Re: Tertiary mammals in the Cretaceaous

["Martin Jehle" <martin.jehle@klinik.uni-regensburg.de>]

> I have been reading Raup's book "The Nemesis Affair."  Yes I know it's a 
> tad old.  But he mentions that several Tertiary type mammals have been 
> found in the Cretaceous well before the meteorite impact.  Being pretty 
> clueless about early mammals, can anybody give some idea what he's 
> talking about?
> 
> Thanks
> 
> Joe Daniel
> 

I'm not a paleontologist, but early mammals are my hobby, so I hope I 
can answer your question. Late Cretaceous mammals in North America were 
mainly multituberculates ( a rodent-like group of small mammals that 
are neither placentals nor marsupials, the two most important groups 
of extant mammals), primitive insectivore-like mammals and marsupials 
(opossum-like animals). Several genera of these animals also 
became extinct at the K/T-boundary. However some members of these groups 
that have been found in the Latest Cretacous are closely related to 
early tertiary (paleocene) mammals. In addition, primitive 
ungulates (the ancestors of today's hoofed mammals) also appear 
slightly BEFORE the K/T-boundary (the most famous genus in 
Protungulatum). This means that the modern (Tertiary-type) forms
from which today's mammals evolved  did not develop after the 
extinction of the dinosaurs, but were already existing before the K/T 
boundary event. 

d