Was Mesopithecus a seed eating colobine? Assessment of cracking, grinding and shearing ability using dental topography

Abstract

Extant colobine monkeys have been historically described as specialized folivores. However, reports on both their behavior and dental metrics tend to ascribe a more varied diet to them. In particular, several species, such as Pygathrix nemaeus and Rhinopithecus roxellana, are dedicated seasonal seed eaters. They use the lophs on their postcanine teeth to crack open the hard endocarp that protects some seeds. This raises the question of whether the bilophodont occlusal pattern of colobine monkeys first evolved as an adaptation to folivory or sclerocarpic foraging. Here, we assess the sclerocarpic foraging ability of the oldest European fossil colobine monkey, Mesopithecus. We use computed microtomograpy to investigate the three-dimensional (3D) dental topography and enamel thickness of upper second molars ascribed to the late Miocene species Mesopithecus pentelicus from Pikermi, Greece. We compare M. pentelicus to a sample of extant Old World monkeys encompassing a wide range of diets. Furthermore, we combine classic dietary categories such as folivory with alternative categories that score the ability to crack, grind and shear mechanically challenging food. The 3D dental topography of M. pentelicus predicts an ability to crack and grind hard foods such as seeds. This is consistent with previous results obtained from dental microwear analysis. However, its relatively thin enamel groups M. pentelicus with other folivorous cercopithecids. We interpret this as a morphological trade-off between the necessity to avoid tooth failure resulting from hard food consumption and the need to process a high amount of leafy material. Our study demonstrates that categories evaluating the cracking, grinding or shearing ability, traditional dietary categories, and dental topography combine well to make a powerful tool for the investigation of diet in extant and extinct primates.

Dental topography and the diet of Homo naledi

“…Besides inferring dietary ecology, dental topography has also been used to predict enamel surface morphology from the shape of the enamel-dentine junction (Skinner et al, 2010;Guy et al, 2015), to investigate evolutionary pressures, such as niche partitioning (Boyer et al, 2012;Godfrey et al, 2012;Berthaume and Schroer, 2017), and to describe and assign a primate fossil to a new species (Boyer et al, 2012). The relationship between tooth shape and food item breakdown have additionally been investigated (Thiery et al, 2017a(Thiery et al, , 2017b, but how foods break down during mastication is not yet fully understood, and the proposed categories (e.g., crushing, grinding) need to be better defined from a fracture mechanics standpoint before this classification system can be used (Berthaume, 2016b;Thiery et al, 2017b).…”

“…Triangle counts of 10,000 are standard for DNE studies (Bunn et al, 2011;Winchester et al, 2014), but tend to oversimplify large and complex teeth (Berthaume and Schroer, 2017). A triangle count of 20,000 was suggested by Berthaume and Schroer (2017), but higher triangle counts have been recommended for other dental topographic metrics (e.g., 22,000 and 55,000; Guy et al, 2013Guy et al, , 2015Lazzari and Guy, 2014;Thiery et al, 2017a). Simplified and full versions of the teeth were imported into CloudCompare (CloudCompare, 2017) and oriented into anatomically correct position, using fossils with portions of the mandible preserved as guides.…”

Ambient occlusion and PCV (portion de ciel visible): A new dental topographic metric and proxy of morphological wear resistance

“…As taller structures do a more efficient job at “shading” the tooth than shorter ones, which are, overall, more exposed to ambient light, we predict teeth with high cusps are likely to have lower average PCV values that teeth with low cusps. In primates, folivores and insectivores tend to have taller crowned M2s with higher cusps compared to omnivores, frugivores, and hard-object feeders [11,15,19,20,24,25]. As such, we predict folivores and insectivores will have lower average PCV values than omnivores, frugivores, and hard-object feeders.…”

A comparison of relief estimates used in three‐dimensional dental topography

“…According to a number of studies, primates whose diets include a majority of insects and leaves tend to possess tooth crowns with higher slope and RFI scores than primates who consume a diet in which the majority component is fruit (Boyer, ; Bunn et al, ; Bunn & Ungar, ; Klukkert, Teaford, & Ungar, ; M'kirera & Ungar, ; Ulhaas, Kullmer, Schrenk, & Henke, ). Primates who consume a large amount of stress limited food, such as seeds, are also characterized by lower slope and RFIs scores (Boyer, ; Ledogar, Winchester, St. Clair, & Boyer, ; Thiery, Gillet, Lazzari, Merceron, & Guy, ; Winchester et al, ).…”