Platypus – A True “Living Fossil”

Classification and Biodiversity of this Group

Phylum –   Chordata Bateson, 1885

Class – Mammalia Linnaeus, 1758

Subclass –  Prototheria Gill, 1872

Order – Monotremata Bonaparte, 1837

Family – Ornithorhynchidae Gray, 1825

Genus – Ornithorhynchus Blumenbach, 1800

Species – Ornithorhynchus anatinus Shaw, 1799

Common Name – Duck -Billed Platypus or Platypus

There are no other known living species of Platypus. So it is often referred to by its common name of Platypus. It is one of five extant species of the Monotremes, others being part of the Echidna.  (Nelson, 2014)

Characteristics of the Platypus

Platypus are homoeothermic, bilaterally symmetrical mammals (Ojo, 2014). Living primarily semi aquatic environments, their front feet have become completely webbed while their back feet are partially webbed. This is an adaptation to aid them in swimming in conjunction with being able to move easier on muddy ground. (Duck-billed Platypus: The Animals Files, 2014).

This mammal lays eggs and doesn’t give birth to live young. It belongs to the species Monotremes. (Duck-billed Platypus: The Animals Files, 2014).  Its young suckle for a few months, feeding on its mother’s milk.

The males are able to produce venom through spurs which are situated on their hind legs. There is not enough venom to kill a human, however is dangerous to smaller animals. This acts as a defence mechanism (Duck-billed Platypus: The Animals Files, 2014).

Their highly adapted bills are extremely sensitive, containing electroreceptors and mechanoreceptors which help detect stimuli beneath the water when searching for food (Duck-billed Platypus: The Animals Files, 2014). The platypus is able to navigate underwater using its bill without having to open its eyes, ears or mouth. As young they posses teeth, but lose them in adult hood when they adopt a keratinised pad which aids in grinding up t heir food (Schmidt-Nielsen, 1997).

Origins and Evolution

The oldest fossil dates back to 100,000 years ago, during the Quaternary period which makes the fossil approximately 110 million years. Platypus existed during the Cretaceous period. Other family members of Monotremes have since been discovered in Argentina which would have originated when Australia and South America were previously joined (Truth, 2016).

There is not much information on the origin of this species.  Encyclopaedia Britannica, 1992, state that Monotremes feature anatomy and development that is seen in the earliest of mammals. The platypus is an extremely unique animal, in both its looks and functions. It is a combination of many animals, including bird, reptile and mammal (Truth, 2016).  This animal has puzzled scientists ever since its discovery in the late 18th Century. Scientists did not initially believe that such a creature could exist (Weston, 2002). It seems to be in the middle of an evolutionary decision, as in some ways it shows evidence of being a mammal, while at the same time displays links to its non mammalian counterparts (Weston, 2002). It has since evolved over time and become well designed for its surrounding environments.

Feet
The platypus has adapted itself into having webbed feet helping it with swimming.  Its front feet are for swimming power while its back feet are used in steering. The webbing is able to fold away, exposing its claws when the Platypus exits the water which allows it to walk on land easily and aids in digging burrows.

Bill and Teeth
It originated on mainland Australia and is claimed to be endemic to Australia. Three platypus teeth fossils were found in South America  in the early 90’s, indicating to us that this species was not totally endemic to Australia (Weston, 2002). (This was during the period when it was known Gondwanaland).  Modern day platypus do not contain teeth in any form as they lose them at a young age. They have a tough plate which they use to grind their food (Truth, 2016).

Platypus have electroreceptors for orientation and navigation (Jones and Sati, 2011) on their bill, despite them having eyes, ears and nose which would is used for navigation on land they close them when in water.  Their bill is extremely sensitive and covered in nerve endings which  they use to find food when underwater.

Spur on Males
Male platypus have spurs on their hind legs. In females this is absent. It is a hollow spur which is connected to venom glands. The enzyme that is injected into a victim has shown similarity to the same enzyme which is found in snakes, yet not in any other mammals which suggest that there may be a possible link between the platypus and reptiles (Jones, K.E.J. and Safi, K. 2011),

Skeleton
Their skeleton is tough and durable which supports strong muscles effective for swimming and digging. Some of their bones are similar in function to those belonging to extinct reptiles, but possibly belonged to mammal ancestors. A platypus leg is very similar to those of mammal and reptile. The rotation and outward nature of their legs is very reptile-like, while the ability of rotating in a ball and socket joint resembles a similarity in mammals. Platypus contain rudimentary ribs in their neck which is indicative to those in reptiles.

Platypus are covered in a layer of fur and feeds it young with milk which is secreted through pores in their skin (Truth, 2016) which is a distinct feature of mammals.

Reproduction
Mammals tend to have two openings, one for excreting bodily waste and another opening through which reproduction can take place in (Noris, 2010). However, this is not the case in the platypus. It has one opening for all processes.

The Australian National University  discovered the Platypus contain ten sex chromosomes in comparison to mammals two XY chromosomes. At the same time the platypus chromosomes are very similar to those found in birds. Platypus also lack a sex determining chromosome, making the sex determination in the platypus unknown (Truth, 2016). An egg laying mammal that in itself is an evolutionary mystery (Gopalakrishnakone and Calvete, 2016).

They were initially seen as primitive creatures. However, its since been realised that they are exceptionally specialised creatures.

What is their ecological function and current conservation status?
Platypus are considered to be top predators within their freshwater environment. They are a vital component to their environment including species living within the ecosystem. They act as an indicator species indicating to us how productive / healthy their surrounding environment may be. Thus, if a platypus is remaining in its current environment, then it means conditions are favourable to other animals within the same ecosystem.

It is vital to protect and preserve the status of the platypus as it will naturally increase the biodiversity of other species within the surrounding environment.

In Australia it is an iconic wild animal which could be used advantageously to create more awareness about protecting our environment, and the animals in the surrounding ecosystem.

According to IUCN its conservation status is listed as “Least Concern”. This is because platypus are widely distributed which would suggest that there must be a fairly large population relative to the population distribution. This of course may not be the case, as there is insufficient data in order to predict the population numbers and their trend over a long period of time (Union, Nature, Resources, 2000).

Hope you enjoyed this post and can take something from it.

Fiona 🙂