You appear to be right about the petroglyph, the pictures I posted do not seem to go out far enough, so I will have to try to find some others to confirm or deny the man image. This of course does not change the fact that when totally outlined the glyph looks much less like a sauropod than in the image on BIBLE.CA
As far as reptiles growing to extremely large sizes -- here is an article about a Galapagos tortoise that just turned 175
While I admit that tortoises are large animals, exactly how old would a tortoise have to be to reach sauropod size ?
I have noticed one other problem with modern reptiles growing to dinosaur size. Look at the legs -- every modern day reptile has splayed legs. Now ... take a look at all dinosaurs, they ALL show legs under their bodies ... like an elephant -- even the juveniles show this. Why? .. the reason is that supporting hundreds of tons with splayed legs, if not impossible would be incredibly inefficient. If indeed given time, reptiles are 'designed' to get as large as dinosaurs, then it is a poor design indeed.
Now we will move on to more authoritative sources
from Discover magazine:
"Fast-growing animals expand their bones continually when they’re young, and some of their old tissue gets destroyed as new bone forms. By contrast, the bones of many slow-growing animals look like tree rings because the animals grow in short bursts.
These microscopic clues survive in fossils. For example, researchers have studied the bones from an 80-million-year-old crocodile called Deinosuchus that could grow to 50 feet long. They concluded that it reached its huge size the way crocodiles do today, growing for 50 years or more.
"Dinosaurs were different. “They did not grow like typical reptiles,” says Kevin Padian, a paleontologist at the University of California at Berkeley. Tyrannosaurus rex, for example, took only 20 years to reach full size. But the biggest dinosaurs were off the charts. Apatosaurus (also called Brontosaurus), one of the long-necked plant eaters known as sauropods, needed only 15 years to reach 25 tons. “They’re just growing faster than anything on land today,” says Padian. "
Here is an article from the National Academy of Sciences discussion sexual maturity and more importantly the growth rate of dinosaurs.
Here's a hit from Google books explaining that modern reptiles do not grow in the same manner as dinosaurs did
And There is also much speculation that dinosaurs were endothermic -- that is warm blooded. - this would remove them from the reptilian model all together -
So as you can see there is little evidence that dinosaurs grew at the same rate as reptiles today.