Platypus - how to identify a transitional species

CACTUSJACKmankin · #1 25th August 2007, 01:02 AM

The duckbilled platypus is indeed a very unusual creature with its furry body combined with namesake bill and egglaying. Due to these oddities it has been used by some creationists as a way to discredit the concept of transitional species, i.e. how can evolutionists seriously talk about mixed taxa when they dont include something that looks like a cross between a bird and a mammal. While the platypus is certainly a mammal and certainly not a bird, it is a very good illustration of how to watch out for creatures that superficially look transitional between taxa but are not.

The first bit is obvious to any paleontologist, the platypus is living thus it cannot be historically transitional. This however doesnt exempt it from being descended from such transitional species.

So let's look at the mosaic, after all transitional species are a mosaic of traits between taxa.
Mammalian: produces milk and covered in fur.
Avian: Duckbill and egg laying.
Both: Webbed feet and warm bloodedness.

Seems very curious as to why scientists have left it out as a transition between mammals and birds. If it is infact a transition between mammals and birds it should place well in the known fossil record of mammals and birds. But it doesnt. Mammals and birds have long been known to have derived from different groups of reptiles, mammals from therapsids and birds from much later therapod dinosaurs. The fossil histories of mammals from reptiles and birds from different reptiles is very solid and the platypus is an incompatable bridge between them. This alone should invalidate it as mammalian-avian transitional.

Furthermore if one looks more closely at the appearently avian characteristics the animal looks even less avian. The egg of egglaying mammals, birds, and reptiles are essentially the same. Thus the fact that a primitive group of mammals retains a reptilian reproductive system is not so surprising. Lastly the duckbill is anything but. Structurally it isnt even close, it's more leathery and bone while a duck's is keratinous. Functionally they could scarcely be more different, the platypus' bill contains electrosense organs that detect the electrical fields created by muscular movements of prey items (acting as a sort of metal detector). The only similarity is that it is a flattened extended mouth.

So what is it? it is a type of primitive egglaying mammal known as a monotreme. Monotremes are well represented in the fossil record. The other known living monotremes are species of echidna, which looks sort of like a anteater-nosed porcupine.

So what have we learned? A transitional must
1) be chronologically relevant.
2) be consistent with established fossil record.
3) have true taxanomic characteristics and not superficially similar ones.
These criterion have been effective in exposing fossil frauds such as archaeoraptor. Paleontologists do have standards and know what to look for. The designation is not so haphazard as you might have believed.

Skaloop · #2 25th August 2007, 01:58 AM

Originally Posted by CACTUSJACKmankin

So let's look at the mosaic, after all transitional species are a mosaic of traits between taxa.
Mammalian: produces milk and covered in fur.
Avian: Duckbill and egg laying.
Both: Webbed feet and warm bloodedness.

To be fair, the bill of the platypus is only superficially the same as that of a duck. It's underlying structure is radically different, and is not at all avian.

Tiberius · #3 25th August 2007, 03:15 AM

perhaps reptilian would be better than avian.

CACTUSJACKmankin · #4 25th August 2007, 10:37 AM

Originally Posted by Skaloop

To be fair, the bill of the platypus is only superficially the same as that of a duck. It's underlying structure is radically different, and is not at all avian.

Originally Posted by Tiberius