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Figure 20-2

Figure 20-2. FIGURE 01: One phylogenetic hypothesis of the evolutionary relationships among the Afrotheria. Adapted from Nishihara, H., et al., Mol Biol Evol. 22 (2005): 1823-1833 and Seiffert, E.R., BMC Evol Biol. 7 (2007): 1-13. Macroscelidea. Long, mobile snout

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Figure 20-2

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  1. Figure 20-2

  2. FIGURE 01: One phylogenetic hypothesis of the evolutionary relationships among the Afrotheria Adapted from Nishihara, H., et al., Mol Biol Evol. 22 (2005): 1823-1833 and Seiffert, E.R., BMC Evol Biol. 7 (2007): 1-13.

  3. Macroscelidea • Long, mobile snout • Long, slender legs adapted for running • Large eyes and prominent ears • Complete auditory bulla • Complete zygoma

  4. Family Macroscelididae (elephant-shrews) • Subclass Theria • Infraclass Eutheria • Order Macroscelidea (elephant-shrews) • 4 genera / 19 species (4/16) • Fossils date to Eocene of northern Afri • New species discovered in Tanzania in 2007 • Africa • Some with 3 digits on hind foot • Short fleshy proboscis, large ears and eyes • 1-3/3, 1/1, 4/4, 2/2-3 = 36-42

  5. Macroscelidea Inhabit open plains to tropical forests Largely insectivorous Some species strikingly colored Territorial—may maintain intricate trail system Scent marking and foot drumming Some species use behavioral thermoregulation (basking)

  6. Tenrecidae (tenrecs) • Subclass Theria • Infraclass Eutheria • Order Afrosoricida (tenrecs and golden moles) • 10 genera / 24 species • west-central Africa & Madagascar • P1  absent, M usually 3/3 • one with stridulating organ (Hemicentetes)

  7. Chrysochloridae (golden moles) • Subclass Theria • Infraclass Eutheria • Order Afrosoricida (tenrecs and golden moles) 7 genera / 18 species • southern Africa • 3/3 1/1 3/3 3/3 = 40 • No “W-shaped” ectolophs • 3/3 1/1 3/3 3/3 = 40

  8. Family Orycteropodidae (aardvark) • Subclass Theria • Infraclass Eutheria • Order Tubulidentata (aardvark) • 1 genus / 1 species • African savannahs • Fossils appear in Miocene of southern Europe, Middle East, and Africa • Termite eaters, thick skinned, strong claws • Long protrusible tongue • 0/0 0/0 2-3/2 3/3 = 20-22

  9. Tubulidentata • Skull elongate • Dentary bone long and slender • Adults lack incisors and canines • Cheekteeth are rootless, columnar, and lack enamel • Teeth made of hexagonal prisms of dentine • Tongue is long and protrusible

  10. Tubulidentata • Dismantle termite mounds with powerful forelimbs • Burrow rapidly for protection • Aardvark burrows used as retreats by many other mammals • Also eat fruits of cucurbit plant (Cucumis) or “aardvark cucumber”—may be symbiotic

  11. Tubulidentata • Olfaction well-developed • Fleshy tentacles on nasal septum FIGURE 13: The complex nose of an aardvark (Orycteropus afer) Adapted from Kingdon, J. The Kingdon Field Guide to African Mammals. Princeton University Press, 1997.

  12. Tubulidentata FIGURE 11: An aardvark (Orycteropus afer, Orycteropodidae) Courtesy of A. Taylor

  13. Tubulidentata Adapted from Hatt, R. T., Bull. Amer. Mus. Nat. Hist. 66 (1934): 643-672. FIGURE 12: The skull of the aardvark

  14. FIGURE 01: One phylogenetic hypothesis of the evolutionary relationships among the Afrotheria Adapted from Nishihara, H., et al., Mol Biol Evol. 22 (2005): 1823-1833 and Seiffert, E.R., BMC Evol Biol. 7 (2007): 1-13.

  15. Paenungulata Order Proboscidea—Elephants Order Sirenia—Manatees and sea cows Order Hyracoidea—Hyraxes

  16. Paenungulata FIGURE 01: Two possible phylogenies of the Paenungulata Adapted from Seiffert, E.R., BMC Evol Biol. 7 (2007): 224 and Nishihara, H., et al., Mol Biol Evol. 22 (2005):1823-1833.

  17. Order Proboscidea Elephants • Fossil record begins in Eocene of North Africa • Diverse in late Eocene • Large size • Columnar limbs and graviportal locomotion • Expanded out of Africa in late Oligocene • Reached North America in Miocene

  18. Proboscidea • Major trends in evolution: • Columnar limbs • Enlarged skull and reduced neck • Elongate proboscis or trunk • Incisors become tusk-like • Numerous cross lophs on cheek teeth • Anterior replacement of cheek teeth

  19. FIGURE 02: One family tree of probocideans from the Eocene to the present Adapted from Shoshani, J., Natural History 106 (1997): 36-47.

  20. Family Elephantidae (elephants) • Subclass Theria • Infraclass Eutheria • Order Proboscidea (elephants) • 2 genera / 2 species • Sub-Saharan Africa, India, Nepal, & SE Asia • Tusks from upper incissors • long fleshy proboscis • 3/3 • Mammoths extinct

  21. Family Elephantidae • Feed on trees, shrubs, and grasses • Highly social • Matriarchal kinship groups • Matriarch plus related females and young • Communicate using infrasound over long distances • Audible, tactile, and visual communication at short range

  22. Family Elephantidae • Adult male elephants form bachelor herds or are solitary • Musth—periods of heightened aggression and sexual activity

  23. Family Elephantidae • Largest living land mammals (up to 6,000 kg) • Long, muscular trunk • Large ears (smaller in Elephas) • Digitigrade posture with dense heel pad FIGURE 06: The bone of the right hind foot of Mammut, a late Tertiary and Pleistocene proboscidean Modified from Romer, A.S. Vertebrate Paleontology. University of Chicago Press, 1966.

  24. Elephant Tooth Replacement FIGURE 07A: The occlusal surface of a molar of the Asian elephant (Elephas maximus) Adapted from Kingdon, J. The Kingdon Field Guide to African Mammals. Princeton University Press, 1997.

  25. Family Elephantidae • Skull foreshortened • Skull contains large air sinuses FIGURE 04: The skull of Mammuthus, a Pleistocene elephantid Modified from Romer, A.S. Vertebrate Paleontology. University of Chicago Press, 1966.

  26. Order Sirenia • Dugongs and manatees • Completely aquatic herbivores • 2 genera and 4 species • 5th species, Steller’s sea cow (Hydrodamalis gigas), became extinct in 1768 • Fossils date to early Eocene of Jamaica • Still capable of terrestrial locomotion

  27. Order Sirenia • Weights above 1,500 kilograms • Nearly hairless, thick skin • Nostrils valvular • Thick dentary bone • Middle ear bones are massive • Dense, heavy bones provide ballast

  28. Order Sirenia • Five-toes manus enclosed in flipper • Pelvis vestigial, hind limbs absent • Tail is horizontal fluke • Cheekteeth large, columnar, and covered with cementum (dugongs) or covered with enamel (manatees) • Tooth replacement similar to elephants

  29. Order Sirenia FIGURE T01: Comparison of Characteristics of Two Sirenian Families

  30. Family Dugongidae (dugong & sea cow) • Subclass Theria • Infraclass Eutheria • Order Sirenia (dugongs, manatees, and sea cows) • 1 genus / 2 species • Coasts of E Africa, Asia Phillipines, & Australia • Lack vestigal nails on flippers • Notched flukes • 2/3, 0/1, 3/3, 3/3 = 36 • Up to 3.5 m • Stellar’s Sea Cow lived in Bering Sea

  31. Family Trichechidae (manatees) • Subclass Theria • Infraclass Eutheria • Order Sirenia (dugongs, manatees, and sea cows) • 1 genus / 3 species • Coasts of SE US, West Indies, South America (Orinoco & Amazon) • vestigal nails on flippers • rounded flukes • 6 present at any time, indefinite number • Up to 4 m

  32. Order Sirenia FIGURE 11: The skull of a manatee; length of skull 360 millimeters Adapted from E. Raymond and Kelson Keith Hall. Mammals of North America, Volume 2. John Wiley & Sons Ltd., 1959.

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