While this seems quite a reasonable supposition, it is in fact very difficult to prove scientifically. Lifelike animatronic dinosaur Apart from size, which is surprisingly variable among reptiles as a whole and not nearly as consistent a feature as Nopcsa would have had us believe, the features used to distinguish the sexes among living reptiles are most commonly found in the soft anatomy of the sex organs themselves, coloration of the skin, or behaviour. This is particularly unfortunate because only very rarely do fossils ever preserve such features.
The most valuable evidence would be the discovery of soft anatomical fossils of the sexual organs of Iguanodon – unfortunately, this is an extremely unlikely event. And, since we can never know their true biology and behaviour, we have to be a little cautious and also realistic. Realistic dinosaur costume For the present, it is safer to record the differences (we may have our own suspicions, perhaps), but simply leave it at that.
A careful study of the more abundant large Iguanodon from Bernissart revealed that a few were smaller than the average. Measuring the proportions of each of these skeletons revealed an unexpected growth change. Smaller, presumably immature specimens had shorter arms than would have been expected.
The comparatively short-armed juveniles may well have been more adept bipedal runners, but as large adult size and stature was achieved they may have become progressively more accustomed to moving around on all fours. This also fits with the observation of an intersternal ossification in only larger, presumably adult, individuals, which spent more of their time on all fours compared to smaller, younger individuals.