Wednesday, November 30, 2005

Fossil dung reveals dinosaurs did graze grass

Fossil dung reveals dinosaurs did graze grass: "One of the most common 'mistakes' in the prehistoric book is not wrong after all; dinosaurs did eat grass, and a surprisingly wide range of it"

Again, scat teaches us history. Whether it be dung found on the driveway, forest floor, or among fossilized remains, it reveals what the excretor (aka the 'pooper') ate. The cliche "What goes in, must come out" may sound archaic to most, but it reflects the truth, although the form may change between the mouth and the 'back door'.

Three points in the report above interested me:

The 'key evidence' verifying grasses on the dinosaur menu was the silica cyrstals present in plant cells found in their fossilzed feces. These microscopic crystals, called opal phytoliths, are specific to plant taxon and even parts of the plant. Phytoliths, Greek for 'plant stones', are produced by plants presumably in response to injury (mechanical, insect or microbial) but also under normal conditions.

Soluble silica in the soil is taken up with water by plant roots and distributed throughout the plant. Dissolved silica is then deposited within or between cell walls. Identification and association with a plant is based on distinctive phytolith sizes and shapes. They may aid in the structural integrity of the cell wall or in defending the plant against damage by rendering them less palatable for herbivores and insects.

Phytoliths are a paleobotonists treasure trove because the intact particles are left after the plant decomposes. They are not degraded from exposure to high temperatures or methods that breakdown carbonized food. Consequently they pass through the digestive process of animals and are excreted along with other undigested substances. Stable isotopes can be extracted from them and used to reconstruct past environmental conditions as well as typing the plant family and possibly even species eaten.

Why did this interest me? I was reminded of a comment my father, a biochemist, made when I was young. The most likely alternate element on this planet that life could have been based on is silicon. Next to carbon, it is the second most abundant element in the Earth, occuring mostly as silica (silica and dioxide) and silicates (silicon, oxygen and metals). Perhaps the primary reason life revolved around carbon, silicon's chemical analog, is because it is more reactive than silicon.

Marine diatoms (an algae) are an example of that alternate life since they extract silica from water to form their unique protective cell walls (made primarily of polymerized silicic acid, a compound comprised of silicon, hydrogen and oxygen). Diatom populations are related directly to the availability of silicon in the water. They may be more energy efficient as well; the silica cell walls require ~8% less energy to synthesis than their organic counterpart.

Considering the heat stability of silicon, life based on the element might be found in environments with high temperatures. Based on these facts, it's not surprising to find silicon-based life in many science fictions stories (e.g. A Martian Odyssey, by Stanley Weisbaum, even the Star Wars series). However, the chirality (right- and left-handed forms of a molecule) of carbon compounds enriches the biology that we know so well and facilitates adaptation within our biochemistry. As far as we know silicon lacks this feature, or at least to the extent of carbon's potential. The handedness of carbon biology serves as a basis for the many interconnections of reactions that constitutes life on this planet. Silicon chemistry offers less complexity.

Who knows what silicon forms lurk in the heart of Earth? (or the Universe, for that matter)

Dinosaur grass
I was astonished reading that grasses were 'believed' to be relatively new. Until ancient poop recently revealed that dinosaurs ate grass (and several types of grasses), their main meal course was believed to be of flowering plants and tree foliage. 'Experts' believed that grasses arrived long after the disappearance of dinosaurs (the end of the Cretaceous period; 65 mill. years ago). Divergent thinking suggests to me that if larger and complex botanical forms existed, the simple grasses probably did as well.

Couple that with fossilized teeth of mammals and dinosaurs strongly suggests that grasses were in their community and food chain. Some mammalian fossils of that period had teeth typically associated with modern grass-grazers, suggesting grass may have been a food source for them as well as others during that era. Until now, the belief otherwise was 'lack of evidence.' On the other hand (chiral thinking), mammals and dinosaurs with teeth similar to today's grass grazers would strongly suggest that perhaps grass was a contemporary biological component of the food chain.

The author of the study commented that the new 'unambiguous evidence' of grass during that period also demonstrated that grasses had diversified. "That suggests that grasses had been around for a long time even back then." My reaction to that statement was WNSS (Well, no shit Sherlock!).

How ironic that feces should tumble their beliefs. Now new textbooks will have to be written.

Coprolites: ancient scat
By any other name, a rose is still a rose. Shit is still shit. Scatology (or coprology) is the study of feces. Such studies reveal a wide range of information about a creature: diet, health, movements, etc. Living in the woods and as a livestock producer, I learned to 'read' scat. It told me what animal was near, what it was eating, and even when it had deposited its load. It told me much about the health of the animals I raised. Now we can learn not only what dinosaurs ate, but also about their environment. All from their excrement.

Coprolites are fossilized feces (or dung, turds, poop, scat; take your pick of terms). They are a prized treasure of paleontologists. And rightfully so. Fossilized dung may serve as index fossils used to define and identify geologic periods of the planet's history, both on land and in water. Even human coprolites have revealed diets of our predecessors. Not all excrement is naughty toilet humor.

So next time you come upon a deposit of dung, overcome your ingrained aversion to body excrement and learn something about the world around you. Or in the past. Just keep your fingers out of your mouth.

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