Image from Blair’s Osteographica Elephantina (1710) showing 6-toed elephant.
“Elephants get a ‘sixth toe’ for Christmas… after a 300 year wait
In 1706, Mr Patrick Blair, a Scottish doctor, was asked to lead a dissection of an elephant that had died near Dundee, and he subsequently published a lengthy 1710 account that was the first detailed anatomical description of an elephant. Blair’s study noted that the elephant had six toes, at least on the front foot, and possibly on both feet. Later descriptions corrected this - elephants have five (not six) toes. A strange toe-like “cartilaginous rod” called the prepollex or prehallux (the “predigits”) was occasionally noted in the fore and hind feet and seems to be the “sixth finger” that Blair saw. What, then, are these predigits?
Almost exactly 300 years later, scientists have solved this mystery. A team lead by Professor John R. Hutchinson of The Royal Veterinary College in London, United Kingdom, has confirmed that the enigmatic predigits are not real toes, but even more interesting than that. Rather, the team found that the predigits are enlarged, elongate versions of small, rounded, tendon-anchoring bones present in many mammals, called the radial or tibial sesamoids. Elephants have turned these humble little bones into massive strut-like structures that rival the size of the true toes. The results of this study are being published in the journal Science on Friday, 23 December 2011
Fascinatingly, Hutchinson’s team found that the giant predigits of elephants form in a very strange pattern, first developing as the cartilaginous rod that previous studies had often dismissed as a minor curiosity, but late in life beginning to turn into bone that formed in haphazardly-positioned patches around the cartilage. Some elephants they studied even lacked bony predigits at adulthood. This is not so unusual, as sesamoid bones in other species tend to be highly variable.”