Ungulata Subungulates –Proboscidea elephants –Hyracoidea hyraxes –Sirenia dugongs and manatees Ungulates –Perrisodactyla odd toed ungulates horses, tapirs, and rhinos –Artiodactyla even toed ungulates
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.
A) Moeritherium, B) Deinotherium, C) Gomphotherium, D) Wooly
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.
Stellar’s Sea Cow (Extinct), Manatee, and Dugong
Sirenian Fossil History There were once at least 20 genera of Sirenians. There are Eocene sirenians from india, Europe, and N. America (Protosiren). Eocene sirenians are unique in that thay have a fifth premolar.
Dugong vs Manatee: Deflected rostrum in Dugong is ‘adaptation’ to bottom feeding.
Perissodactyla and Artiodactyla Both forms of modern ungulates are digitigrade. Teeth are usually hypsodont. Limbs operate in a single plane, and are designed for cursorial locomotion. Calcaneum usually does not articulate with the fibula.
A) Tapir B) Rhino C) Horse D) Pig E) Deer F) Camel G) Pronghorn Calcaneum is shaded and articulates w/ Astragalus (H)
Perissodactyla Horses, Tapirs, and Rhinos. Odd toed ungulates, with the 3rd digit bearing most of the weight (Mesaxonic). Teeth are usually hypsodont and lophodont. Horses and tapirs have upper incisors, rhinos generally do not. Stomach is simple, but they have a cecum. Gut retention times are half that of ruminating artiodactyls. Thus, only about 70% as efficient.
Perissodactyla: Fossil History The Condylarthra are ancestral to the Perissodactyla, as well as the Artiodactyla, Proboscidea, Sirenia, and Cetaceans. It is not necessarily true that the Perissodactyla and Artiodactyla are monophyletic. Based on 67 hard and soft morphological characters, we can propose the following:
Ungulate Evolution Note the implications: –Closest relatives of the perissodactyls are the cetaceans. –Mammals invaded wate completely at least twice independently (Cetceans and Sirens). –Note the close relationship between hyraxes, elephants, and sirenians.
Perissodactyl Evoltuion Originally 14 families at their peak in the Eocene. By the end of the Oligocene there were only 4 families. They were the dominant ‘medium to large’ herbivores of the Tertiary. Both the Brontotheres and Chalicotheres went extinct.
Chalico- there: went extinct in the Pleistocene Note the fore-limb dominance.
Tapirs Origin and early differentiation in the Paleocene Heptodon is one of the earliest, and comes from the Eocene of Wyoming. Modern Tapirus is remarkably similar to Heptodon, but bigger. Both have 4 toes in front and 3 in rear, both have ulna and fibula complete and unfused.
Tapirs Both Heptodon and Taprius have complete dentition w/ a small diastemma; upper canine is reduced and lateral incisor is caniniform. Upper molars have 3 lophs, the lower molear have 2 transverse lophs (as in Rhinos)
Tapirs This similarity in structure is one of the reasons why tapirs and rhinos are generally considered to share a common ancestor. The cladogram for Perissodactyla lumps tapirs and rhinos, with horses as the outlying sister group.
Tapirs Tapirs persist in S. America and Central America, and in Southeast Asia. Can you explain this distribution? Hyrachyus (Family Hyrachyidae) may be transitional between tapirs and rhinos. It was abundant in the eocene of n. America and Europe. Hyracodontids and Amynodontids were abundant in the Eocene and oligocene of N. America and Asia.
Hyracodontids About 12 genera Moderate size Slender limbs like horses w/ light builds. Cursorial incisors were spatulate (primitive) and equal sized. Canines were moderate size.
Hyracodontids In the Oligocene, from Hyracodont lineage, came a series of gigantic hornless rhinos in the subfamily Indricotherinae Indricotherinae ranged from central Asia to China. Indricotherium was the largest land mammal to ever live.
Hyracodontids Indricotherium was 5.4m tall at the shoulders, had a long neck and a skull which was 1.3m long. Could reach vegetation 8m above the ground. Had a probable weight of 30 tons, 4.5 times greater than Loxodonta, and about twice as great as the largest Mammoth.
Amynodontids About 10 genera Large heavy bodies Short stocky limbs Short faces Prominent canine tusks. The bulk of the Amynodontid radiation was over by the close of the Oligocene.
Rhinocerotidae Hyracodontids during the Oligocene obtained a unique dental variation: chisel like I 1 and tusk like I 2. This formed the basis of a 2 nd radiation… the Rhinocerotidae.
Rhinocerotidae About 50 genera N. America, Eurasia, and Africa from the Miocene to Pleistocene. Rhinocerotids included wooly rhinos and rhinos w/ horns (Elasmotherium) as long as 2m. Wooly rhinos show up as cave paintings by palaeolithic man.
Rhinocerotidae Elasmotherium’s horn was not nasal like most, but originated on the forehead. It had no incisors. Today, rhinos occur only in India, Java, Sumatra, and Africa.
Chalicotheres From the Eocene on in N. America, Eurasia, and Africa. Simple premolars and bunolophodont molars. Probably a bipedal browser. Had long forearms and hooked claws - very un-ungulate like.
Chalico- there: went extinct in the Pleistocene Note the fore-limb dominance.
Titanotheres (=Brontotheres) From the early Eocene to early Oligocene of N. America and eastern Asia. Medium to very large size. Probably succeeded in Asia by Indricothere Rhinos. Had graviportal limbs and nasal horns which were probably covered by skin.
Horses Evolution of horses has been used as best example of gradualism. Over 55 million years, the progression from Eohippus to Equus has involved: –Increase in size from small lamb size to present size. –Reduction of toes from 3 to 1. –Increased complexity of enamel pattern on molars.
Horses Eohippus (= Hyracotherium) Eocene of N. America, W. Europe, and E. Asia. 4 toes fromt, 3 rear. Horses died out (Together w/ horse-like Tapirs) in W. Eeurope by the Oligocene. Also died out in Asia by this time.
Horses. In Oligocene, N. America horses are Mesohippus and Miohippus. Sheep size, 3 toes w/ middle digit largest. Snout elongating. Premolars beginning to look like molars w/ lophs and lophids.
Horses. By Miocene, Anchitherium had split off from other N. American horses, and migrated through Europe and Asia. By the end of the Miocene, forest-dwelling Hypohippus migrated into China. From Oligocene Anchitheres came the Miocene Parahippus, a precursor to mid- miocene Merychippus.
Horses. Merychippus is first grazer horse. True hypsodont cheek teeth, elaborately lophed and had cementum. Had fused ulna/radius and tibia/fibula to improve gallop and minimize twisting of legs. All later horses evolved from Merychippus.
Horses First successful descendent of Merychippus were the Hipparionines, which included as many as 6 lineages. They invaded the old world several times and were finally extinct by the late Pleistocene. In the late Miocene, Merychippus was replaced by Pliohippus, the 1 st one-toed horse.
Horses Pliohippus gave rise to Equus during the Pleistocene of N. America, from where it radiated to the old world. Equus became extinct in the N. American recent. Why?
Artiodactyla 1/3 of all mammalian genera are Herbivores. Of these, 50% are Artiodactyla or Perissodactyla. Origin is probably I the Palaeocene. Today, there are 6 genera of Perissodactyls vs. about 80 genera of Artiodactyls. Whereas perissodactyls were once most diverse, artiodactyls now have significant edge. Why?
Artiodactyls Primary axis of support is between 3 rd and 4 th toes (paraxonic). 2 nd and 5 th digits are absent or non- functional. Pigs (Suiformes) are plantigrade, while ruminants are digitigrade (Unguligrade). Dentition varies from bunodont and brachydont to solenodont and hypsodont.
Artiodactyls Upper incisors and canines are reduced or absent. Suids and Tayasuids have non-ruminating stomachs while more derived families have 4 chambered ruminating stomachs.
Suiformes: Suidae 5 genera and 16 species. Simple stomachs and bunodont teeth, large ever-growing canines. Cartilaginous disk on snout. Endemic to Europe, Africa, and Asia. Introduced almost everywhere else.
Suiformes: Tayassuidae Least specialized of the suiformes. Peccaries - legs are thin and feet end in hooves. Upper canines point downward rather than upward as in pigs. Restricted to the New World, from the desert southwest to Argentina.
Suiformes: Hippopotamidae 2 species only. Little or no hair, also lack sweat glands for thermoregulation. They do have glandular skin that produces pigmented secretions to protect against sunlight. Bunodont cheek-teeth, ever-growing tusk-like lower canines and incisors, with alveoli for canines anterior to those for incisors.
Hippos Not ruminants, but septa in stomach increase gut retention times. H. amphibius grazes on land at night fo rup to 6 hrs. Hexaprotodon liberiensis is less aquatic. Both are African.
Tylopoda: Camelidae North American origin in Eocene, extinct here by the Pleistocene. 3 genera and 6 species Dromedaries, Bactracians, Quanaco, Llama, Alpaca, and Vicugna. Small head, long snout, cleft upper lip, long thin neck, long legs w/ canon bone. Upper and lower canines, and selenodont cheek teeth. Toes spread out under load.
Tylopoda: Camelidae Outer spatulate upper incisor is retained in adults. 3-chambered stomachs and a cecum. Dromedary was once throughout the Middle East, but now exists only in domestication. Bactracians were once throughout Asia, but are now restricted to the Gobi.
Tylopoda: Camelidae Vicunas and Llamas are restricted to S. America. Camelids consume plants w/ high salt content, foods avoided by other grazers. Unique gaits in Camels. Heat and water strategies - the hump is not what you think.
Ruminantia: Tragulidae 3 genera and 4 species of Chevrotains in Africa and Asia. Most underived of all ruminants, once had a worldwide distribution. Mouse deer is smallest artiodactyl at 2.5kg. No antlers, but curved upper canines. 3-chambered ruminating stomach.
Cervidae 16 genera and 42 extant species, ranging in size from the pudu at 8kg to Alces alces at 800kg. Absent only from sub-Saharan Africa and Antarctica, were introduced to Australia and New Zealand. Sexually dimorphic - males have antlers, females (except caribou) do not. Why?