What Did California Look Like During The Barstovian?

[Zephyr]

Hi all, this is my next installment of questions concerning the Barstovian/Luisian. This concerns the lay of the land.

I've read that grass may not have evolved until 15 Ma and not been

abundant until about 7 or 8 Ma and yet we know that horses with

hypsodont teeth were present during the Barstovian. I would imagine that they fed on C3 grasses as C4 were just evolving or was their hypsodonty tied with the emergence of C4? Does anyone know specifically which C3 and C4 grasses were present? I think Caroline Stromberg is saying that extensive grasslands did not take off until the great drying and cooling phase of 5.5 - 6 Ma. On the other hand I also came across a Science article that tells of grass phytoliths found way back in Cretaceous coprolites. So I'm not sure what was present in California during the time?

http://www.sciencemag.org/content/310/5751/1126.summary

I'm trying to get more information on the climate and plant life. California at the time is usually described as a wooded savannah. But I'm having a hard time pinning down what it may have actually looked like. I've read variously that it was subtropical, desert and yet also "very wet" with numerous lakes and pools of water so I'm not sure how to picture it. Visually it has been described as similar to modern day Akagera park in Rwanda, The Sonoran desert of Mexico and the Mississippi River Valley. I have a list of plants but it is from the Hemphillian time and I'm not sure if that is representative of what was present during the Barstovian/Luisian. As to climate I've read from different sources of lots of rain mostly in summer to little rain in summer by this time. This site:

http://www.agu.org/journals/ABS/2009/2009GL040279.shtml

talks of "extreme" weathering worldwide because of the Middle Miocene

Climate Optimum, so it would seem there was lots of rain? As to topography, my understanding is that mountains were about 1/2 their present height and heading toward level.

I know I have a lot here but if anyone could shed some up-to-date light on any of this I would be grateful. I realize that it may sound as if I am trying to get someone to do my research for me however I have already done a lot of research on my own but am at an impasse on some of these questions. Why do I want it? I am trying to get info on a story I want to write about California during the time.

Thank you.

Edited January 22, 2011 by Zephyray

[Auspex]

Grasses evolved at least 55 MYA, with precursors dated to 65 MYA.

My link

[piranha]

Zephyray, check this recent thread on grass evolution with many great resources from Joe (Fruitbat's pdf library).

There is a superb mix of info and even a smattering of Kranz Anatomy in relation to photosynthetic strategies!

Enjoy! LINK

[Zephyr]

Thanks Auspex. Seems to be a mystery. Grass phytoliths were back in the Cretadeous but no grass fossils older than the middle Miocene I think.

I wonder though. Other plants also take up silica like willow and cottonwood. Don't know though if they look like grass phytoliths so as to possibly be confused with them? I happen to have a horse and she readily browses on trees when the grass is gone. She not only eats the leaves she even strips the bark off branches and eats that. Willow included even though it's bitter when I toss some into her pen. I've actually had to protect the trunks of trees by wrapping them in chicken wire. Horses in pens are also known to chew on any wood they can. They call it cribbing. It's generally thought to result from boredom and to be bad for them because some think it can cause the swallowing of air and lead to colic, which can be dengerous. I'm not so sure though. I get the idea that they are actually getting something from the wood. When I let my horse out of her pen to graze and she decides to browse and chew on the bark I don't get the idea that she's bored, but that she likes it.

Piranha, that Tennessee grass report is interesting. Previously I had only heard of grass phytoliths in the Cretaceous in India. And I read that entire thread. A lot there.

[Fruitbat]

Zephyray...

Here are a few of articles you might find useful in this context. Unfortunately, I have to go out and do some grocery shopping or I'd spend some more time on this thread.

Janis, C.M., J. Damuth and J.M. Theodor (2004). The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome. Palaeo, 207.

Lambert, W.D. (2006). Functional Convergence of Ecosystems: Evidence from Body Mass Distributions of North American Late Miocene Mammal Faunas. Ecosystems, 9.

Pagnac, D. (2009). Revised large mammal biostratigraphy and biochronology of the Barstow Formation (Middle Miocene), California. PaleoBios, 29(2).

Retallack, G.J., S. Tanaka and T.Tate (2002). Late Miocene advent of tall grassland paleosols in Oregon. Palaeo, 183.

-Joe

[Zephyr]

Here are a few of articles you might find useful in this context.

Thanks much Fruitbat. I've read some of these authors works and will look at those you link to here.

:-)