Analysing the taphonomy of Mesozoic lizard aggregates from Uña (eastern Spain) by X-ray controlled decay experiments

Abstract

Well-preserved lizard bone aggregates from the Lower Cretaceous (Barremian) coals of Una (eastern Spain) show varying combinations of skeletal elements which obviously represent different stages of disarticulation. Unfortunately, this does not give information about the mode and timing of decomposition, besides the fact that the soft tissue decayed while the bone was very well preserved. Due to the absence of appropriate documentation of the decomposition sequence of an extant lizard carcass, an actualistic palaeontological experiment was conducted using a carcass of one individual of the iguanid Oplurus cuvieri. To get information about the invisible sub-integumentary disarticulation of the skeleton, this process was continuously documented using X-rays. The general agreement of the experiments with the fossil stages of preservation is consistent with a subaquatic decay process for the Una lizards. Also, the experiments record an unambiguous order of disarticulation and dissociation under undisturbed conditions. Even if the influence of currents is left out in this experiment, predictions can be made for transportation processes, taking the susceptibility to detachment into account.