The Platypus: Officially Very Strange

Dennis_De_Bacle

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#31
Re: What really is the Platypus?

Goldstein said:
Looks like either monemes must have diverged from the ancestors of modern mammals some time after they evolved hair and milk, but before they evolved "proper" nipples or the current mammalian arrangement of sex chromosomes, or else hair and milk were independently evolved twice... the question is, is hair and milk being independently evolved twice likely?
As it looks like the inner ear evolved twice it may be quite likely. link
 

Anome

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#32
Well, monotremes are definitely closely related to mammals. They did split off before the development of nipples, and the placenta, for that matter. It would seem that they also split off before our sex chromosomes stabilised.

The inner ear thing is interesting, but you have to remember that they started with the same set of bones as mammals at the point they split. Once that groundwork was done, the final outcome, while not a given, is not quite as surprising.
 

Human_84

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#33
The Platypus

Not many people know very much about this:

It was originally thought that the first platypus specimens that were sent to England, were nothing more than an elaborate hoax. This was a fairly logical reaction to an animal that would seem impossible because it had a muzzle like a duck's bill, a tail like a beaver and which laid eggs but suckled its young. All of these attributes seemed contradictory to the knowledge scientists had in those days. But since then a lot of investigation has been done in order to find out more about this 'hoax' of a creature.

The platypus is roughly half the size of a household cat. The adult male's average length is about 50cm and its weight is approximately 1.7kg. The female, however, is smaller and will reach an average length of 44cm and weigh about 0.9kg. This difference in size and weight between the males and the females is called sexual dimorphism. See the table below for more information about the size of platypuses.
 

Rubyait

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#34
'First platypus' still intact


It may be more than 200 years old, but the story of the "first platypus" is still told in Australian schools.

When European settlers sent back a specimen of this bizarre creature, scientists were baffled and concluded it was probably a fake.

It was only when more examples arrived from "Down Under" that the issue was resolved.

But what happened to that original specimen that so famously bamboozled the experts?

Well it's still intact in a London museum, and in surprisingly good condition.

The first photographs of it were published in an Australian newspaper on Saturday.

The Natural History Museum is understandably protective of the delicate specimen, but recently agreed to photograph it under special conditions.

Because this was the individual used for the first scientific description of a platypus (Ornithorhynchus anatinus), it has become what is called a "holotype" or "type specimen".

Every creature on Earth has one "type specimen", and it is used as the standard to determine if later discoveries are a new species or sub-species.

Despite its status, the platypus holotype is not typical - mainly because it is so small.

"Actually, it is a juvenile male," explains mammal curator Daphne Hills.

It is perhaps not surprising that a young animal was the first to be caught and shipped to London.

As Ms Hills suggests, "he was probably young, stupid and easy to catch".

The platypus holotype is too valuable to be put on public display.

Instead, it is kept in a sealed box in a cupboard on the third floor of the museum's north-west block, dubbed "The Mammal Tower".

It is a humble resting place for a fascinating piece of Australia's natural history, but it ensures the holotype is protected from changes in temperature or humidity.

Missing skull

There is a bit more to the tale of the "first platypus" - and the clues can be found on a paper tag attached to its right hind leg.

The platypus was first classified by the museum's acclaimed naturalist George Shaw (the man who was sceptical about its validity).

After that, it became "lost" among other specimens until it was uncovered by another of the museum's legendary figures - Michael Rogers Oldfield Thomas.

Oldfield Thomas' notes include an observation that a spur has broken off from one of its feet (all platypuses are born with spurs on their hind feet, but females lose theirs early in life).

And he noted something more significant was missing - the animal's skull.

When type specimens are preserved, it is common to keep skins and skulls together, and Shaw's description from 1799 indicates this was the case with the platypus.

However by the time Oldfield Thomas "re-discovered" the animal, the skull was gone. Its whereabouts are still unknown.

http://news.bbc.co.uk/1/hi/sci/tech/4547151.stm
 
A

Anonymous

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#35
Stormkhan said:
I've always considered the duck-billed platypus to be the single piece of evidence that Mother Nature/Divine Creator/Deity of your choice has a sense of humour.
I've always thought that the human act of reproduction was fairly convincing evidence of an all-powerful sense of humour. Well, it makes me laugh, anyway. Perhaps I'm doing it all wrong :shock:

Merlin
 

rynner2

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#36
Duck-billed platypus is dismissed by Oxford scientists as daffy
Mark Henderson, Science Editor

When the first duck-billed platypus specimens were sent from Australia to Europe at the end of the 18th century, the bizarre combination of mammal, bird and reptile features led many zoologists to consider them a hoax.

The reason for that first impression has now been revealed: the first analysis of its DNA code has shown that at a genetic level the platypus is indeed a unique amalgam of mammal, reptile and bird.

The platypus genome, sequenced from a female named Glennie, has allowed scientists to examine how evolution shaped not only the strange egg-laying mammal, but also relatives such as human beings. It may even offer insights into human diseases, by revealing genes that are critical to the mammalian immune system.

“This is our ticket back in time, to when all mammals laid eggs while suckling their young on milk,” said Chris Ponting, of the University of Oxford, one of the leaders of the international research team.

“The platyus genome is extremely important, because it is the missing link in our understanding of how we and other mammals first evolved.”

Francis Collins, director of the US National Human Genome Research Institute, said: “At first glance, the platypus appears as if it was the result of an evolutionary accident. But as weird as this animal looks, its genome sequence is priceless for understanding how fundamental mammalian biological processes have evolved.

“Comparisons of the platypus genome to those of other mammals will provide new insights into the history, structure and function of our own genome.”

The platypus code has already been compared with those of people, mice, dogs, opossums and chickens, as well as the draft sequence of the green anole lizard to examine its similarity to reptiles. This has shown that although it diverged from other mammals about 166 million years ago it still shares about 82 per cent of its genes with very different relatives, such as people and mice.

Other aspects of its genome, however, appear distinctly avian or reptilian in character. Ewan Birney, of the European Bioinformatics Institute, who led the genome analysis, said: “The platypus looks like a strange blend of mammalian, bird-like and reptilian features and now we know that the genome is an equally bizarre mix of all of these. It is much more of a melange than anyone expected.”

The male platypus is unique among mammals in having venomous spurs on its hind legs, with which it injects rivals and predators with painful poison. The genes that produce this venom are very similar to those found in snakes. Other reptilian characteristics include genes that support egg-laying.

The animal's sex chromosomes have similarities with those of birds. It has ten sex chromosomes, where most mammals, including humans, have only two.

Mammalian characteristics include an unexpectedly high number of genes involved in detecting scent, which is surprising because the creature spends most of its time under water with its nostrils closed.

The genetic code of the platypus, which has the Latin name Ornithorhynchus anatinus, meaning “duck-like bird-snout”, should shed light on its ability to detect prey under water using an electro-sensory organ in its bill.

The sequence, which is published in the journal Nature, shows that the platypus genome contains approximately 2.2 billion DNA letters, and about 18,500 genes. This compares with 3 billion letters and an estimated 21,500 genes in the human genome. Comparisons between the two genomes should help scientists to understand the function of genes that are critical to human health.

Mark Batzer, of Louisiana State University, said: “This is a huge genetic step. We're learning a lot about mammalian gene regulation and immune systems, which has huge implications for disease susceptibility research.”

The platypus is a monotreme, from a group of mammals that diverged from the marsupials and placental mammals about 166 million years ago.

http://www.timesonline.co.uk/tol/news/u ... 889495.ece
 

EnolaGaia

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#37
You were live-born ... First - thank your mama ... Second - thank the proto-platypus of 300 million years ago.

The modern platypus is the unique surviving representative of the sort of proto-mammal that introduced the innovations allowing mammalian mothers to carry new offspring to term while deeply interconnected via a placenta. The most important of these innovations was the development of blood platelets that could automatically suppress blood loss when the connecting channel was ruptured.

Platelet cells of ancient proto-platypus paved way for human pregnancy

Without a 300-million-year-old platypus-like species and its novel platelets, humans wouldn't be able to give birth. That's according to a new opinion piece published Wednesday in the journal Biology Letters.

Authors of the research-backed editorial claim platelet cells, which prevent mammals from non-stop bleeding, were a prerequisite for the evolution of placental development in mammals.

While many animals have evolved the development of a placenta, only eutherian mammals, including humans, are characterized by haemochorial placentation, a deep, invasive placenta that provides a fetus with direct access to a mother's blood.

According to researchers at the University College London and Yale University, moms would hemorrhage during birth without platelet cells. ...

Scientists determined these vital cells were first evolved by an egg-laying, duck-billed-platypus-like animal living some 300 million years ago. The trait was passed on when the first groups of mammals -- including monotremes, the first mammal group, as well as marsupials and eutherian mammals -- diverged from the proto-platypus lineage.
FULL STORY: https://www.upi.com/Science_News/20...-paved-way-for-human-pregnancy/2831562760257/

CITED ARTICLE: https://royalsocietypublishing.org/doi/10.1098/rsbl.2019.0374
 
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