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Comment to “Primates in the Eocene” by Gingerich (2012)

Authors:
Christopher C Gilbert at City University of New York - Hunter College
Christopher C Gilbert
Stephanie A. Maiolino at Stony Brook University
Stephanie A. Maiolino
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Abstract

In his recent article “Primates in the Eocene”, Gingerich (2012) presented a broad review of Eocene primate radiations and their place in the primate evolutionary tree, with a particular focus on Adapoidea. While synthetic reviews of early primate evolution are always welcome additions to the literature, within his larger analysis Gingerich (2012) specifically discussed two issues that deserve special comment, the first relating to the evolution of grooming claws within Adapoidea and the second relating to his phylogenetic interpretation of Darwinius and Adapoidea within the order Primates, which was supposedly based on a modification of our own final matrix in Maiolino et al. (2012). Unfortunately, as we will demonstrate below, in both cases the interpretations of Gingerich (2012) are unlikely to be correct.First, Gingerich (2012) characterises the morphology of Notharctus pedal distal phalanges as “ambiguous”. In fact, there is very little ambiguity involved. The analyses provided in ...
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... Similarity in time, place, and morphology to the point of confusion is compelling-if not infallible-evidence of a close phylogenetic relationship. And still, in spite of this early linkage, some authors, such as Gilbert and Maiolino (2015), would classify Tarsioidea and Adapoidea in separate suborders, Haplorhini and Strepsirrhini respectively, in the order Primates. Maiolino et al. (2012) described the morphology of pedal distal phalanges in the early Eocene primate Notharctus tenebrosus and concluded that Notharctus had a grooming claw on the second toe, on pedal digit II. ...
... Maiolino et al. (2012) described the morphology of pedal distal phalanges in the early Eocene primate Notharctus tenebrosus and concluded that Notharctus had a grooming claw on the second toe, on pedal digit II. In their comment, Gilbert and Maiolino (2015) claim that pedal distal phalanges bearing grooming claws are readily separated from other 'unguis' forms on the basis of their facet-shaft angle (FSA), and volar feature length (VFL) as a proportion of total phalanx length (TPL). However, FSA and VFL/TPL are related to the positioning of distal phalanges in a grasping foot and by themselves indicate little about phalanx shape. ...
... Discriminant analysis of feet with and without grooming claws, analysed foot by foot rather than phalanx by phalanx, indicated that Notharctus falls in an ambiguous middle ground between primates with grooming claws and primates that lack them. Gilbert and Maiolino (2015) question my recent characterisation of the morphology of pedal distal phalanges in Notharctus as 'ambiguous,' arguing, as they did before , that morphology shows Notharctus to have had a grooming claw on pedal digit II. However, the strongest case for 'ambiguity' in the interpretation of Notharctus grooming claws is provided by Maiolino et al. (2012) in their figure 13 (reproduced here as Fig. 1). ...
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Article
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Article
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