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.…”

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.…”

Rolling bones: A preliminary study of micromammal abrasion on different initial taphonomic stages

“…Our results show that abrasion by clay + silts in water cause mild or absent bone rounding and polishing in agreement with previous experiments carried out by Fernández-Jalvo and Andrews (2003) and Fernández-Jalvo et al (2014). The for-FIGURE 6.…”

“…Final experiments show greater surface loss in fossils (23.7%) than in modern weathered (18.57%) or non-modified bones (9%). These results corroborate previous observations done by Fernández-Jalvo and Andrews (2003) on large mammal fossil bone fragments and by Fernández-Jalvo et al (2014) on fossil small mammal remains from Olduvai Gorge. Here we introduced new variable, digested fossils, which showed an intense rounding producing a loss of the shape in some of the specimens (Figure 4).…”

Temnodontosaurus bromalites from the Lower Jurassic of Germany: hunting, digestive taphonomy and prey preferences in a macropredatory ichthyosaur

“…All of these feature have been previously reported in SEM studies on digested bone tissue (e.g. Denys et al 1995;Fern andez-Jalvo et al 2014;Terry et al 2018;Guillaud et al 2019;Gordon et al 2020;Serafini et al 2022). The analysis failed to show the dense parallel fissures previously described in some digested bone (Terry et al 2018).…”

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.…”

Rolling bones: A preliminary study of micromammal abrasion on different initial taphonomic stages

“…Our results show that abrasion by clay + silts in water cause mild or absent bone rounding and polishing in agreement with previous experiments carried out by Fernández-Jalvo and Andrews (2003) and Fernández-Jalvo et al (2014). The for-FIGURE 6.…”

“…Final experiments show greater surface loss in fossils (23.7%) than in modern weathered (18.57%) or non-modified bones (9%). These results corroborate previous observations done by Fernández-Jalvo and Andrews (2003) on large mammal fossil bone fragments and by Fernández-Jalvo et al (2014) on fossil small mammal remains from Olduvai Gorge. Here we introduced new variable, digested fossils, which showed an intense rounding producing a loss of the shape in some of the specimens (Figure 4).…”

Temnodontosaurus bromalites from the Lower Jurassic of Germany: hunting, digestive taphonomy and prey preferences in a macropredatory ichthyosaur

“…All of these feature have been previously reported in SEM studies on digested bone tissue (e.g. Denys et al 1995;Fern andez-Jalvo et al 2014;Terry et al 2018;Guillaud et al 2019;Gordon et al 2020;Serafini et al 2022). The analysis failed to show the dense parallel fissures previously described in some digested bone (Terry et al 2018).…”

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.…”

Rolling bones: A preliminary study of micromammal abrasion on different initial taphonomic stages

“…Our results show that abrasion by clay + silts in water cause mild or absent bone rounding and polishing in agreement with previous experiments carried out by Fernández-Jalvo and Andrews (2003) and Fernández-Jalvo et al (2014). The for-FIGURE 6.…”

“…Final experiments show greater surface loss in fossils (23.7%) than in modern weathered (18.57%) or non-modified bones (9%). These results corroborate previous observations done by Fernández-Jalvo and Andrews (2003) on large mammal fossil bone fragments and by Fernández-Jalvo et al (2014) on fossil small mammal remains from Olduvai Gorge. Here we introduced new variable, digested fossils, which showed an intense rounding producing a loss of the shape in some of the specimens (Figure 4).…”

Temnodontosaurus bromalites from the Lower Jurassic of Germany: hunting, digestive taphonomy and prey preferences in a macropredatory ichthyosaur

“…All of these feature have been previously reported in SEM studies on digested bone tissue (e.g. Denys et al 1995;Fern andez-Jalvo et al 2014;Terry et al 2018;Guillaud et al 2019;Gordon et al 2020;Serafini et al 2022). The analysis failed to show the dense parallel fissures previously described in some digested bone (Terry et al 2018).…”