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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
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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