1. PROBOSCIDEA and 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: Proboscidea Hyracoidea Sirenia
Carpal & tarsal bones x x x
Short, hoof-like nails 5/4 or 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: kg
Rhinocerotidae: kg
Hippopotamidae: kg
Elephantidae: 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 2 species, 6 subspecies Loxodonta africana M I forest
savanna C
2 species, 6 subspecies