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PROBOSCIDEA and the Subungulate Radiation

PROBOSCIDEA and the Subungulate Radiation. Mammalogy EEOB 625 8 March 2004. The Subungulate Radiation. Orders Proboscidea, Hyracoidea, & Sirenia Descendants of a common ancestor: Condylartha , but does this make them close all that closely related?

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PROBOSCIDEA and the Subungulate Radiation

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  1. PROBOSCIDEAand the Subungulate Radiation Mammalogy EEOB 625 8 March 2004

  2. The Subungulate Radiation • Orders Proboscidea, Hyracoidea, & Sirenia • Descendants of a common ancestor: Condylartha, but does this make them close all that closely related? • Morphology & agreement in cladistic analyses • Hyracoidea as a sister group to Proboscidea & Sirenia, or • Perhaps more closely related to Perissodactyla

  3. Colbert 1955

  4. Similarities among the Subungulates . Character states: ProboscideaHyracoideaSirenia Carpal & tarsal bones x x x Short, hoof-like nails 5/4 or 4/3 4 /3 4/ No clavicle x x x Pectoral mammaries x x x Abdominal testes x x x Horizontal molariform tooth replacement x x x

  5. Range of Body Mass in Mammals • 3 g in Sorex hoyi to 7500 kg in elephants • Most mammals – 10 to 100 g (0.001 – 0.1 kg) • Relatively few (10 orders) > 10 kg • Orders with species > 100 kg? (5-7) • The largest: Bovidae: 1000 kg • Rhinocerotidae: 2000 kg • Hippopotamidae: 4500 kg • Elephantidae: 7500 kg • Advantages & Disadvantages of large body size

  6. Origin & Evolution of Proboscidea I • Subungulate descendants of Condylartha - First fossils in Eocene, Elephantidae Miocene - Moeritherium of Oligocene ‑ pig‑like - Dinotherium & Primelephas (Trilophodon):ancestral? • Morphological trends in divergent forms • Rapid evolution of three genera of “modern” elephants during the Pliocene & Pleistocene • Elephas: greatest in adaptive radiation?

  7. Vaughan ‘00

  8. Elephants from the Oligocene to Pleistocene Mastodons Dinotherium Moeritherium Fig. 143, Colbert ‘55

  9. Recent Radiation of Elephantidae: since the Pliocene Fig. 18.5, Feldhamer

  10. Origin & Evolution of Proboscidea II • Morphological trends in divergent forms - increased body size: graviportal locomotion - shortening of the skull & mandible - upper or lower incisors as tusks - lengthening of legs • Special features of modern elephants - graviportal adaptations of legs & feet - proboscis with hydrostatic muscle, - dental formula: - 1/0, 0/0, 3/3, 3/3 - sequential replacement of cheek teeth

  11. Fig. 18.2, Feldhamer

  12. Diphyodonty: modified for diet and long life 45-60 years Fig. 18.4, Feldhamer

  13. Rapid Evolution of Modern Elephants During the Pleistocene • Similar to the time scale for humans Mastodons & Mammoths of Ohio • Elephant Fossils & Ohio Historical Society • Differences in molars & feeding habits (?) mastodons: with cusps (bunodont) mammoths: lophodont (vertical plates)

  14. Ohio Historical Society

  15. Rapid evolution Pliocene + - similar time scale to humans - elephants in Ohio Dental morphology and feeding habits of mastodons & mammoths: bunodont vs. lophodont Ohio Historical Society

  16. Elephas maximus Loxodonta africana M I forest S C savanna 2 species, 6 subspecies

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