Locomotory adaptations in entoptychine gophers (Rodentia: Geomyidae) and the mosaic evolution of fossoriality

Abstract

Pocket gophers (family Geomyidae) are the dominant burrowing rodents in North America today. Their fossil record is also incredibly rich; in particular, entoptychine gophers, a diverse extinct subfamily of the Geomyidae, are known from countless teeth and jaws from Oligocene and Miocene-aged deposits of the western United States and Mexico. Their postcranial remains, however, are much rarer and little studied. Yet, they offer the opportunity to investigate the locomotion of fossil gophers, shed light on the evolution of fossoriality, and enable ecomorphological comparisons with contemporaneous rodents. We present herein a quantitative study of the cranial and postcranial remains of eight different species of entoptychine gophers as well as many contemporary rodent species. We find a range of burrowing capabilities within Entoptychinae, including semifossorial scratch-digging animals and fossorial taxa with cranial adaptations to burrowing. Our results suggest the repeated evolution of chisel-tooth digging across genera. Comparisons between entoptychine gophers and contemporaneous rodent taxa show little ecomorphological overlap and suggest that the succession of burrowing rodent taxa on the landscape may have had more to do with habitat partitioning than competition. K E Y W O R D S burrowing, Castoridae, ecomorphology, functional morphology, Heteromyidae, resource partitioning

Evolution of woodcutting behaviour in Early Pliocene beaver driven by consumption of woody plants

“…fossil burrows, cut wood, and stable isotope measurements) and skeletal-dental morphology is mapped onto a simplified phylogenetic tree in Fig. 8 42 , 84 – 87 .

Figure 8 Simplified Castoridae phylogeny showing behavioural reconstructions, including new evidence of woody plant consumption in Dipoides sp.

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“…fossil burrows, cut wood, and stable isotope measurements) and skeletal-dental morphology is mapped onto a simplified phylogenetic tree in Fig. 8 42,[84][85][86][87] .…”

Postnatal development of the largest subterranean mammal (Bathyergus suillus): Morphology, osteogenesis, and modularity of the appendicular skeleton

“…6 With the exception of few ontogenetic studies mostly focused on cranial anatomy, [7][8][9][10][11][12][13] most of the research assessing the musculoskeletal phenotype of extant and extinct subterranean and fossorial mammals has focused on morphofunctional comparisons of adults only (or at "endpoints" of ontogeny) where most of somatic (and/or skeletal) growth of the individual has been attained. [14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31] In addition, most of these studies have focused on few specimens and have used a particular anatomical dimension for analysis, either their external morphology (2D or 3D) or their bone microanatomy.…”

Three‐dimensional geometric morphometric analysis of the humerus: Comparative postweaning ontogeny between fossorial and semiaquatic water voles (Arvicola)

“…Among fossorial rodent species three methods of digging can be found (Stein, 2000): scratch-digging (i.e., claws of the manus are used to break up soil; e.g., Ctenomys, Bathyergus, Geomys); head-lift (i.e., incisors in concert with the skull form a powerful drill, that works like a spade to remove and loose the soil; e.g., Nannospalax, Ellobius), and chisel-tooth digging (i.e., incisors are used to break down the ground; e.g., Cryptomys). Depending on the mode of digging different adaptations of the appendicular skeleton or skull have been described (Calede, Samuels, & Chen, 2019;Hildebrand, 1988;Samuels & Valkenburgh, 2009;Stein, 2000). As for Arvicola, fossorial water voles (A. scherman) are chisel-tooth diggers that build complex burrow systems in harder soils (Airoldi, 1976;Airoldi & De Werra, 1993;Laville, 1989).…”