figure 01: phylogenetic relationships of monotremes data from westerman, m. and edwards, d. platypus...

FIGURE 01: Phylogenetic relationships of monotremes

Data from Westerman, M. and Edwards, D. Platypus and Echidnas (ML Augee, ed.). Royal Zoology Society of New South Wales, 1992.; Kielan-Jaworowska, Z., Cifelli, R.L. and Luo, Z-X. Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. Columbia University Press, 2004.; and Warren, W.C., et al., Nature 453 (2008): 175-184.

Paleontology

Teinolophus 112–121 million year old basal platypus from Australia

Monotrematum 62–63 million year old platypus from South America

Fossil record is poor and incomplete

Ornithorhynchidae (platypus)

Subclass Prototheria Order Monotremata

1 genus / 1 species Australia

leathery bill hindlimb poison Dense, velvety pelage Eye and ear openings covered by skin folds

when submerged Feet webbed

Ornithorhynchidae

FIGURE 08: Skeleton of the duck-billed platypus, Ornithorhynchus anatinus

Reproduction Cloaca present Testis abdominal

Mammae lack nipples Long lactation periods

FIGURE 04: Anatomy of the female reproductive tract of monotremesAdapted from Szalay, F. S., Novacek, M. J., and McKenna, M. C. Mammal Phylogeny. Springer-Verlag, 1993.

Tachyglossidae (echidnas)

Subclass Prototheria Order Monotremata

2 genera / 2 species Australia & New Guinea

edentate spiny sticky tongue

Morphology

Beak-like rostrum

Adults are toothless

Sclerotic cartilages in eyes

Lacrimal and frontal bones absent

Septomaxilla bone present

No auditory bulla—cochlea simple

Morphology

Shoulder girdle retains ancestral features

FIGURE 03: Bones of monotremes

Derived Characters

Rostrum covered with mechanoreceptors and/or electroreceptors

Reduced dentition

Modified skull morphology

FIGURE 02: Skull of the spiny anteater Tachyglossus

aculeatus. Length of skull 111 millimeters.

Reproduction

Courtesy of Michael L. Augee

FIGURE 05: Ventral view of a live echidna (Tachyglossus aculeatus)

Courtesy of P. Rismiller and M. McKelvey

FIGURE 20.04: Young echidna emerging from the egg

Tachyglossidae

Tachyglossus is capable of daily torpor and seasonal hibernation

Diet consists largely of insects, earthworms, and other soil arthropods

Morphology

Palatal vacuities present Medially inflected angular process on dentary Unusual pattern of tooth replacement Hindfeet may be specialized (e.g. for arboral

or saltatorial locomotion) Epipubic bones present

Figure 5.29

Reproduction Marsupium present in 50% of metatherians

Reproduction

Gestation is short (8–45 days)

Young born tiny and poorly developed

Newborns crawl to marsupium and attach to nipple

Lactation period is long

Paleontology

Fossil metatherians include:

Thyacoleo—a lion-like predator

Diprotodon—a rhino-sized metatherian

Procoptodon—massive grazing animal

Many smaller forms

Paleontology

FIGURE 05: Fossil skull of Procoptodon goliah

Adapted from Tedford, R.H., University of California Publications in Geological Science 64 (1967): 1–165.

Paleontology

South American radiation rivaled that in Australia

Evolved from basal insectivorous or omnivorous stock

Convergence with eutherians

Over 130 living and fossil genera

Paleontology

Borhyaenidae—convergent with canids and bears

Thylacosmilidae—convergent with saber-toothed cats

Argyrolagidae—convergent with kangaroo rats and jerboas

Paleontology

Modified from Romer, A.S. Vertebrate Paleontology. University of Chicago Press, 1966.

Paleontology

FIGURE 08: Microtragulus (Argyrolagidae), an extinct

bipedal metatherian from theMio-Pliocene of Argentina

Adapted from Simpson, G.G., Bulletin Museum Comparative Zoology 139 (1970): 1–86.

Paleontology

Panamanian land bridge established ~2.5 million years ago

Northern eutherians moved southward

Some metatherians moved northward

Metatherian diversity begins to decline

Metatherians vs. Eutherians

I. Metatherians less diverse today than eutherians:

There are no flying or marine metatherians Some extremely productive food sources

not part of metatherian diet (e.g. marine plankton and flying insects)

II. Metatherians far more conservative morphologically (e.g. no fins or wings)


III. Metatherians have not been able to exploit great size.

Although there were large metatherians in the Pleistocene, the largest living metatherian is the red kangaroo.

IV. Metatherians have never evolved highly social behavior.


V. Metatherians are less diverse than eutherians.

Only about 6% (335) of the total number of species of living mammals (5,420) are metatherians.

Are metatherians adaptively and competitively inferior to eutherians?


1. The metatherian mode of reproduction is probably more ancestral than that of eutherians.

Metatherians have a brief gestation period and bear almost embryonic young.

The metatherian need for precocious grasping forelimbs at birth may preclude the development of wings, flippers, or other specializations of the forelimb.


2. The cerebral cortex develops more rapidly and attains

greater volume in eutherians than in marsupials.

The brain and nervous system develop best in the highly nutritive, stable, oxygen-rich environment provided by the placenta.

3. Behavioral plasticity is greater in eutherians.

Cooperative social systems, dominance hierarchies, and territoriality are rare in metatherians.


4. Antipredator behavior is more highly developed in eutherians.

Unified herd action, cooperative defense of young,

complex vocal and visual communication, and sustained

high-speed running are absent in metatherians.

5. The relatively low diploid number of chromosomes may be related to the lack of evolutionary flexibility in metatherians.


6. The extended gestation of eutherians produces young that are far more endothermic and allows eutherians to better exploit colder climates.

7. Metatherians tend to have larger litter sizes than eutherians, but eutherians dominate by increasing their population sizes much more rapidly.

South American Metatherians

Didelphimorphia 17 genera and 87 living species Southeastern Canada to southern Argentina Braincase long and narrow Prominent sagittal crest Marsupium present or absent Tail usually prehensile

Family Didelphidae (American opossums and opossums)

Subclass Theria Infraclass Metatheria

Order Didelphimorphia (American marsupials) 17 genera / 60+ species (17/87) North & South America

5/4 1/1 3/3 4/4=50

Caenolestidae (shrew opossums)


Order Paucituberculata (shrew opossums)

3 genus / 5 species (3/6) South America Andes No marsupium Lower incissors procumbent

Microbiotheriidae (monito del monte)


Order Microbiotheria (monito del monte)

1 genus / 1 species Southern Andes Relict of Australidelphia May hibernate

Notoryctidae (marsupial moles)


Order Notoryctemorphia (marsupial moles) 1 genus / 2 species (1/1) Australia

ecological convergent of Chrysochloridae Eyes vestigial and lensless Ears lack pinnae Cornified skin on nose Enlarged claws for digging Marsupium opens posteriorly

Family Thylacinidae (Tasmanian wolf and thylacine) Infraclass Metatheria (marsupial mammals)

Order Dasyuromorphia (dasyuroid marsupials and marsupial carnivores)

1 genus / 1 species Australia

probably extinct digitigrade ecological equivalent of placental dogs

Family Thylacinidae

© FLPA/Hugh Clark/age fotostock

FIGURE 15B: The thylacine (Thylacinus cynocephalus, Thylacinidae)

Family Myrmecobiidae (numbat)

Infraclass Metatheria (marsupial mammals) Order Dasyuromorphia (dasyuroid marsupials

and marsupial carnivores) 1 genus / 1 species Australia

ant & termite specialists reduced dentition, small & spaced long sticky tongue banded pelage pattern

Family Dasyuridae (dasyurids)

Subclass Theria Infraclass Metatheria (marsupial mammals)

Order Dasyuromorphia (dasyuroid marsupials and marsupial carnivores)

15 genera / 61 species (18/67) Australia & New Guinea

4/3 1/1 2-3/2-3 4/4=42-46

Family Dasyuridae

FIGURE 13A: Skull of a dasyurid marsupial

FIGURE 15A: The Tasmanian devil (Sarcophilus harrisii, Dasyuridae)

© Patsy A. Jacks/ShutterStock, Inc.

Peramelidae (bandicoots and echymiperas)


Order Peramelemorphia (bandicoots and bilbies)

2 genera / 7 species (6,18) Australia & New Guinea 4th digit of hind foot

Order Peramelemorphia

Hindfeet modified for cursorial locomotion

Peroryctinae (spiny bilbies)



4 genus / 11 species Australia & New Guinea 4th digit of hind foot

Order Peramelemorphia

Family Thylacomyidae (bilbies) Family Chaeropodidae (pig-footed bandicoot

—extinct)

FIGURE 17: The sole remaining thylacomyid

species, the bilby Macrotis lagotis

Courtesy of Anthony Robinson

Thylacomyidae (bilbies)



1 genus / 2 species Australia & New Guinea Nocturnal, invertivores Dig burrows, occupy during day 1 extinct, 1 endangered

Chaeropodidae (pig-footed bandicoot)



1 genus / 1 species Australia & New Guinea Front didactyl (2&3), rear monodactyl (4) Extinct

Order Diprotodontia

Family Vombatidae (wombats)

Family Phascolarctidae (koala)

Family Burramyidae (pygmy possums)

Family Phalangeridae (possums and cuscuses)

Family Tarsipedidae (noolbenger)

Family Acrobatidae (feathertail glider and feathertail possum)

Family Pseudocheiridae (ringtail possums and gliders)

Family Petauridae (trioks, Leadbeater’s possum, lesser gliders)

Family Hypsiprymnodontidae (musky rat-kangaroo)

Family Potoroidae (potoroos, rat-kangaroos, bettongs)

Family Macropodidae (kangaroos, euros, wallabies)

Phascolarctidae (koalas)


Order Diprotodontia (kangaroos, possums, wallabies, and relatives)

1 genus / 1 species (Phascolarctos cinereus) Australia

eucalyptus specialist 8–12 kilograms Fairly sedentary Microbial fermentation in caecum Single young dependent on mother for 1 year

Family Phascolarctidae

FIGURE 21: Skull of the koala

Vombatidae (wombats)



2 genera / 3 species Australia

Stocky bodies up to 36 kilograms Limbs short and powerful Tail vestigial Marsupium opens posteriorly Excavate extensive networks of tunnels

Family Vombatidae

FIGURE 19: Hairy-nosed wombat (Lasiorhinus, Vombatidae)

© Timothy Craig Lubcke/ShutterStock, Inc.

FIGURE 09D: Wombat skull

Phalangeridae (brushtail possums and cuscuses) Subclass Theria Infraclass Metatheria


6 genera / 18 species Australia & New Guinea

Family Phalangeridae

FIGURE 23A: A male common spotted cuscus

(Spilocuscus maculatus)

© Stuart Wilson/Photo Researchers, Inc.© Gary Unwin/ShutterStock, Inc.

FIGURE 23B: The Australian brushtail possum

(Trichosurus vulpecula)

Burramyidae (pygmy possums)



2 genera / 5 species Australia Small, delicately built

(up to 40 grams) Mountain pygmy

possum capable of hibernation

Family Burramyidae

Pygmy possums 2 genera and five species Small, delicately built (up to 40 grams) Mountain pygmy possum capable of

hibernation

Courtesy of Anthony Robinson

FIGURE 22: A pygmy possum (Cercartetus

concinnus, Burramyidae)

Pseudocheiridae (ringtail possums)



5-6 genera / 14 species (6/17) Australia

Ringtail possums and the greater glider Tail prehensile Microbial fermentation in caecum Greater glider largest gliding metatherian Largely herbivorous

Family Pseudocheiridae

FIGURE 24: Painted ringtail (Pseudochirulus forbesi;

Pseudocheiridae)

Courtesy of Pavel German

Petauridae (gliders, Leadbeater's possum, and striped possums) Subclass Theria Infraclass Metatheria

Order Diprotodontia (kangaroos, possums, wallabies, & relatives)

3 genera / 10 species (3/11) Australia

Body sizes between 100 and 700 grams Tail long, bushy, and prehensile Dark dorsal stripe on head and back The lesser gliders have gliding membrane Nocturnal and arboreal (except trioks=terrestrial) Scent marking used in sugar gliders

Family Petauridae

FIGURE 25: The sugar glider

(Petaurus breviceps; Petauridae)

© Alan & Sandy Carey/Photo Researchers, Inc.

Tarsipedidae (honey possum)



1 genera / 1 species (Tarsipes rostratus) Australia

noolbender elongate rostrum / nectar feeder Long, prehensile tail Long, bristled tongue used to extract nectar Jaw muscles and teeth reduced

Acrobatidae (feathertail gliders & pygmy gliders) Subclass Theria Infraclass Metatheria


2 genera / 2 species Australia

Feather-like hairs on tail tip Feathertail glider has a gliding membrane between elbows

and knees Feathertail gliders exhibit embryonic diapause Feathertail possums (from New Guinea) are larger and lack

gliding membrane

Hypsiprymnodontidae (musky rat kangaroo)



1 genus / 1 species (Hypsiprymnodon moschatus) Australia

Formerly lumped in Potoroidae Quadrapedal Omnivorous Inhabits rain forest and riparian areas Retains all digits on hindfeet—quadrupedal

Potoroidae (bettongs, potoroos, rat kangaroos) Subclass Theria Infraclass Metatheria



Retain slightly prehensile tail

Well-developed upper canines

Macropodidae (kangaroos, wallabies)

Subclass Theria Infraclass Metatheria Order Diprotodontia (kangaroos, possums, wallabies, & relatives)


3/1, 10/0, 2/2, 4/4=32 or 34 900 grams to 90 kilograms Marsupium opens anteriorly Broad diastema Highly specialized for jumping Hindlimbs elongate (especially 4th metatarsal) Digits 2 & 3 small and syndactylous

Family Macropodidae

Adapted from Marshall, L.G., Proceedings of the Royal Society Victoria 85 (1972): 51–60.

FIGURE 28: The right foot bones of some macropodid marsupials

Family Macropodidae

© FLPA/David Hosking/age fotostock

© John Cancalosi/age fotostock

FIGURE 27B-C: Two kinds of macropodid marsupials

Family Macropodidae

Macropodids are convergent with ungulates Browsing and grazing lifestyle Cursorial Specialized digestive system for microbial

fermentation of plant material

FIGURE 29: Comparison of the

digestive systems of (A) a kangaroo

(Macropus giganteus) and

(B) a sheep (Ovis aries).

Adapted from Dawson, T. J. Kangaroos: Biology of the largest marsupial. Cornell University Press, 1995.

figure 01: phylogenetic relationships of monotremes data from westerman, m. and edwards, d. platypus...

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