PROBOSCIDEAand the

Subungulate Radiation

MammalogyEEOB 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?

• Morphology & agreement in cladistic analyses

• Hyracoidea as a sister group to Proboscidea & Sirenia, or

• Perhaps more closely related to Perissodactyla

Colbert 1955

.

Character states: Proboscidea Hyracoidea Sirenia

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

Similarities among the Subungulates

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

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?

Vaughan ‘00

Fig. 143, Colbert ‘55

MoeritheriumDinotherium

Mastodons

Elephants from the Oligocene to Pleistocene

Fig. 18.5, Feldhamer

Recent Radiation of Elephantidae: since the Pliocene

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

Fig. 18.2, Feldhamer

Diphyodonty: modified for diet and long life

Fig. 18.4, Feldhamer

45-60 years

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)

Ohio Historical Society

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

Elephas maximus

2 species, 6 subspecies

forest

savanna

I

C

M

S

Loxodonta africana