Jaw Adductor Muscles across Lepidosaurs: A Reappraisal

Abstract

The exact homologies of tetrapod jaw muscles remain unresolved, and this provides a barrier for phylogenetic analysis and tracing character evolution. Here, lepidosaur jaw muscles are surveyed using direct examination of species from 23 families and published descriptions of species from 10 families. A revised nomenclature is applied according to proposed homologies with Latimeria. Among lepidosaurs, variation was found in many aspects of jaw muscle anatomy. The superficial layers mm. levator and retractor anguli oris (LAO and RAO) are present in Sphenodon but not all squamates. The external jaw adductor muscles universally present in lepidosaurs are homologous with the main adductor muscle, A2, of Latimeria and include four layers: superficialis (A2-SUP), medialis (A2-M), profundus (A2-PRO), and posterior (A2-PVM). The A2-SUP appears divided in Agamidae, Gekkota, Xantusiidae, and Varanidae. The A2-M is layered lateromedial in lizards but anteroposterior in snakes. The names pseudotemporalis (PS) and pterygomandibularis (PTM) are recommended for subdivisions of the internal adductors of reptiles and amphibians, because the homology of this muscle with the A3 0 and A3 00 of Latimeria remains inconclusive. The intramandibularis of lepidosaurs and Latimeria (A-x) are homologous. The distribution of six jaw muscle characters was found to plot more parsimoniously on phylogenies based on morphological rather than and molecular data. Character mapping indicates that Squamata presents reduction in the divisions of the A2-M, Scincoidea presents reduction or loss of LAO, and two apomorphic features are found for the Gekkota. Anat Rec, 294:1765Rec, 294: -1782Rec, 294: , 2011. V V C 2011 Wiley-Liss, Inc.Key words: Lizard; jaw muscles; skull; Sphenodon; Squamata

Homology of the Jaw Muscles in Lizards and Snakes—A Solution from a Comparative Gnathostome Approach

“…Both have concluded that this part of the muscle is better regarded as MAME medialis, the muscle that in lizards inserts on the lateral face of the Bodenaponeurose, but Haas () desisted from renaming it in the interest of consistency with other literature. The solution adopted here, MAME superficialis, is consistent with the situation in Sphenodon and lizards (Daza et al, ), turtles (Jones et al, ), crocodilians, and birds (Holliday and Witmer, ) in which a muscle inserts over a broad area on the lateral face of the mandible—this represents the most lateral, caudal end of the folded sheet morphology. In addition, the finding of continuity or near‐continuity of the MAME superficialis and MAME medialis, for example in Antaresia (Fig.…”

An Amphisbaenian Skull from the European Miocene and the Evolution of Mediterranean Worm Lizards

“…There is however some variability in the number of tooth positions among extant amphisbaenians. Thus, a count of nine dentary teeth has been also reported for several species of Amphisbaena , such as Amphisbaena fuliginosa [61], and it is also observable in the Amphisbaena alba figured in the literature [62], [63]. We further report a posteriorly located ninth small tooth in an extant Blanus strauchi dentary from Vic Siirt (Turkey) in the S. Bailon personal collection.…”

Lizards and amphisbaenians (Reptilia, Squamata) from the late Eocene of Sossís (Catalonia, Spain)

“…The main diagnostic character is the presence of nine dentary teeth, rather than a maximum of eight as in other amphisbaenians (Smith, 2009a). However, at least one specimen of Amphisbaena alba from Bolivia also has nine dentary teeth (Figure 11, p. 1774 in Daza et al, 2011), and the original description of Anniealexandria (Smith, 2009a) noted similarities with Amphisbaena.…”