so, um, what exactly stood in for the T-Rex?
Easy answer undercover. Noah didn't bring full-grown T.Rex's on the ark. They brought young ones not yet full-grown! Jeez...
This is from a JW site...www.jw-archive.org...and they posted this article " T.Rex Toddler Answers Noah's Ark Questions "
In 2006, the fossil of a juvenile Tyrannosaurus-like dinosaur named Tarbosaurus was collected from the Gobi Desert. Investigators examined the fossil in detail this year and estimated that the creature died at two to three years of age. This young specimen not only offers insights into the growth and development of these dinosaurs, it also sheds light on certain misconceptions connected to the biblical account of Noah's Ark.
The first objection assumes that Noah and his family had to have taken full-grown dinosaurs on board the Ark, which is typically presumed to have been smaller than its actual biblical dimensions. The Ark was at least 45 feet high, minus the required dimensions for hull structure. 3 If the three decks that the Lord specified for its construction were evenly spaced from bottom to top, they would have offered about 15 feet of clearance. Tyrannosaurs could reach 40 feet in length, and the adults would therefore not have fit well on such a deck.
But why would Noah have taken older dinosaurs on board, when younger ones would have fit just fine? The juvenile Tarbosaurus under investigation would have stood waist-high next to most men, and therefore it would have been easily accommodated on the Ark.