Main Points...Taxonomy: about 2500 species Distribution: cosmopolitan Characteristics: --2...

Main Points

1) Diversity, phylogeny, and systematics-- Infraclass Metatheria (Marsupialia) continued, Orders Diprotodontia

through Peramelina-- Infraclass Eutheria, Orders Lagomorpha through Cetacea

2) The Great American Interchange-- dispersal (contrast with vicariance)-- example: recent range expansion of nine-banded armadillos

3) Evolution of body size on islands-- the island rule-- example: sloth evolution in the Caribbean

Pre-reading: Weds 18 Sep = Sykes et al 2014Mon 23 Sep = NA

Terms: vestigial, diprotodont, syndactyly, saltatorial, placenta, vicariance, cosmopolitan, coprophagy, cecum, myrmecophagy, dispersal, folivore, enamel, island rule, cursorial, ruminant, Cetartiodactyla, fusiform, echolocation, baleen 1

Order Notoryctemorphia: marsupial “mole”

Taxonomy: 1 species (monotypic order)

Distribution: Australasian

2

Order Notoryctemorphia: marsupial “mole”

Taxonomy: 1 species (monotypic order)

Distribution: Australasian

Characteristics:-- no pinnae-- eyes vestigial, ears reduced-- enlarged claws

3

Order Diprotodontia: kangaroos, wallabies, phalangers, possums, wombats

Taxonomy: 117 species

Distribution: Australasian

hairy-nosed wombat koala

red kangaroo

dingiso

4

5

Taxonomy: 117 species

Distribution: Australasian

Characteristics:-- diprotodont teeth-- syndactyly

Order Diprotodontia: kangaroos, wallabies, phalangers, possums, wombats

Order Peramelina: bandicoots

Taxonomy: 21 species

Distribution: Australasian

rabbit-eared bandicootEastern barred bandicoot

6

long-nosed bandicoot

Order Peramelina: bandicoots

Taxonomy: 21 species

Distribution: Australasian

Characteristics:-- saltatorial locomotion (convergent with lagomorphs)-- placenta, in addition to marsupium

rabbit-eared bandicoot

7

long-nosed bandicoot

Eastern barred bandicoot

• Vicariance = formation of geographic barriers across preexisting geographic ranges

8

Historical biogeography

9

Subclass Prototheria Subclass TheriaInfraclass Eutheria

Theria

Gomez et al. 2016.

Eutheria

Subclass Theria, Infraclass Eutheria

Taxonomy: 19 orders

Distribution: cosmopolitan, but many orders are restricted to a single zoogeographic region

10

Subclass Theria, Infraclass Eutheria

Taxonomy: 19 orders

Distribution: cosmopolitan, but many orders are restricted to a single zoogeographic region

Diagnostic characters:1) dental formula = 4/4, 1/1, 4/4, 2/3 = 44-46 teeth (but many exceptions)

2) brain and braincase are relatively large

3) no marsupium or cloaca

4) placenta

5) ankle bones

11

Order Lagomorpha: hares, rabbits, pikas

Taxonomy: 80 species

Distribution: cosmopolitan

Characteristics: -- 4 continuously growing upper incisors-- saltatorial-- coprophagic-- cecum

black-lipped pikablack-tailed jackrabbit mountain cottontail

12

Annamite striped rabbit

13

Order Rodentia: rodents

Taxonomy: about 2500 species

Distribution: cosmopolitan

Characteristics: -- 2 continuously growing upper incisors-- skull and jaw musculature adapted for gnawing-- some species coprophagic, with cecum naked mole rat

capybara

Lord Derby’s anomalure

14

Gambian pouched rat

Order Cingulata: armadillos

Taxonomy: 21 species

Distribution: Neotropical, 1 species Nearctic

Characteristics: -- bony plates on head and body-- fossorial or semi-fossorial-- myrmecophagous

pink fairy armadillo

giant armadilloscreaming hairy armadillo

15

16

• Dispersal (biogeographic context) =

movement across preexisting (geographic) barriers after their removal

Historical biogeography

The Great American Interchange

Joining of Nearctic and Neotropical zoogeographic regions roughly 3 MYA-- dispersal of many Nearctic taxa south; few Neotropical taxa dispersed north

17

The Great American Interchange

18

Joining of Nearctic and Neotropical zoogeographic regions roughly 3 MYA-- dispersal of many Nearctic taxa south; few Neotropical taxa dispersed north-- mass extinction of Neotropical metatherians

19

Recent dispersal by the nine-banded armadillo

1972

1994

• northward expansion of 10 km/year since 1940s

Taulman and Robbins. 1996.

20

• northward expansion of 10 km/year since 1940s

• likely limited by rainfall (to the west) and temperature (to the north)

Red = 2009 distributionPink = predicted future distribution

1972

1994

Taulman and Robbins. 1996.

Recent dispersal by the nine-banded armadillo

Order Pilosa: true anteaters and sloths

giant anteatercommon silky anteater

Hoffman’s two-toed sloth

Taxonomy: 10 species

Distribution: Neotropical

21

Order Pilosa: true anteaters and sloths

giant anteatercommon silky anteater

Hoffman’s two-toed sloth

Taxonomy: 10 species

Distribution: Neotropical

22

Characteristics:-- incomplete zygomatic arches-- myrmecophagous (anteaters) or folivorous (sloths)-- no enamel on cheek teeth

Evolution of gigantism and dwarfism

• island rule = on islands, the tendency for small species to increase in size (gigantism), and large species to decrease in size (dwarfism), over evolutionary time scales

23

brown-throated sloth (~7 kg)pygmy sloth (~3 kg)

brown-throated sloth (~7 kg)pygmy sloth (~3 kg)

24

Evolution of gigantism and dwarfism

Discussion Q: come up with a hypothesis for why the island rule exists. What does your hypothesis predict with respect to the size of sloths on Caribbean islands?

25

brown-throated sloth (~7 kg)pygmy sloth (~3 kg)

26

Evolution of gigantism and dwarfism

Anderson and Handley. 2002.

Order Artiodactyla: even-toed ungulates

Taxonomy: 220 species

Distribution: cosmopolitan, excepting Australasia

Characteristics: -- cursorial or aquatic-- weight borne on 3rd and 4th digit-- many with ruminant stomach or cecum-- folivorous or omnivorous

Siberianmusk deer

bactrian camelriver

hippopotamusbighorn sheep

27

28

Discussion Q: Wong describes the history of how artiodactyls (and hippos in particular) were discovered to be ancestral to whales. What was the most convincing piece of evidence for this?

29

Discussion Q: Wong describes the history of how artiodactyls (and hippos in particular) were discovered to be ancestral to whales. What was the most convincing piece of evidence for this?

fossil whale fossil whalepronghorn

30

31

32

33

34

35

36

37

38

Cetartiodactyla

Taxonomy: 78 species

Distribution: Oceanic, rivers of Neotropical and Oriental

Characteristics:-- fusiform body with modified forelimbs and vestigial hind limbs-- nostrils located posteriorly on cranium

Order Cetacea: whales, dolphins, porpoises

39

Taxonomy: 67 species

Distribution: Oceanic, rivers of Neotropical and Oriental regions

Characteristics:-- single nostril-- homodont dentition-- echolocation

Suborder Odontoceti: toothed whales

narwalsorca and harbor porpoise baiji

40

Taxonomy: 11 species

Distribution: Oceanic (no rivers)

Characteristics:-- two nostrils-- baleen

Suborder Mysticeti: baleen whales

41

blue whale

bowhead whale

gray whale