Mammal family tree shaken (dinosaur, evolution, agnostic, science, Article)

[painted wolf]

A new discovery of a 115 million year old Monotreme (platypuss ancestor) is causing a bit of a stir in the mammal paleontology world.

Mammals are defined by certen charictoristics such as hair, milk, and the presence of three little bones in the ear....

This latest find however hints that the most diagnostic of the skeletal signs of mammal-dom may have evolved in mammals indipendantly at least twice. This comes as a surprize because the complexity of the ear bone arrangement is so great that it was thought to only be able to happin once. (Although some embyologists had been suggesting this very idea.)

The jawbone shows a definate ridge where the two smaller bones had not yet seperated completely from the jawbone.

The find hints that the most basal ancestor for both the monotreme and the Marsupial/Placental mammal groups was more primitive than previously thought, and likely didn't have mammal like ears yet.
It also indicates that both lines of mammals had similer selective pressures put on them that made the three bone ear develop convergantly.

article can be found here: http://www.nature.com/news/2005/0502...050207-16.html

aparently mammal evolution is more complex than previously thought.

wa:do

[Scuba Pete]

It also indicates that both lines of mammals had similer selective pressures put on them

Sounds like "God" to me... pardon the pun! And you don't need an anvil to fall on you to see it. Well actually, this kind of find is rather ear-y. You know, lobe or leave em? You can see I am trying to stirrup some interest and hammer a point home at the same time.

[Novo]

Thats incredibly interesting, Keep us updated on all the new information coming in regarding this discovery.

[Paw]

Stirrup some interest......that's another pun. One pun too many.

I think, as science progresses, we are going to find more complex things such as this. This is why it is very difficult to classify animals. You might, for example, find an animal with all the features of a mammal, except it has feathers. What do you do? Create a new order?

[kiwimac]

Net Doc,

Eye 'ear you've been a bit hearty with all the puns. Well I'm a liver and let liver kind of guy but puns make me want to vent my spleen. So what I am saying is toe the line and don't be so handy with the puns next time!

[painted wolf]

I think if you were to find said animal you would have to... it would be so bizzar that it couldn't be in either group.
Feathers and fur are so different that the existance of a 'cat' like animal with feathers would be cause for a new group.

NetDoc- much as I would like to agree, I can't.
Selective pressures often cause different groups to develop similer characteristics. Marsupial 'mice' and placental mice for instance or finches and sparrows.

I do wonder how this will effect the monotremes in the future in terms of phylogeny. I also wonder now that we know that the last common ancestor between us didn't have 'mammal' ears how many fossils will have to re-examined. We have numerous creatures that are very close to the mammal line that have been excluded due to absence of features such as the three bone ear. Perhaps mammals are older than we thought. They may predate the Dinosaurs...

it will be intersting to see how this plays out. I have to say I love it when new information makes me take a new look at the world around me!

wa:do