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Re: ERECT LEGS, WALKING SPEEDS & METABOLICS (was naked mole
Ah, CC Peterson, you have missed something. ALthough it is easy to see why.
Large size does not allow dinosaurs to escape from the link between erect legs
and high aerobic capacity for two reasons. For one thing, erect legs first
appeared in very small protodinosaurs, and many dinosaurs were small. Giant
dinosaurs merely inherited erect legs - why people keep saying that dinosaurs
had erect legs BECAUSE they were so big escapes moi.
Second. Yes, it might SEEM that land giants should be able to walk fast even
if they had low aerobic exercise capacity. But think about it for a second.
Being gigantic in 1 G is very hard to do. If anything giant size itself may
force high AEC on land. More specifically, the mass specific cost of
locomotion decreases with size. Problem is, so does mass specific AEC. The
exact slopes for both are iffy, but they both decrease in parallel. What it
all means in the end is that a giant reptile still has such a pathetic AEC
that it cannot sustain a mammal-like walking speed. A 50 tonne tachyaerobic
animal has an AEC of only 8000 kcal/h. Since it costs over 4000 kcal for such
an animal to walk a kilometer, it can aerobically sustain a walking speed of
only 2 km/h. But sauropods regularly walked 3-5 km/h, the same high speed
observed in elephants. Conclusion. Sauropod energetics were probably more like
those of elephants than reptiles.