Friday, February 17, 2012

Notharctus had transitional lemur-like grooming claw

Source Maiolino et al. 2012 PLoS ONE
Recently in PLoS ONE: a study providing evidence that the early Eocene primate Notharctus tenebrosus had a transitional grooming claw on its second digit. Grooming claws are important because they are a classic feature which distinguishes between anthropoid primates (monkeys, apes, and humans) and prosimian primates (primates with a grooming claw: tarsiers, lemurs, lorises, etc). Certain European fossil adapiform primates have controversially been claimed to have a nail, thus linking them with anthropoids. This new study describes a grooming claw on the foot skeleton of a North American adapiform, and its grooming claw is quite nail-like with a wide apical tuft. This might be seen as further evidence supporting a link between adapiforms like Darwinius with anthropoids, except for the fact that a thorough cladistic analysis links adapiforms (including Darwinius) with strepsirrhines (lemurs and lorises). Thus, the authors conclude that there may have been substantial homoplasy in the second pedal digit, with multiple taxa evolving nails.

Thursday, February 16, 2012

Independent team reinterprets Ardipithecus paleoenvironment

Modern day Awash River

Two scientists from the University of New Orleans and Tulane University recently published a reinterpretation (subscription required) of the sedimentary context at the main Ardipithecus site, AramisThis work is based on their own independent geological field work at the site. Results are in agreement with a previous critique (discussed in this post) to the Ardi team's interpretation of the isotopic evidence. These new sedimentological data suggest that Ardi lived in a river-margin forest in an otherwise more open wooded-grassland context. This is in contrast to the interpretations of the Ardi team, which vigorously argued that Ardi lived in a habitat of extensive closed-woodland with true forest patches. 

This new interpretation of the Ardi habitat sounds like a mosaic habitat....which is interesting in light of White and colleagues insistence that characterizations of hominins as preferring mosaic habitats were "unwarranted assertions" based on studying "mixed assemblages" (White et al., 2009:78).