For sauropods to have reached such gigantic sizes makes sense as it helped keep them invulnerable from theropods which could also grow to large sizes.
However in the case of Indricotherium. If it could grow to be some 15 ft at the hip (same as Apatosaurus) and some 20-23 ft tall (as tall as Kent A. Stevens' Brachiosaurus) then the difference in size between predator and prey is just insane as the largest creodonts seemed to reach 4-4.5 feet at the shoulder and Walking With Beasts showed Andrewsarchus as standing about 6 ft tall (Which is still absolutely puny in comparison). Are there any ideas on how an increased size would have provided the animal with any sort of advantage?
I'm not too familiar with mammals, so I'm going to go out on a ledge here and suggest that they did it to be able to obtain food sources that other contemporary animals could not. ???
| QUOTE |
| An oft-cited nutritional advantage of large body size is that larger animals have lower relative energy requirements and that, due to their increased gastrointestinal tract (GIT) capacity, they achieve longer ingesta passage rates, which allows them to use forage of lower quality. |
[emphasis added]
Another somewhat different take on it.
Optimal body size and an animal's diet
| QUOTE |
| A simple optimization model is developed here which considers food search, capture, and eating rates and the metabolic cost of these activities for animals of different sizes. The optimization criterion is defined as the net caloric gain a consumer accrues per day. This model does produce an optimum intermediate body size which increases with food quality - not the reverse. This discrepancy is accounted for, however, because the model also predicts that body size should be even more sensitive to increases in food abundance. In nature, many poor quality foods are also relatively abundant foods, hence the consumers eating them may maximize their daily energetic profit by evolving a relatively large body size. Optimum consumer body size also decreases with increases in consumer metabolic rate and prey speed. |
| QUOTE |
| Animals probably do not optimize their anatomy for the purpose of running very fast, which occurs only on rare occasions, but for reducing costs of locomotion. |
Google scholar is noting that this paper deals with Indricotherium, but I can't see if they are specifically saying that the size or a portion of the size is due to having adapted the anatomy for more effiecient locomotion and the like. Might be worth looking up the paper if you are really intersted.
hth