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Boyer diss 2009 1046..

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CHAPTER 5:<br />

CHARACTER STATE RECONSTRUCTIONS FOR THE ANCESTRAL<br />

PLESIADAPID AND EVALUATION OF THEIR PHYLOGENETIC<br />

IMPLICATIONS<br />

ABSTRACT<br />

New information on plesiadapid crania and postcrania allows for better-supported<br />

interpretations of the morphological characteristics of the common ancestor of the family<br />

Plesiadapidae, as well as better-supported inferences regarding soft anatomical structures.<br />

The implications of this new information for testing hypotheses of euarchontan<br />

(plesiadapiforms, euprimates, scandentians, and dermopterans) phylogenetic relationships<br />

are evaluated cladistically in this chapter in the context of previously published matrices.<br />

Specifically, a new species-level cladistic analysis based on a matrix of 32 dental<br />

characters and 30 taxa was used to reconstruct relationships among plesiadapids. Next,<br />

new information on non-dental osteological characters and soft anatomy was optimized<br />

onto this cladogram, thus providing an hypothesis for character states in the most basal<br />

plesiadapid skull and postcranial skeleton. Finally, the ancestral reconstruction for<br />

Plesiadapidae was used to reassess the phylogenetic position of the group with cladistic<br />

analysis of a published matrix of 20 taxa and 173 characters that samples the cranium,<br />

dentition, and postcranium.<br />

The cranium of the ancestral plesiadapid is reconstructed as having enlarged<br />

premaxillae that broadly contact the frontals; a laterally-positioned, intratympanic,<br />

transpromontorial route for the internal carotid plexus; a non-functional internal carotid<br />

artery; a non-tubular external auditory meatus; and a petrosal bulla. Plesiadapis cookei<br />

and P. tricuspidens appear derived in their tubular external auditory meati and maxillae<br />

lacking extensive dorsal exposure of molar tooth roots. P. tricuspidens is apparently<br />

autapomorphic among plesiadapids in having an increased relative size and posterior<br />

projection of the premaxilla, correlated narrowing of the frontal contact of the nasal, an<br />

increased relative size of the glenoid fossa and decreased prominence and posterior<br />

projection of the nuchal crests. Nannodectes gidleyi is autapomorphic in the increased<br />

relative size of its glenoid fossa, and the apparent lack of an intratympanic route for the<br />

internal carotid plexus. Postcranially, the ancestor of the Plesiadapidae can now be<br />

recognized to have had a humerus with a laterally facing deltopectoral crest, and a lateral<br />

ridge on the ulnar trochlea; an entocuneiform with a large plantodistal process; claws on<br />

all digits; an innominate with a short pubic symphysis; and an axis with a cranially<br />

projecting spinous process.<br />

Analyses of a partition of the revised higher level matrix reveals that new<br />

information on the cranium alone does not support previous hypotheses for the<br />

phylogenetic relationships of some euarchontans. However, analysis of the entire matrix<br />

failed to overturn the previously recovered topology for euarchontan relationships.<br />

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