156 



E.N. ARNOLD 



Fig. 1 Head and skull of Holaspis. a. Head from above; b. Head from 

 side; c. Skull from above; d. Skull from side, fn frontonasal scale, fp 

 frontoparietal suture, pa palpebral bone, pm premaxilla, r rostral scale, 

 io inferior orbital foramen, so supraocular osteoderms, t triangular scale 

 covering area occupied by interparietal and paired frontoparietal scales 

 in most other lacertid lizards. 



a full impression of the extent of the dorsoventral flattening, largely 

 because in fixed material shrinkage of the jaw muscles pulls the 

 kinetic skull into its most retracted position in which the vertical 

 extent is greatest (Arnold 1998a). Also, unlike other lacertids, the 

 whole of the limbs and tail are depressed in Holaspis. 



Head. The parietal area of the head (Fig. la, b) is flat and 

 unarched and the snout is flattened above, being wedge-shaped in 

 lateral view. The rostral shield is large, extending far on to the top of 

 the snout and contacting the frontonasal scale very broadly. The 

 nostrils are placed on the sides of the snout and are set well back 

 from its tip. The area of the top of the head usually occupied by the 

 interparietal and paired frontoparietal scales in other lacertids is 

 covered in Holaspis by a single large triangular scale. The lower 

 eyelid has a 'window' composed of enlarged semi-transparent scales. 

 In H. guentheri these number 1-5 (mean 3.5, n = 15) while in H. 

 laevis there are usually 2-4 (mean 2.3, n = 8) that are sometimes 

 black-edged. The scales on the temporal area vary in size: dorsally 

 and posteriorly they are typically large and polygonal, whereas 

 anteriorly they are much smaller and diagonally elongated, running 

 backwards and downwards from behind the eye in irregular lines 

 that are separated by somewhat expansible hinge regions. 



The low skull (Fig.lc, d) is more delicately constructed and thin- 

 boned than in any other lacertid lizard and the roof of the parietal 

 region is so flexible in alcohol-preserved material that it can easily 

 be deflected downwards. As in other lacertids, comparatively im- 

 mobile sutures in the skull, such as that between the frontal and nasal 

 bones, show a considerable overlap between the elements involved, 

 giving a measure of rigidity in spite of the thinness of the compo- 

 nents. In contrast, the frontoparietal suture, one of the main sites of 



Fig. 2 Scleral ossicles of left eye of lizards, a. Typical lacertid lizard; b. 

 Holaspis; c. Platysaurus (Cordylidae). Ossicles are numbered according 

 to the system of Gugg (1939); see Underwood (1970). 



cranial kinesis, is a relatively simple abutment without the complex 

 interdigitation found at this site in other lacertid lizards. 



The body of the premaxilla is peculiar in forming a broad semicir- 

 cular boss that is convex above and supports the extensive rostral 

 scale. The nasal openings of the skull are situated posterior to this 

 boss and are extremely large. They extend backwards so that the 

 primary nasal cavities are broadly exposed dorsally. Of the bony 

 elements normally roofing the orbits of lacertid lizards, only the 

 palpebral bone is present in its entirety. The usual array of four 

 supraocular osteoderms is greatly reduced; the first being absent and 

 the others only present in adults, where they are limited to a narrow 

 medial fringe. The inferior orbital foramen is very large. Pterygoid 

 teeth are absent. The mandibles are slender and shallow and their 

 retroarticular processes are directed somewhat ventrally. 



Scleral OSSICLES. In the eye, the scleral ossicles are reduced, 

 from the usual lizard number of fourteen that is present in all other 

 lacertids, to twelve. This is by the loss of two out of the sequence 

 made up of ossicles 5 to 9 (Fig. 2b). The twelve ossicles present are 

 so shaped and arranged that the scleral ring is incomplete peripher- 

 ally. Instead of extending from the area of the pupil to the vertical 

 equator of the eye, the ring is strongly emarginated above and below. 

 Dorsally this emargination is produced by the loss of the two 

 ossicles, their neighbours extending across the gap so formed and 

 overlapping only in the pupillar region. The ventral gap in the outer 

 part of the ring is largely a result of the peripheral, radially directed 

 part of ossicle 14 being missing but the peripheral sections of 

 ossicles 1 and 13 are also skewed away from the gap thus increasing 

 its extent. 



BODY. The neck of Holaspis is dorsoventrally flattened, with the 

 skin at the sides forming a prominent sharp-edged flap in many 

 preserved specimens that is also visible in live animals (Fig. 2, 

 Schi0tz, 1960). The flap apparently gains some support from the 

 first branchial and hyoid horns of the hyoid apparatus and its edge is 

 sometimes marked by a longitudinally oval area of somewhat 

 enlarged scales. In other preserved material, in which the pharyngeal 

 cavity is expanded dorsoventrally, the flaps are barely apparent, 

 suggesting that they are homologous with the slight skin folds which 

 occur in this region in many lacertid lizards and which are necessary 

 for pharyngeal enlargement. 



The body is strongly depressed and arched in transverse section, 

 being convex above and flat beneath. Posterior to the sternally 

 connected ribs, the trunk has an elongated oval outline when viewed 

 from above and the lateral edges of the body form distinct ridges. 

 The dorsal integument consists of two very different types of scaling 

 (Fig. 3a). Running along the vertebral region from nape to tail is a 

 band of enlarged, broad plates. These are arranged in two longitudi- 

 nal series, which are slightly staggered relative to each other. Each 

 plate slightly overlaps the one immediately behind it and also, 

 medially, the plate diagonally posterior to it in the other row. The 

 hinge regions between the plates allow flexibility in the vertical 

 plane but do not permit the plates to move much relative to each 

 other in the plane of the integument. 



The lateral areas of the dorsal integument are made up of small 

 granular scales. At the broadest part of the dorsum, there are 30 to 41 

 of these on each side, between the vertebral and ventral plates. These 

 small scales often show a differentiation in arrangement between the 

 anterior and posterior regions of the back. On the neck and shoul- 

 ders, they are non-imbricate and firmly bonded together so that they 

 can only move slightly relative to one and other. Further back they 

 may gradually alter, so that beyond the sternally connected ribs the 

 scales are completely different in character. Here, they are lined up 

 in two directions: they are arranged in rows running steeply 



