Mammalian Paleontology Final Exam

5 Changes during the Eocene-Oligocene Transition and the Impacts

1. Tectonic separation between Antarctica and Australia - new oceanic gateway and Antarctic circulatory current —glaciers form in antarctica
2. Falling eustatic sea levels - glacier formation sucks up seawater; Turgai strait retreats between Asia and Europe
3. Biotic interchante between Asia and Europe — imbalanced exchange, Asia had larger land area and greater diversity so Asian taxa did better than European taxa
4. Grand Coupure - Eu taxa that went extinct— paleotheres, apatemyids and pseudosciurid rodents
5. Balkanatolia Archipelago - continent of islands that included African and Laurasian taxa— was getting colonized from everywhere

Balkanatolia Colonization Patterns (why its a necessary first step to reach europe)

a. ruminants & rhinocerotoids colonize balkanatolia before reaching europe AFTER the grand coupure

b. after they leave, brontotheres and other rhinocerotoids come to balkanatolia then to EU

Faunal Changes of Eocene-Oligocene of North America

1. Brontotheres & Primates go extinct

   primates like tropical but Olig of N.Am is too cold

2. Hypertragulus appears — selenodont artiodactyl

Floral & Faunal Changes of Eocene-Oligocene of Asia

1. Floral Changes: hardwood forest to sage brush biome

2. Faunal Changes: from large perissodactyls to lagomorphs

Differential Survival Pattern of Primates in Eocene-Oligocene

Eocene: anthropoids do good in Asia & lemurs do good in Africa

Oligocene: lemurs do good in Asia & anthropoids do good in Africa

Timing of Collision between Eurasia and Africa

Debated, but occurred in the Oligocene-Miocene boundary

African Taxa Present BEFORE Collision with Eurasia

1. Arsinotherium (Embrithopods)

2. Hyracoids

3. Chilgatherium & other proboscideans

4. Hyaenodonts

What is the ‘Proboscidean Datum’?

The first appearance of proboscideans outside of Africa (late oligocene)

Aftermath of African Taxa after Eurasian Collision with Africa (Extinctions & Immigrations)

Extinctions:

1. Embrithopods

2. Ptolemai-ids

3. Some Marsupials

4. Antilohyrax (afrothere that looks very similar to artiodactyls)

Immigrations:

1. Perissodactyls—chalicotheres & rhinos

2. Artiodactyls—suidae & ruminants

3. Lagomorphs

4. Rodents—Anomalurids, Hystricomorphs, Pedetidae, Porcupines, Mice

Pedetidae & Anomaluridae are closely-related rodent taxa, but Anomalurids are found in Africa before Pedetids, why may this be?

Anomalurids are arboreal, which is better for sweepstakes dispersal than the ground-living pedetids.

Which taxa shows evidence for a late Oligocene (28 Ma) split between old world monkeys and apes? list 2 features it has that are characteristic of apes

Saadanius — prognathic face & tubular ectotympanic bone

List 2 opposing theories for island evolution and descibe what they say dictates island evolution

1. Macarthur and Wilson model — rapid turnover ; colonization and extinction are mediated by distance from mainland and island size

   disregards in situ speciation

2. Vicariance biogeography — stability ; tectonic movement

“Island Effects” in regards to evolutionary trends

1. Large taxa get small & small taxa get large

2. adaptations to avoid predation are lost (flying,running)

3. brain size reduction (minimize energy cost of maintaining brain tissue)

4 Factors Affecting Island Evolution

1. Limited resources

2. limited space

3. geographic isolation

4. less or no predation

There are only 4 orders of mammals on Madagascar today. List them. Which of these lineages is monophyletic on Madagascar. Why is this important?

1. Rodents

2. Primates

3. carnivorans

4. afroinsectiphiles

All four are monophyletic and it’s important because it means each order only colonized Madagascar one time.

List the 4 Great American Biotic Interchange Events & when they occurred. State how many S.Am taxa moved north & how many N.Am taxa moved south for the first half (1& 2) and the second half (3 & 4).

GABI 1 (2.5 Ma) & GABI 2 (1.8 Ma)

• S.Am taxa moving north — 7 (rodents, cingulates, ground sloths)

• N.Am taxa moving south — 8 (rodent, carnivores, proboscidean, perissodactyls, artiodactyls)

GABI 3 (0.8 Ma) & GABI 4 (125 Ka)

• S.Am taxa moving north — 1 (opossum)

• N.Am taxa moving south — 6 (mustelids, cervids, peccaries, rabbits, horses, carnivorans)

How could glacial oscillations affect the dispersal ability of North and South American taxa? What did Central America look like during interglacial and glacial periods?

Glaical oscillations coincide with the 4 interchange intervals. Glacial periods increased the dispersal ability of taxa.

During interglacial periods, Central America was characterized by rainforest biomes, which stifled the dispersal of taxa, particularly large taxa.

Glacial period Central America was characterized by savannah biomes, which made it easier to disperse.

Also, glacial periods took up sea water, lowering the sea level around the Panama connection between North and South america. The larger land mass aided in easier dispersal.

How many taxa that originated in North America and how many taxa that originated in South America went extinct at the end of the Pleistocene? What are the 4 possibilites postulated for this differential extinction? Finally, what 3 factors impact these possibilites

N.Am: Gomphotheres only

S.Am: Many; toxodonts, glyptodonts, ground sloths, etc.

4 possibilites:

1. higher dispersal of N.Am taxa

2. higher speciation of N.Am taxa

3. more extinction of S.Am taxa

4. larger pool of N.Am taxa

3 factors impacting the differential extinction:

1. competition - S.Am outcompeted by N.Am ungulates

2. predation - absence of efficient mammal S.Am predators meant S.am taxa were not prepared for incoming N.Am carnivores

3. cyclical climate change

Final Results of the Great American Biotic Interchange:

4 taxa in North America are derived from South American ancestors

53% of living South american taxa are derived from North American ancestors

What are the two proposed factors responsible for the megafaunal collapse at the end of the Pleistocene? What were the impacts of both factors?

Humanity and climate change.

Humanity:

1. predation/hunting - Blitzkrieg overkill

2. habitat alteration - fire, etc.

3. hunting & disease caused by commensal animals (dogs & rats)

Climate:

1. habitat loss

2. changing floral diversity - coevolutionary disequilibrium

What is the problem with climate change as an explanation for the late-Pleistocene megafauna collapse?

why didn’t the previous climate oscillations cause a megafaunal collapse?

Give 2 reasons and 2 pieces of evidence that humans were the main cause of the late-Pleistocene megafauna collapse.

1. carribean ground sloths persisted longer than mainland groundsloths—they lived until humans arrived in carribean, then went extinct

2. less genera went extinct in Eurasia & Africa— humans originated in Africa & were already present in Eurasia prior to megafaunal collapse

3. evidence of hunting: mastodon rib embedded with a projectile

4. evidence of habitat alteration: reduction in numbers of megafauna (lowered concentration of poop fungus) followed by increase in human activity (increased concentration of charcoal)

Living and Extinct Clades of Perissodactyls (7 total)

Equids

Tapirs

Rhinocerotids

Brontotheres

Chalicotheres

Rhinocerotoids

Paleotheres

2 Stem/Close Relatives of Perissodactyls

Cambaytheres & Phenacodontids

3 Synapomorphies of Perissodactyls

1. mesaxonic— odd number of toes

2. concave navicular facet on astragalus

3. pi-shaped upper molars

Which taxa do these belong to?

Tapir

Which taxa do these belong to? 

Rhinos

Which taxa do these belong to?

Brontotheres

Which taxa do these belong to?

Chalicotheres

Which taxa do these belong to?

Paleotheres

Which taxa do these belong to?

Rhinocerotoids

Which taxa is though to be the ancestor of all perissodactyls?

Hyracotherium

Give the 2 major features of equid evolution and explain the adaptive benefit of each. What are these two things associated with?

1. monodactyl limbs (one toe) with elongated metacarpal — aids in running

2. hyposodont cheek teeth (high crowned teeth) — eating grass

these things are associated with the spread of grasslands during the Miocene

When and what is the Hipparion Datum? Where did equids evolve?

10-11 Ma; appearance of equids throughout the old world. Equids evolved in North America.

4 Living Clades of Artiodactyls

1. Suids & Peccaries

2. Camels

3. Hippos & Whales

4. Ruminants

5 synapomorphies of artiodactyls

1. double pulley astragalus

2. paraxonic — even number of toes ( axis passes btwn digits 3 & 4)

3. deciduous p4 “baby tooth” has 3 lobes

4. selenodont upper molars

5. tall greater trochanter of femur and narrow patellar groove

Basal artiodactyls are thought to either be Wutuhyus of China or Diacodexis of Wyoming. Describe features of both taxa. Which taxon is more derived?

Wutuhyus is pig-like with bunodont teeth. Diacodexis has a double-pulley astragalus and artiodactyl femur morphology, as well as paraxonic toes. Diacodexis is more derived than Wutuhyus

List the 2 living clades of Cetacea and the 4 extinct Archaeocete clades

Living:

1. Mysteceti - baleen

2. Odontoceti - teeth and sonar

Extinct Archaeocetes:

1. Pakicetids - most basal

2. Ambulocetids

3. Protocetids

4. Basilosaurids - 1st fully aquatic

Necessary changes for Cetaceans to become marine

1. Reproductive changes: tail first birth (ancestral mammal is head first)

2. Skeletal changes:

   a. elongated vertebral column

   b. shorter limbs and longer skull

   c. osteosclerotic bones

3. Hearing changes:

   a. remove eardrum

   b. auditory bullae enlarged and separated from skull w/ Involucrum to conduct sound

Living (7) and Extinct (1) Clades of Afrotheria (the two general clades and then the Orders within)

Paeungulata:

1. Proboscidea - elephants

2. Sirenia - manatees

3. Hyracoid - hyrax

4. Embrithpods (extinct)

Afroinsectiphilia:

1. Tubulidentata - aardvarks

2. Macroscelidea - elephant shrews

3. Chrysochloridae - golden moles

4. Tenrecidae - tenrecs

2 synapomorphies of Afrotherians

1. large cotylar fossa of astragalus

2. transverse ectal facet on calcaneus

3 Paleocene African Mammals:

1. Todralestidae

2. Eritherium — oldest potential relative of proboscideans

3. Ocepeia — transitionary from insectivorous to herbivorous

Dispersal btwn Africa and Eurasia was possible, but limited in the paleocene. Which taxon shows us this?

Hyaenodonts found in both Africa and Asia in late paleocene

5 Afrotherian taxa present during the Eocene of Africa and features of each

1. Numidotherium — early proboscidean with aquatic affinity

2. Nementchatherium — macroscelidean

3. Hyracoids — looked similar to early perissodactyls; W-shaped ectoloph as well

4. Embrithopods — made it out of Africa before collision with Eurasia (perhaps Balkanatolia?)

5. Tubulidentata — aardvark; confined to Africa until collision w/Asia

Describe the dentition of aardvarks (Tubulidentata). What challenge does this dentition raise in regards to their position in the Afrothere phylogenetic tree?

Dentition is highly simplified with smooth cheek teeth. aardvarks are placed at the base of Afroinsectiphilia, but with such derived teeth, it makes this position unstable. Many Afroinsectiphiles have teeth adapted for insectivory and are less derived than aardvark teeth.

Sirenian adaptations to life in water:

1. swollen ribs & dense bones (pachyosteosclerosis)

2. changing body proportions:

   1. neck shortened

   2. center of buoyancy equal to center of gravity; body axis is aligned with water—more efficient swimming

   3. larger thoracic cavity

3. forelimbs are flippers and hindlimbs are gone

What taxon do these teeth belong to?

Elephant shrew

Which taxon do these teeth belong to?

Dimaitherium (hyracoid)

Which taxon do these teeth belong to?

Tubulidentata (aardvark)

Which drawing represents the body of modern manatees? What does the B &the G represent in these drawings? What is important about their position relative to each other?

Number 3; The b is the center of buoyancy and the g is the center of gravity. As the center of buoyancy is shifted to be equal in position to the center of gravity, the axis of the body becomes aligned with the water (green line), which makes swimming more efficient

Clades of Xenarthra:

1. Cingulata — armadillos & glyptodonts

2. Vermilingua — anteaters

3. Folivora — tree sloths & ground sloths

2 Synapomorphies of Xenarthra

1. Xenarthrous joints — accessory joints between vertebrae that fortify the skeleton

2. simplification or loss of teeth

Who is sister to Xenarthra? What do we know about the ancestor of Xenarthra?

Afrotheres

Xenarthran ancestor was likely a good digger

Cingulata: give one synapomorphy & describe the dentition

carapace made of osteoderms

dentition: euhypsodont (ever growing & closed roots) ; no enamel—only dentine

What are Glyptodonts? How are they related to others in their clade? What unique morphological trait are they hypothesized to have used for intraspecific combat?

Large, armored cingulates that are nested within living cingulates.

Most closely related to the pink fairy armadillo.

They are thought to have used their giant club tail for intraspecific combat.

3 Examples of Extinct Ground Sloths

1. Megalonyx

2. Megatherium

3. Paramylodon

Fun facts! Briefly describe the historical story around the discovery of ground sloths in America.

Thomas Jefferson found the claw of Megalonyx and thought it was a lion that may not be extinct, which catalyzed the expedition of Lewis and Clark.

List two diagnostic skull features of tree sloths and describe the two living groups and their differences

Skull features:

1. incomplete zygomatic arch

2. extended processes on zygomatic arch

Living Groups:

1. Bradypodidae — 3 toed sloth; peg like upper teeth

2. Choloepus — 2 toed sloth; canine-like 1st cheek teeth; scoopy part at symphysis of dentary

Are tree sloths more closely related to each other or to extinct ground sloths? Did they evolve suspensory arboreality independently or is it homologous?

Tree sloths are more closely related to ground sloths and evolved suspensory arboreality independently.

When did South America and Africa split? When did South America and North America connect?

S.Am and Africa split 120 Ma in Cretaceous and S.Am and N.Am collided 2.5 Ma in Pleistocene.

Four South American fossil groups that survived the meteor impact (cretaceous-paleocene boundary):

1. Monotremes

2. Gondwanatheres — similar molars to multituberculates (corn)

3. Molinodus — oldest S.Am placental; condylarth that emigrated from N.Am; duplicated protocone

4. Notoungulates — external shearing

Give the main synapomorphy of Notoungulates and list & briefly describe the 8 groups.

Main synapomorphy: external shearing

1. Pyrotheres — bilophodont; high nasal opening on skull

2. Toxodon — hypselodont tusks; hypsodont molars; largest notoungulates

3. Notioprogonian — buccal shearing

4. Typotheres — teeth look like a face 🥴

5. Hegetotheres — extremely hypsodont upper teeth; rabbit like

6. Litopterns — primitive dentition but evolved extreme monodactyly earlier before horses did

7. Astrapotheres — lightning beasts

8. Xenungulates — “foreign ungulates” ; maybe convergent with Uintatheres

Eurohippus messelensis

pregnant perissodactyl mare and fetus from germany

Embolotherium andrewsi

late Eocene brontothere; no brontotheres made it to the Oligocene

Diacodexis metsiacus

early Eocene artiodactyl

Rodhocetus kasrani

semiaquatic cetacean from Pakistan

Ocepeia dauoiensis

old Afrotherian taxa but neither small nor insectivorous

Pezosiren portelli

quadruped Sirenian of Jamaica

Litovoi tholocephalos

dome-headed multituberculate from an island; tiny brain

Arsinotherium giganteum

Embrithopod from right before collision of Africa & Eurasia

Nesodon taweretus

toxodont with rhino-like dentition

What structure are these? What group do they belong to and what is their function?

Xenarthrous joints; belong to xenarthrans; fortify vertebrae for digging

Which group do these teeth belong to?

Cingulates / armadillos

Which group do these teeth belong to?

Glyptodonts

Whose skull is this?

Glyptodont skull!

Whose skull is this?

Bradypopodidae — 3 toed sloth

Whose skull is this?

Choloepus — 2 toed sloth

Whose phalanges are these?

Fossil anteater

Which taxon has this skull and teeth?

Pyrotheres

Which taxon do these teeth belong to?

Toxodon

Which taxon do these teeth belong to?

Notioprogonian

Which taxon do these teeth belong to?

Typotheres

Which taxon do these teeth belong to?

Hegetotheres

Which taxon does this skull and these teeth belong to?

Astrapotheres

Which taxon do these teeth belong to?

Xenungulates

Which taxon do these teeth belong to?

Arctostylopids

Which taxon do these teeth belong to?

Molinodus

Review: earliest ancestor of mammals

Synapsids

Review: 3 basic mammal teeth prior to tribosphenic teeth

1. Triconodont

2. Symmetrodont

3. Docodont

Review: What did the ancestral mammal likely look like?

small and insectivorous

Review: The 2 evolutionary innovations of mammals

1. unique jaw joint (dentary-squamosal) and 3 middle ear bones — allows greater bite force and better hearing

2. enlarged brain — neocortex and olfactory bulb larger

Review: Name the 4 Paleocene North American Ages

Puercan, Torejonian, Tiffanian, and Clarkforkian

Review: What likely caused the rapid warming at the paleocene-eocene boundary?

Carbon isotope excursion due to thermally-induced release of methane hydrates from ocean column & sediment

Review: List the 3 Clades of Euarchontoglires and the 7 clades of Laurasiatheres

Euarchontoglires:

1. Primates

2. Rodentia

3. Lagomorpha

Laurasiatheres:

1. Lipotyphla

2. Perissodactyla

3. Chiroptera

4. Carnivora

5. Pholidota

6. Cetacea

7. Artiodactyla

Review: What factors allow an animal to be ‘eligible’ for sweepstakes dispersal? What climate conditions allowed for sweepstakes dispersal? Which 3 groups made it from Asia to Africa and South America through sweepstakes dispersal?

Factors:

1. arboreal or riverbank living

2. living in social groups

3. small body size

Climate conditions: monsoons made natural rafts & wind carried across ocean barriers

3 groups that won the sweepstakes:

1. Hystricognathous rodents

2. Anomalurid rodents

3. Anthropoid primates