Subungulates Proboscidea elephants Hyracoidea hyraxes Sirenia dugongs and manatees Ungulates Perrisodactyla odd toed ungulates horses, tapirs, and rhinos Artiodactyla even toed ungulates Ungulata
Subungulates • This seems to be an odd grouping of organisms. However, it is not by accident, and does not represent another ‘garbage’ group. • Proboscideans, Hyraxes, and Sirenians are all derived from Condylarthrans, that evolved in the Paleocene about 65mya.
Subungulates • The Paenungulata was one group within the Condylarthra, and by the Eocene of Africa, they gave rise to the Proboscidea, Sirenia, and Hyracoidea. • If that is the case, you would expect some morphological similarities between the groups.
Subungualta • They all lack clavicles. • They all have short nails on their digits. • Females have 2 pectoral mammae (Hyraxes have 2 inguinal pairs as well). • All females have a bicornuate uterus. • All males have abdominal testes and have no baculum. • All are non-ruminating, hind gut fermenting, herbivores. • All have a cecum. • Elephants and Sirenia have horizontal molariform tooth replacement.
Subungulata • Proboscideans and Sirenians were much more diverse during the Oligocene and Miocene. • Their future does not look promising.
Proboscidea • There is but 1 family (Elephantidae) and 2 species: African elephant - Loxodonta africana, and Asian elephant - Elaphas maximus. • African elephants are much larger than Indian (Asian) elephants. The teeth differ, Africans have higher shoulders, larger ears, and a more complex trunk.
Proboscidea • Reproduction is not easy • Females are sexually mature by 9 to 12 years, with peak reproductive value between 25 and 45 years. Gestation is 22 months, but estrus lasts only 2 to 4 days, with about 4 years between estrus events. • Copulation is no simple deal either. • There is sexual dimorphism, and young small males generally do not reproduce.
Proboscideans • Size of the males tusks seems to be an important character for reproduction. African elephant females look for a minimum tusk length, and will not mate with ‘short’ males even if no ‘long’ males are available. This has some implications for the ivory industry.
Proboscideans • African elephant males weigh up to 7500kg, while Indian elephants weigh about 4500kg. • They exhibit indeterminant growth. • They have graviportal limbs, and are capable of one gait only.
Proboscideans • Feldhammer claims that large size in elephants is a consequence of ‘competition’ with other herbivores. • Is this the most parsimonious explanation? • Does it reduce the importance of predation? • What about the cost of transport? • What does large size mean for an endotherm?
Proboscideans • Elephants are inefficient herbivores, and require large home ranges. They are usually found in groups. Thus, as they move long distances each day, they are capable of significant habitat modification. • Consider what it means to be so large. How is it possible that 50% of what passes through the gut of an elephant is undigested?
Proboscideans • The trunk of elephants is actually part of the upper lip and the nostrils. • It is prehensile, and is essential since the animal can not reach the ground with its mouth. • It is used to manipulate food, suck up water (and then spray water into the mouth), and suck up dust and mud as well.
Proboscideans • Dental formula is 1/0, 0/0, 3/3, 3/3 = 28. • Tusks are dentine (with only the tip covered in enamel). • Tooth replacement is horizontal, they are worn and replaced from the rear. Note: although they have 6 molariform teeth in each jaw, only one is functional at any time.
Proboscideans • Elephants were once much more diverse than they are today. • In the Pleistocene they were in Europe and North America. In fact, until just recently, there were 2 species in N. America at the same time, mastadons (Mammut americanus), and Mammoths.
Proboscideans • Oldest fossils are from the Eocene of Africa • We have fossil evidence from Asia, Europe, Africa, and N. America. • Moeritheriids were relatively small (1m) in Africa during the Eocene and Oligocene, while Deinotheriids were in Asia and Europe from the Miocene to the Pliocene.
Proboscideans • The Deinotheriids had weird tusks, based on the lower incisors rather than upper. • Gomphotheriidae were contemporaries, and had tusks in upper and lower jaws. • Mammutidae were the mastodons from the early Miocene. • Stegodontidae were from the mid-Miocene.
Proboscideans • Only the Elephantidae persist today. • The genus Primelephas from the late Miocene/early Pliocene is probably ancestral to modern elephants as well as the Wooly Mammoths.
Hyracoidea • There are 5 species of rock hyraxes, and 3 species of bush hyraxes, all inhabiting rocky habitats in Africa and the middle east. • Were first thought to be rodents, but are clearly subungulates. • They are not ruminants, but have a large cecum as well as a smaller paired cecum.
Hyraxes • Have a mid-dorsal gland surrounded by light hair. • They have unique pads on the feet, which function as suction cups on rocky surfaces. Glands on the feet provide moisture for ‘suction’ • Toes have hoof-like nails (except 2nd on rear, which has a grooming claw).
Hyraxes • They have no canines, and have a diastemma, hence the early confusion with rodents. • Upper incisors are pointed and triangular with no enamel on posterior. • Unlike elephants and sirenians, dentition is not replaced horizontally.
Modern Hyrax vs. Megalohyrax from the Oligocene. Note the diastemma in the modern form.
Hyraxes • Fossils are known from the Eocene of Europe and Africa. • There is always the speculations that the diversity of Hyraxes suffered as a consequence of competition with ungulates. More about this later.
Sirenians • These are the dugongs and manatees. • 2 families: monotypic Dugongidae from western Pacific, and Trichechidae (3 species) form the Atlantic. • Essentially tropical, feeding on aquatic vegetation. • Poor thermoregulatory abilities and low metabolic rates - hence warm waters.
Sirenian Morphology • Large fusiform bodies - valvular nostrils, no pinnae, horizontal tail, no external hind-limbs, and flipper-like fore-limbs. • Dense bone to facilitate negative bouyancy. • Lungs run nearly length of body to even out bouyant forces. • Teeth replaced horizontally.