The use of gross dental wear in dietary studies of extinct lagomorphs

Abstract

Studies of paleoenvironments have commonly focused on large mammalian herbivores such as ungulates. Many localities, however, have yielded large numbers of small mammalian herbivores, including lagomorphs and rodents. These fossils represent an untapped paleoecological resource. However, the fossils are often in the form of isolated teeth, and microwear analysis cannot be used due to taphonomic alteration. As a result, we use ungulate gross dental wear as a model. The dental wear features of extant western Canadian lagomorphs are identified and used to create dietary categories that can be applied to make predictions about the diets of extinct forms. The Horse Local Fauna of the Cypress Hills Formation of Saskatchewan has yielded approximately 2,500 fossil specimens, of which nearly 300 are lagomorphs. Two leporid species (rabbits and hares) are present in the Horse Local Fauna, Palaeolagus temnodon and Megalagus brachyodon. Qualitative analysis of the gross dental wear of the lagomorphs of the Horse Local Fauna indicates that M. brachyodon was mainly folivorous and P. temnodon was primarily frugivorous, suggesting that the contemporaneous ecosystem was tree dominated. Gross dental wear analysis allows the use of small herbivores and isolated teeth in paleoecological studies. Studying the diets of small herbivorous mammals will allow more nearly complete reconstructions of past environments and will become increasingly important as more detailed reconstructions are required by paleontologists.

Phylogenetic signal in tooth wear dietary niche proxies

“…For mammals, the two most commonly employed sets of proxies are tooth macrowear (also referred to as mesowear) and microwear (microscopic tooth wear). Analytical tooth wear methods such as mesowear and microwear involve quantification of macroscopic and microscopic features on the occlusal surfaces of teeth in an attempt to characterize the diets of individuals and, in turn, the Eltonian niches of entire species (DeSantis & Haupt, ; DeSantis et al., ; Donohue, DeSantis, Schubert, & Ungar, ; Fortelius & Solounias, ; Fraser, Mallon, Furr, & Theodor, ; Fraser & Theodor, , , ; Fraser, Zybutz, Lightner, & Theodor, ; Grine & Kay, ; Haupt, DeSantis, Green, & Ungar, ; Hedberg & DeSantis, ; Semprebon, Godfrey, Solounias, Sutherland, & Jungers, ; Solounias, Moelleken, & Plavcan, ). Tooth wear data are then typically compared to observed dietary data (e.g., gut contents, fecal contents, personal observations) in a reference population or sample of species (i.e., the training dataset) to create a set of regression coefficients or discriminant functions that can be used to infer the diets of species and individuals for which independent dietary data are unavailable (Barr & Scott, ; Fraser & Theodor, ).…”

“…The most widely employed methods for dietary inference include mesowear, the visual scoring of macroscopic tooth wear (Fortelius & Solounias, ; Fraser et al., ; Kaiser & Fortelius, ; Kaiser & Solounias, ), and microwear, the quantification of microscopic marks on the chewing surfaces of the teeth at either low or high magnification (Grine & Kay, ; Merceron, Blondel, Bonis, Koufos, & Viriot, ; Semprebon et al., ; Solounias & Semprebon, ; Ungar et al., ). Both mesowear and microwear have proven to be extremely useful tools for inferring the dietary preferences of extant and extinct mammals (and nonmammals) from numerous families (DeSantis & Haupt, ; DeSantis et al., ; Donohue et al., ; Fortelius & Solounias, ; Fraser & Theodor, , , ; Fraser et al., , ; Grine & Kay, ; Haupt et al., ; Hedberg & DeSantis, ; Semprebon et al., ; Solounias et al., ).…”

Controlled feeding experiments with diets of different abrasiveness reveal slow development of mesowear signal in goats (Capra aegagrus hircus)

“…However, taxon-specific conditions also need be to considered. For example, as mentioned in the Introduction, a mesowear signal in lagomorphs (Fraser and Theodor, 2010;Ulbricht et al, 2015) must develop with 1-2 weeks, given the rate at which cheek-tooth tissue is being replaced.…”

“…However, a more simplified version of the scoring system using a set of gauges has also been introduced (Mihlbachler et al, 2011). Owing to species-or taxon-specific adaptations and exceptions, various modified mesowear scoring systems have been developed for equids (Kaiser and Fortelius, 2003), lagomorphs (Fraser and Theodor, 2010), rhinoceroses (Taylor et al, 2013), marsupials (Butler et al, 2014) and small mammals (Kropacheva et al, 2017;Ulbricht et al, 2015). Mesowear has also been applied to fossil taxonomic lineages such as Chalicotheriidae (Schulz et al, 2007) and notoungulates (Croft and Weinstein, 2008), and in some cases alternative scoring systems using angles and gauges have been used for taxa such as proboscideans (Saarinen et al, 2015) and…”

“…However, the length of time this signal takes to develop has not been investigated thus far. Most likely, this period is short in lagomorphs and rodents, where a reliable signal can be obtained (Fraser and Theodor, 2010;Ulbricht et al, 2015) even though the cheek-tooth crowns are completely replaced within 1-2 weeks (Müller et al, 2014(Müller et al, , 2015.…”