a201-11f-12-OurRelativesThroughPlatyrrhines - Introduction...

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Introduction to Biological Anthropology: Notes 12 An introduction to our relatives – Strepsirrhines, tarsiers, and platyrrhines Copyright Bruce Owen 2011 - Order: Primates - We looked at the characteristics of primates last time - Mammals descended from earlier vertebrates - at some point, some vertebrates developed lactation, fur, and other features of mammals - all the descendents of those first mammals inherited these traits - since primates are among these descendents, the mammalian traits are ancestral to all primates - these descendents of the first mammals are the clade of mammals - in the Linnaean taxonomic (naming) system, this is the Class Mammalia - At some point, some mammals developed the basic primate characteristics - grasping hands and feet, postorbital bar, etc. - all of the descendents of these first mammals inherited those traits - the basic primate traits are ancestral to all primates - some lineages, like ours, have lost some of these ancestral traits - we lack grasping feet, for example - but even so, grasping feet are the ancestral form of feet for humans - we have a new, derived type of foot that has been modified from the ancestral form to facilitate efficient bipedal walking - the descendents of these first creatures with grasping hands and feet are the clade of the primates - in the Linnaean taxonomic system, this is the Order Primates - Later yet, some of these early primates developed a “dry” nose - with the sensory tissues located inside the head - rather than outside, as in “wet” nose or rhinarium , that you see on a dog or cat - the descendents of the first dry-nosed primates are the haplorrhines , or dry-nosed primates - Boyd and Silk use an older term for most of these: anthropoids - the others continued with the wet noses that they had inherited from the first primates - the descendents of these primates are the strepsirrhines , or wet-nosed primates - Boyd and Silk use an older term for these: prosimians - how do we know that dry noses were the new ( derived ) trait, and wet noses were the original ( ancestral ) trait inherited from earlier mammals? - by looking at outgroups: species that are even more distant relatives than any primates - if we are interested in primates, then dogs and horses are outgroups - both dogs and horses have wet noses (rhinaria) - so the wet nose must have been present in the common ancestor of dogs, horses, and primates - perhaps even the first mammals, ancestors of all mammals - so the wet nose is the ancestral form of nose for mammals - and the dry nose must be a derived trait
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a201-11f-12-OurRelativesThroughPlatyrrhines - Introduction...

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