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Biol Lett. 2005 Jun 22;1(2):196-9.

Trilobite spines and beetle horns: sexual selection in the Palaeozoic?

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  • 1School of Biological Sciences, Queen Mary, University of London, London, UK.


Raphiophorid trilobites commonly bore median cephalic protuberances such as spines or bulbs, showing a remarkable variety of form. It is unlikely that their primary function was for protection or in hydrodynamics. A case is made that they were secondary sexual features, by comparison with similar morphological structures developed on rhinoceros beetles and other arthropods. This interpretation is supported by four lines of evidence: their ontogeny, their diversity, the existence of plausible examples of sexual dimorphs in some cases and the fact that they show positive allometry.

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