Developmental Osteology of the Parafrontal Bones of the Sphaerodactylidae

Abstract

Well-resolved phylogenetic hypotheses and ontogenetic data are often necessary for investigating the evolution of structural novelty. The Sphaerodactylidae comprises 12 genera of predominantly miniaturized geckos. The genera Aristelliger and Teratoscincus are exceptions, with taxa reaching snout-to-vent lengths far exceeding those of other sphaerodactylids. These two genera possess enigmatic, supraorbital ossifications-parafrontal bones-which are encountered nowhere else among squamates. At the time of their discovery, these structures were believed to be the result of evolutionary convergence. Although relationships between other sphaerodactylids remain unresolved, recent molecular and morphological data have supported a close relationship between Aristelliger and Teratoscincus. We investigated the ontogeny of parafrontal bones to better understand relationships between sphaerodactylid body size and the presence of parafrontals, and to evaluate whether ontogenetic data support the homology of parafrontals between Aristelliger and Teratoscincus. We hypothesize that the parafrontals of Aristelliger and Teratoscincus are homologous and that there is a threshold body size in sphaerodactylids below which parafrontals do not develop, thus explaining their absence from the miniaturized taxa. The presence of parafrontals was investigated in all sphaerodactylid genera using cleared-and-stained, radiographed, and skeletonized specimens. Total surface area of parafrontals was measured for seven species of Aristelliger and six species of Teratoscincus throughout their ontogeny. Histology was used to investigate the cellular composition of the parafrontals throughout their ontogeny. Our data suggest that parafrontals have evolved in parallel from a homologous, parafrontal precursor and that the onset of parafrontal development is not strictly dependent on a threshold body size. Anat Rec, 301:581-606, 2018. © 2017 Wiley Periodicals, Inc.

A review of the osteoderms of lizards (Reptilia: Squamata)

“…ODs are rare in gekkotans, but have been reported from a small number of species across two different clades: Gekkonidae and Phyllodactylidae (Schmidt, 1912 a ; Levrat‐Calviac, 1986 ; Levrat‐Calviac & Zylberberg, 1986 ; Vickaryous et al ., 2015 ; Paluh et al ., 2017 ; Scherz et al ., 2017 ; Laver et al ., 2020 ). It is worth noting that small, superficially OD‐like elements have been described for two genera of sphaerodactylid geckos ( Aristelliger and Teratoscincus ) (Bauer & Russell, 1989 ; Griffing et al ., 2018 ). These irregularly shaped elements, known as parafrontal bones, form within a layer of connective tissue above the orbit but deep to the dermis.…”

Conserved ZZ/ZW sex chromosomes in Caribbean croaking geckos (Aristelliger: Sphaerodactylidae)

“…The sphaerodactylid genus Aristelliger , commonly known as croaking geckos, is comprised of nine species distributed in the Caribbean and Central America (Bauer & Russell, 1993; Diaz & Hedges, 2009; Schwartz & Henderson, 1991). This charismatic group diverged from its sister genus Quedenfeldtia approximately 70 million years ago (Gamble, Bauer, et al, 2011) and differs from other New World sphaerodactylids in being nocturnal, arboreal, possessing large basal adhesive toepads, and exhibiting the largest range of body sizes of all sphaerodactylids (Griffing, Daza, DeBoer, & Bauer, 2018; Henderson & Powell, 2009; Schwartz & Henderson, 1991). As previously mentioned, Aristelliger expectatus represents the only sphaerodactylid species with a confirmed ZZ/ZW sex chromosome system (Gamble et al., 2015).…”

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

“…There is no indication of a lachrymal bone, an element absent in most gekkotans (Webb, 1951), but recorded as present in some eublepharids ( Eublepharis macularius, Coleonyx variegatus ) and the gekkonid Pachydactylus bicolor (Daza and Bauer, 2010; Griffing et al . 2017).…”

“…However, it is also possible that the sliver‐like ossification identified by these authors as the postfrontal is a neomorph in the fibrous supraorbital fascia, analogous to the parafrontal bones of some sphaerodactylid gekkotans (Griffing et al . 2017).…”