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

Abstract

Five nominal elements comprise the circumorbital series of bones in gekkotans: prefrontal, postfrontal, postorbital, jugal, and lacrimal. Determination of the homology of two of these, the postfrontal and postorbital, has been particularly problematic. Two conflicting hypothesis exist relating to these: either the postorbital is lost and the postfrontal remains or they fuse during development to form a combined element, the postorbitofrontal. Such a combined element apparently occurs in at least some members of all lizard clades. There is, however, no direct developmental evidence that supports either theory. To overcome that, we investigate the sequence and pattern of ossification in the circumorbital region in a developmental series of the Leopard gecko. We posit that both the postfrontal and postorbital appear during development. Contrary to previous predictions they neither fuses to each other, nor do either degenerate. Instead, the postfrontal shifts anteriorly and fuses with the frontal to become indistinguishable from it by the time of hatching, and the postorbital persists as a robust independent element bounding the frontoparietal suture. These observations accord, in part, with both hypotheses of homology of these elements and result in the recognition of a new pattern, placing in doubt the existence of the composite postorbitofrontal. The phylogenetic implications of these findings may prove to be far reaching if similar and conserved patterns of development are encountered in other clades.

Jaw Adductor Muscles across Lepidosaurs: A Reappraisal

“…These two clades present a reduced jugal bone and only one bone in the posterodorsal edge of the eye socket, termed the postorbitofrontal. For an alternative interpretation of this bone in the Gekkota see Wise and Russell (2010).…”

You Can't Run, but You Can Hide: The Skeleton of the Sand‐Swimmer LizardCalyptommatus leiolepis(Squamata: Gymnophthalmidae)

“…In squamates, usually the bone that participates in the postorbital bar and the upper temporal bar is the postorbital, while the postfrontal usually clasps the frontoparietal suture (Evans, ). Developmental data for gekkotans have shown that in Eublepharis macularius , the postorbitofrontal corresponds only to the postfrontal, but this interpretation is conditioned to an anterior shift of the postorbital to a parafrontal position and its successive fusion with the frontal bone (Wise and Russell, ). In Calyptommatus , the postorbitofrontal is indeed formed by the fusion of a well‐developed postorbital and reduced postfrontal (Roscito and Rodrigues, ).…”

Embryonic skull development in the gecko,Tarentola annularis(Squamata: Gekkota: Phyllodactylidae)

“…They also gave some consideration to dermal skull development in geckos, and this was also examined by Brock (1932: Lygodactylus , Pachydactylus ), El‐Toubi and Kamal, 1961a,b,c: Ptyodactylus ), Rieppel, 1992: Cyrtodactylus ), Wise et al . (2009, Eublepharis ), and Wise and Russell, 2010: circumorbital bones). However, to date, there has been no detailed description of pre‐hatching dermatocranial development in a gekkotan, based on a full embryonic staging series.…”