trex was the fat bulky robust boy 25km/h
giga was the more agile fragile speedier one estimated speed of 50km/h which is absolutely insane for an animal this size.
Okay - that is just insane. NO way is Giganotosaurus twice as fast as a Tyrannosaurus rex.
It is funny how you quote the lowest maximum speed estimates for T.rex, yet quote the highest maximum speed estimates for Giganotosaurus.
Fact is - Giganotosaurus is built for hunting sauropods - which are some of the slowest moving dinosaurs ever. In addition it has relatively short lower legs, and no real adaptions for running.
T.rex on the other hand likely hunted Hadrosaurs, and ceratopsians which tend to be a bit swifter moving prey. And it was descended from fairly fast running ancestors.
The fastest speed attributed to a carcharodontosaur - was based on tracks believed to be from juvenile Acrocanthosaurus(maybe one ton) - with a speed estimated at about 40 kph/25 mph. A fully grown 7-8 ton Giganotosaurus likely wouldn't be capable of more than 24-25 kph/15 mph.
Meanwhile - A juvenile T.rex (assuming Nanotyrannus is actually a juvenile T.rex) has been estimated to be capable of running about 55 kph/34 mph. A 7-8 ton adult T.rex was most likely capable 29-36 kph/18-22 mph as a maximum speed.
I have serious doubts that any theropod over 5 tons would be capable of running more than 45 kph/28 mph.
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