The evolution of micro-cursoriality in mammals

Abstract

In this study we report on the evolution of micro-cursoriality, a unique case of cursoriality in mammals smaller than 1 kg. We obtained new running speed and limb morphology data for two species of elephantshrews (Elephantulus spp., Macroscelidae) from Namaqualand, South Africa, which we compared with published data for other mammals. Elephantulus maximum running speeds were higher than those of most mammals smaller than 1 kg. Elephantulus also possess exceptionally high metatarsal:femur ratios (1.07) that are typically associated with fast unguligrade cursors. Cursoriality evolved in the Artiodactyla, Perissodactyla and Carnivora coincident with global cooling and the replacement of forests with open landscapes in the Oligocene and Miocene. The majority of mammal species, though, remained non-cursorial, plantigrade and small (<1 kg). The extraordinary running speed and digitigrady of elephant-shrews was established in the Early Eocene in the earliest macroscelid Prodiacodon, but was probably inherited from Paleocene, Holarctic stem macroscelids. Micro-cursoriality in macroscelids evolved from the plesiomorphic plantigrade foot of the possum-like ancestral mammal earlier than in other mammalian crown groups. Microcursoriality evolved first in forests, presumably in response to selection for rapid running speeds facilitated by local knowledge, in order to avoid predators. During the Miocene, micro-cursoriality was pre-adaptive to open, arid habitats, and became more derived in the newly evolved Elephantulus and Macroscelides elephant-shrews with trail running.

Vertical leaping mechanics of the Lesser Egyptian Jerboa reveal specialization for maneuverability rather than elastic energy storage

“…Elephant shrews ( Elephantulus spp. , Macroscelidae) would provide the most informative comparison, as they are the only identified group of micro-cursorial quadrupedal mammals [48]. Evidence of thinner tendons than expected by geometric similarity in elephant shrew hindlimbs would suggest that animals of small size may not be constrained to have stiff tendons with low elastic energy storage.…”

Where Have All the Giants Gone? How Animals Deal with the Problem of Size

“…Optimum body mass for speed is denoted by the peak of each curvilinear relationship. Original data reported in [40,46–51]. (B) Frequency distribution for the body masses of extant running mammals [52] ( n = 2,919; yellow bars) and extinct dinosaur species [1] ( n = 406; red bars) shown with the relationship of optimum mass for speed in nonfelid mammals.…”

Space use and the evolution of social monogamy in eastern rock sengis

“…We used instantaneous sampling of focal animals at 10-min intervals, where an individual is followed continuously to record the locations of sengis during our observation periods (Martin & Bateson, 2007). As the fast, cursorial movement of sengis allows them to move across their home range within minutes (Lovegrove & Mowoe, 2014), a 10-min interval between successive locations is adequate to avoid statistical autocorrelation (Otis & White, 1999;Schubert, Schradin, Rödel, Pillay, & Ribble, 2009). This was validated by conducting a 48-hr continuous observation of one male and one female during BS14.…”