Fractal dimension and cheek teeth crown complexity in the giant rodent Eumegamys paranensis

Abstract

In this work, we analyse cheek teeth crown complexity through the calculation of fractal dimension in the giant caviomorph rodent Eumegamys paranensis (Late Miocene of Argentina) and evaluate its functional significance. Our results indicate that, in all teeth of Eumegamys paranensis, the fractal dimension was around 1.5, similar to the Koch quadratic curve type two. The anterior portions of the molars, with the highest values of fractal dimension, are interpreted as areas that supported greater occlusal pressures. Crown complexity in E. paranensis is related to the increased mechanical capacity to process relatively demanding food items and to allow more food to be divided in each masticatory cycle. Eumegamys paranensis would have been a mixed feeder, consuming a variable diet obtained close to the ground. This feeding behaviour is compatible with the heterogeneous environment inferred for the Mesopotamic area during the Late Miocene. E. paranensis was probably a wide ranging species, being able to eat close to water bodies and in gallery forests that occurred in the surrounding of the pre‐Paraná river system.

Teeth complexity, hypsodonty and body mass in Santacrucian (Early Miocene) notoungulates (Mammalia)

“…We followed two procedures to quantify tooth complexity, by means of occlusal enamel length (OEL) as the perimeter of enamel infolding of the tooth (Famoso et al 2013;Fig. 2C), and the enamel crests complexity (ECC) as the fractal dimension (D) of enamel infolding (Candela et al 2013). These authors use D, defined as the identification and quantification of self-similarity in invariant scale, to evaluate how an object (enamel edges) fills the available space (tooth occlusal surface area), as in Stone & Telford (2005).…”

“…Following Candela et al (2013), fractal dimension was calculated as a mean of twelve repetitions using random box positions by box counting method (Fig. 2D), implemented in FracLac 2.5 Release 1d-ImageJ Plugin, using four pixels as a minor box unit, and a series of a power formula of base two with 1028 pixels as a major box unit.…”

“…Reguero et al (2010) suggested that in typotheres, the occlusal design plays an important role in the relationship between hypsodonty and body mass (BM), and that these three factors form a complex of characters. Candela et al (2013) proposed that chewing efficiency of the dynomid rodent could be functionally more related to ECC than hypsodonty. These authors remarked that the relationship of ECC and hypsodonty with factors such as teeth effectiveness, food physical attributes and the ingestion of soil particles, remains elusive.…”

“…Using fractal dimension, Candela et al (2013) quantified the enamel crest complexity (ECC) of a gigantic hypsodont dynomid rodent to evaluate chewing efficiency. Famoso et al (2013) measured the occlusal enamel length (OEL) in ungulate teeth, finding that it was constrained by the occlusal tooth area and diet.…”

Un nuevo Notungulado Hipsodonte (Hegetotheriidae, Pachyrukhinae) del Mioceno tardío de la Cordillera Oriental, provincia de Salta, Noroeste de Argentina.

“…In the context of hypsodont species, this ungulate was probably a wide ranging species that lived in gallery forests, being able to eat close to water bodies of a system river and lagoons that occurred in the foodplains developed under humid and subtropical climate. Other hypsodont species, the giant rodent Eumegamys paranensis from the late Miocene of Argentina, adds to the examples of hypsodont but not grasser species (Candela et al, 2013) dwellers of forested habits, developed under warm and humid climate, where the grasses were not predominant.…”