[T]he primary difference between the two species is cold tolerance: A. pigra can and does live at higher altitudes than A. palliata, ranging high enough that it must tolerate freezing temperatures
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Larger monkeys with larger, more complex molars, differences in throat anatomy, and greater cold tolerance, in contrast to a smaller, more cosmopolitan species, with the opportunity for gene flow during interglacials. They sound like Neanderhowlers.

Labels: Genetics