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Re: Paleogene Titanosaurs in South America? Paleogene ammonoids in the Persian Gulf? Not quite, but analogous...

You can find reworked seeds and leaves in clasts (chunks) of older sediments. I find mud pebbles with occasional leaves in them mixed into the pure channel sands in the Hell Creek. The mud chunk was ripped up and moved down river, rounded as it traveled. They were probably (no doubt) contemporaneous though. Therefore the question of whether the plant frag was a fossil at the time it was ripped up is the real issue. It is possible to find Hell Creek clasts in Holocene sediments too which of course could hold true for any older sediment exposed, fragmented and reworked. There is almost always a compositional difference between the clast and the sediment it is encased in otherwise it would be hard to identify as a clast. Of course you also find individual fossil frags being reworked like wood chunks, pollen etc. Leaves are pretty delicate for that though unless they are encased in something else.

Frank (Rooster) Bliss
MS Biostratigraphy
Weston, Wyoming

On Apr 11, 2008, at 4:19 PM, David Marjanovic wrote:

And the fossils really aren't reworked? What are they, seeds?

So I can answer my own questions: the fossils are leaves, which are probably impossible to rework.

The paper also mentions pollen of Podocarpaceae from the Miocene of... Alaska. Geographically, this is a major surprise, too...

Seed plant phylogeny seems to be a headache. All molecular phylogenies I've seen find a monophyletic Gymnospermae, which is quite surprising from a morphological point of view.