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

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.

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

FIGURE 03: Bones of monotremes 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 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

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

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.

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.

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.

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)

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.

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?

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.

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.

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.

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.

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

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

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

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

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

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

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

Order Peramelemorphia Hindfeet modified for cursorial locomotion

Peroryctinae (spiny bilbies) Subclass Theria Infraclass Metatheria Order Peramelemorphia (bandicoots and 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) 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

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

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) 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

Family Phascolarctidae FIGURE 21: Skull of the koala

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

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

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

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)

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

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

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

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

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

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

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

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

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

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

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.

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

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.