There is a planet on which all dinosaurs can survive. Aliens have transported at least 2 M-F pairs of dinosaurs from the Triassic, Jurassic, and cretaceous time periods.
A T rex pack has an Allosaurus egg in their nest that they will take care of along with 5 baby T rexes.
Length: 38 feet
Height: 16.5 feet
Weight: 1.4 tons
Length: 40 feet
Height: 15-20 feet
Weight: 6-7 tons(as much as an elephant)
I know some people are going to say "Obviously not since they lived in different time periods."
However like I said in the background info, on this fictional planet Allosaurus and T rex live at the same time.
So the question is:
Could Allosaurus breed with T rex to produce fertile offspring since both are theropods and would have similar DNA? There have been some cases of successful hybrids of animals in different genera(How else could a pumapard(hybrid between leopard and puma) exist?) as well as interspecies hybrids and hybrids of subspecies.
From the characteristics it looks like it would most likely be a male T rex breeding with a female allosaurus.
However dinosaur mating is not very well known. It could be like how lizards mate or it could be completely different.