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Topic 13 – Origins of Order Cetacea

Topic 13 – Origins of Order Cetacea. Cetaceans are Mammals A. Phylogeny of extant lineages. 1998. Topic 13 – Origins of Cetacea. Cetaceans are Mammals B. Shared mammalian characteristics -warm-blooded -breathe air via lungs -live young -mammary glands.

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Topic 13 – Origins of Order Cetacea

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  1. Topic 13 – Origins of Order Cetacea • Cetaceans are Mammals • A. Phylogeny of extant lineages 1998

  2. Topic 13 – Origins of Cetacea • Cetaceans are Mammals • B. Shared mammalian characteristics • -warm-blooded • -breathe air via lungs • -live young • -mammary glands Baby cetaceans swim on side, nurse from nipples concealed in abdominal mammary slits

  3. Topic 13 – Origins of Cetacea • Cetaceans are Mammals • B. Shared mammalian characteristics • -warm-blooded • -breathe air via lungs • -live young • -mammary glands • -hair (snout, chin, behind blow hole)

  4. Topic 13 – Origins of Cetacea They are not fish: e.g., tail (“fluke”) and mobility of cetaceans Fluke of a humpback whale Tail fin of a yellow-taill snapper

  5. Topic 13 – Origins of Cetacea They are not fish: e.g., blowhole sperm whale surfacing sperm whale starts to exhale just below surface

  6. Topic 13 – Origins of Order Cetacea II. The order Cetacea Toothed whales

  7. Topic 13 – Origins of Order Cetacea II. The order Cetacea Baleen whales

  8. Topic 13 – Origins of Order Cetacea Baleen whales Baleen = in two parallel rows of plates from upper jaw = modified epidermis = keratin (stiff, elastic) plus hydroxyapatite (bony mineral) w/ trace Ca, Mn, Cu, B, Fe.

  9. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea Terrestrial >> semi-terrestrial origin among the ungulates 1998

  10. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea A. Terrestrial >> semi-terrestrial origin among the ungulates • Necessary evidence: • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs • Nostril migration 1998

  11. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic 1998

  12. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic (Marine) • cetaceans b. sirenians c. pinnipeds d. otters 1998

  13. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • sirenians • Evolved from protoungulates, related to elephants, aardvarks, etc. • ca. 40 Ma • Dugongs = shallow coastal waters of Indo-Pacific • & Manatees = shallow costal waters & rivers of Caribbean, Amazon, West Africa • Hind legs lost, but foreflippers have remained pliable for maneuvering • Habitat: shallow coastal waters, freshwater rivers 1998

  14. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Pinnipeds (“fin-feet” or “wing-feet”) • Evolved from “bear-like”, carnivore ancestors ca. 30 Ma • Seals, sea lions, and walruses Bull elephant seals, CA, USA 1998

  15. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Pinnipeds (“fin-feet” or “wing-feet”) • Evolved from “bear-like”, carnivore ancestors ca. 30 Ma • Seals, sea lions, and walruses Bull elephant seals, CA, USA 1998

  16. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Pinnipeds (“fin-feet” or “wing-feet”) • Evolved from “bear-like”, carnivore ancestors ca. 30 Ma • Seals, sea lions, and walruses Bull elephant seals, CA, USA 1998

  17. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Pinnipeds (“fin-feet” or “wing-feet”) • Evolved from “bear-like”, carnivore ancestors ca. 30 Ma • Seals, sea lions, and walruses 1998 CA sea lion

  18. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Pinnipeds (“fin-feet” or “wing-feet”) • Evolved from “bear-like”, carnivore ancestors ca. 30 Ma • Seals, sea lions, and walruses Pacific Walrus

  19. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Otters (13 spp.) • Related to badgers, weasels, polecats; evolved ca. 5-7 Ma • Least streamlined of marine mammals. • Hind feet >> flippers, front limbs are those of terrestrial carnivore Pacific sea otter

  20. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> semi-aquatic >> aquatic • Otters (13 spp.) • Related to badgers, weasels, polecats; evolved ca. 5-7 Ma • Least streamlined of marine mammals. • Hind feet >> flippers, front limbs are those of terrestrial carnivore Northern river otter

  21. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic 1998

  22. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea 1998

  23. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea Fossils 1998

  24. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs 1998 Modern cetaceans: vesitigial pelvis & hind limbs: occasional atavisms

  25. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs basilosaurids & dorudontids 1998

  26. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : basilosaurids and dorudontids (ca. 40-30 Ma) Basilosaurus had 2 tiny legs, probably used as claspers when mating. 1998

  27. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : basilosaurids and dorudontids (ca. 40-30 Ma) Durodon, had 2 tiny legs, probably used as claspers when mating. 1998

  28. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : basilosaurids and dorudontids (ca. 40-30 Ma) 1998

  29. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs protocetids 1998

  30. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : protocetids (ca. 45-35 Ma) e.g., Rodhocetus: fore and hind limbs could support body on land; Therefore, likely to have been amphibious. Unclear at present if they had flukes. 1998

  31. Doubled-pulleyed Astragalus of Rodhocetus and Artiocetus (pronghorn in middle)

  32. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : ambulocetids & remingtonocetid (ca. 50-40 Ma) ambulocetids & remingtonocetids 1998

  33. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : ambulocetids & remingtonocetid (ca. 50-40 Ma) 1998

  34. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : ambulocetids & remingtonocetid (ca. 50-40 Ma) 1998

  35. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 4. Hind legs >> no legs : ambulocetids & remingtonocetid (ca. 50-40 Ma) 1998

  36. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs • Nostril migration Nasal drift in cetaceans 1998

  37. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • 5. Nostril migration Nasal drift in cetaceans ambulocetids & remingtonocetids 1998

  38. Topic 13 – Origins of Order Cetacea III. Evolutionary origins of Cetacea • Phylogenetic evidence • Terrestrial >> aquatic • Front limbs >> flippers • Hind legs >> no legs • Nostril migration 1998

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