Carnivorous reptile feeding strategies and postmortem food-processing behaviors: tooth traces on bones from the Upper Triassic Grabowa Formation (southern Poland)

Carnivores make traces on bones with their teeth when feeding. A true predatory bite trace (predichnia) forms when a predator catches and kills its prey or attempts to do so. Both predators and scavengers may leave their nonpredatory feeding traces during postmortem food processing. Despite the interpretative uncertainties as to the ethology such ichnofossils may represent, the bite traces have been traditionally classified as predichnia—traces of predation. Previously, there was no alternative ethological category available for workers to classify them. The present paper fills that gap and describes tooth-made ichnofossils from the continental Upper Triassic Grabowa Formation of southern Poland. It discusses modes the serration and striations might have formed along Linichnus edges, potential makers of the trace fossils, feeding strategies, and food-processing behaviors the ichnites may represent. All the bite traces are thought to act as a record of carnivorous behaviors and are classified as sarcophagichnia, a new ethological category (traces of feeding on a body). Finally, all the studied bite traces were likely inflicted postmortem and are classified as necrophagichnia (traces of feeding on an already dead body), most likely produced by scavengers in the studied cases. Data on recent carnivores link these ichnites with postmortem food-processing behaviors, such as dismembering and defleshing. Scavenging could, in fact, have been a preferred carnivorous feeding strategy in the seasonal Norian climate of the area. Dry seasons could have perhaps increased vertebrate mortality rates and provided plenty of carcasses for carnivores to feed on.