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Why does a tuatara have a row of spines down its back?
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tuatara
The species is the sole living member of the reptile order Rhynchocephalia.
The tuatara possesses a series of broad, scale-derived spines extending down the midline of its back from the nape onto the tail. These spines play a functional role in the animal's social behavior: males erect these spines during courtship to accentuate their body size as they approach and circle a female. Additionally, males may erect the crest on their head and neck as part of a display to defend their territory against other males.1