Digestion versus abrasion features in rodent bones

Abstract

The origin of most fossil small mammal assemblages is predation by avian or mammalian predators. Bone corrosion by gastric juices observed in these fossils is direct evidence of digestion, and traits of digestion indicate the type of predator involved. However, certain features observed in digested bones, such as rounding and polishing, are similar to the rounding and polishing produced by other processes, particularly abrasion, in which predation is not involved. Misidentification of digestion has major repercussions in palaeoenvironmental and palaeoclimatic interpretations as well as interpretations of biostratigraphy and potential reworking. Digestion is directional and progressive process, primarily affecting the most mineralized tissues (enamel) advancing from the tips to the centre of the anatomical element. In contrast, abrasion identically affects any type of osseous tissue homogeneously rounding the entire skeletal element. Microscopically, digested bones display a distinctive chemical corrosion (‘tornlike’ appearance), whilst abraded bones appear smooth with microstriations and pitting microwear. Here, we present the results of a series of experiments designed to establish new and clear criteria to distinguish bone rounding and polishing caused by digestion from that originating from abrasion.

Modifications on fossils of neoepiblemids and other South American rodents

“…This process results from the friction between bone or teeth and sediments immersed in water and often acts on protuberances and irregular structures on the isolated dental elements (Fernández‐Jalvo et al . ). As a result, mechanical abrasion tends to produce rounded and homogeneous surfaces, affecting the entire tooth, and removing the enamel and dentine equally (Fernández‐Jalvo et al .…”

“…; Cohen ), and also in laboratory experiments (Fernández‐Jalvo et al . ). Andrews (), and Andrews & Fernández‐Jalvo () illustrated several teeth and dentaries (with cheek teeth) of arvicolines with a pattern that resembles our sample.…”

“…As a result, mechanical abrasion tends to produce rounded and homogeneous surfaces, affecting the entire tooth, and removing the enamel and dentine equally (Fernández‐Jalvo et al . ), differing from the pattern found here.…”

Microvertebrates preserved in mammal burrows from the Holocene of the Argentine Pampas: a taphonomic and paleoecological approach

“…Badgley 1986;Behrensmeyer and Hook 1992). Considering their usefulness for biochronologic, biostratigraphic, paleoenvironmental, paleoclimatic and paleoecologic studies, it is essential to know the processes that took part in the formation of the assemblages (Andrews 1990;Fernández-Jalvo et al 2014). In this sense, burrows have been proposed as favourable contexts for the preservation of skeletal elements Behrensmeyer and Hook (1992;and references therein).…”

Seasonal variation in prey composition and digestion in small mammal predator assemblages

“…Digestion of rodent incisors nearly always starts at the occlusal tip of the incisor (as shown for the murid incisor in Figure c) and progresses along the crown as moderate digestion (Figure d). With heavy digestion, all or nearly all the enamel is lost and the dentine is strongly penetrated (Fernández‐Jalvo & Andrews, ; Fernández‐Jalvo et al, ; Barham et al, ). The degrees of digestion of the Neuadd sample of arvicolid incisors are higher than for molars (Table ): 64.3%, N = 344 (Table ), with 50.4% incisors lightly digested.…”