Infraclass Metatheria (Marsupialia)

Download an outline of this lecture as an ADOBE PDF document.

• Learn more about marsupials from
  1. the University of California Museum of Paleontology or 
  2. the University of Michigan Animal Diversity Web 
  3. Unique Australian Mammals

The marsupials or metatherians are almost certainly a monophyletic group.  The following characters, other than 1-3, are for the most part primitive for eutherians and metatherians.

Characters

1. cheek teeth consist of 3 premolars and 4 molars [Fig. 10.8]
2. only the third deciduous premolar is replaced
3. neonate attached to nipple for extended period of lactation [Fig. 9.16]
4. large palatal vacuities are typically present [Fig. 10.17C]
5. inflected angular process
6. choriovitelline placenta in most [Fig. 9.11A]
7. marsupium in most
8. epipubic bones in both sexes
9. uteri completely separate, double lateral vaginal canals [figs. 9.8, 10.1B]
10. penis bifurcate, without baculum
11. scrotum anterior to penis 

Biogeography

1. The Mesozoic World [Fig. 4.11]
   1. Pangea
   2. Gondwana and Laurasia
   3. a North American origin
   4. the South America, Antarctica, Australia connection [Fig. 10.13]

2.   Wallace's Line

3. Many marsupials, especially in Australia, occupy similar niches as placental mammals elsewhere as a result of  convergent evolution:

   1. similar features from different ancestors as a result of ecological equivalence  [Fig. 26.11]
   2.   convergence in placental and marsupial mammals- Dr. George Johnson's Backgrounder
   3. Another term used to describe convergence is ecomorph.  Ecomorphs are distantly related taxa with similar morphologies that occupy similar niches.   Ecomorphs typically are similar in both dietary preferences, feeding adaptations, and locomotor adaptations.
   4. Thylacosmilus an extinct South American marsupial sabertooth [Fig. 10.12]

Infraclass Metatheria: 

• 7 orders, 18 families, 250 species 
• A phylogeny of Recent families of marsupials [Fig. 10.15].

Order Didelphimorphia Family Didelphidae   American opossums [15 genera, 63 species] Neotropical and Nearctic didelphids tend to be unspecialized. 5/4 incisors prehensile tail opposable big toe (hallux) paired sperm [Fig. 10.9], also occurs in the Caenolestidae. most are omnivorous. Didelphis virginiana [Fig 26.5] the Caluromyinae are folivorous; Marmosa and other mouse opossums [Thylamyinae and Marmosinae] are insectivorous. Chironectes (from northern S. A.), the water opossum, has webbed feet adapted to its swimming lifestyle. It is exclusively piscivorous I Dedelplimorphi from the Italian L’Associazione TERRAMBIENTE.

Order Paucituberculata
Family Caenolestidae (Nt)

1. opossum-rats [3 genera, 6 species] [Fig. 10.16]
2. distributed throughout the higher forested elevations of the Andes in South America.
3. small, shrew-like animals of insectivorous and omnivorous habits
4. large, procumbent, medial lower incisors are used to stab their prey.

Order Microbiotheria

Family Microbiotheriidae (South America)

1. a single living species Dromiciops australis
   1. small mouse-like insectivores 
   2. enlarged bullae [Fig. 10.17]
   3. incisors 5/4
2. DNA hybridization data suggests they are related to Australian dasyurids
3. eats mistletoe fruit and deposits the sticky seeds intact onto the trunks of shrubs [Amico, G. and Aizen, M.A. 2000. Mistletoe seed dispersal by a marsupial. Nature 408(6815):929-930.]

Order Dasyuromorphia (A)

Family Dasyuridae[15 genera, 61 species] marsupial "mice" [Fig. 24.6], native "cats", and "Tasmanian Devil" 4/3 incisors tail not prehensile pouch usually absent, if present opens posteriorly ecological equivalent of didelphids insectivores, carnivores, and scavengers Sarcophilus; the Tasmanian Devil 4-10 kg Sarcophilus from Tasmania Online Males of the marsupial mouse Antechinus and the Brush-tailed Marsupial Mouse are semelparous.  Almost all other mammal species are iteroparous.	Antechinus stuartii; Broad-footed Marsupial Mouse Dr. Lloyd Glenn Ingles; © 2001 California Academy of Sciences
Family Myrmecobiidae Myrmecobius: the numbat or marsupial "anteater" [Fig. 10.19] myrmecophagous long extensible tongue for feeding on ants or termites.
Family Thylacinidae Tasmanian "tiger or wolf" Thylacinus cynocephalus; 1500-2000 mm long [fig 10.18] extinct in Australia and New Guinea, almost certainly in Tasmania Visit The Thylacine Museum  at C. Campbell's LIVING PLANET.

Order Notoryctemorpha (A)

Family Notoryctidae

1. marsupial "mole" [Fig. 10.30]
2. the only completely fossorial marsupial
   1. fossorial adaptations

Syndactyla (A) [fig. 10.14, Table 10.2]

Characters

1. Syndactyly
2. dilambdodont molars

Order Peramelorpha

Characteristics

• bandicoots: 2 families, 8 genera, 21 species
• "fused" but nonvillous chorioallantoic placenta in at least 3 genera
• terrestrial omnivores - rat size to ca. 5-7 Kg.
• hopping locomotion, enlarged digit IV of foot [fig. 10.20]

Families

1. Family Peramelidae non-spiny bandicoots bilbies or rabbit-eared bandicoots [fig 10.21A] big-footed bandicoot [fig. 10.21B] Perameles nasuta -- Long-nosed Bandicoot; photograph to right by Dr. Lloyd Glenn Ingles,  © California Academy of Sciences.

2. Family Peroryctidae
   1. bandicoots that mainly occur in New Guinea 

Order Diprotodontia  

• diprotodont  (vs. polyprotodont) [fig. 10.14, table 10.2]
• 10 families, 117 species
• many arboreal diprotodonts have schizodactylous forefeet [Fig. 10.22]

Families

 

Family Vombatidae wombats  1/1 incisors, diastema [fig 10.23] semi-fossorial Vombatus ursinus Cal Photos © 2005 Sharon Chester

1. Family Phascolarctidae koala [Fig. 6.16] tail vestigial Folivory feed primarily on Eucalyptus leaves hindgut fermentation specializations [Fig. 6.14] chorioallantoic placenta without villi Australian koala foundation the koala's page koalas from the BigZoo



2. Family Tarsipedidae
1. honey possum: nectar feeder; pollinator [Fig. 6.16]
2. long tongue with bristles at tip [Fig. 10.29]
3. long prehensile tail

Phalangeroids 

3. Family Acrobatidae
   1. feathertail glider and feathertail possum
4. Family Burramyidae
   1. 2 genera and 5 species of pigmy possums 
   2. brushy tongues [Fig. 10.27]
   3. includes some gliding species
   4. known only as fossils until 1966
5. Family Pseudocheiridae
   1. ringtail possums and the greater glider [Fig. 10.28A]
   2. formerly included in the Petauridae
   3. ringtails have a strongly prehensile tail
   4. copraphagy and bacterial fermentation in the caecum

6. Family Petauridae lesser gliders [Fig. 10.28B] Petaurus has a furred gliding membrane like a flying squirrel; sugar gliders are sold as pets. Petaurus australis Fluffy Glider Possum;  photograph to right by Dr. Robert Thomas and Margaret Orr; California Academy of Sciences striped possums lack a gliding membrane, have an elongate fourth finger Leadbeater's Possum (Gymnobelideus leadbeateri) from Australia National University.

7. Family Phalangeridae large possums (phalangers) and cuscuses highly arboreal, slow moving: loris-like prehensile tail opposable hallux and thumb. photograph of Trichosurus vulpecula, Brush-tailed Possum

   image © Dr. RobertThomas and Margaret Orr, California Academy of Sciences.

Superfamily Macropodoidea

8. Family Potoridae
   1. potoroos, bettongs, and the musky rat-kangaroo
   2. Tasmanian bettong from Tasmania Online
      



9. Family Macropodidae kangaroos and wallabies 11 genera; 56 species locomotion [Fig. 5.13] mainly terrestrial arboreal {Lumholtz tree-kangaroo page} digitigrade bipedal hopping (ricochetal) [p. 72; Fig. 10.26] relationship between metabolic rate and hopping speed in red kangaroos  Hop, Skip, and Soar: Studying animal locomotion at Harvard's Concord Field Station ecological equivalent of ungulates foregut fermentation [p. 88] kangaroo reproduction embryonic diapause: a variant of delayed implantation [Fig. 9.17]

   ©2000 ZooNet/Montgomery Zoo

THE MARSUPIAL-PLACENTAL DICHOTOMY [Table 10.1]

Return to: