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Re: Dinosaur Dreaming report 2003



> --
> [...]
>
> This is the first monotreme that shows evidence for the presence of any
> bone in the lower jaw besides the dentary. One of the three additional
> bones became part of the middle ear of all the living mammals.

Oh, wow.

> This means that the monotremes must have split apart from
> the common stock of marsupials and placentals
> at a primitive stage where the transition in
> function of this bone had not taken place.
> --

Indeed.

> (assuming that monotremes have the same structure of inner ear bones);

Don't they? Living ones, I mean?

> or surely it's possible that Teinolophos represents a dead-end
> branch of monotremes that retained primitive charactersitics
> long after other monotreme species
> had already given rise to the placental/marsupial line?

This would mean that it's not a monotreme (and neither are the "other
monotreme species").

> Just because it's a monotreme doesn't mean it is ancestral
> to modern monotremes (or placentals/marsupials for that matter).
>[...]
> --

It does mean that it is not ancestral to placentals + marsupials.

Thanks for the information on the sedimentology. :-)