Paleobiological forensic study of an upper Miocene Pelobates tadpole (Anura, Pelobatidae) from the Tresjuncos lagerstätte of central Spain

Abstract

ABSTRACTA paleobiological reconstruction of the last hours of life of an exceptionally well-preserved fossil tadpole is carried out through morphological and taphonomic analyses, allowing inferences to be made about its identification, developmental stage, physical condition, health, behavior, death, and burial. The tadpole was recovered from an upper Miocene (Turolian, MN13) diatomaceous konservat-lagerstätte deposit near Tresjuncos (Cuenca Province, Spain). The specimen belongs to an unnamed species of Pelobates (Pelobatidae) of the westernmost Palearctic phylogenetic clade. Its gigantic size was due neither to metabolic (hypothyroidism) nor to ecological (overwintering) causes but merely reflects an optimum living environment. Dying at Gosner developmental stage 41, the ossification pattern of the tadpole is slightly discordant with that of extant Pelobates cultripes, a greater degree for the skull and vertebral column in the fossil. The tadpole, seemingly in excellent health, had an intestine containing abundant remains of an epiphytic/epipelic diatom, different from the planktonic species surrounding the fossilized body. Death was probably violent, as revealed by a fossil hollow trace similar to hematomas made by egret beak strikes. Rapid burial coincided with an occurrence of massive planktonic diatom sedimentation distant from the lakeshore.