Abstract
Morphological variation in the attachment sites of the ligamentum lamina nuchae and ligamentainterspinalia to the 2nd to 7th cervical vertebrae is described in four species of Equus, and enthesis patterns inrelation to these attachment sites are explored. This comparative study provides new insights with respect tothis variation in the zebrine and asinine clades within Equus. In zebrines (Equus caballus, E. quagga boehmiand E. przewalskii), the ligamentum lamina nuchae attaches to the eminence of the cervical dorsal spinesfrom either the 2nd to 5th, and or 2nd to 7th. These attachments resemble digits and between each digit anaperture is apparent. The ligamenta interspinalia attach to the base of each cervical dorsal spine from the 2ndto 7th before progressing caudally onto the thoracic dorsal spines. Three enthesis patterns per cervical dorsalspine correspond to the size and shape of these ligaments. In contrast, in asinines (as represented by Equusasinus), the ligamentum lamina nuchae attaches without digitation to the complete sagittal ridge of the cervicalvertebra including the dorsal spine and exhibits no ligamenta interspinalia. Consequently, the enthesispattern is represented by a raised sagittal ridge only, excluding the 7th cervical dorsal spine. These differencesbetween the ligamentum lamina nuchae and ligamenta interspinalia attachment sites create distinct enthesispatterns that differentiate zebrines from asinines. Findings include: differing ligamentous morphology; associatedenthesis patterns corresponding to attachment sites of the ligaments to the cervical vertebrae; influencesin dorsal spine morphology subject to the presence or absence of the ligaments; and the postulation ofevolutionary functional adaptions in response to environmental influences between the two Equus clades.These results may be useful for palaeontologists in the identification of isolated cervical vertebrae.
Highlights
Comparative morphology examines the body structures of different species, partly to understand the adaptive changes they have undergone through evolutionary processes (Blits 1999)
The findings revealed the lig. lamina nuchae in E. przewalskii, E. asinus and E. quagga boehmi attaches from the 2nd – 7th cervical vertebrae, whereas in E. caballus the most common attachment is from the 2nd– 5th (MayDavis and Kleine 2014; May-Davis et al 2018, 2020)
Functional anatomy: In E. przewalskii, E. quagga boehmi and E. asinus, the lig. lamina nuchae consists of a bilateral sheet of yellow ligamentous elastin fibres that arise from the dorsal spines of the 2nd and 3rd thoracic vertebrae and lig. funiculus nuchae; after which they traverse cranioventral and insert onto the dorsal spines of the 2nd to 7th cervical vertebrae
Summary
Comparative morphology examines the body structures of different species, partly to understand the adaptive changes they have undergone through evolutionary processes (Blits 1999). The two clades are distinguished by distinct phenotypic variations of the splanchnologia, angiologia, integument, and musculoskeletal system (MacFadden 1992, 2005; Burnham 2002; Orlando 2015; Burden and Thiemann 2015). This became further evident when a recent comparative study investigated the cervical attachments of the lig. This became further evident when a recent comparative study investigated the cervical attachments of the lig. lamina nuchae (the sheet portion of the 2-part ligamentum nuchae) in four species of Equus: E. caballus, E. przewalskii, E. asinus and E. quagga boehmi (May-Davis et al 2018).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
