Lectures 5 and 6 Flashcards
Monotreme Reproduction
Cloaca present
Testes are abdominal
Mammae lack nipples
Long lactation periods
Female echidnas have folds of skin along the abdomen in place of typical pouch
Order Monotremata
Family Tachyglossidae
Etymology
Tachy = fast speed
Gloss = tongue
Fast tongued
Order Monotremata
Family Tachyglossidae
Thick bodies covered with short spines
Rostrum slender and beak-like
Rostrum bears electro-receptors in Tachyglossus
-Can detect very faint electric signals
Slender, delicate dentary bones
Long protrusible tongue
Limbs powerfully built for digging
-Need to be able to break into ant/termite mounds
AKA “spiny anteaters”
Little hairs on tongue help pick up ants
Electro-receptors on distal tip of beak (only about 200-300 electroreceptors)
Spines protect against predators, do NOT dislodge like porcupine quills
Echidna Love Train
Males awaken from hibernation before females
Smell out females and wait for her to wake up
Sometimes will nudge females to try to wake her up
Female awakens from hibernation and is not immediately ready to mate, she will smell around while males follow her
Males will make hierarchy
Order Monotremata
Family Ornithorhynchidae
Etymology
Ornitho = bird
Rhynch = beak
Bird-like beaked mammal
Order Monotremata
Family Ornithorhynchidae
Semi-aquatic lifestyle
Dense velvety pelage and wooly underfur
Eye and ear openings covered by skin folds when submerged
Webbed feet
Inhabits streams, rivers, and lakes
Primarily hunts on bottom for crustaceans, insect larvae, and other food
Take refuge in burrows in stream banks
Primarily NOCTURNAL mammals
Monotypic family: Only ONE species
Young have teeth, but teeth are absent in adults
Egg tooth used for hatching
Gums covered by horny plates
Platypus Bill
40k electroreceptors
60k mechanoreceptors
Mechanoreceptors detect by touch
Electroreceptors detect faint electric signals (i.e. heartbeat); platypus finds food by sweeping head back and forth like a mine sweeper or metal detector
Platypus Spurs
Males have medially directed spurs on ankles
Connected to venom glands
Venom production increases during breeding season
Function:
- True answer UNKNOWN
- Intraspecific competition (fight other males)
- Subdue females for mating (not supported well, venom pretty strong and could potentially cause damage)
Adaptive Radiation of Crown Mammals
Monotremes: 5-7 extant species
Marsupials
Placentals
Class Mammalia Subclass Prototheria Subclass Theria Infraclass Metatheria Infraclass Eutheria
Metatherians and eutherians diverged in ___________
late Jurassic
Infraclass Metatheria
Known as marsupials for the marsupium
-Only ~50% living marsupials have marsupium
Give birth at early stage of development
- Short gestation, long lactation
- Choriovitelline placenta (lack villi)
2 Centers of diversification:
Modern centers of diversity are the Australian region and the Neotropics (S and C America)
Metatherian Morphology
Function of palatal vacuities is to allow for extra vascularization
Palatal vacuities present on cranium (Good way to ID marsupials)
Medially inflected angular process on dentary
Hindfeet may be specialized
-e.g. for arboreal or saltatorial (leaping) locomotion
Epubic bones present
Marsupium may be present
Koala Toes
Big toe opposable
Used to grasp branches (common in arboreal mammals)
Syndactyly: 2nd and 3rd digits fused
Bandicoot toes
Hopping like kangaroos
Long plantorial surface (common in hopping animals)
Tree kangaroo toes
Secondarily adapted to arboreal habit
No opposable big toe, evolved primitive grasping function
Epipubic bones in Virginia opossum
Paired epipubic bones: Come off pubis/pelvic girdle
Role:
- Initially thought to support pouches, but ALL marsupials have epipubic bones, NOT all have pouches; bones are present in males, too (most don’t have pouches, a few males do)
- ACTUAL purpose: Point of origin for muscles involved in locomotion
Monotremes also have epipubic bones
Hopping marsupials have ___________ pouches
Anterior-facing
Allows for CURSORIAL locomotion
Burrowing marsupials have ____________ puches
Posterior-facing
Protects young from dirt
Metatherian Paleontology
Fossil record dates to early Cretaceous of Asia (140-130Mya)
-But diverged from Eutheria much earlier than this
Souther continents served as centers of metatherian radiations
Metatherians reached Australia via Antarctica
Antarctica and Australia contiguous until about 55Mya
S America (mostly) isolated
S American radiation rivaled that in Australia
-Diversification about 140Mya in Asia
Most living metatherians found in Australia
Evolved from basal insectivorous or omnivorous mammalian stock
Lots of convergence with eutherians
Over 130 living and fossil genera
-Not a very diverse group now, historically diverse group
Examples of Convergence
Borhyaenidae
-Convergent with canids and bears
Thylacosmilidae
-Convergent with saber-toothed cats
Argyrolagidae
-Convergentw ith kangaroo rates and jerboas
Metatherians vs. Eutherians
Are modern metetherians adaptively and competitively inferior to eutherians?
-NO, different approach to solving evolutionary problems
Metatherians less diverse today than eutherians
No flying or marine metatherians
Some extremely productive food sources not part of metatherian diet (e.g. marine plankton and flying insects)
Metatherians far more conservative morphologically
No marsupials with fins or wings
Metatherians have not exploited great size
Largest living metatherian is the red kangaroo (100kg)
Metatherians have never evolved highly social behavior
No herding metatherians
-Kangaroos eat together, exploit same food source, do NOT travel as a unit
Metatherians are less diverse than eutherians
About 6% of living mammals are metatherians
~390 species of metatherians
~6500 living species of mammals
Metatherian mode of reproduction is probably more ancestral than that of eutherians
Very brief gestation period
Bear almost embryonic young
Forelimbs are most developed part of this embryonic young, UNABLE to develop into other specializations because they’re needed for climbing to nipples
Extended gestation of eutherians produces young that are far more endothermic
Eutherians seem better able to exploit colder climates
Investment of energy by the mother is probably lower in metatherians
Adcantage in unpredictable environments;
- Can replace young quickly
- Able to go into estress much more quickly, not too much energy lost
South American metatherians
Superorder Ameridelphia
Order Didelphimorphia
Family Didelphidae
Includes opossums in S America and common/Virginia opossums
Order Didelphimorphia
Family Didelphidae
Southeastern Canada to southern Argentina
Braincase long and narrow
Prominent sagittal crest
50 total teeth! (5/4 incisors)
Marsupium may be present or absent
Tail usually prehensile
Some are immune to snake venom
South American metatherians
Superorder Ameridelphia
Order Paucituberculata
Family Caenolestidae
Monotypic family
Shrew-like marsupials
Disconnected/disjunct distribution on Andes mountains
No marsupium
Lower incisors procumbent (stick out anteriorly)
Elongate heads and small eyes
Large olfactory bulbs
-Indicates that it relies heavily on sense of smell
South American Metatherians
Superorder Australidelphia
Order Microbiotheria
Family Microbiotheriidae
Only member of Superorder Australidelphia found in S America, NOT found in Australia
Monotypic family
Monito del monte
-“Little bush monkey”
3-5in; ~20g
Southern Andes Mountains
Scansorial/Arboreal
-Scansorial = spends a lot of time on ground
Primarily insectivorous
- Sole disperser of misteltoe seeds
- If they go extinct, the mistletoe would, too
May undergo hibernation
Goes between ground and trees
Superorder Australidelphia
Order Microbiotheria
Family Microbiotheriidae
Why is it found in S America?
Backwards migration hypothesis:
-Relict of an Australidelphian radiation back into S America (i.e. back-migration)
Accepted hypothesis:
- Relict of the lineage that colonized Australia via Antarctica
- -Shares common ancestor with all of the other Australian metatherians
4 Extant Orders of Metatherians
Dasyuromorphia
Peramelemorphia
Notoryctemorphia
Diprotodontia
Order Dasyuromorphia
Family Dasyuridae
Marsupial Carnivores
Diversity in sizes
-Shrew-sized to size of small dog
Carnivorous and insectivorous forms
- Specialized teeth reflect diet
- Upper molars have sharp cusps for slicing
Tasmanian devil
- Formerly widespread in Australia
- Now restricted to Tasmania
- Devil Facial Tumor Disease
- -80% decline in population
Order Dasyuromorphia
Family Myrmecobiidae
Monotypic family: (Myrmecobius fasciatus)
Numbat
Eats termites
- Long, protrusible tongue
- Teeth small
Diurnal
Order Dasyuromorphia
Family Thylacinidae X
“Thylacine” or Tasmanian wolf
EXTINCT
Widespread over Australia until about 3500 years ago when dingos were introduced
Last known thylacine died in a zoo in 1936
Females and males both had pouches
Features convergent to dogs
Order Notoryctemorphia
Family Notoryctidae
Marsupial moles
Fossorial adaptations
- Eyes vestigial and lenseless
- Ears lack pinnae
- Cornified skin on nose
- Enlarged claws for digging
- Marsupium opens posteriorly
Order Peramelemorphia
Family Peramelidae
Bandicoots
Large ears, pointed snout
Omnivorous
Hind feet specialized for cursorial locomotion:
-2nd and 3rd toes fused (syndactyly), a feature shared with Diprotodontia
Dig shallow burrows
-Pouch present, facing posteriorly
Order Diprotodontia
Family Vombatidae (wombats) Family Phascolarctidae (koalas) Family Phalangeridae (possums and cuscuses) Family Tarsipedidae (noolbenger, honey possum) Family Macropodidae (kangaroos, euros, wallabies)
Diprotodonts have 2 procumbent lower incisors
Order Diprotodontia
Family Vombatidae
Stocky bodies up to 36kg
Limbs short and powerful
Tail vestigial
Excavate extensive networks of tunnels
Marsupium opens POSTERIORLY
Zygomatic arches robust
Cranium flattened
Wide mastoid process
Wide diastema (anterior premolars lost)
incisors 1/1
Conspicuous depression in jugal and maxillary (origin of masseter)
Biliphodont cheekteeth
Syndactylous
Lower incisors diprotodont
Wombats are
herbivores
Order Dipotodontia
Family Phascolarctidae
Monotypic family - koalas
8-12kg
Specialized arboreal herbivore
- Eucalyptus
- -Low-quality diet: No protein, takes a lot of energy
Fairly sedentary (low quality diet)
Microbial fermentation in caecum
-Caecum is first part of intestine
Single young dependent on mother for 1 year
Cellulase breaks down cellulose; mammals lack this, they need some sort of bacteria to break down cell wall of plants
order Diprotodontia
Family Phalangeridae
Cuscus and possums
Large-ish possums
Includes cuscusses and brushtail possums
Omnivorous
Some have adapted to living in suburban areas
Primarily arboreal
- First 2 digits of front foot (pollex) opposable
- Prehensile tail
- Bare skin on part of tail (on distal-most end)
- Opposable first toe
order Diprotodontia
Family Tarsipedidae
Monotypic family
Honey possum, or noolbenger
nectivorous
Long-p prehensile tail
Long, bristled tongue used to extract nectar
jaw muscles and teeth reduced
Mammal with liquid diet?
Honey possum
Vampire bats
Modifications: Long tongue to lap up/suck things
Order Diprotodontia
Family Macropodidae
Kangaroos, wallabies, quokka
900g to 90kg
Marsupium opens anteriorly
Broad diastema
Highly specialized for bipedal jumping
- Hindlims elongate (especially 4th metatarsal)
- Digits 2 and 3 small and syndactylous
Digit 1 ABSENT
Macropods CONVERGENT with ungulates
- Cursorial
- Browsing/grazing
- Specialized digestive system for microbial fermentation of plant material (foregut fermenters)
