Griffing Aaron H, Daza Juan D, DeBoer Jonathan C, Bauer Aaron M
Department of Biology, Villanova University, 800 Lancaster Avenue, Villanova, Pennsylvania.
Department of Biological Sciences, Sam Houston State University, 1900 Avenue I, Huntsville, Texas.
Anat Rec (Hoboken). 2018 Apr;301(4):581-606. doi: 10.1002/ar.23749. Epub 2017 Dec 27.
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.
对于研究结构新奇性的进化而言，解析度高的系统发育假说和个体发育数据往往是必要的。球趾虎科包含12个主要为小型化的壁虎属。阿里斯特利趾虎属和沙虎属是例外，其类群的吻肛长度远超其他球趾虎科成员。这两个属拥有神秘的眶上骨化结构——副额骨，在有鳞目其他类群中未见。在它们被发现时，这些结构被认为是进化趋同的结果。尽管其他球趾虎科成员之间的关系尚未明确，但最近的分子和形态学数据支持了阿里斯特利趾虎属和沙虎属之间存在密切关系。我们研究了副额骨的个体发育，以更好地理解球趾虎科体型大小与副额骨存在之间的关系，并评估个体发育数据是否支持阿里斯特利趾虎属和沙虎属副额骨的同源性。我们假设阿里斯特利趾虎属和沙虎属的副额骨是同源的，并且球趾虎科存在一个体型阈值，低于该阈值副额骨不会发育，这就解释了它们在小型化类群中不存在的原因。我们使用透明和染色、射线照相以及骨骼标本，对所有球趾虎科属的副额骨存在情况进行了研究。在阿里斯特利趾虎属的7个物种和沙虎属的6个物种的整个个体发育过程中，测量了副额骨的总表面积。组织学用于研究副额骨在整个个体发育过程中的细胞组成。我们的数据表明，副额骨是从同源的副额骨前体平行进化而来的，并且副额骨发育的开始并不严格依赖于体型阈值。《解剖学记录》，301:581 - 606，2018年。©2017威利期刊公司
