Primate Evolution: Exploring Cenozoic Era Mammal Adaptations

ANTH 161 Name___________________________ Human Origins Section _______________________ 1 of 11 Lab 9 Primate Evolution Introduction The Cenozoic Era (65 million years ago) marks the beginning of primate evolution. This is also known as the age of mammals. Two events prompted the adaptive radiation of the mammals: 1. The emergence of Angiosperms (flowering plants) provided a high-caloric food source for warm-blooded animals. Mammals were a minor part of the fauna before the arrival of the angiosperms, but with high-quality food, more and larger warm-blooded animals were possible. 2. The extinction of the dinosaurs opened ecological niches, enabling mammals to proliferate. Previously mammals could only come out at night when cold-blooded reptiles were inactive. Their extinction enabled mammals to be active in the day and night. Primates evolved from generalized, tree-dwelling, nocturnal mammals into a variety of families, genera, and species, most of which are now extinct. Each epoch is characterized by environmental, geological, and skeletal changes that offered primates new opportunities. Mutations provided a selective advantage, which allowed organisms to adapt to new environments. Species with less advantageous adaptations remained in their old ecological niches or died. The Cenozoic Era Fill in the last column for the Paleocene through the Miocene Epoch Dates Primate Event Species Holocene 10 kya - present Pleistocene 2.5 mya – 10 kya Pliocene 5 – 2.5 mya Miocene 23 - 5 mya Oligocene 34-23 mya Eocene 55 - 34 mya Paleocene 65 - 55 mya

ANTH 161 Name___________________________ Human Origins Section _______________________ 2 of 11 Exercise 1: Paleocene Primates - Plesiadapiforms The Paleocene begins with cool, dry global temperatures and the mass extinction of dinosaurs and many other species of plants and animals. Temperatures rose during the Paleocene and by the end it was extremely warm, with dense rainforests and ice-free poles. The Plesiadapis (Plesi = close to; adapis = lemur-like) was the first primate-like mammal that appeared in the Paleocene. Plesiadapis was a very successful and diverse mammal with over 140 named species in 11 different families found in North America, Europe and Asia. Two fossils from Menat, France had the preserved outlines of skin and hair. This is how we know that Plesiadapis had a bushy tail. Plesiadapis

ANTH 161 Name___________________________ Human Origins Section _______________________ 3 of 11 Compare the illustration of a Plesiadapis with the skull of a modern prosimian. Feature Plesiadapis Prosimian (Slow Loris) Post-orbital bar or closure ( bar | closure | neither ) Position of eye orbits ( side | forward ) Brain-case size relative to snout length ( small | large ) Incisor size relative to canines and molars ( small | large ) Prognathism: length of snout relative to cranium ( more | less ) Why do some researchers consider plesiadapiforms to be members of the primate order? HINT: To answer these questions you will need to look at the laminated info sheets). ________________________________________________________________________________ ________________________________________________________________________________ Which of the plesiadapiform’s features are unlike those of primates? ________________________________________________________________________________ ________________________________________________________________________________

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ANTH 161 Name___________________________ Human Origins Section _______________________ 4 of 11 Exercise 2: Eocene Primates: Adapids and Omomyids The Eocene began with very warm global temperatures. Forests and wetlands covered the planet with tropical plants appearing even at the poles. Half way through the Eocene the climate changed dramatically, with many places experiencing seasonal variations in climate. Deciduous trees proliferated. By the end of the Eocene, the global climate was very cold at the poles where the Antarctic polar cap formed. Many new species of mammals appeared in the Eocene including hoofed animals. Eocene animals of all sorts were very small, and the largest weighed no more than 20 lbs. Adapids are members of the family Adapidae. They are ancestral to the strepsirrhines . Members of the family Omomyidae (the Omomyids) are considered to be quite similar to the Tarsier, and therefore likely ancestors to the haplorrhines . Adapis Skull Fun Fact: George Cuvier , a Catastrophist , named this genus. He originally thought the disjointed remains were of an elephant. Adapis was a non-scientific name for the Hyrax - a furry animal that look like a guinea pig, but is more closely related to elephants and manatees. They are found in Africa and Southwest Asia.

ANTH 161 Name___________________________ Human Origins Section _______________________ 5 of 11 Omomyid Skull and Rendering What Adapis might have looked like Eocene clues: deciduous trees, lots of foliage Omomyids: Necrolemur, Pseudoloris and Microchoerus Note the easy to remember Eocene primate names: Necrolemur = Dead Lemur Pseudoloris = Fake Loris

ANTH 161 Name___________________________ Human Origins Section _______________________ 6 of 11 Compare the fossil and living forms listed below, using the skeletons and illustrations provided ( Adapis [picture], Ringtailed lemur [cast], Omomyid [cast and illustration], Tarsier [cast]). Feature Adapis Lemur Omomyid Tarsier Post-orbital bar or closure ( bar | closure ) Position of orbits ( front | side ) Prognathism ( small | medium ) Braincase size relative to snout length ( small | large ) Size of anterior vs posterior dentition ( larger to smaller | smaller to larger ) Questions : 1) Look at the relative size of the tarsier’s orbits, the monkey ’s and the lemur ’s (see other stations). What can we tell about their activity patterns (diurnal vs nocturnal) from fossilized remains? ________________________________________________________________________________ 2) Adapids are thought to be ancestral to what modern forms? ______________________________ 3) Omomyids are thought to be ancestral to what modern forms? ____________________________

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ANTH 161 Name___________________________ Human Origins Section _______________________ 7 of 11 Exercise 3: Oligocene Primates – Age of the Monkeys The Oligocene was a time of transition during which ecosystems started to adopt their modern appearance. Continental drift permitted ocean currents to circulate differently, changing global climates and climatic zones. Grasslands expanded, temperate deciduous forests expanded in the northern and southern hemispheres, palms and other tropical species retreated closer to the equator and polar ice caps increased, lowering sea levels. Fayum, Egypt carries our best evidence for Oligocene primates and the evolution of Anthropoids. In Oligocene times the region was warm, wet and seasonal with abundant forest vegetation, wetlands lakes and streams. Apidium is a small arboreal quadruped similar to a squirrel monkey that appeared around 36 mya. Some researchers believe an animal like it may be ancestral to both platyrrhines and catarrhines. Aegyptopithecus appeared 33 mya. It was a medium-sized monkey, perhaps as big as a female howler monkey (13.2 lbs). It was likely a diurnal, arboreal quadruped. Aegyptopithecus was likely an early catarrhine and may be ancestral to both Old World monkeys and hominoids. Aegyptopithecus (easy to remember Oligocene Primate name: Egypt = Fayum) Apidium Fun Fact : Was named for the Egyptian bull god, Apis because early researchers thought it was a tiny cow

ANTH 161 Name___________________________ Human Origins Section _______________________ 8 of 11 Feature Apidium New World Monkey Aegyptopithecus Old World Monkey Chimpanzee Post-orbital closure ( present | absent ) Dental Formula Molar cusp Pattern ( bilophodont | Y5 ) Questions: What features were similar between Apidium and a New World Monkey? ________________________________________________________________________________ ________________________________________________________________________________ What features were similar between Aegyptopithecus and an Old World Monkey? ________________________________________________________________________ ________________________________________________________________________________ What emphasis did Aegyptopithecus place on vision? Why? ___________________________________________________________________________ ________________________________________________________________________________ How is Aegyptopithecus anthropoid-like?________________________________________________ How is Aegyptopithecus prosimian-like? _________________________________________________ Should Aegyptopithecus should be classified as an anthropoid? If so, as a catarrhine or platyrrhine? ________________________________________________________________________________ ________________________________________________________________________________ Molar cusp patterns The cusps are the high points on your molars. The dots indicate the cusps Top: Bilophodont = 4 cusps in two parallel lines Bottom: Y5 = 5 cusps arranged such that the low points make a “Y” shape

ANTH 161 Name___________________________ Human Origins Section _______________________ 9 of 11 A note about teeth, teeth and well…teeth: Molar cusp patterns differ between primate species. For example, the bilophodont molar pattern has four cusps while the Y-5 molar has five cusps. The Y-5 cusp pattern appears like a “Y” and the bilophodont has cusps in two parallel lines. Why is this relevant to primate evolution? This difference shows a branching off-point that further distinguishes primates. Refer back to your human skeleton and primate taxonomy labs. Notice how the cranium as a whole affects each individual element. The teeth respond to the size of the mandible, the maxilla, the temporal bone, and the sagittal keel or crest. These are all examples of selective adaptations in response to the environment. Each primate throughout the Cenozoic has an adaptation based on the shared, evolved ancestral condition, that determined the success of their survival. Consider : What is the relationship between the cranium, post-cranium, and locomotion? Why does this matter for primate evolution? Keep this in mind for your upcoming labs. These are examples of dental arcades that you might see. You only need to know three general patterns : Rectangle (R), Arch (A), and Parabola (P) (left to right).

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ANTH 161 Name___________________________ Human Origins Section _______________________ 10 of 11 Exercise 4: Miocene Primates: Planet of the Apes The Miocene (23 – 5 mya) was overall warmer and wetter than our present global climate, but temperatures declined throughout the epoch. Africa’s collision with Eurasia enabled the spread of plants and animals. Tropical forests formed a continuous belt, allowing the newly evolved Ape species to proliferate and diversify. During the Miocene there were nearly 30 genera and over 100 species of apes, varying in size, diet and anatomy. Miocene apes have both ape and monkey characteristics, making relationships between fossil species and modern primates difficult to sort out. Proconsul is a well-known genus from the early-middle Miocene (20 – 18 mya) in East Africa. Like the apes it has no tail, but unlike apes its fore and hind limbs are the same length and its shoulder and arm are not adapted for suspension. Morotopithecus, which existed at roughly the same time and place, and had much longer forelimbs that were adapted for suspension and vertical climbing. Proconsul Morotopithecus Feature Proconsul Morotopithecus Chimpanzee Gorilla Old World Monkey Shape of Dental Arcade (Draw) HINT: Refer to page 9 Molar Cusp Pattern (bilophodont | Y5) Questions: Whose molars are relatively larger? What does this imply about diet? ________________________________________________________________________________ What does canine size imply in males? ________________________________________________________________________________ ________________________________________________________________________________

ANTH 161 Name___________________________ Human Origins Section _______________________ 11 of 11 Exercise 5: Miocene Primates – The Later Hominoids Sivapithecus (12.5 – 8.5 mya) is another genus from the Miocene, found in India, Pakistan and Nepal. Sivapithecus shares a number of traits with the modern Orangutan ( Pongo pygmaeus ). The lineage that became Orangutans split from the other Miocene hominoids first. Sivapthecus’ skull looks similar to Orangutans, but aspects of the post-cranial (below the skull) skeleton suggest that it was more terrestrial than modern Orangutans. Feature OWM Human Sivapithecus Orangutan Gorilla Canine Size ( S | M | L | XL ) Temporal Fossa shallow | med | deep | N/A) Supraorbital Tori ( S | M | L ) Questions: Based on what we know about primate teeth, what might Proconsul’s diet have been like? Also, what do the size of Proconsul’s canines suggest about its social structure? ________________________________________________________________________________ ________________________________________________________________________________ What are general trends that separate monkey-like ancestors, monkeys, ape-like ancestors, and apes from one another? What are some features that stay the same? Write a minimum of three sentences. ________________________________________________________________________________ ________________________________________________________________________________ Reconstructed Skull of Sivapithecus

Kami Export - Lab 9. Primate Evolution

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