Scaphohippus, A New Genus of Horse (Mammalia: Equidae) from the Barstow Formation of California

Pagnac, Darrin

doi:10.1007/s10914-005-9002-2

Cited by 12 publications

(6 citation statements)

References 11 publications

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“…That is, the sample for “Merychippini” may be dominated by ancestral forms of Hipparionini, producing the observed connection between the tribes. We suspect this may be the case because more of the equin “ Merychippus ” have been split out into their own genera [5] , [43] , [44] , [45] , [46] .…”

Section: Discussionmentioning

confidence: 99%

“…Even for published species of equids, there are ongoing controversies about the validity of names. Major problem areas include genera and species split from the paraphyletic form genus “ Merychippus ” [5] , [43] , [44] , [45] , [46] as well as the number and identity of Plio-Pleistocene and recent Equus species [5] , [42] , [47] , [48] . There has been controversy as to the validity of the number of genera and species that belong to Hipparionini [5] , [15] , [37] , [43] , [45] , [49] , [50] .…”

Section: Methodsmentioning

confidence: 99%

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Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

Famoso

Davis

2014

PLoS ONE

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Four groups of equids, “Anchitheriinae,” Merychippine-grade Equinae, Hipparionini, and Equini, coexisted in the middle Miocene, but only the Equini remains after 16 Myr of evolution and extinction. Each group is distinct in its occlusal enamel pattern. These patterns have been compared qualitatively but rarely quantitatively. The processes influencing the evolution of these occlusal patterns have not been thoroughly investigated with respect to phylogeny, tooth position, and climate through geologic time. We investigated Occlusal Enamel Index, a quantitative method for the analysis of the complexity of occlusal patterns. We used analyses of variance and an analysis of co-variance to test whether equid teeth increase resistive cutting area for food processing during mastication, as expressed in occlusal enamel complexity, in response to increased abrasion in their diet. Results suggest that occlusal enamel complexity was influenced by climate, phylogeny, and tooth position through time. Occlusal enamel complexity in middle Miocene to Modern horses increased as the animals experienced increased tooth abrasion and a cooling climate.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

Famoso

Davis

2014

PLoS ONE

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“…The North American genera Protohippus, Calippus, and Scaphohippus (= "Merychippus" sumani and "M." intermontanus) were originally placed within the Equini, basal to the above-mentioned Equini taxa (see e.g., Hulbert and MacFadden, 1991;MacFadden, 1992MacFadden, , 1998. More recent analyses have assigned them to their own tribe, Protohippini, as the sister taxon to the Hipparionini (e.g., Kelly, 1995Kelly, , 1998Pagnac, 2006), and we include them with the hipparionins in our discussions here.…”

Section: A Brief History Of the Radiation Of The Equinae (Family Equidae)mentioning

confidence: 99%

The Evolution of Equid Monodactyly: A Review Including a New Hypothesis

Janis

Bernor

2019

Front. Ecol. Evol.

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The traditional story of horse evolution is well-known: over time, horses became larger, they attained higher-crowned teeth, and they changed from having three toes (tridactyly) to a single toe (monodactyly). Evolution is often perceived as a progression toward some optimum outcome, in this case the "Noble Steed." However, the evolutionary advantages of monodactyly are not entirely clear, other than the notion that it must somehow be "more efficient," especially at the larger body size of the genus Equus. It is not commonly appreciated that the reduction of the digits to the monodactyl condition was not the main anatomical foot transition in equid history. Rather, the most important change was the transformation of the original "pad foot" into the more derived "spring foot," with the acquisition of an unguligrade limb posture, characteristic of the family Equinae. Species within the Equinae tribes-Hipparionini, Protohippini, and Equini-evolved hypsodont teeth and diverged into both small and large body sizes, but monodactyly evolved only within the Equini. Despite the Plio-Pleistocene success of Equus, Hipparionini was by far the richest tribe for most of the Neogene, in terms of taxonomic diversity, numbers of individuals, and biogeographic distribution; but hipparionins remained persistently tridactyl over their duration (17-1 Ma). We propose that the adaptive reasons for monodactyly must be considered in the context of reasons why this morphology never evolved in the Hipparionini. Additionally, Equus inherited monodactyly from smaller species of Equini, and consideration of Miocene taxa such as Pliohippus is critical for any evolutionary hypothesis about the origins of monodactyly. We review the literature on equid locomotor biomechanics and evolution, and propose two novel hypotheses. (1) The foot morphology of derived Equini is primarily an adaptation for increasing locomotor efficiency via elastic energy storage, and the accompanying digit reduction may be circumstantial rather than adaptive. (2) Differences in foraging behavior and locomotor gait selection in Equini during late Miocene climatic change may have been a prime reason for the evolution of monodactyl horses from tridactyl ones.

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“…This species, which was formerly placed in the genus Merychippus, albeit with some hesitancy, byPajak and Vincelette (1991), has been reassigned more recently to Scaphohippus intermontanus(Pagnac, 2006). https://doi.org/10.5194/fr-24-151-2021 Foss.…”

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confidence: 99%

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

Vincelette

2021

Foss. Rec.

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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.

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Scaphohippus, A New Genus of Horse (Mammalia: Equidae) from the Barstow Formation of California

Cited by 12 publications

References 11 publications

Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

Occlusal Enamel Complexity in Middle Miocene to Holocene Equids (Equidae: Perissodactyla) of North America

The Evolution of Equid Monodactyly: A Review Including a New Hypothesis

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

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