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Dinosaur exaggerated structures not explained by species recognition hypothesis

From: Ben Creisler

A new online paper:

D. W. E. Hone & D. Naish (2013)
The ‘species recognition hypothesis’ does not explain the presence and
evolution of exaggerated structures in non-avialan dinosaurs.
Journal of Zoology (advance online publication)
DOI: 10.1111/jzo.12035

The hypothesis that the exaggerated structures in various non-avialan
dinosaurs (e.g. horns, crests, plates) primarily functioned in species
recognition, allowing individuals of a species to recognize one
another, is critically examined. While multifunctionality for many
such structures is probable given extant analogues, invoking species
recognition as the primary selective mechanism driving the evolution
of such structures is problematic given the lack of evidence for this
in extant species. Furthermore, some of the evidence presented does
not support the hypothesis as claimed or is equivocal or erroneous.
Suggestions that certain evolutionary patterns of diversification in
these exaggerated structures are indicative of a role in species
recognition are unreliable, as both a degree of phylogenetic
directionality and of randomness are seen in extant species where
similar structures function in sexual selection. Claims that an
absence of sexual dimorphism in the exaggerated structures of
non-avialan dinosaurs rule against a role in sexual selection ignores
the possible existence of mutual sexual selection and is also
sometimes limited in view of sample sizes. The suggestion that the
existence of species recognition is supported by the presence of
exaggerated structures in sympatric, closely related relatives is also
erroneous because adorned dinosaur species sometimes exist in the
absence of unadorned relatives. We conclude that species recognition
was not the evolutionary mechanism most likely to be driving the
appearance and persistence of exaggerated structures in non-avialan