Primate Origin

More documents

Recommendations

Info

traits. For example, these Miocene primates have the following ape-like features: relatively large body size, thick molar enamel, and no tail. However, Proconsul species retain some monkey-like features, such as certain morphological aspects of their backbone and pelvis. Other ape-like fossils, such as Afropithecus and Kenyapithecus, from the early Miocene also exhibit a variety of ape-like, monkey-like, and unique features. Thus, these early Miocene apes were probably better suited to travelling on top of tree branches rather than hanging or swinging below tree limbs, as seen in extant apes. Nonetheless, these cranial and postcranial features in early Miocene apes provide strong evidence for transitional changes in primate evolution. MIDDLE MIOCENE APES During the middle Miocene (16.0–11.6 MYA), African apes moved across land bridges to colonize Eurasia and eventually parts of eastern Europe and Asia. Furthermore, David Begun (2003) hypothesizes that in the early stages of the middle Miocene epoch some European apes migrated back to Africa. However, these African immigrants did not last long, as most species appear to have gone extinct by about 13 MYA. Some of the best known and most interesting apes from middle Miocene are Dryopithecus from Europe and Sivapithecus from modern-day India and Pakistan. These primates were large, with body mass estimates of 20 to 90 kg. Just as in extant apes, Dryopithecus and Sivapithecus had teeth suited for masticating fruit pulp, shortened snouts, and long, strongly built jaws. A reduced snout represents a derived primate feature reflecting a reduced reliance on olfaction. The cranium of Sivapithecus is very similar to that of extant orangutans, although the postcrania of these two taxa have little in common. Dryopithecus brains were similar in size and proportions to those seen in extant chimpanzees, which are remarkably clever! Morphological interpretations of Dryopithecus and Sivapithecus postcrania reveal strong affinities to the suspensory locomotion utilized by extant apes. In sum, Dryopithecus and Sivapithecus were more ape-like than monkey-like. Figure 5.12 Reconstructed skull from Proconsul africanus. © S. M. Lehman
LATE MIOCENE APES The late Miocene epoch lasted from 11.6 to 5.3 MYA, and experienced a continuous, gradual decline in global temperatures. In many regions of the world, temperate and tropical forests contracted in size due to reduced rainfall and temperatures. Although these changes likely resulted in the extinction of many ape taxa in Europe and parts of Asia, other taxa travelled to or continued to exist in the tropical zones of Africa and Southeast Asia. Consequently, some fossil apes, such as Dryopithecus and Sivapithecus, from the middle Miocene survived into the late Miocene. In addition, paleoanthropologists have recovered remains of some latecomers to the ape lineage, such as Oreopithecus, Ouranopithecus, Lufengpithecus, and Ankarapithecus. Oreopithecus is perhaps the best known of all the Miocene apes due to the abundant fossils discovered in Italy. This ape had the classic catarrhine dental formula of 2.1.2.3., and its dental morphology indicates a folivorous diet, which is a rather remarkable adaptation in the ape lineage. Most extant apes, except for some species of gorilla, are more frugivorous than folivorous. Although the body mass for Oreopithecus is estimated to be approximately 30 kg, which is rather large, this primate had a small brain, which is not an ape-like trait. Examination of the numerous postcranial remains for Oreopithecus indicates suspensory locomotion, just like in modern apes. Ouranopithecus was a large-bodied ape (70–110 kg) from what is modern-day Greece. This ape likely had a diet of hard, gritty foods. Like Sivapithecus, the face of Ouranopithecus is similar to that seen in modern orangutans. No postcranial materials have been recovered. Lufengpithecus was another large ape (50 kg), but from parts of southern China. These apes had extreme sexual dimorphism in their dentition and cranial features, which are similar to those seen in Dryopithecus specimens. You’re probably just about ready to scream if you read about even one more -pithecus; but hold on, we have to consider only one more fascinating ape from the late Miocene. Ankarapithecus was a large-bodied (82 kg) ape from what is modern-day Turkey, and had teeth with very thick enamel and large jaws with which it likely masticated hard or gritty foods. Ankarapithecus retained the primitive trait of a prognathic face, which differs markedly from the flatter, more derived face of Sivapithecus. Now we can turn to the few monkeys known from the Miocene. MIOCENE MONKEYS Although there were plenty of apes running around during the Miocene, this epoch seems to have supported few monkeys. Of the fossil monkeys that have been found, most have been recovered from the early to middle Miocene deposits in Africa and some isolated sites in Eurasia. Very few fossil monkeys have been found from the late Miocene. The reasons for this temporal variation in the fossil monkey assemblage are unknown at this time. What we do know is that the earliest Old World monkeys belong to a unique primate family called the Victoriapithecidae. Victoriapithecids ranged in body mass from 7 to 25 kg. They exhibit an interesting mixture of dental features, being more primitive than those seen in extant Old World monkeys yet more derived than those observed in Oligocene monkeys. For example, victoriapithecids have bilophodont molars with low molar cusps, as in cercopithecines. However, their mandibular morphology differs from that seen in earlier fossil monkeys and extant cercopithecines. Their postcranial morphology provides tantalizing evidence for partial terrestriality, which is not typically associated with the primitive arboreal lifestyle of fossil monkeys. The consensus of many paleoanthropologists is that victoriapithecids represent a mosaic of primitive and derived features indicative of a clade that eventually evolved into colobines and cercopithecines. Prognathic ■ A forward or projecting aspect of anatomy, typically referring to the face.
Page 1 and 2: Primate Origin GOALS By the end of
Page 3 and 4: adult teeth. Teeth are found in the
Page 5 and 6: POSTCRANIAL SKELETON AND LOCOMOTION
Page 7 and 8: properties of foods eaten by primat
Page 9 and 10: animals during a leap. Conversely,
Page 11 and 12: TABLE 5.1 EPOCHS OF THE CENOZOIC ER
Page 13 and 14: Eocene Primates: Are We There Yet?
Page 15 and 16: Formatter: For some reason I can’
Page 17 and 18: size and intersexual size differenc
Page 19: Miocene Primates: Planet of the Ape
Page 23 and 24: Pliocene Primates: Return of the Mo
Page 25 and 26: Figure 5.15 Just because evolutiona

Primate Origin

Create successful ePaper yourself

Delete template?

Save as template?