Head Morphology and Degree of Variation in Lacerta bilineata, Podarcis muralis and Podarcis sicula

Abstract

SUMMARY:The morphology of cephalic scales in Lacertids is organised in well defined geometrical structures. The variation of these elements is related to the underlying bone growth and morphogenesis, but it is also associated with the muscular system and the sutural dynamics. In this paper, the patterns of variation of the cephalic scales have been compared between three common Mediterranean species: Podarcis muralis, Podarcis sicula and Lacerta bilineata. The morphospace generated by the morphological relationships within the cephalic system in these three species is investigated in order to consider their degree of variation and their anatomical peculiarities. Generally, Lacerta is 64% larger than Podarcis, shows a relative reduction of the frontal scale, enlarged fronto-parietal structures, and stretched occipital area. L. bilineata shows the smaller degree of variation within the shape space, while P. muralis shows the highest values. The morphology of the two genera is definitely different mostly because of allometric variation. Non-allometric distinctions between the three species are subtle but detectable. The degree and pattern of variation are interpreted in terms of possible environmental pressures and of functional cranial dynamics associated with the fronto-parietal suture, respectively. In this sense, the structural relationships between bones and scales are of particular interest to further investigate ontogeny and phylogeny in reptiles.

Earliest world record of green lizards (Lacertilia, Lacertidae) from the Lower Miocene of Central Europe

“…3A). Their proportions are approximately 3:2, in some individual cases even nearly 3:1 [see, e.g., in Bruner et al 2005;Bruner & Costantini 2009 (Fig. 7c)].…”

A Sensitivity Analysis to the Role of the Fronto‐Parietal Suture in Lacerta Bilineata: A Preliminary Finite Element Study

“…It is widely considered to have a major evolutionary and ontogenetic role as a structural element during growth and development (Frazzetta, 1962;Smith and Hylander, 1985;Herrel et al, 2000;Metzger, 2002). Shape analyses revealed relevant patterns of morphological variation associated with this suture, related to allometric changes (Bruner and Costantini, 2009). The position of the suture within the spatial framework of cephalic scales is constant, independent of the species and of the allometric changes, suggesting a certain morphogenetic and phylogenetic stability (Costantini et al, 2010).…”

The Relationship Between Cephalic Scales and Bones in Lizards: A Preliminary Microtomographic Survey on Three Lacertid Species

“…Taking into account the specific morphology of the interparietal area in the western green lizard and the possible relationship with the underlying pineal system (Bruner and Costantini, 2009), the dimensions (length and width) of the parietal foramen were measured and compared. The average between the length and width of the foramen was used as index of size.…”

“…Taking into consideration the exploratory and preliminary nature of this survey and the limited number of specimens, correlation between size and shape has been analyzed pooling the data from the three species, most of all to verify whether or not the position of the fronto-parietal suture changes with size. Differences among these three groups are largely based on common allometric variation, although with some minor size-free traits (Bruner and Costantini, 2009).…”

“…Hence, differences between species may be due to species-specific traits more than to allometric variations. Lacerta bilineata probably shows at the same time specific interparietal scale morphology and long pineal extensions (Bruner and Costantini, 2009). On the other hand, according to the present data, it seems that P. muralis may display a different morphology of the parietal foramen when compared with the other two species, having a relatively larger (compared with the head length) and more elongated passage.…”