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Alphadon

A small mouse-like mammal with a prehensile tail

WWD - Prehistoric Planet

Alphadon is thought to have been a small mouse-like mammal with a prehensile tail and feet adapted for climbing trees.

They call it home

Alphadon lived in Late Cretaceous North America just as flowering plants were beginning to transform the landscape. They lived in an environment of rivers, deltas and marshes.

What we heard about their hearing

What we heard about their hearing

Alphadon, which lived a nocturnal lifestyle up in the trees, might have had excellent hearing.


What big teeth you have

What big teeth you have

Alphadon had a generalised dental pattern allowing it to feed on a variety of different foodstuffs including plants, insects and small vertebrates.


Nose knowledge

Nose knowledge

Alphadon probably had an excellent sense of smell, which would have allowed it to track down food during the dead of night.

The most fantastic find

The most fantastic find

Alphadon was first discovered by George Gaylord Simpson in 1929 when he uncovered the teeth of this early marsupial. The teeth, along with the isolated jaw and skull fragments, remain the only fossils of Alphadon. As a result, much of its biology is inferred from its closest living relative, the opossum. Perhaps one day we will be lucky enough to find an entire or partial skeleton of Alphadon, which would give us a better idea of the evolution of these early marsupials.

Alphadon features

Alphadon features Height: 0.05m (0.16ft)
Length: 0.3m (0.98ft)
Weight: 0.1kg (0.21lbs)
Top speed: 6.5kph (4.03mph)
Vision: Alphadon probably had excellent binocular vision for a life hunting and foraging in the trees.
Skin: Alphadon was a mammal and would have been covered in fur to help maintain a constant body temperature, just like mammals today.
Brain: Didelphid marsupials today have the smallest brains of all mammals and Alphadon would probably have been the same. Despite its lack of brain power, it was still more intelligent than many dinosaurs!
Prey: Alphadon was omnivorous, feeding on fruits, invertebrates and possibly the small vertebrates of the Late Cretaceous.
Bite: Alphadon teeth had high and sharp cusps, well adapted for piercing and perfect for crushing the hard shells of insects.
Nest: Based on comparison with its living relative, the opossum, Alphadon might have given birth after just 14 days of gestation to a single tiny joey. At just a tenth the weight of a paper clip, the joey would attach itself to its mother's teat until it was old enough to venture out on its own.

Alphadon facts and theories

Alphadon facts and theories

  1. Like so many fossil mammals from the age of dinosaurs, Alphadon is mostly known from teeth. These teeth are quite small – just a few millimetres across – and they must be studied using microscopes. Why are mammal teeth so common but bones much rarer? Because the enamel in teeth is so hard and resistant to decay that teeth are easily fossilised.
  2. Alphadon was a member of the Metatheria, a group that includes living marsupials. It was likely very similar in appearance and behaviour to the didelphids, which includes today's opossums.
  3. Alphadon were born tiny and helpless and would have needed excellent parental care. It is likely that the mother would carry her young on her body like modern marsupials do today.
  4. Alphadon might have had large whiskers for sensing its surroundings in the dark.
  5. Alphadon was easy prey for dinosaurs like Troodon, so living high in the trees would have kept it safer from attack.
  6. Alphadon could have taken full advantage of the new flowering plants of the Cretaceous and developed a close relationship and dependence on them.