|
In 1991, a fossil tooth belonging to a different kind of ancient platypus (originally described as Monotrematum sudamericanum but now probably regarded as another Obdurodon
species) was discovered in the Patagonian desert of Argentina. The tooth was found in sediments deposited over 60 million years ago, at the time when Australia and South America were still joined as part of the southern supercontinent Gondwana.
Fossils belonging to three other extinct platypus species (Obdurodon insignis, Obdurodon dicksoni, and Obdurodon sp. A) have been found in Australian sediments deposited between 25 and 15 million years ago, while a leg bone from the first close relative of the modern platypus (Ornithorhynchus sp.) has been dated to about 4.5 million years ago.
The earliest known remains of the platypus in its current form (Ornithorhynchus anatinus) date back to around 100,000 years ago.
The platypus is sometimes described as a ‘living fossil’ because of
this ancient lineage and its combination of mammalian and reptilian features.
Description
The platypus has a streamlined body, with the male averaging 50
centimetres long and weighing about 1.7 kilograms. Females platypus
are smaller. It has a broad horizontally flattened tail, that
stabilises it underwater, as well as stores fat. The characteristic
bill has thousands of touch-sensitive and electro-sensitive pores
that can detect the electric currents generated by small prey. The
eyes and ears lie in a furrow that closes when the platypus is
submerged. Its waterproof fur coat consists of an inner layer of fine hairs
that trap air and an outer layer of longer, flat-bladed hairs, that
give insulation ensuring that it can survive, sometimes up to 12 hours each day in water as cold as 0 degrees Celsius.
With its webbed feet, the platypus swims with alternate strokes of
the forefeet only, with the webbing folding back for walking and burrowing, and during the
return stroke in swimming. The young of both sexes have a spur on each hind leg. The
female sheds hers during the first year but the
adult males retain them all their life. The spur in the adult are
about 1.5 cm long, and
connected to a venom gland capable of
inflicting a painful wound. It is thought that males, who become aggressive during the
mating season, use these spurs to sometimes hurt each other. The venom can cause excruciating pain in humans and is
strong enough to kill a dog.
Platypus are capable of many vocalisations including a
soft growling sound when disturbed. In the wild the Platypus is known to live
for at least 12 years.
Breeding
The Platypus is a seasonal breeder with males and
females reaching sexual maturity at an age of two
years. Mating occurs from September onwards, although it seems to
occur
later in southern areas. Incubation of the eggs take
about six to ten days. They hatch about early November and the young
are
suckled by the female for about 4 to 5 months. The female has no
teats, hence the young are suckled by producing milk in large glands under her skin which can be up to
one-third of her body’s length. The milk oozes out
onto a patch of fur and the young Platypus sucks it up. Platypus
milk has about 60 times more iron than the milk of cows.
The milk also contains about 40 per cent
solids, compared with only 12 per cent solids in cow’s milk.
The nesting burrows are about three to eight metres long and are
usually found above water level. The female fills
the chamber of the burrow with wet leaves, creating a moist atmosphere
for incubation.
Foraging and Diet
The Platypus is an opportunistic predator, feeding on all kinds
of insect larvae, freshwater shrimp,
bivalve molluscs, frogs and fish eggs. Foraging consists of repeated
dives between 20 and 90 seconds duration. After
successful dives, the platypus will sort and chew the captured prey.
Horny buccal pads are used by the adult to
grind the food as only juveniles have teeth. While the platypus is
submerged food is held in special cheek pouches.
Source: Australian
Platypus Conservancy. |
