ungulates and subungulates l.
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Ungulates and Subungulates. Subungulates Proboscidea elephants Hyracoidea hyraxes Sirenia dugongs and manatees. Ungulates Perrisodactyla odd toed ungulates horses, tapirs, and rhinos Artiodactyla even toed ungulates. Ungulata. Subungulates.

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Ungulates and Subungulates

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dugongs and manatees



odd toed ungulates

horses, tapirs, and rhinos


even toed ungulates

  • 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.
  • 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.
  • 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.
  • Proboscideans and Sirenians were much more diverse during the Oligocene and Miocene.
  • Their future does not look promising.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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?
  • 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?
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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).
  • 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.
  • 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.
  • 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
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.
dugongs vs manatees
Dugongs vs. Manatees
  • Dugongs eat aquatic vegetation which is much softer than that consumed by manatees.
  • Feldhammer uses competition to explain distribution of species.
sirenian fossil history
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
Dugong vs Manatee: Deflected rostrum in Dugong is ‘adaptation’ to bottom feeding.
perissodactyla and artiodactyla
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) TapirB) RhinoC) HorseD) PigE) DeerF) CamelG) PronghornCalcaneum is shaded and articulates w/ Astragalus (H)
  • 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
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
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
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.
  • 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.
  • 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)
  • Compare the teeth of Tapirus with those of the rhino
  • 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 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.
  • About 12 genera
  • Moderate size
  • Slender limbs like horses w/ light builds.
  • Cursorial
  • incisors were spatulate (primitive) and equal sized.
  • Canines were moderate size.
  • 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.
  • 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.
  • 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.
  • Hyracodontids during the Oligocene obtained a unique dental variation: chisel like I1 and tusk like I2. This formed the basis of a 2nd radiation… the 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.
  • 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.
  • 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.
titanotheres brontotheres
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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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.
  • 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 1st one-toed horse.
  • 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?
  • 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?
  • Currently there are 12 famillies of herbivores, there are 24 extinct families.
  • Origin is probably in northern continents with movements into southern ones (except Australia).
  • Primary axis of support is between 3rd and 4th toes (paraxonic).
  • 2nd and 5th 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.
  • 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
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
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
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.
  • 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
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 camelidae119
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 camelidae120
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
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.
ruminantia giraffidae
Ruminantia: Giraffidae
  • 2 genera and 2 species: Giraffa camelopardalis and Okapia johnstoni.
  • Small brachydont teeth, prehensile tongues, ossicones.
  • Consider circulatory problems of great height.
ruminantia moschidae
Ruminantia: Moschidae
  • 4 species of musk deer.
  • Lack antlers, but have curved canines.
  • Distributed from Siberia to the Himalayas.
  • 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?
ruminantia antilocapridae
Ruminantia: Antilocapridae
  • 1 genus, 1 species.
  • Restricted to N. America and Mexico.
  • Unique horns.
  • Forage on Artemisia tridenta.
ruminantia bovidae
Ruminantia: Bovidae
  • 45 genera and 137 species.
  • 4 chambered ruminating stomachs.
  • All have 2 horns except the the four-horned antelope.
  • Worldwide distributin except S. America and Australia. Why?