Thursday, December 6, 2012

This is an interesting post about fossil mammals

That's kind of a goofy title, but I was originally going to call this post "Non-tribosphenic mammal found in Miocene of South America!"  But I don't think that would entice anyone to read it, which is a shame.  So I went with the more explanatory title, which I guess worked, because you're reading it.

What's it all about?  Let's start with the Mesozoic.  In terms of conventional science, the Mesozoic is the age of dinosaurs.  It starts about 250 million years ago and ends about 65 million years ago.  The big Mesozoic land animals were dinosaurs, but there were some odd-looking birds and mammals too.  The mammals in particular were really strange, well outside the classification of any modern mammals.

For example, modern mammal groups all have tribosphenic teeth, molars with three cusps.  In the Mesozoic, however, there are mammals without tribosphenic teeth, which means they're unlike any mammal alive today.  From an evolutionary perspective, these are mammalian lineages that died out early on when the modern tribosphenic mammals began diversifying in the Cenozoic, after the extinction of the dinosaurs.

Or so we thought.  Last week's PNAS published a new study of the fossil Necrolestes from the Miocene of South America.  The authors of the study argue that Necrolestes is actually a nontribosphenic mammal.  If they're right, that means that in South America at least, not all nontribosphenic mammals died out.  According to conventional dating, the Miocene begins 23 million years ago, so Necrolestes outlasts the dinosaurs and many other nontribosphenic mammals by some 40 million years.  See?  Isn't that neat?

What does it mean for creationists?  Well, if the Mesozoic represents the Flood and the Miocene is post-Flood, then we have a very different bunch of mammals preserved  in the Flood sediments than are alive today.  Were these Mesozoic mammals included on the Ark?  Presumably Noah would have included them if he kept alive two of every kind.  So what happened to them?  Since they're generally not found in post-Flood sediments, wouldn't it be easier to just assume that they weren't on the Ark?  Not any more.  I think Necrolestes confirms that the Mesozoic mammal kinds were on the Ark just like everything else.

It's a small confirmation, I know, but I'll take what I can get.

Rougier et al. 2012. The Miocene mammal Necrolestes demonstrates the survival of a Mesozoic nontherian lineage into the late Cenozoic of South America. PNAS 109:20053-20058.

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