This article contains speculation, information which has not been confirmed by a reliable source, and should not be considered an indication of the final game.Brontodons are spiked mammoth like creatures.
From the official site:
The brontodon is a huge roaming herbivore who grazes alone or in very small groups. It has a prehensile upper-lip which it uses to pluck low-growing vegetation, short forelimbs and thick folded skin about its body. Its most discernible feature is a series of rounded dorsal plates and dull bony knobs which adorn its spine. These provide some measure of defense from other predators.
Brontodons are not overly aggressive but they are territorial and can become quickly riled up. There are well-documented cases of brontodons using their tusks to flip entire vehicles over. They also have a devastating stomp attack. As the beast has no means of attacking ranged, mercenaries are advised to attack from a distance.
The brontodons are the first of what the locals call the modificada aberração—-the modified freaks. They were genetically engineered during the Nine Year Winter, before the arrival of the Melding. As resources became scarcer and scarcer, cattle and other sources of meat were tagged so they could be more easily tracked and controlled. Eventually the captains of industry decided a different approach had to be taken. The brontodon was designed by splicing genetic material between three different species, resulting in an animal with as much meat as twelve cattle. Not surprisingly, this accounts for why the Accord refer to them as an MRU-—meal ready unit. A single brontodon can feed an entire brigade for one meal…provided they can bring it down. Their thick skin and armor plates can provide a serious challenge.
It should also be noted that the Chosen have recently been thinning the brontodon population for unknown reasons. The carcass remains that have been found have been completely eviscerated.
Brontodon.com is a Firefall fansite named after this creature.