Microbiotheriidae

The microbiotheriidae (Microbiotheriidae) are the only current family of the order Microbiotheria that, until relatively recently, were believed to be extinct. It includes three living species grouped in one genus, Dromiciops, although other species are known in a fossil state. They are the closest American marsupials to those existing in Australia since it is a reinvasion of marsupials to the lands of Gondwana that ended up becoming present-day South America.

Features

The skull is described as having an elongated rostrum and caudally expanded nasal bone. Paraoccipital process is not described. The tympanic bulb is highly developed and occupies a relatively large area of the skull base.

The dental formula is the one that appears in the attached table. They are polyprotodontous animals with a dentition characterized by spatula-shaped incisors, those of the upper jaw arranged in an arc.

As in most marsupials, the brain is relatively underdeveloped for mammals, with barely marked gyri, although the lobes are well defined.

Classification

• Family Microbiotheriidae
  • Gender Dromiciops (Ameghino, 1894)
    • Dromiciops gliroids (Thomas, 1894)
  • Gender Eomicrobiotherium† (Marshall, 1982)
  • Gender Ideodelphys† (Ameghino, 1902)
    • Ideodelphys microscopicus† (Ameghino, 1902)
  • Gender Khasia† (Marshall & Muizon, 1988)
    • Khasia cordillerensis† (Marshall & Muizon, 1988)
  • Gender Microbiotherium† (Ameghino, 1887)
    • Microbiotherium acclinum†
    • Microbiotherium forticulum†
    • Microbiotherium gallegosense†
    • Microbiotherium patagonicum†
    • Microbiotherium tehuelchum†
    • Microbiotherium tortor†
  • Gender Mirandatherium† (Paula Couto, 1952)
    • Mirandatherium alipioi† (Paula Couto, 1952)