Mammalogy -- Quiz Three

Notoryctemorphia - Marsupial moles

Australasia; low diversity (2 spp.); fossorial with fusiform (torpedo-shaped; compact) body, vestigal eyes, fused digits, and scoop-like claws → predators

Dasyuromorphia - Carnivorous marsupials

Australasia; Med. diversity (75 spp.); various carnivorous diets

EX: Tasmanian devil, quolls, numbat, planigales, dunnarts, thylacine

Thylacine

Tasmanian tiger; Convergent evo. → look like canids; extirpated from Australia 3,000 years ago (introduction of the dingo); extirpated from Tasmania in 1930s; last captive individual died in 1936 :(

Tasmanian devil

Largest living carnivorous marsupial; strongest bite force per pound of any living mammal (eat bone marrow); removed from Australia about 3,000 years ago by dingoes; populations declining due to devil facial tumor disease (contagious cancer spread via bites); resistance to DFTD is limited by the low genetic diversity (esp. MHC) → 60% decline :(

Other members of Dasyuromorphia

• Mugaras → can eat mice

• Antechinus → males die off after breeding

• Planigales → smallest

• Quolls → threatened by invasive (and poisonous) cane toads

Numbats

HIghly specialized for a diet of ants and termites (myrmecophagy) → elongated rostrum and tongue; pops. in decline due to introduced red foxes and feral cats

Diprotodontia - Iconic marsupials

Koalas, wombats, possums, kangaroos (all of the charismatic guys); Australasia; high diversity (155 spp.); mostly herbivores; many terrestrial, some arboreal; diprotodont teeth → prominent lower incisors

Pleistocene Diprotodonts

Thylacoleo (marsupial lion) → strongest bite relative to body size of any mammal ever; giant wombats; short-faced kangaroo

Koalas

Eat leaves, stems, flowers, and bark of Eucalyptus; reduced energy requirements; inactive ~ 20 hours a day (poor quality nutrition)

Wombats

Semifossorial; largest burrowing herbivores; make extensive warrens; grazers; slow → slow metabolism (poor nutrition from grass → silica)

Gliders and possums

Sugar gliders; feathertail glider; greater glider

Ringtail possum; pygmy possum; honey possum (nectarivorous pollinator); brushtail possum (ecological disaster in New Zealand)

Potoroos and bettongs

Many are endangered or extinct due to the introduction of cats (shipboard and agricultural pest control) and red foxes (recreational fox hunting; establishing familiar wildlife in a foreign land [bro])

Long-nosed potoroo (mycophagous)

Northern bettong

Kangaroos, wallaroos, and wallabies

Grazers → ecological and morphological parallels to deer, sheep, and goats

• Large, sac-like stomach to ferment grass (regurgitate and rechew food)

• Marching molars in large kangaroos

• Hypsodont teeth

Tree kangaroos (arboreal), common wallaroo, red-necked wallaby, eastern grey kangaroo, red kangaroo

Disparity in diversity between Metatherians and Eutherians

Metatherians have much lower morpho. diversity, no fully-aquatic spp., and no spp. capable of powered flight

• Short gestation periods

  • Longer total investment (much longer period from conception to weaning)

  • Higher percentage of time spent lactating (2x more energetically costly than gestation)

• Born super chuds (way altricial) → due to gestation time; hind limbs just limb buds; organogenesis has barely just begun → must crawl from vv to nipple without help from their mother

  • Strong developmental constraint on forelimb evolution → front limbs must grow strong early to crawl, limiting how much they can vary or specialize compared to hind limbs

Eutherians have lower overall energy cost of repro. and may have a competitive advantage

• Rate of front limb evolution is much faster

Placentals (Eutherians)

Well-developed, complex placenta (true placenta) → exchanges nutrients and waste between mother and fetus → allows for longer development and protection inside womb; gestation = development inside womb

Metatherians have simple and short-lived placenta

Four embryonic membranes - Placentals

Amnion → surrounds embryo; same function as in all mammals

Yolk sac → nutrient storage; forms part of umbilical cord

Chorion → gas exchange

Allantois → waste collection

Chorion + Allantois → chorioallantoic complex placenta

Afterbirth → placenta, umbilical cord, and amniotic sac expelled from mother’s body

Placentals → Long gestation; born relatively precocial

Phylogeny review

Monophyletic → group containing all descendants of a common ancestor

Polyphyletic → group containing some (but not all) descendants from multiple ancestors → Edentata order thrown out

Four major clades

Xenarthra (2 orders)

Afrotheria (6 orders)

Laurasiatheria (6 orders)

Euarchontoglires (5 orders)

Xenarthra

Cingulata - Armadillos

Pilosa - Sloths and anteaters

Found only in Western Hemisphere; misclassified as Edentata; sister group to Afrotheria; one of the Four Clades(TM); many disparate and highly derived anatomical and ecological specializations

Xenarthra cont.

Arose in South America; remained there until GABI; many oldest fossils include osteoderm scutes (earliest had armor)

Osteoderm → bony deposit or plate that grows directly within an animal’s skin layer

Scute → keratinized outer scale that covers the bony osteoderm

Pleistocene Xenarthra

Giant ground sloths; three-toed sloths; all large forms went extinct by about 10 Kya (end of ice age) → mainly due to human hunting (and some climate change)

Cingulata - Armadillos

Mostly S. Am., some in N. Am.; medium diversity (21 spp.); armored carapace made of osteoderm scutes (anti-predator when they burrow or roll into a ball); short legs with long claws; insectivorous/carnivorous

• Nine-banded armadillo → rapid expansion across US; first observed in TX in 1840s → huge range expansion from S. Am. → it’s coming

Pilosa - Sloths and anteaters

Mostly S. Am.; some range into N. Am.; low diversity (16 spp.)

Anteaters

Highly specialized for myrmecophagy (ants and termites) → lack teeth (edentate) → long, protrusible tongue; mostly terrestrial, some arboreal

• Giant anteater → coarse fur and small eyes (protection from ants); strong forelimbs with long claws (digging termite mounds and killing jaguars)

Sloths

Arboreal and folivorous (eat leaves); sloths can have greenish color from algae growing in fur; can swim

Two-toed and three-toed are distantly related (diverged 40 mya); no fossil record of arboreal sloths; independently converged on lifestyle and locomotion

Xenarthra - traits

• Extra vertebral articulations (synapomorphy) → supplementary interlocking facets on vertebrae → stiffen spine to support powerful digging and/or heavy carapaces

• Simplified teeth (no I or C); remaining teeth are peg-like and ever-growing, if they have them at all (some are edentate)

  • Two-toed sloths have canine-like teeth used to shear leaves off of trees and as defense

• Low metabolism → lowest metabolic rates among eutherians (limited to tropical and semi-tropical habitats; unclear why this evolved, and why it’s consistent throughout the lineage → us. directly linked to low quality food sources

Afrotheria - orders

• Sea cows

• Hyraxes

• Elephants

• Aardvarks

• Elephant shrews

• Tenrecs, golden moles

Elephants - origins

Originated in Africa → migrated to Europe and Asia, and then later to N. Am. using the Beringia Land Bridge (mammoths!1!)

Now → Africa and SE Asia; low diversity (3 spp.); all at risk (poaching, habitat loss)

• African savannah elephant

• African forest elephant → especially at risk (very slow life histories; takes a long time to double population)

• Asian elephant

Elephants - cont.

Communication → use high-frequency sounds at close range and ultra-low-frequency seismic waves (and stomping) for long-distance communication

• Seismic communication → detect vibrations using a combination of mechanoreceptors in foot-pad and the inner ear (via bone conduction through the skeleton)

Largest living terrestrial animal → foot cushions to absorb impact and not shatter their bones by their pure mass → have to walk on toes

• Slow life histories → long lifespans and slow repro. rates make them highly vulnerable to decline

• Ecosystem engineer → consume massive quantities of vegetation daily (clears paths, disperses seeds, engineers habitats)

Trunk → made from muscular nose and modified upper lip → strong and sensitive

Highly specialized teeth → herbivorous; tusks are modified upper incisors (ever-growing); marching molars

Sea cows - Manatees and dugongs

Cosmopolitan; Low diversity (4 spp.); obligately aquatic (shallow warm coastal areas → thin blubber and slow metabolism) and herbivorous (unlike whales); threatened due to poaching, accidental take, boat collisions, habitat loss

• Similar adaptations to whales → large, no fur, paddle-like forelimbs, no external hindlimbs

• Marching molars

• Largest aquatic herbivores

Hyraxes - Dassies and conies

Africa and Arabian Peninsula; low diversity (4 spp.); herbivorous; social; CLR of elephants → mini tusks, but no marching molars

Elephant shrews

Africa; low diversity (15 spp.); highly mobile snout → trait shared by many orders in Afrotheria; insectivorous/omnivorous; highly cursorial; monogamous

Tubulidentata - Aardvark

Africa; low diversity (1 spp.); myrmecophagous; mobile snout; “earth pig” → sparse hair

Tenrecs, golden moles, etc.

Africa; med. diversity (51 spp.); insectivorous/carnivorous

• Convergence with other moles

  • Wedge-shaped skull, fusiform body, vestigial eyes, scoop-like claws

Philodota - Pangolins!!

Sister taxa to Carnivora (form a clade)

Africa and S Asia; low diversity (8 spp.); myrmecophagus; some terrestrial, some arboreal → arboreal have a prehensile tail

All spp. of conservation concern → #1 illegally-traded animal → scales for trad. medicines; meat eaten locally (and by rich people) :(

Pangolin traits

Scales

• Modified guard hairs; made out of keratin; grow, wear down, and occasionally shed (don’t get replaced)

• Predation defense → roll into a ball

• Defense against ants and termites (don’t get caught up in fur)

Claws

• Arboreal → front and back feet

• Terrestrial → only front feet

Keratin

Protein; forms outer protective layers of many animals

• Humans → hair, fingernails

• Armadillo scutes

• Anteater, sloth, and aardvark claws

• Claws, hooves, and horns of many spp.

Carnivora

Spans four orders of magnitude → male northern elephant seal to least weasel; high diversity (290 spp.); cosmopolitan (esp. Africa and SE Asia); carnivores, omnivores, and herbivores → not natively in Australia → dingoes introduced 4 kya, red foxes introduced 150 ya

Carnivora does not equal carnivore → most spp. consume meat as major parts of their diets, but this is a large group that has developed many different lifestyles and diets → e.g., pandas

• Most spp. eat some variety, often seasonally (Grizzly bears)

Carnivora - traits

• #1 synapomorphy → most spp. have carnassial teeth → specialized for shearing (scissor-like) to cut organs and muscle

  • Paired upper premolar and lower molar (P4/M1)

  • Best developed in the predaceous felids, hyaenids, canids, mustelids

• Simple, short digestive tract

• Most are digitigrade → walk on their toes

  • Allows them to make longer, faster strides

  • Acts like a spring to save energy while running → absorbs shock

  • Helped them hunt in grasslands as env. changed

• Baculum → penis bone

  • Most have it (not a synapomorphy, though); prolongs copulation; blocks rivals from female

Carnivora - major families

Feliformia → cat relatives

Caniformia → dog relatives

Pinnipedia → seals and allies

Felidae - Big and small cats

36 spp.; cosmopolitan (and found in diverse habitats); most cats have the same general body plan and life history → nocturnal, solitary, predatory; strictly carnivorous/hypercarnivorous → relatively few teeth, large canines, well-developed carnassials

Most carnivorous family

Cats - hunting

Two common killing tactics:

• Neck crunch (small prey [and small predators]) → bite back of neck to separate vertebrae and sever spinal cord

• Suffocation (large prey [and large predators]) → bite throat to block windpipe

Exceptions:

• Jaguars → literally just crush the skull

• Smilodon → used sabers as precision ice picks after the prey was immobilized with its strong body

Cats - claws

Most spp. have retractable claws → keeps them sharp for climbing and ambushing prey; domestic cat declawing involves an amputation of the distal phalanges, which can cause digits to curl under foot and cause pain when walking :(

Exception: Cheetahs → need their claws out constantly for grip while running/making tight turns at high speeds