ANT%20151%2006

ANT%20151%2006 - Lecture 6 F o s s il a n d M o d e rn P ro...

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1 Lecture 6 Fossil and Modern Prosimians, Part I Last time – the Paleocene radiation of the plesiadapids and the origin of euprimates With their claws, unrotated eyes, and long snouts, plesiadapiforms hardly made the primate grade, but they may have had some synapomorphies (shared derived traits) with later primates. Now more about the euprimates – primates that make the grade and clade We looked briefly at Altiatlasius from the Paleocene of Morocco. • 10 isolated teeth • Upper molars with broad trigons • Lower molars have low trigonids • and broad talonid basins, a basic mammalian tooth shape It is by the Eocene times that we see some primates that look more like the familiar forms of today. • All of these primates had nails instead of claws, unlike the majority of the plesiadapiforms. • They also had opposable big toes. Plesiadapiform Eocene Prosimian These cute little beasts of the Eocene showed a more modern skull morphology. • Snouts are reduced relative to the plesiadapiforms • Eyes shifted more forward with a post-orbital bar • Brains are becoming larger These Eocene creatures also show a more modern primate molar dention • Talonids and trigonids closer to lying on the same plane • Most have grown spit out their primitive paraconids Fig 2.6
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2 Anterior Dentition • Canine and incisor size is variable, but none of them have the large, ever growing, “gliriform” incisors found in the Plesiadapiformes Plesiadapiformes Gliriform incisor Eocene Primates We know a lot about the Eocene There are lots of thick successions of fossiliforous strata on all continents. And everything is well studied, partly because there are rich fossil beds in London and Paris that have been known for over 100 years. At the beginning of the Eocene (~55 mya), N. America and Europe where connected. This allowed for a flood of immigrant fauna from N. America into Europe. Early Eocene climates were warm, moist and not very seasonal. But by the late- middle Eocene the temperature began to decline rapidly. By 50 mya India and Asia are well into exchanging plants and animals. South America is still connected with Antarctica, but Africa and Australia remain isolated. • In the northern continents there is continued cooling, increased seasonality, and lots of microclimates developing. • Some of these areas become noticeably drier. By ~48 my the land link between Europe and N. America ends. From this point on mammalian fauna become remarkably distinct on these continents. Europe continues to be warm and not very seasonal, but N. America becomes drier and more seasonal in places.
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3 Eocene mammalian radiation! • The first horses
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ANT%20151%2006 - Lecture 6 F o s s il a n d M o d e rn P ro...

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