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Catarrhines have narrow nostrils that face downwards and have the dental formula:
2.1.2.3
2.1.2.3
giving 32 teeth.
Catarrhines are diurnal and generally much larger than platyrhhines. There are many more terrestrial catarrhines than in the other primate infraorders. They all have flat nails on their digits and members of the Cercopithecoidea superfamily have ischial callosities. The tails of catarrhines are not prehensile and, when present, generally serve as balancing organs.
It's the work of many scientists.
For information, I do not have or pretend to have an exhaustive knowledge of every branch on the descent of life, and have no intention of going back and back and back until you catch me out, not least because I freely admit I'd simply be cutting and pasting off other websites anyway.
The information is widely available (even use Wikipedia if you can't be bothered to find anything more credible) and I seriously beg you go and actually read it rather than implying that my personal ignorance is any reflection on whether evolution is credible. For reference, I'd recommend the same primer I suggested to Sherman: Carl Zimmer's Evolution: The Triumph of an Idea.