Mesozoic Grass

[DC]

While the exact dates are misty I recall a few articles about the Mesozoic grass more than a decade ago.  It was from Late Cretaceous India, which was an island.  I recall that the study seemed to show titianosaur teeth showed striations that would have been caused by the eating grasses.  Grasses incorporate silica which in mammals requires specialized teeth. There may also have been pollen.   Grass really takes off in the Oligocene when large parts of the world dry out because of the glaciation of Antarctica.  Sauropods are large and would not have been picky eaters so if there was grass I would expect them to eat it. 

[triceratops83]

You'd think that if it was having an impact on their teeth, those titanosaurs were probably munching on it pretty regularly.

[SBell]

You'd think that if it was having an impact on their teeth, those titanosaurs were probably munching on it pretty regularly.

Dinosaurs lost teeth constantly, like other reptiles, fish, sharks, etc. So marks were not uncommon--the teeth were not as hard as a mammal tooth (which are meant to be 'permanent'). So given that the teeth were on a fossil, the animal died soon after eating the grasses (or the teeth were scattered, shed remains, I don't know the study in particular). Make of that what you will.

[triceratops83]

Taking constantly shed teeth into account, grass must really be a pain to specialize in, if it causes damage that quickly.

[Mamasaurus]

If sauropods were eating grass, they wouldn't need to chew it, so no need for specialized teeth. All the teeth needed to do was pull the grass up from the ground. The gastroliths in the stomach and their incredible guts would do the rest.

I am curious though, is grass really much tougher to digest than pine needles?  Sauropods are renowned for their extremely efficient digestive systems, and if you look at coniferous forests today, there aren't very many animals that routinely eat pine needles. So surely a digestive system that could handle conifers with ease wouldn't really need to specialize on grass. I'm not sure on the nutrient value between grass and conifers, but when you're that big you're not going to be picky.

If I recall correctly, I believe that study on Mesezoic grasses in India proposed that grass may have been more widespread than we would think in the Cretaceous.  India was separate from the mainland for millions of years, and yet there were many different grasses like bamboo, rice, and forage varieties that are in common with grass silica found in other coprolites on the mainland.  So even though I don't think there were vast plains and Savannah's like there are now, it wouldn't be inconceivable to think of relatively widespread patches of grass between the ferns and flowering plants.

[tyrantqueen]

Not everyone agrees that sauropods utilised gastroliths. It was argued that the supposed preserved gastroliths were actually sedimentary phenomena.

I remember reading about the subject in Biology of the Sauropod Dinosaurs: Understanding the Life of Giants. Interesting book but definitely not easy reading.

[DinoLord]

I remember reading about the subject in Biology of the Sauropod Dinosaurs: Understanding the Life of Giants. Interesting book but definitely not easy reading.

It's a very technical volume indeed, but has a lot of good information on sauropod diet/digestion. One interesting factoid mentioned is that based on experiments,  certain pines (such as Araucaria) were tough to extract nutrients from initially but would provide much greater nutritive value after substantial gut fermentation. I don't think the researchers conducted trials with grasses, but I imagine there could potentially be a similar process at play. However not all fibrous plants yielded increased nutritive value further in the fermentation process, so it's hard to say what the situation with grasses was.

[Newt]

Many of the modern mammals that rely on fermentation (ruminants, horses, rhinos, elephants, rabbits, etc.) eat a lot of grass, so presumably fermentation of grass works for them. Also, see silage (pre-fermented grass fed to livestock).

Re: silica - grasses do indeed sequester silica, and it can be hard on chewers (the lifespan of wild elephants is limited by how rapidly their permanent molars wear down, which is mainly due to grass), but as mentioned, dinosaurs didn't have to be so precious with their teeth as mammals. Besides, grasses don't sequester anywhere near as much silica as horsetails, which would have been a much more prevalent Mesozoic fodder. In fact, horsetails, or "scouring rushes", were traditionally used to clean cast-iron pots and pans, thanks to their abrasive, silica-laden stems.

Grasses really don't try very hard to discourage herbivores. The secret to their success has been their ability to spring back from being browsed more rapidly than their competitors.

[stargatedalek]

Hoatzin and iguana are other interesting animals to consider, given they are closely related to their carnivorous or omnivorous ancestors and had to adapt relatively quickly to a leaf based diet. Don't quote me on this but if I recall correctly a specialized bacteria for digesting leaves is why an iguana smells worse than a monitor lizard and why hoatzin are called "stink birds".

And then of course there's grazing waterfowl, which as opposed to a specialized digestive system have a really fast one to remove waste quickly from their systems and consume larger quantities to get the nutrients.

[DinoLord]

Pretty much any herbivorous animal relies on intestinal bacteria to ferment ingested plant material into short chain fatty acids.

[stargatedalek]

Pretty much any herbivorous animal relies on intestinal bacteria to ferment ingested plant material into short chain fatty acids.

This is true, but both iguanas and hoatzin are infamous for their smell even among herbivorous animals, although perhaps due to their diminutive size and in the case of iguanas due to being compared to carnivorous lizards.  And being descended from animals that didn't eat leaves I figured they made a good analogue to sauropods.