Root traces in fossil bones from the Huayquerian (Late Miocene) faunal assemblage of Telén, La Pampa, Argentina

Abstract

One of the exposures of the Cerro Azul Formation in northern La Pampa (Argentina) has yielded a Huayquerian (Upper Miocene) faunal assemblage. The degree of bioerosion caused by roots on mandibles of Paedotherium minor (Mammalia, Notoungulata, Hegetotheriidae) was analyzed, in an attempt to throw light upon the events that affected the remains after deposition. According to the features observed on the specimens, two types of traces were dentified. These were referred to the ethological categories Sphenoichnia and Corrosichnia. The first type is interpreted as the marks produced by rootlets growing on the skeletal element/sediment boundary after burial. These traces would indicate the development of a herbaceous cover on the soil where the remains were deposited and later buried and may be another feature helpful in the identification of these paleosols. The second type implies a surface dissolution of the hard substrate, which in this case is the fossil itself. The characteristics of the remains that show this kind of trace may suggest that root growth has affected them only in recent stages.