Few things have stirred up more debate than the diminutive forelimbs of T. rex and its close cousins.
The original idea, from Henry Fairfield Osborn in 1906, was that they had evolved to somehow support copulation.
Since this time many other theories have come and gone. Some suggested that small arms helped the dinosaur to get up off the floor, or to pin down prey. Others thought that the limbs were used for caring for eggs in their nest, or for scraping a little bed in the sand before sleeping.
Nowadays, perhaps the most accepted view is that the T. rex forearms are nothing more than vestigial organs – like ostrich wings – that had found themselves without purpose and were shrinking out of existence.
However, fossils suggest that the forearm-powering muscles were actually enormous.
Why would vestigial arms need such biceps’? Some palaeontologists now find themselves drawn back to the theory that the limbs were involved in reproduction, perhaps as subtle signalling devices to demonstrate a male’s intention to mate, or display structures informing males of a female’s receptivity.
