Members of both sexes possessed a large tuberous knob of bone exostosis situated at the base of the carpometacarpus of each wrist. Other wing bones also sometimes show similar structures. The knob was cauliflower-like in appearance, and consisted of up to two or three lobes. The knobs were about half the length of the metacarpus, were larger in males than females, and described as the size of a musket ball. One study measured the largest knob to be in diameter. The knobs vary in size across individuals, and were entirely absent from 58% of specimens examined for the study. These are thought to be immature birds, or birds without territory. The carpometacarpi of males without the knobs were smaller on average than those with it, but there was little difference between the females. In life, the knobs would have been covered by tough cartilaginous or keratinous integument, which would have made them appear even larger. Carpal spurs and knobs are also known from other extant as well as extinct birds. Within Columbidae, the crowned pigeons and the Viti Levu giant pigeon have outgrowths on the carpometacarpus which are similar to those of the female Rodrigues solitaire. Other well known examples are the steamer ducks, the torrent duck, sheathbills, screamers, the spur-winged goose, and the extinct Jamaican ibis, "Xenicibis xympithecus".