A twist in the tail

Re-examining the skeletal evidence from first principles, the anatomy of the skeletons from Bernissart reveal some disconcerting features. One of the most obvious concerns the massive tail of Iguanodon. The well-known reconstruction shows the animal (Figure 12) propped, in true kangaroo style, using its tail and hind

legs tripod-like. To adopt this posture, the tail curves upward to the hip. In sharp contrast, all the documentary and fossil evidence points to this animal normally holding its tail essentially straight or somewhat downwardly curved. This is clearly seen in the specimens arranged on banks of plaster in the museum, and in the wonderful pencil sketches made of their skeletons before they were exhibited (Figure 20). It could of course be argued that this shape was simply an artefact of preservation, but this explanation is definitely not plausible here. The backbone was in effect 'trussed' on either side by a trellis-like arrangement of long bony tendons that held the backbone quite deliberately straight; these can be seen in Figure 20. As a result, the heavy, muscled tail served as an enormous cantilever to balance the weight of the front part of the body at the hips. The truth is that the upward sweep of the tail seen in Dollo's reconstructions would have been physically impossible for these animals in life. Careful examination of the skeleton revealed that M the tail was deliberately broken in several places to achieve the | upward bend - a case perhaps of Louis Dollo making the skeleton £ fit his personal ideas a little over-zealously.

This discovery disturbs the pose of the remainder of the skeleton. If the tail is straightened so that it can adopt a more 'natural' shape, then the tilt of the body changes dramatically, with the backbone becoming more horizontal and balanced at the hip. As a result the chest is lower, bringing the arms and hands closer to the ground and raising questions about their likely function.

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