Determining the gait of Miocene, Pliocene, and Pleistocene horses from fossilized trackways

Abstract

Abstract. Much work has been done on the study of vertebrate gaits over the past several decades and efforts undertaken to apply this to fossil tracks, especially dinosaurs and mammals such as cats, dogs, camels, and horses. This work seeks to expand upon such studies and in particular to study footprints laid down in sand by modern horses and apply such studies to determine the gaits of fossil horse trackways. It thus builds upon the work of Renders (1984a, b) and Kienapfel et al. (2014) and suggests additional measurements that can be taken on horse footprints. In this study the footprints left in the sand by 15 horses of various breeds with various gaits were videotaped, photographed, described, and measured in order to determine characteristics useful in distinguishing gaits. These results were then applied to two new sets of fossil footprints, those of the middle Miocene merychippine horse Scaphohippus intermontanus that I personally examined and measured and those from the late Pleistocene horse Equus conversidens, previously illustrated and described in the literature (McNeil et al., 2007). The latter horse exhibits a fast gallop of around 9.4 m/s, but it is the former whose footprints are quite unique. The quantitative and visual features of these prints are suggestive of a medium-fast gait involving apparent “understepping” of diagonal couplets and hind feet that overlap the centerline. The gait that most closely matches the footprints of Scaphohippus is the “artificial” gait of a slow rack or tölt, or pace, around 1.9 m/s, though an atypical trot of a horse with major conformation issues or which is weaving (swaying) from side to side is a less likely possibility. This intimates, along with the earlier study of Renders (1984a, b), who found the artificial gait of the running walk displayed by Pliocene hipparionine horses, that ancient horses possessed a much greater variety of gaits than modern horses and that over time they lost these abilities with the exception of certain gaited breeds.

Laterally Coordinated Gaits in the Modern Horse (Equus ferus caballus)

“…a duty factor of 0.55 to 0.75), yielding support structures containing lots of three-feet support phases (54%), alternating with bilateral (24%) then diagonal (22%) support phases (see gait diagram a in Figure 1), i.e. 3-2D-3-2 L [3,4,22]. In the typical walk the front foot duration of ground contact is 0.95-1.04 that of the hind foot, the timing of the steps are fairly even (lateral advanced placement of 0.20-0.24 of the stride length and diagonal advanced placement of 0.26), independent of each other or square (lateral advanced liftoff of 0.25 and ipsilateral overlap of front and hand limbs for 44% of the stride), and with each foot remaining flat on the ground as the one after it comes down [6,7].…”

“…In the typical walk the front foot duration of ground contact is 0.95-1.04 that of the hind foot, the timing of the steps are fairly even (lateral advanced placement of 0.20-0.24 of the stride length and diagonal advanced placement of 0.26), independent of each other or square (lateral advanced liftoff of 0.25 and ipsilateral overlap of front and hand limbs for 44% of the stride), and with each foot remaining flat on the ground as the one after it comes down [6,7]. The hind feet often cap and so overlap the vacated location of the ipsilateral front feet when they land or slightly overstep them up to a [1,4,7,13,14,28] Overstep (% of stride length) 0.01-0.10 0.15-0.25 Not Reported Not Reported Not Reported [5,7,8,17,22] Table 1. Temporal and linear kinematic parameters of the ipsilaterally coordinated gaits of horses reported in previous studies.…”

“…hoof-length, or more technically by 3-19 cm or 0.01 to 0.10 of the stride length, resulting in footprints in lateral pairs that are generally parallel with each other and just to the side of the centerline [5,7,8,22,32]. In gaited horse breeds the walk may be extended with the hind legs overstepping the ipsilateral front legs somewhat, in which case it is often called a flat walk or dog walk.…”

Presentation1.pdf

“…Like Icelandic horses, the simulation switches to a "running tölt" at faster speeds: a four-beat symmetrical gait with single-humped ground reaction force profiles in all limbs (Figure 6C). The tölt is a rare gait in mammals (Vincelette, 2021), and unheard of in archosaurs, though it has been detected in fossil horse trackways (Renders, 1984;Vincelette, 2021). At speeds above 0.4, however, the simulations differ markedly from fossil trackways in the track phase.…”

“…Such models may be useful in paleontological research, where soft-body details including musculature geometry, fiber length, and tendon length are not usually preserved. Indeed, the gaits of fossil organisms are often very difficult to be determined from trackways, although some attempts have been broadly successful (see Nyakatura et al, 2019;Vincelette, 2021).…”