May-Davis, S.; Hunter, R.; White, R. Morphology of the Ventral Process of the Sixth Cervical Vertebra in Extinct and Extant Equus: Functional Implications. Animals2023, 13, 1672.
May-Davis, S.; Hunter, R.; White, R. Morphology of the Ventral Process of the Sixth Cervical Vertebra in Extinct and Extant Equus: Functional Implications. Animals 2023, 13, 1672.
May-Davis, S.; Hunter, R.; White, R. Morphology of the Ventral Process of the Sixth Cervical Vertebra in Extinct and Extant Equus: Functional Implications. Animals2023, 13, 1672.
May-Davis, S.; Hunter, R.; White, R. Morphology of the Ventral Process of the Sixth Cervical Vertebra in Extinct and Extant Equus: Functional Implications. Animals 2023, 13, 1672.
Abstract
This study examined the ventral process of C6 in extinct and extant Equus (sister taxa to Equus ferus caballus only) with the purpose of describing normal morphology and identifying anomalous variations relevant to recent studies describing a congenital malformation in E. ferus caballus. Overall, 83 specimens from 9 museums and 3 research/educational facilities were examined – 71 extinct specimens from 12 species and 12 extant specimens from 5 species. The lateral view revealed a large convexity existed in the ventral process between the cranial ventral tubercle (CrVT) and the caudal ventral tubercle (CVT) in the earliest ancestor Hyracotherium grangeri 55mya that receded throughout the millennia to a smaller convexity in E. ferus caballus and sister taxa. The CrVT was visibly shorter and narrower than the CVT with a constricted section directly ventral to the transverse process essentially demarcating the CrVT and CVT. No congenital malformations were evident. As the ventral process of C6 is an integral component for muscle attachment in supporting the head/neck during posture and locomotion, this would indicate the caudal module in the cervical column might be compromised when a partial or complete absence of the CVT is detected via radiographs in modern E. ferus caballus.
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