Peer Review #1 of "Morphometric variation of extant platyrrhine molars: taxonomic implications for fossil platyrrhines (v0.1)" [peer_review]

SB Cooke
2016 unpublished
The phylogenetic position of many fossil platyrrhines with respect to extant ones is not yet clear. Two main hypotheses have been proposed: the layered or successive radiations hypothesis suggests that Patagonian fossils are Middle Miocene stem platyrrhines lacking modern descendants, whereas the long lineage hypothesis argues for an evolutionary continuity of all fossil platyrrhines with the extant ones. Our geometric morphometric analysis of a 15 landmark-based configuration of platyrrhines'
more » ... irst and second lower molars suggest that morphological stasis, may explain the reduced molar shape variation observed. Platyrrhine lower molar shape might be a primitive retention of the ancestral state affected by strong ecological constraints thoughout the radiation the main platyrrhine families. The Patagonian fossil specimens showed two distinct morphological patterns of lower molars, Callicebus -like and Saguinus -like, which might be the precursors of the extant forms, whereas the Middle Miocene specimens, though showing morphological resemblances with the Patagonian fossils, also displayed new, derived molar patternss, Alouatta-like and Pitheciinae -like, thereby suggesting that despite the overall morphological stasis of molars, phenotypic diversification of molar shape was already settled during the Middle Miocene. Manuscript to be reviewed 17 ABSTRACT 18 The phylogenetic position of many fossil platyrrhines with respect to extant ones is not yet 19 clear. Two main hypotheses have been proposed: the layered or successive radiations hypothesis 20 suggests that Patagonian fossils are Middle Miocene stem platyrrhines lacking modern 21 descendants, whereas the long lineage hypothesis argues for an evolutionary continuity of all 22 fossil platyrrhines with the extant ones. Our geometric morphometric analysis of a 15 landmark-23 based configuration of platyrrhines' first and second lower molars suggest that morphological 24 stasis, may explain the reduced molar shape variation observed. Platyrrhine lower molar shape 25 might be a primitive retention of the ancestral state affected by strong ecological constraints 26 thoughout the radiation the main platyrrhine families. The Patagonian fossil specimens showed 27 two distinct morphological patterns of lower molars, Callicebus-like and Saguinus-like, which 28 might be the precursors of the extant forms, whereas the Middle Miocene specimens, though 29 showing morphological resemblances with the Patagonian fossils, also diplayed new, derived 30 molar patternss, Alouatta-like and Pitheciinae-like, thereby suggesting that despite the overall 31 morphological stasis of molars, phenotypic diversification of molar shape was already settled 32 during the Middle Miocene.
doi:10.7287/peerj.1967v0.1/reviews/1 fatcat:5vgrfiaue5gg7emdxf2u2mhwzu