Myological diversity of the masticatory apparatus of herbivorous mammals

ERCOLI, MARCOS DARÍO; ÁLVAREZ, ALICIA; WARBURTON, NATALIE M.; JANIS, CHRISTINE M.; POTAPOVA, ELENA G.; HERRING, SUSAN W.; CASSINI, GUILLERMO H.; TARQUINI, JULIANA; KUZNETZOV, ALEXANDER

Cairns

Congreso; International Congress of Vertebrate Morphology; 2023

International Society for Vertebrate Morphology

Masticatory muscle configurations, functions and dietary habits evolved in a diverse array of ecomorphotypes across mammalian lineages. Herbivorous mammals are traditionally classified as "ungulate-grinding" or "rodent-gnawing" morphotypes, although these categories do not adequately encompass the diversity of herbivores. We compiled topographical and weight data for masticatory muscles for 104 herbivorous and 10 non-herbivorous extant species of 14 orders, including novel data for 31 taxa. Additionally, we included inferred data for four extinct taxa. We constructed a myological phylomorphospace and proposed a comprehensive scheme of 15 masticatory mammalian morphotypes. Almost identical muscle proportions between early mammaliaforms and mammals and extant carnivores were recognized. Extant herbivores diversified along 13 morphotypes distributed along two main pathways, that did not reflect the traditional types. A complex scenario and different morphotypes are proposed for plesiomorphic herbivorous mammals, and one herbivorous morphotype cannot be differentiated from carnivores and generalized ones only considering muscle proportions. Differing from Turnbull’s proposal, the large disparity of rodents cannot be encompassed by a single category or pathway. Features of some derived extant euungulates and diprotodonts resemble rodents, but only extant wombats and some extinct South American native ungulates closely converged with them, the latter including a morphotype falling outside the extant pathways. The here proposed scheme could be useful to understand the herbivore diversity and for selection of extant models when palaeobiological reconstructions are attempted.