—u appear to climb least: a. Holaspis guentheri, b. Takydromus septentrionalis, c. Gastropholis vittata, d. Gastropholis echinata, e. 
Lacerta perspicillata, f. Lacerta pater, g. Lacerta oxycephala, h. Lacerta mosorensis, i. Lacerta jayakari, j. Algyroides nigropunctatus, k. Lacerta 
bedriagae, |. Poromera fordi, m. Podarcis hispanica, n. Podarcis muralis, p. Lacerta viridis, q. Podarcis melisellensis, r. Podarcis sicula, s. Lacerta 
laevis, t. Podarcis peloponnesiaca, u. Lacerta trilineata, y. Psammodromus algirus. 
