_ NICHE, MORPHOLOGY AND LOCOMOTION IN LACERTID LIZARDS 
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Fig. 9 Digits of pes of lacertids in lateral view. a. Ground dweller, 
Lacerta agilis, digit 4. b—d. Climbing species, Lacerta oxycephala, 
digits 3, 4 and 5. e. Climbing species, Lacerta perspicillata showing 
alternative pattern of flexion in digit 5. 
deep and strongly recurved. The prominence on the terminal pha- 
lanx, to which the ventral tendon of the digit is attached, is situated 
well away from the centre of rotation of the claw, conferring 
considerable mechanical advantage (Fig. 17b). The tendon stands 
well away from the articulation when the claw is ventriflected; it also 
_ tends to do the same under the downflexed joint between phalanges 
1 and 2 in digits 3 and 4 (Fig. 17b), and 2 and 3 in digit 5. 
Articulations within the digit except for the most distal one are 
simple, consisting of a single protruberance at the distal end of each 
phalanx that fits into a cup on the adjoining one. These confer 
| substantial mobility in both the vertical and horizontal planes. As in 
ground dwellers, digits 2-4 can curve laterally and swing mesially 
around their base until their proximal phalanges are in line with their 
metatarsals. Unlike those of ground dwellers, the digits themselves 
can bend quite abruptly in a mesial direction, as a result especially of 
flexibility at their penultimate articulations but also, to some extent, 
of that at the articulations between phalanges | and 2 in digits 3 and 
4 and that between 2 and 3 in digit 5. Toe 5 is not only lateromesially 
mobile at its base but also at other joints. 



77 
dorsal tendon 


phalanx 
ventral tendon 
Fig. 10 Diagramatic transverse sections of toe 4 of a. Lacerta agilis and 
b. Lacerta oxycephala, showing differences in relative cross sectional 
area of phalanx and ventral tendon. 
Variations in the direction of kinking in toe 5 of lacertids 
Most climbing lacertids possess a pattern of kinking in toe 5 like that 
found in Lacerta oxycephala and described above (Fig. 9d, called 
here pattern A). However, a minority possess a condition where 
phalanx 2 is directed downwards, 3 upwards and 4 downwards (Fig. 
9e, called here pattern B). Pattern B is found in Lacerta I. laevis, L. 
l. troodica, many L. kulzeri, L. chlorogaster, L. dugesii and L. 
perspicillata, Algyroides, and the Equatorial African group (Fig. 2) 
of the Armatured clade; it occurs in weaker form in Jakydromus and 
Poromera. This variant has consequently evolved perhaps seven 
times and, at least in Equatorial African group, in L. chlorogaster 
and probably elsewhere, seems likely to have had developed in 
ancestors that exhibited pattern A. In spite of pattern B originating 
on several occasions, the details of kinking in toe 5 are often stable 
across quite large and varied clades, for instance the Equatorial 
African group. Interestingly, many of the lacertid taxa showing 
pattern B are known to climb on vegetable structures, such as tree 
boles and flimsy herbage, which might at first sight suggest that it 
confers some performance advantage in these specialised situations 
(but see below) 
Patterns of digital kinking in climbers of other families 
Many other lizards that climb habitually have kinked digits on the 
pes and also often on the manus. Attention will be directed here to 
forms with simple toes, without the complex adhesive pads that 
occur in many geckoes and anoles. As in the digits of lacertids, the 
distal part of toes consists of an upwardly directed arc which may 
contain three phalanges (pattern A) or just two (pattern B). 
These patterns occur in various combinations on digits 3, 4 and 5 of 
the pes and a particular combination for these three toes can be 
specified simply by a three letter code, for instance for lacertids this 
would be most usually B.B.A but sometimes B.B.B. There is also 
some variation in the orientation of the more proximal phalanges of 
toes 3—5 but this will not be discussed further here. Observed patterns 
in the distal parts of toes 3—5 in a range of lizards are given below. 
A.A.A. Petrosaurus mearnsi (Phrynosomatidae); Plica plica# 
(Tropiduridae); Gonocephalus modestus#, Draco blanfordii# 
(Agamidae); Agamura persica, Cyrtodactylus consobrinus# 
(Gekkonidae); Xantusia henshawi, Lepidophyma flavimaculata 
(Xantusiidae); Platysaurus, Pseudocordylus (Cordylidae); Mabuya 
quinquetaeniata (Scincidae). 
A.B.A Tropidurus torquatus (Tropiduridae). 
B.B.A Agama caudospinosa (Agamidae), most lacertids. 
B.B.B. Varanus indicus#, V. mitchelli#, V. tristis# (Varanidae); 
Cryptoblepharus boutoni (Scincidae); several lacertids# . 
B.A.B. Cnemaspis africanus #(Gekkonidae). 
