Jones had replaced Shane Rose just days earlier after his horse, Taurus, was ruled out due to a soft tissue injury.
Vets assessed Jones’s horse, Allofasudden, today after the horse sustained an injury to the left fore foot causing it to go lame.
Equestrian Section Manager Brett Mace said “The reality is this is the nature of our sport.
“Horses can sustain these injuries and before you know it, a sporting dream can come to an end.
“Megan would have been an asset to the team and this has been a very difficult time for her and her support team.
“There is no doubt that losing two horses just prior to the start of our Olympic campaign is less than ideal”.
The Eventing Team travels with three reserves and this latest omission from the team will give Sam Griffiths and Happy Times their first Olympic berth. Luckily Griffiths has plenty of international experience having represented Australia at the 2010 World Equestrian Games and other major competitions.
“Sam comes into the team with strong, consistent performances and we’re confident he’ll contribute well to the overall team performance,” said Mace.
“The rest of the team are getting on with their individual preparations ahead of Saturday’s competition and are onsite at the Greenwich Park venue daily working their horses.
“We remain confident of achieving the goals we set out to do here in London and that’s to walk away with a medal. We’re in the fortunate position of being able to draw on strong depth of talent in both riders and horses from within the Australian ranks.”