Analysis of the Form-Function Relationship: Digging Behavior as a Case Study

Biomechanical adaptations for burrowing in the incisor enamel microstructure of Geomyidae and Heteromyidae (Rodentia: Geomyoidea)

“…We detected modified radial enamel close to the EDJ exclusively within Geomyoidea but not in Geomorpha outgroups, such as Heliscomyidae; nor was modified radial enamel reported to occur in the lower incisors of Eomyidae (Wahlert & Koenigswald, 1985) or Florentiamyidae (Wahlert, 1983). As this enamel type was found to be biomechanically beneficial for reducing tension and bending forces in high-crowned teeth, we assume a similar form-function association in Geomyidae and Heteromyidae (Pfretzschner, 1993(Pfretzschner, , 1994Vassallo et al, 2021). Consequently, we explain the presence of modified radial enamel as an adaptation to prevent structural failure triggered by increased mechanical stress acting on this tooth position due to regular burrowing activities (including chisel-tooth digging) and feeding on abrasive, fiber-rich plants and plant parts that grow underground (e.g., forbs, roots, stems, bulbs, tubers).…”

The forelimbs of Octodontidae (Rodentia: Mammalia): substrate use, morphology, and phylogenetic signal

“…Consequently, shortening of the forelimb (reducing out-lever) and enlargement of muscular attachments (increasing both in-lever and the area of insertion) occur in order to improve mechanical advantage for muscles involved in digging (e.g., hand flexor musculature; see Hildebrand, 1985;Stein, 2000;Polly, 2007;Van Valkenburgh, 2008, Vizcaíno et al, 2016). Some authors have studied the forelimb and hindlimb adaptations, especially the digging capacity of Ctenomys (family Ctenomyidae), and concluded that the greater development of the medial epicondyle could be an early specialization for digging (Elissamburu and Vizcaíno, 2004;Morgan and Verzi, 2006;Lessa et al, 2008;Elissamburu and De Santis, 2011;Morgan and Álvarez, 2013;Morgan et al, 2017;Vassallo et al, 2019). Also, this represents one of the main characters by which to recognize the digging fossorial forms.…”

Functional morphology and fiber types of the masseter muscles of two caviomorph rodents with contrasting lifestyles, Ctenomys talarum (Ctenomyidae) and Cavia aperea (Caviidae)

“…As scratch‐diggers, they have robust arm bones and well‐stabilized joint surfaces that provide greater resistance to forces generated during burrowing (Echeverría et al, 2014). Craniodental specializations for digging include large skulls with strong rostra, robust zygomatic arches, short and tall jaws, and large, strong, and procumbent incisors (Vassallo et al, 2019). Preliminary studies of muscles of the forelimbs and masticatory apparatus of C. talarum have shown a heterogeneous fiber type composition with prevalence of FOG fibers probably linked to the sustained effort required during digging (Álvarez et al, 2012; Vassallo et al, 2019).…”

“…Craniodental specializations for digging include large skulls with strong rostra, robust zygomatic arches, short and tall jaws, and large, strong, and procumbent incisors (Vassallo et al, 2019). Preliminary studies of muscles of the forelimbs and masticatory apparatus of C. talarum have shown a heterogeneous fiber type composition with prevalence of FOG fibers probably linked to the sustained effort required during digging (Álvarez et al, 2012; Vassallo et al, 2019). In comparison, most cavioids have graceful skulls and incisors, with an elongated rostrum and diastema (Álvarez et al, 2013).…”

“…The masseter muscles are highly developed (60–80% of the total mass of the mandibular muscles), mainly the m. masseter superficialis and m. masseter profundus (syn. Masseter lateralis; Álvarez & Arnal, 2015; Cox & Jeffery, 2011; Vassallo et al, 2019).…”