Re: Platypuses may be older than we think...

[David Marjanovic <david.marjanovic@gmx.at>]

So. Here is the surprisingly short SVP meeting abstract (p. 137A):

Timothy Rowe, Thomas Rich, Patricia Vickers-Rich, Mark Springer & Michael 
Woodburne*: Fossil evidence on divergence timing of the platypus and echidna 
clades

"Monotremes have left a poor fossil record, and paleontology has been 
virtually mute during nearly two decades of discussion about molecular clock 
estimates of the timing of divergence between the platypus and echidna 
clades. Molecular clock estimates of the divergence between platypus and 
echidnas range from 17-80 [sic] Ma. New evidence from high-resolution X-ray 
computed tomography indicates that *Teinolophos*, an Early Cretaceous fossil 
from Australia's Flat Rocks locality (121-112.5 Ma), lies within the crown 
clade Monotremata, as a basal platypus. Divergence of the two monotreme 
clades therefore had occurred in or before the Early Cretaceous. 
*Teinolophos* is a platypus in both phylogenetic and ecological aspects, 
suggesting that monotremes have evolved at much slower rates than therian 
mammals. Only relaxed molecular clock estimates of divergence times have 
proven compatible with the fossil record."

* Institutional address given as "Museum of Northern Arizona, Flagstaff, AZ, 
Vanuatu".

Doesn't seem to address the question of whether the echidnas, with their 
reduced electro-sense, are secondarily terrestrial, perhaps having evolved 
on some part of northern New Guinea when it started emerging from the sea in 
the Miocene or so. In that case we'd have to expect that *Teinolophos* "is a 
platypus in [...] ecological aspects" like *Steropodon* and *Kollikodon*.