What are some thoughts as to why the dinosaurs grew so large?

Question

I have a few ideas. They're probably wrong but here goes.

1) Maybe because animals lived so long back then and maybe if we lived 900 years like Adam we would be huge, too.

2) Maybe because there was more oxygen in the air back then.

3) Maybe living things just grew bigger before the asteroid hit that killed them off. After it hit it changed the molecule structure of things so they began to grow smaller.

4) Maybe they had so much space to roam, kind a like fish grow large in a large fish tank and stay small in a smaller one.

What are some opinions on this?? Any other ideas?

Answer 1

Reptiles grow throughout their lifetimes, so a very old reptile would be very large. Mammals stop growing when they reach a certain age.

Answer 2

I think idea #4 is the best too. But it was definietly a combination of things that made them that way, so your other ideas may have contributed but to a lesser extent. I think it was natural selection, the biggest dinosaurs were the ones that got more food. Possibly, because plants were taller back then too, so brontasaurus had to grow enormous necks. And T-Rex had huge jaws and massive strength giving him an advantage for catching prey. I also agree that back then brawns counted more than brains. I guess that in every ecosystem a food chain naturally develops, where there must exist everything from the tiniest cell to the largest blue whale, so they can eat each other, and if the top predators survive a long time they get big. It's interesting to note that humans too, in a population where there are abundant resources, grow taller over time. It would be interesting to see how tall we will get, but I digress. I hope I at least gave you something to think about.

^_^

Answer 3

There was enough food available to fuel such large bodies. Then the asteroid or whatever hits the planet and the huge cloud of dust kills off the plants. Suddenly food is much less abundant and found in much smaller portions so that the large, costly bodies starved to death leaving only the smaller ones. Just a theory. No evidence.

Either that or god made them that way :P

Answer 4

They had for the most part all evolved directly from water, and were still spending a large amount of time in it still. Large Dinosaurs spent menial amounts of time on land because it tired them (their large weight), they preferred shallow water, so that they could wallow or at least have a bit of support. This can be seen easily when you look at the sides of large Dino's bodies, they have ripple marks which indicate the desired spot of water height when wallowing. This is also shown in Bronchiosauri' noses, which is above their eyes, since they sometimes went far below the regular depth.

Answer 5

Maybe because there was not Man around. All the creatures who survived was because of sheer force and power not brains but brawn. Once brains got involved we started killing big things they have more meat on them. More food. Look at the American Buffalo or the California Brown Bear. Both hunted to near extinction. All the big animals are on the list. I think it is our fault.

Answer 6

The cells of these gigantic beings are also large compared to humans and present day animals which are small and one more thing the cell division of their cells is faster

Answer 7

I think answer #4 sounds right. I think it is a great possibility that there was more dry land thousands of years ago and like everything else...they had to adapt to their smaller surroundings.

Answer 8

there have been several extinctions over this history of the world. it is a well known fact, by scientists that animals keep getting bigger and bigger, and when they are at thier biggest, another extinction occurs

Answer 9

I think it was just because of their small brain size and need for more muscles to survive. the bigger the body mass, the more muscle accessible.

Answer 10

Because back than, dinosaurs ate their own feces. Did you know, eating feces gives your bones multiple growrth spurts. If you continually eat feces for a whole year, I gaurantee, you'll see results. I've been eating feces for 5 years, I am 7 foot 5.