The Circumorbital Bones of the Gekkota (Reptilia: Squamata)

Abstract

The enormous variation of the orbit in lepidosaurs is better conceptualized in terms of composition and configuration. Broadly, the orbit varies from having totally closed rim to being open posteriorly. Two processes are responsible for changes in the components of the circumorbital series, element loss and fusion. The resulting contacts among elements are the main factors determining orbital configuration. Here, we present a revision of the gekkotan circumorbital bones in the general context of the Lepidosauria. From observations of a sample of 105 species of gekkotans prepared using different techniques, we describe the main changes in the orbit and corroborate the presence or absence of some of the ambiguous elements such as the lacrimal and the jugal. The supraorbital bones of squamates are reviewed and some problems of homology are evaluated using recent phylogenenetic hypothesis. Anat Rec, 293:402-413, 2010. V V C 2009 Wiley-Liss, Inc.

Jaw Adductor Muscles across Lepidosaurs: A Reappraisal

“…Fast and slow optimizations were identical in the molecular Luther (1914), Haas (1973), Gomes (1974), Holliday and Witmer (2007), and Jones et al (2009a). topology, whereas in the morphological topology, the optimization of RAO fluctuated. Although there is not much difference between these two hypotheses in terms of number of steps, we favored a discussion of the results onto a morphological framework (Conrad, 2008), because it is the most updated and comprehensive morphological treatment of the group and facilitates the interpretation of morphological data (Daza and Bauer, 2010). The proposed nomenclature and the equivalent terms used in seven publications dealing with lepidosaurian jaw muscles (Lakjer, 1926;Haas, 1973;Gomes, 1974;Rieppel, 1980a;Zaher, 1994;Herrel et al, 1999a;Jones et al, 2009a) is presented in Table 1.…”

“…6,(8)(9)(10); one of the divisions inserts onto the jugal and the other onto the jaw. Following the nomenclature used in the present work, we propose that these bundles should accordingly be named as A2-SUPj (the j referring to jugalis) and A2-SUPm (the m referring to mandibularis; see also Daza and Bauer, 2010). The orientation, origin, and insertion of the A2-SUPm are essentially similar to those of an undivided A2-SUP.…”

“…In some gekkotans and varanids, there is also a well-developed POT extending between the jugal and postobitofrontal (Fig. 13), which plays a role in the closing of the orbit posteriorly (Mertens, 1942;Daza and Bauer, 2010). In snakes, the A2-SUP corresponds to a composite muscle of two bundles, named as adductor externus superficialis and adductor externus temporalis (Fig.…”

“…6. Postorbital tendon between jugal and postorbital (postorbitofrontal): absent, this contact being bony by abutting of the jugal onto the postorbital (postorbitofrontal) or being totally absent (0); present, a postorbital ligament connects these two elements (1), previously discussed (Mertens, 1942;Daza and Bauer, 2010).…”

“…The A2-SUP is undivided in the majority of squamates but appears entirely or partially divided four lizard clades: Agamidae, Xantusiidae, Gekkota, and Varanidae, the later two having an incomplete eye socket. The development of a partially or complete divided A2-SUP and a POT in Gekkota and the Varanidae could be influenced with the lost of contact between the jugal and the postorbital (Daza and Bauer, 2010). These two clades present a reduced jugal bone and only one bone in the posterodorsal edge of the eye socket, termed the postorbitofrontal.…”