The sclerotic ring : evolutionary trends in squamates

Abstract

The sclerotic ring consists of several bones that form in the sclera of many reptiles. This element has not been well studied in squamates. Squamates are a diverse order of reptiles with a rich fossil record, but debated phylogeny. Squamates are particularly interesting because many species have secondarily lost their sclerotic rings. My research investigates the presence of sclerotic rings in squamates and traces the lineage of these bones across evolutionary time. This research shows that three losses of the sclerotic ring in squamates are supported when considering evolutionary and developmental evidence. Species that lack, or have a reduced, sclerotic ring, are united by their headfirst burrowing lifestyle. Additionally, I have shown that size of the sclerotic ring is related to environment and behaviour. This research will help expand our knowledge of these fascinating bones and will be useful for future phylogenetic analyses.