(782.5) Functional Modularization in the Neck Muscles of the Gerenuk (Litocranius walleri)

Poster Board Number: C55
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Odd poster #s – 10:15 am – 11:15 am
Even poster #s – 11:15 am – 12:15 pm

Kevin Manfredi (Midwestern University), Justin Georgi (Midwestern University), K.E. Townsend (Midwestern University)

The gerenuk (Litocranius walleri) is an African ruminant that feeds on high growing foliage by standing erect on its hindlimbs and extending its long neck. We hypothesize that extensive myological adaptation would be present in the muscles that facilitate head stability and movement, as well as muscles that anchor the neck. The vertebral musculature from the atlas to the thoracic vertebrae of a gerenuk specimen was dissected and compared to that of other ruminants. Several muscles were found to have narrowed or shifted caudally along the vertebral column, resulting in their cranial-most attachment point being the fifth cervical vertebrae (C5). Similarly, two muscles were found to have shifted cranially, resulting in their caudal-most attachment point also being C5. Caudally shifted muscles include m. serratus ventralis cervicis, the scalene muscles, m. rhomboideus cervicis, and the cervical part of the trapezius. Cranially shifted muscles include m. splenius cervicis and m. longissimus capitis. These shifts indicate a significant degree of modularization occurring between head movement muscles and neck stability muscles, with C5 being the boundary. Further adaptation that was not part of modularization around C5 was found in the segmental muscles attaching between vertebral processes. Segments of m. intertransversarii and m. multifidi have elongated and undergone specialization at the cranial attachments. The segments of m. spinalis cervicis were found to have a complex configuration that interdigitates with the multifidi. Additionally, m. levator claviculae and m. iliocostalis cervicis were present, neither of which have been previously described in ruminants. Previously published work reported that osteological adaptation in the gerenuk neck is especially pronounced in C1 – C4, which is consistent with our findings of myological modularization occurring with C5 as the boundary.