Admittedly I have not read the report (sorry, we don't have subscription to it here at work and I don't think I can convince anyone here that it is work related either), but based on the abstract and a popular press article you can put some of the pieces together, although I wish I could see more about what they used for the rheology properties of the mud. For instance, the abstract states:
Ideal, semi-infinite elastic–plastic substrates displayed a ‘Goldilocks’ quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired.But I would imagine that if the mud were very soft, it would also relax and destroy the track. Swallowing up an entire animal would be something that could happen only in a deep mud pit.
Maybe I'll just have to ask a few of my older colleagues around here about what it was really like.