A Field Report: On the Nature of Monotremes

By Jeremy Rosen, Scientician and Expert on Curiosities.


Above: Blurred photo of mammals in the wild by mechanic Andrew Commons

The basics of monotreme physiology are quite diverse. The name derives from the fact that monotremes have a cloaca, a urogenital opening consisting of one hole. Like reptiles and birds, monotremes lay eggs, in this case soft leathery ones. Modern monotremes have no teeth and modified snouts or beaks. Monotremes also have a single bone in their lower jaw, three inner ear bones, high metabolic rates, hair, and they produce milk to nourish the young, in accordance with the morphology and physiognomy of other mammals. Monotremes come in three flavours: platypus, Ornithorhynchus anatinus; and echidnas of two varieties, Tachyglossus aculeatus and Zaglossus bruijnii.

The platypus, Ornithorhynchus anatinus, is a semi-aquatic monotreme with fore and aft webbed feet and a flattened tail similar to that of the placental beaver. The tail acts as a stabilizer, but also stores fat. Platypi inhabit rivers and streams in Eastern Australia from Cooktown to Tasmania in the South. While laying eggs and having some bones similar to those of reptiles, the platypus is overall entirely mammalian. The coat of the platypus is one of the most waterproof in existence. An inner layer of fine hairs traps air and an outer layer of longer, flat-bladed hairs, gives excellent insulation for the animal. While sometimes referred to as primitive, the platypus is considered to be quite evolved and sophisticated.

Some interesting features of the platypus, beyond the leathery and sensitive “duck bill,” include the male’s spur and the female’s milk producing glands. The spur is located next to each of the rear feet in all young platypi. After the first year, the females of the species shed their spurs, but the males retain them. The spur is connected to a venom sack and produces a painful wound. The venom is powerful enough to kill a dog and often causes severe damage to the males during mating season, when they become aggressive. The female’s milk glands are also quite interesting. Female platypi have no teats. Milk is produced in large glands under their skin, then the milk oozes out onto a patch of fur and the young ingest it from this point.

The echidna, comprising the genera Tachyglossus and Zaglossus, are spine-covered, slender-snouted mammals with claws. They live throughout Australia and New Guinea. The echidna produces an egg which is transferred to a pouch, where it hatches. The young are suckled from milk glands in the pouch similar to those of the platypus. Young echidna, like platypi, have teeth which they later lose.

Above: Taxidermed platypulan innards.

The coat of the echidna is comprised of coarse hair and spines, which are modified hair, like human fingernails and rhinoceros horn. The echidna doesn’t need a thick coat like the platypus because it is predominantly diurnal, foraging for insects with its long, sticky tongue. Like the platypus, the echidna has a cloaca used for excretion and reproduction.

Current scientific theory states that monotremata are a concurrent branch with other mammals that evolved alongside placental mammals. They are somehow related to marsupials, displaying similar, if more primitive physiognomy, but it is believed that they are not primitive forebears, but another branch along with marsupials. All in all, monotremata fits within the mammalian profile, nursing their young, having hair and maintaining a warm-blooded metabolism. Monotremes are cool.

Faithfully submitted to the Royal Tractor Repair and Maintenance Society of Outer Mongolia, on this the Fourth Day of May, 2003 A.D.

Dr. Jeremy-Joseph Rosen holds the distinguished Lord Rosemary Chair at the Salisbury College of Science at the University of Pretoria. Through his continued travels and expeditions, he has unearthed many biological curiosities, amongst them The Forked Fox, the Nine Toed Plute, and the Hammer Toad.

Pictured is Dr. Rosen on his expedition to Peking, Chinastan with TV personality Jamie Farr.