Review Questions
1. The goal of this question is not to have you memorize details about micro- and megabats but to get comfortable with thinking about alternative cladogram hypotheses. Cowen presents one possible cladogram depicting a clade, (dermopterans + plesiadapids), as sister taxon to primates (Fig. 21.3, p. 338), and these together form a clade that is sister taxon with "bats." Bats can be separated into two clearly different subgroups, "microbats," the ones that echo-locate, plus "megabats," including fruit bats, which locate food visually with stereoscopic color vision that is similar to that of primates. Some recent studies based on DNA sequence comparisons have favored "bat monophyly," with micro- and megabats as sister taxa, and with a primates+dermopterans clade more distantly related. This supports the view in Fig. 21.3. An alternative view is that bats are paraphyletic, with megabats more closely related to the primates + (dermopterans + plesiadapids) clade, than they are to microbats. Draw these two competing cladograms (you can ignore pleiadapids if you wish), and explain the implications of each view for explaining the presence of stereoscopic color vision in megabats and primates, but not in microbats. Can the "bat monophyly" cladogram be the most parsimonious one once all evidence is considered? How might this visual similarity be explained otherwise instead of as due to common ancestry? Why are similarities in the visual systems of cats and owls relevant to this question?
2. The primates referred to as "prosomians" include lemurs, lorises, and tarsiers. But recent analyses have supported tarsiers as the sister taxon of anthropoids ("monkeys" and apes) and thus the prosimian grouping as paraphyletic (i.e., including the ancestry of primates and all descendants except anthropoids. Give three other examples of paraphyletic vertebrate groups that have been abandoned. Recent biologists have generally converted to classifications that are cladistic (i.e., they only recognize monophyletic groupings, or clades, that are thought to include an ancestor and all of its descendants).
3. What is the likely habitat and ecology of early primates? (See image at top of HOL Ch. 21 Web site.) What are features common to primates? What are features common to anthropoid primates? What evolutionary novelties do New World primates have compared to Old World primates? According to the cladogram in Fig. 21.9, why is the anthropoid grouping "monkeys" thought to be paraphyletic?
4. What are hominoids? What evolutionary novelties are shared by hominoids? What are hominids? Why are "panids" considered to be paraphyletic?
5. Give an example of an extinct sivapithecid that lived only 300,000 years before present. Sivapithecids used to be considered as early hominids (based on jaw structure, as covered in lecture), but have more recently been considered more closely related to what living hominoid?
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