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Sauropod neck evolution in Journal of Zoology
From: Ben Creisler
M.P. Taylor, D.W.E. Hone, M.J. Wedel, & Darren Naish (2011).
The long necks of sauropods did not evolve primarily through sexual
Journal of Zoology (advance online publication)
It has recently been argued that the elongate necks of sauropod dinosaurs
evolved primarily through selection for their use as sexual and dominance
signals, and not as an adaptation for accessing a large ?feeding envelope?
as traditionally thought. Here we explore this idea and show that all six
arguments that have been advanced in support of the sexual selection
hypothesis are flawed: there is no evidence for sexual dimorphism in the
necks of sauropods; neither is there any evidence that they were used in
dominance displays; long necks provided significant survival benefits in
allowing high browsing and energetically efficient grazing; their fitness
cost was likely less than has been assumed; their positive allometry
through ontogeny is uninformative given that ontogenetic allometry is
common in animals; apparent lack of correlation between neck and leg length
across phylogeny is illusory due to over-representation of mamenchisaurids
in a previously analysed dataset, and in any case is not informative as the
unique morphology of sauropod necks suggests they, rather than legs, may
have been cheaper to elongate when evolving increased vertical reach. In no
speciose, morphologically varied, long-lived tetrapod clade has sexual
selection consistently acted on a single part of the body, and it is
unlikely that Sauropoda is the exception to this. In summary, there is no
convincing evidence that sexual selection was the primary force driving the
evolution of sauropod necks. While a subsidiary role for sexual selection
cannot be discounted, the traditional hypothesis that sauropod necks
evolved primarily due to the feeding benefits that they conferred is, by
comparison, far better supported.
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