Glencoe Brontosaurus, redone as an Apatasaurus, featuring a
skull from
the Dinosaur Studio
All the foraminae are fenestrated
More on this model can be seen at The Old Bone
Odori
How large does a brain have to be? Although we usually feel that as a body gets larger the brain must also expand, we really have no definite basis for that assumption. A brain has a lot of functions, but many of them involve automatic behavior. An order to breathe or a signal to release a hormone can be performed by a small number of nerve cells and yet have a major effect on a distant organ as a large muscle unit reacts or a distant gland releases large supply of an active substance. An order for a leg to walk can require the same number of brain cells in a large animal as in a small one, it's just that larger muscles are following the orders. Delicacy of movement and fine motor coordination certainly benefit from more neurons, but when the beast being controlled weighs forty tons or more, does delicacy really matter? At that size, an animal makes its own path rather than worrying about staying on a trail. Many functions, such as finding food and mates can be hard-wired into fairly small units of nerve tissue and still leave some room for variability in their expression. Tiny lizards and fish, and even insects, can show relatively complex behavior with brains the size of a pinhead. Great intellectual function was almost certainly lacking in Dinosaurs as it is in practically every creature known, but that is not really a disadvantage for survival in most cases.
We wonder how these giant meat sources defended themselves against hungry and well armed predators. It has been suggested that they used their tails as whips and that is certainly plausible. Anyone who has ever tried to handle a two pound iguana that wants to be left alone knows how much havoc a flailing tail can wreak. An advantage of this defense is that it would not require a lot of mental power to be effective. They also could have used their massive necks and heads as clubs. A predator would have had to be very lucky to grab a neck as it swung by without getting slapped into the next era. The largest contemporary carnivores were a fraction of the weight of a medium sized sauropod and I doubt that any predator would ever have attacked a fully grown adult. The penalty for such a rash act would likely have been pulverization. As a modern example, elephants have no serious predators unless they are very young or very sick. Their mere size is too intimidating. Now young sauropods would have been in jeopardy until they put on a lot of weight. Herds certainly could have provided some security, although I suspect that the greatest threat to growing up would have involved getting stepped on by their elders. Mortality was probably very high when they were young. They may have made up for this by building a lot of nests and laying a lot of eggs. After all, there is a practical limit to egg size which is approached in much smaller animals than sauropods, but a huge dinosaur could make a huge number of eggs without spending very much energy relative to her size.
Now about that size... One of the great mysteries about these long-necked giants is how they managed to get enough nutrition to grow and sustain their incredible bulk. Most of the plants available to them were probably tough, such as conifers and cycads. The tender deciduous leaves and grasses that nourish our contemporary large herbivores had not yet evolved. In addition to the marginal quality of their food supplies, their harvesting eqiupment seemed marginal at best. Their dentition was generally rake-like arrays of pencil shaped teeth. Some had spoon shaped nippers, but nothing to chop up the vegetation so it could be exposed to their digestive juices. They probably did some additional grinding in their crops, using gastroliths to mash the foliage their teeth provided. Even at that, they would still have required a very complex gut to process this type of plant material with its low nutritional value. Did they develop multichambered stomachs and use their gastroliths for pulping as effectively as modern ruminants use complex teeth to chew their cud? Maybe, but I can suggest an easier solution to the need for extended digestive processing. Refection: don't take two bites at the apple; just eat the apple twice. Hind gut fermentation uses a large cecum as a storage vat that allows bacteria to work over tough plant food and break it down to usable nutrients. There is still a problem. The cecum's walls are not good for absorption of anything but water. Nutrient assimilation has to occur in the small intestine, but to get to the cecum for the all-important bacterial processing, the food has already gone through the small bowel. Since the intestinal tract is a one-way system, there is only one way for the food to get back to where it will do any good. It has to go out and get back in again. Refection is used successfully by many animals, including rabbits, langurs and to some extent, elephants. By using their colons to do most of the work, the giant dinosaurs could get away with simple teeth. They would have had to rake the first time and scoop the second, but neither requires particularly strong or complex dentition. It may have been an advantage for these animals to have a small brain if this was the daily culinary experience they had to to expect. This type of nutrition may also explain the structure of sauropod necks. Traditionally, we think that they evolved long necks in order to reach leaves high in trees. Obviously they were long, but in many cases, careful analysis of their skeletons indicates that they were not really able to raise their heads very far at all. Perhaps they evolved to reach around rather than up. This may provide another weapon for their defensive arsenals. Toxic halitosis could have had a protective effect, even when they were babies. Perhaps this seems rather gross to you, but that is your penalty for having such a large brain.
Camarasaurus skull 1:10, sculpted by Lascha Tskondia for Ants. It is now
available from Echoes In Time. It came in a brownish fossil finish
that I darkened with a series of washes to make it look more like the
heavily stained fossils from the Morrison Formation.
Triceratops skull 1:10, also sculpted by Lascha Tskondia. I obtained
this model in "bone" white and painted it to look more like a fossil
as it appears after around sixty-five million
years
in the ground.
I have more images of this skull along with many
others featured in
the pages of The
Old Bone Odori, the new series of pages in this website.
ORNITHISCIANS
Lindberg's JP Corythosaurus
This is the Lindberg JP Dilophosaurus, minus frill.
The head was reconstructed by lengthening the jaws,
adding the sub-nasal gap and making new teeth from
sprue. The legs were were altered to a striding position.
This is the Elasmosaurus. It needs paint and a
support.
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