Skull anatomy of the miniaturized gecko Sphaerodactylus roosevelti (Squamata: Gekkota)

Abstract

A detailed description of the skull and jaw of the gecko Sphaerodactylus roosevelti is presented. The bones are described articulated and isolated with special consideration given to the type of suture among joining elements. S. roosevelti was compared with 109 gekkotan species to evaluate the osteological variation and to find characters for cladistic analysis. Changes in the skull associated with the miniaturization process are discussed within the sphaerodactylid geckos. A noticeable increase of overlapping sutures was observed in the snout of the smallest sphaerodactylids compared to other gekkotans. This pattern is convergent with that in miniaturized pygopodids and may be attributed to adaptations for decreasing mechanical resistance of the cranium during feeding or burrowing. New cranial characters support Sphaerodactylinae as a monophyletic group and should be useful for resolving questions such as their relationship with other gekkotans.

Development of the Dorsal Circumorbital Bones in the Leopard Gecko (Eublepharis macularius) and Its Bearing on the Homology of These Elements in the Gekkota

“…In the latter case the postfrontal contacts the frontal and parietal and bridges the suture between these bones, and the postorbital contacts the postfrontal but is excluded from contact with the frontal and parietal by the intervening postfrontal (consistent with the condition figured for Elgaria coerulea by Maisano, 2001). Daza and Bauer's (2010) conclusion about the identity of the single element that subtends and spans the frontoparietal suture in the dorsal rim of the orbit was that it is the result of such fusion (Daza and Bauer, 2010), in accordance with an earlier proposal of Daza et al (2008). They identified this putatively combined element as the postorbitofrontal, adopting the most conservative interpretation because it does not necessitate the loss of either element.…”

The Circumorbital Bones of the Gekkota (Reptilia: Squamata)

“…2). Apparently, this fusion also took place in the Gekkota (Daza et al, 2008) where only one bone bounds the orbit posterodorsally (Fig. 1, see below).…”

“…This has been interpreted as a putative synapomorphy of a clade of nonminiaturized sphaerodactylids (Daza et al, 2008). This structure differs from the thickened skin of the upper surface of the head that roofs the orbit and fills the gap between the prefrontal and the postfrontal bones in other lizards (Underwood, 1970).…”

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

“…Considering the assumptions that were made in this study, care should be taken in interpretation of results about the evolution of the cranial kinesis and upper temporal fenestra. Nevertheless, considering that the high level of strain present in the FP models with interdigitated suture, that is, M1a-5a could be reduced with the incorporation of the muscle forces, the cranial movement at the FP joint (see Frazzetta, 1962;Metzger, 2002;Payne et al, 2011) that occurs in geckoes (Herrel et al, 2000;Daza et al, 2008) and varanids (Smith and Hylander, 1985) is unlikely to be present in L. bilineata. In fact, this study suggests that such an active movement can impose an increase in the level of strain in the parietal area and therefore a scarce or null kinetic movement at this junction.…”

“…However, the role and function of sutures in the adult skull has been the subject of debate among functional morphologists and palaeontologists. In fact, in a lot of taxa, many sutures do not fuse after the growth and developmental processes have effectively terminated, and the possible biomechanical roles of these elements during ontogeny and phylogeny are still not fully understood (Frazzetta, 1962;Herring, 1972;De Vree and Gans, 1987;Jaslow, 1990;Thomson, 1995;Herrel et al, 2000;Mao, 2002;Evans, 2003;Rayfield, 2005b;Markey et al, 2006;Daza et al, 2008;Moreno et al, 2008;Hipsley et al, 2009;Jasinoski et al, 2009Jasinoski et al, , 2010Moazen et al, 2009a,b;Wang et al, 2010Wang et al, , 2012Reed et al, 2011;Jones et al, 2011). Micromovement at sutures may potentially lead to a uniform pattern of load distribution across the skull.…”