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 2014 Mon 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 dingiso Taxonomy: 117 species
Distribution: Australasian
red kangaroo hairy-nosed wombat koala
4 Order Diprotodontia: kangaroos, wallabies, phalangers, possums, wombats
Taxonomy: 117 species
Distribution: Australasian
Characteristics: -- diprotodont teeth -- syndactyly
5 Order Peramelina: bandicoots
Taxonomy: 21 species
Distribution: Australasian
long-nosed bandicoot rabbit-eared bandicoot Eastern barred bandicoot
6 Order Peramelina: bandicoots
Taxonomy: 21 species
Distribution: Australasian
Characteristics: -- saltatorial locomotion (convergent with lagomorphs) -- placenta, in addition to marsupium long-nosed bandicoot rabbit-eared bandicoot Eastern barred bandicoot
7 Historical biogeography
• Vicariance = formation of geographic barriers across preexisting geographic ranges
8 Subclass Prototheria Subclass Theria Infraclass Eutheria
Eutheria Theria
Gomez et al. 9 2016. 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 Annamite striped rabbit
Distribution: cosmopolitan
Characteristics: -- 4 continuously growing upper incisors -- saltatorial -- coprophagic -- cecum mountain cottontail black-tailed jackrabbit black-lipped pika
12 13 Order Rodentia: rodents Lord Derby’s anomalure
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 Gambian pouched rat
14 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 screaming hairy armadillo giant armadillo
15 Historical biogeography
• Dispersal (biogeographic context) = movement across preexisting (geographic) barriers after their removal
16 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
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
18 Recent dispersal by the nine-banded armadillo
1972 • northward expansion of 10 km/year since 1940s
1994
19 Taulman and Robbins. 1996. Recent dispersal by the nine-banded armadillo
1972 • northward expansion of 10 km/year since 1940s
• likely limited by rainfall (to the west) and temperature (to the north)
1994
Red = 2009 distribution Pink = predicted future distribution
20 Taulman and Robbins. 1996. Order Pilosa: true anteaters and sloths
Taxonomy: 10 species
Distribution: Neotropical
common Hoffman’s giant anteater silky anteater two-toed sloth
21 Order Pilosa: true anteaters and sloths
Taxonomy: 10 species
Distribution: Neotropical
Characteristics: -- incomplete zygomatic arches -- myrmecophagous (anteaters) or folivorous (sloths) -- no enamel on cheek teeth
common Hoffman’s giant anteater silky anteater two-toed sloth
22 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
pygmy sloth (~3 kg) brown-throated sloth (~7 kg)
23 Evolution of gigantism and dwarfism
pygmy sloth (~3 kg) brown-throated sloth (~7 kg)
24 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?
pygmy sloth (~3 kg) brown-throated sloth (~7 kg)
25 Evolution of gigantism and dwarfism
26 Anderson and Handley. 2002. Order Artiodactyla: even-toed ungulates
Taxonomy: 220 species
Distribution: cosmopolitan, excepting Australasia
Characteristics: Siberian -- cursorial or aquatic musk deer -- weight borne on 3rd and 4th digit -- many with ruminant stomach or cecum -- folivorous or omnivorous river hippopotamus bactrian camel bighorn sheep
27 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?
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?
fossil whale pronghorn fossil whale
29 30 31 32 33 34 35 36 37 Cetartiodactyla
38 Order Cetacea: whales, dolphins, porpoises
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
39 Suborder Odontoceti: toothed whales
Taxonomy: 67 species
Distribution: Oceanic, rivers of Neotropical and Oriental regions
Characteristics: -- single nostril -- homodont dentition -- echolocation
orca and harbor porpoise narwals baiji
40 Suborder Mysticeti: baleen whales
Taxonomy: 11 species gray whale
Distribution: Oceanic (no rivers)
Characteristics: -- two nostrils -- baleen
blue whale bowhead whale
41