1. 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):

2. 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

3. 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

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

8. FIGURE 04: Anatomy of the female reproductive tract of monotremes
Reproduction
Cloaca present
Testis abdominal
Mammae lack nipples
Long lactation periods
FIGURE 04: Anatomy of the female reproductive tract of monotremes
Adapted from Szalay, F. S., Novacek, M. J., and McKenna, M. C. Mammal Phylogeny. Springer-Verlag, 1993.

9. Tachyglossidae (echidnas)
Subclass Prototheria
Order Monotremata
2 genera / 2 species
Australia & New Guinea
edentate
spiny
sticky tongue

11. Morphology Beak-like rostrum Adults are toothless
Sclerotic cartilages in eyes
Lacrimal and frontal bones absent
Septomaxilla bone present
No auditory bulla—cochlea simple

12. FIGURE 03: Bones of monotremes
Morphology
Shoulder girdle retains ancestral features
FIGURE 03: Bones of monotremes

14. 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.

16. Reproduction
FIGURE 05: Ventral view of a live echidna (Tachyglossus aculeatus)
FIGURE 20.04: Young echidna emerging from the egg
Courtesy of P. Rismiller and M. McKelvey
Courtesy of Michael L. Augee

17. Tachyglossidae
Tachyglossus is capable of daily torpor and seasonal hibernation
Diet consists largely of insects, earthworms, and other soil arthropods

19. 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

20. Figure 5.29

22. Reproduction
Marsupium present in 50% of metatherians

23. 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

24. Paleontology Fossil metatherians include:
Thyacoleo—a lion-like predator
Diprotodon—a rhino-sized metatherian
Procoptodon—massive grazing animal
Many smaller forms

25. FIGURE 05: Fossil skull of Procoptodon goliah
Paleontology
FIGURE 05: Fossil skull of Procoptodon goliah
Adapted from Tedford, R.H., University of California Publications in Geological Science 64 (1967): 1–165.

26. Paleontology South American radiation rivaled that in Australia
Evolved from basal insectivorous or omnivorous stock
Convergence with eutherians
Over 130 living and fossil genera

27. Paleontology Borhyaenidae—convergent with canids and bears
Thylacosmilidae—convergent with saber- toothed cats
Argyrolagidae—convergent with kangaroo rats and jerboas

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

29. Mio-Pliocene of Argentina
Paleontology
FIGURE 08: Microtragulus (Argyrolagidae), an extinct bipedal metatherian from the
Mio-Pliocene of Argentina
Adapted from Simpson, G.G., Bulletin Museum Comparative Zoology 139 (1970): 1–86.

30. Paleontology Panamanian land bridge established ~2.5 million years ago
Northern eutherians moved southward
Some metatherians moved northward
Metatherian diversity begins to decline

31. 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)

32. Metatherians vs. Eutherians
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.

33. Metatherians vs. Eutherians
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?

34. Metatherians vs. Eutherians
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.

35. Metatherians vs. Eutherians
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.
Behavioral plasticity is greater in eutherians.
Cooperative social systems, dominance hierarchies, and territoriality are rare in metatherians.

36. Metatherians vs. Eutherians
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.

37. Metatherians vs. Eutherians
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.

38. 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

39. 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

42. Caenolestidae (shrew opossums)
Subclass Theria
Infraclass Metatheria
Order Paucituberculata (shrew opossums)
3 genus / 5 species (3/6)
South America
Andes
No marsupium
Lower incissors procumbent

45. Microbiotheriidae (monito del monte)
Subclass Theria
Infraclass Metatheria
Order Microbiotheria (monito del monte)
1 genus / 1 species
Southern Andes
Relict of Australidelphia
May hibernate

48. Notoryctidae (marsupial moles)
Subclass Theria
Infraclass Metatheria
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

50. 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

52. FIGURE 15B: The thylacine (Thylacinus cynocephalus, Thylacinidae)
Family Thylacinidae
FIGURE 15B: The thylacine (Thylacinus cynocephalus, Thylacinidae)
© FLPA/Hugh Clark/age fotostock

53. 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

55. 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

58. Family Dasyuridae FIGURE 13A: Skull of a dasyurid marsupial
© Patsy A. Jacks/ShutterStock, Inc.
FIGURE 13A: Skull of a dasyurid marsupial
FIGURE 15A: The Tasmanian devil (Sarcophilus harrisii, Dasyuridae)

60. Peramelidae (bandicoots and echymiperas)
Subclass Theria
Infraclass Metatheria
Order Peramelemorphia (bandicoots and bilbies)
2 genera / 7 species (6,18)
Australia & New Guinea
4th digit of hind foot

62. Order Peramelemorphia
Hindfeet modified for cursorial locomotion

64. Peroryctinae (spiny bilbies)
Subclass Theria
Infraclass Metatheria
Order Peramelemorphia (bandicoots and bilbies)
4 genus / 11 species
Australia & New Guinea
4th digit of hind foot

65. 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

66. Thylacomyidae (bilbies)
Subclass Theria
Infraclass Metatheria
Order Peramelemorphia (bandicoots and bilbies)
1 genus / 2 species
Australia & New Guinea
Nocturnal, invertivores
Dig burrows, occupy during day
1 extinct, 1 endangered

67. Chaeropodidae (pig-footed bandicoot)
Subclass Theria
Infraclass Metatheria
Order Peramelemorphia (bandicoots and bilbies)
1 genus / 1 species
Australia & New Guinea
Front didactyl (2&3), rear monodactyl (4)
Extinct

68. 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)

69. Phascolarctidae (koalas)
Subclass Theria
Infraclass Metatheria
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

71. Family Phascolarctidae
FIGURE 21: Skull of the koala

73. Vombatidae (wombats) Subclass Theria Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
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

75. FIGURE 19: Hairy-nosed wombat (Lasiorhinus, Vombatidae)
Family Vombatidae
© Timothy Craig Lubcke/ShutterStock, Inc.
FIGURE 19: Hairy-nosed wombat (Lasiorhinus, Vombatidae)
FIGURE 09D: Wombat skull

77. Phalangeridae (brushtail possums and cuscuses)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
6 genera / 18 species
Australia & New Guinea

80. Family Phalangeridae FIGURE 23A: A male common spotted cuscus
© Gary Unwin/ShutterStock, Inc.
© Stuart Wilson/Photo Researchers, Inc.
FIGURE 23A: A male common spotted cuscus
(Spilocuscus maculatus)
FIGURE 23B: The Australian brushtail possum
(Trichosurus vulpecula)

81. Burramyidae (pygmy possums)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
2 genera / 5 species
Australia
Small, delicately built (up to 40 grams)
Mountain pygmy possum capable of hibernation

82. FIGURE 22: A pygmy possum (Cercartetus concinnus, Burramyidae)
Family Burramyidae
Pygmy possums
2 genera and five species
Small, delicately built (up to 40 grams)
Mountain pygmy possum capable of hibernation
FIGURE 22: A pygmy possum (Cercartetus concinnus, Burramyidae)
Courtesy of Anthony Robinson

84. Pseudocheiridae (ringtail possums)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
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

86. Family Pseudocheiridae
FIGURE 24: Painted ringtail (Pseudochirulus forbesi; Pseudocheiridae)
Courtesy of Pavel German

87. 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

89. FIGURE 25: The sugar glider (Petaurus breviceps; Petauridae)
Family Petauridae
FIGURE 25: The sugar glider (Petaurus breviceps; Petauridae)
© Alan & Sandy Carey/Photo Researchers, Inc.

91. Tarsipedidae (honey possum)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
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

93. Acrobatidae (feathertail gliders & pygmy gliders)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
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

95. Hypsiprymnodontidae (musky rat kangaroo)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
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

96. Potoroidae (bettongs, potoroos, rat kangaroos)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, and relatives)
5 genera / 9 species (4/10)
Australia
Retain slightly prehensile tail
Well-developed upper canines

99. Macropodidae (kangaroos, wallabies)
Subclass Theria
Infraclass Metatheria
Order Diprotodontia (kangaroos, possums, wallabies, & relatives)
11 genera / 54 species (11/65)
Australia
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

100. FIGURE 28: The right foot bones of some macropodid marsupials
Family Macropodidae
FIGURE 28: The right foot bones of some macropodid marsupials
Adapted from Marshall, L.G., Proceedings of the Royal Society Victoria 85 (1972): 51–60.

101. FIGURE 27B-C: Two kinds of macropodid marsupials
Family Macropodidae
FIGURE 27B-C: Two kinds of macropodid marsupials
© John Cancalosi/age fotostock
© FLPA/David Hosking/age fotostock

104. Family Macropodidae Macropodids are convergent with ungulates
Browsing and grazing lifestyle
Cursorial
Specialized digestive system for microbial fermentation of plant material

105. 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.