A comparative morphological study of the sixth and seventh spinous processes of the cervical vertebrae in extinct and extant species of Equus.
The lateral profile of the 6th and 7th cervical spinous processes (CSPs) were examined in four extant
species of Equus (n=33); E. caballus (n=26), E. przewalskii (n=3), E. quagga boehmi (n=1), E. asinus (n=3)
and compared to pre-domesticated Equus specimens (n=66) representing three known species: E. occidentalis
(n=56), E. mosbachensis (n=2), E. curvedins/insulatis (n=1) and unknown Equus species (n=7) from five museums.
Six common morphological profiles were revealed: cuneate, curvate, falcate, rudimentary, scalenate,
and truncate. For the 6th CSP, the distribution of these morphologies amongst extant Equus is: cuneate, only
E. asinus; curvate, E. caballus and E. przewalskii always in combination with ligamentum lamina nuchae (lig.
lamina nuchae) attachments from the 2nd through to 7th CSP inclusive; falcate, E. caballus and E. przewalskii
always in combination with lig. lamina nuchae attachments from the 2nd through to 7th CSP inclusive;
rudimentary, E. caballus always associated with lig. lamina nuchae attachments from the 2nd through to 5th
CSP inclusive; scalenate, E. caballus in association with lig. lamina nuchae attachments from the 2nd through
to 5th (n=11) or 7th (n=4) CSP inclusive; truncate, not present. The 6th CSP in museum specimens of Equus
exhibits one of four profiles: cuneate (n=10), curvate (n=14), scalenate (n=11) and truncate (n=4). For the 7th
CSP, the distribution of these morphologies amongst extant Equus is: curvate, E. caballus mostly associated
with lig. lamina nuchae attachments from the 2nd through to 5th CSP inclusive, falcate, E. caballus mostly associated
with lig. lamina nuchae attachments from the 2nd through to 7th CSP inclusive, scalenate, E. caballus
associated with lig. lamina nuchae attachments from the 2nd through to 5th CSP inclusive. Only Rancho La
Brea and Tar Pits Museum provided samples suitable for examination of the 7th CSP. These exhibited four
profiles: curvate (n=7), falcate (n=11), scalenate (n=2), and truncate (n=7). These findings suggest that the
lateral profile of the 6th CSP is of potential use in identification of species; attachments of the lig. lamina nuchae
alter the morphology of the 6th and 7th CSP; and that attachments of the lig. lamina nuchae on the 2nd
to 7th CSP were likely present in species of Equus prior to domestication.
Arnold, M.A. Arnold’s Glossary of Anatomy. The University of Sydney, Anatomy and Histology. https://anatomy.usyd.edu.au/glossary/index.cgi Retrieved 12th March 2021.
Arnold, P. 2020. Evolution of the mammalian neck and development, morpho-functional, and paleontological perspectives.
Journal of Mammalian Evolution. DOI 10.1007/s10914–020– 09506–9.
Arnold, P., E. Amson, and M.S. Fischer. 2017. Differential scaling patterns of vertebrae and the evolution of neck length in
mammals. Evolution 71:1587–1599.
Brown, K.E., W.A. Akersten, and E. Scott. 2015. Equus occidentalis Leidy from “Asphalto” Kern County, California. Science
Buchholtz, E.A., H.D. Bailin, S.A. Laves, J.T. Yang, M-Y. Chan, and L.E. Drozd. 2012. Fixed cervical count and the origin
of the mammalian diaphragm. Evolution and Development 14:399–411.
Denoix, J-M. 1999. Spinal biomechanics and functional anatomy. Veterinary Clinics of North America: Equine Practice
Dunbar, D.C., J.M. Macpherson, R.W. Simmons, and A. Zarcades. 2008. Stabilization and moonily of the head, neck
and trunk in horses during over-ground locomotion; comparisons with humans and other primates. Journal of Experimental Biology 211:3889–3907.
Gasse, H., W. Van Den Broeck, and P. Simeons. 2017. Nomina Anatomica Veterinaria. 6th ed. Published by the Editorial
Committee for the World Association of Veterinary Anatomists. Hanover, Ghent, Columbia MO and Rio de Janeiro. 160 pp.
Geigl, E-M. and T. Grange. 2012. Eurasian wild asses in time and space: Morphological versus genetic diversity. Annals of
Gellman, K.S. and J.E.A. Bertram. 2002. The equine nuchal ligament 2: passive dynamic energy exchange in locomotion.
Veterinary and Comparative Orthopaedics and Traumatology 1:7–14.
Getty, R. 1975. Equine osteology; pp. 255–348 in S. Sisson, and J.D. Grossman (eds.), The Anatomy of Domestic Animals.
Saunders, Philadelphia USA.
Haussler, K.K. June 2016. Functional anatomy and clinical biomechanics of the equine cervical spine. Paper presented at the
AAEP Conference 360˚Pain in the Neck, Fort Collins Colorado.
Lyman, R.L. 2012. A historical sketch on the concepts of archaeological association, context and provenience. Journal of
Archaeological Method and Theory 19:207–240.
MacFadden, B.J. 1992. Fossil Horses: Systematics, Paleobiology, and Evolution of the Family Equidae. Cambridge University
Press. Cambridge UK. 367 pp.
May-Davis, S. and J. Kleine. 2014. Variations and implications of the gross anatomy in the equine nuchal ligament lamellae.
Journal of Equine Veterinary Science 34:1110–1113.
May-Davis, S., W.Y. Brown, and Z. Vermeulen. 2018. The disappearing lamellae: implications of new findings in the family
Equidae suggest the loss of nuchal ligament lamellae on C6 and C7 occurred after domestication. Journal of Equine Veterinary Science 68:108–114.
May-Davis, S., R. Hunter, and W.Y. Brown. 2020a. A comparative morphological study of the ligamentum lamina nuchae and ligamenta interspinalia reveals entheses patterns at the sites of attachment from the second to seventh cervical vertebrae in four extant species of Equus. Vertebrate Anatomy Morphology Palaeontology 8:170−181.
May-Davis, S., F. Minowa, and W.Y. Brown. 2020b. An in situ and ultrasound study of Yonaguni ponies revealed the rare
finding of the nuchal ligament lamellae from C2–C7. Journal of Equine Science 31:93–94.
May-Davis, S., Z. Vermeulen, R. Hunter, and W. Brown. 2020c. Rare finding of a full nuchal ligament lamellae with attachment points from C2–C7 in one Australian Stock Horse. Journal of Equine Veterinary Science 84:102847.
Mol, D., K. Post, J.W.F. Reumer, J. van der Plicht, J. de Vos, B. van Geel, G. van Reenen, J.P. Pals, and J. Glimmerveen. 2006.
The Eurogeal – first report of the palaeontological, palynological and archaeological investigations of this part of the North Sea. Quaternary International 142–143:178–185.
Muir, J. 1871. The Malayan tapir. Journal of Anatomy and Physiology 6:131–172.
Nussey, D.H., A.J. Wilson, and J.E. Brommer. 2007. The evolutionary ecology of individuals phenotypic platicity in wild
populations. Journal of Evolutionary Biology 20:831–844.
Orlando L., M. Mashkour, A. Burke, C.J. Douady, V. Eisenmann, and C. Hanni. 2006. Geographic distribution of an
extinct equid (Equus hydruntinus: Mammalia, Equidae) revealed by morphological and genetical analyses of fossils. Molecular Ecology 15:2083–2093.
Pellow, B.J., M.J. Henwood, and R.C. Carolin. 2010. eFlora: Vascular plants of the Sydney region. The University of Sydney
(5th ed). Retrieved 12th March 2021.
Schmaltz, R. 1924. Atlas der Anatomie des Pferdes. Verlagsbuchhandlung von Richard Schoetz: Berlin Germany. Plate 17b.
Singh, B. 2018. Dyce, Sack and Wensing’s Textbook of Veterinary Anatomy. Elsevier, Missouri, USA. 1606 pp.
Sisson, S. 1910. A Textbook of Veterinary Anatomy. W.B. Saunders, Philadelphia, USA. 724 pp.
Sisson, S. 1953. Equine syndesmology; pp. 209–246 in S. Sisson and J.D. Grossman (eds.), The Anatomy of Domestic Animals. Fourth edition. W.B. Saunders, Philadelphia USA.
Sisson, S. 1975. Equine syndesmology; pp. 349–375 in S. Sisson and J.D. Grossman (eds.), The Anatomy of Domestic Animals. Fifth edition. W.B. Saunders, Philadelphia, USA.
Wood, A.R., R.M. Bebej, C.L. Manz, D.L. Begun, and P.D. Gingerich. 2011. Postcranial functional morphology of
Hyracotherium (Equidae, Perissodactyla) and locomotion in the earliest horses. Journal of Mammalian Evolution 18:1–32.
Zsoldos, R.R. and T.F. Licka. 2015. The equine neck and its function during movement and locomotion. Zoology 118:364–376.
How to Cite
Copyright (c) 2021 Sharon May-Davis, Robert Hunter, Wendy Y. Brown
This work is licensed under a Creative Commons Attribution 4.0 International License.
Submission of an article to Vertebrate Anatomy Morphology Palaeontology will be taken to mean that the article is an original work and not previously published or under consideration for publication elsewhere.
If the article is accepted for publication, it will be published on-line under Creative Commons Attribution 4.0 International (CC By 4.0) meaning:
Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.