An in situ and ultrasound study of Yonaguni ponies revealed the rare finding of the nuchal ligament lamellae from C2–C7

The Yonaguni pony is a rare breed of pony that has remained isolated on the westernmost island of Japan and may well retain normal morphological traits currently lost in most domestic horses (Equus caballus), such as the attachment of the nuchal ligament lamellae (NLL) from C2–C7. Recent research has found that NLL attachments are no longer present at C6 and C7 in most modern domesticated horses. This study investigated the attachments of the NLL in three Yonaguni ponies; 2 were examined in situ(deceased), and 1 was examined in vivo via ultrasound. The aim was to verify the attachments and compare the morphology to that in equids from previous studies. The in situ (2/2) and in vivo (1/1) findings revealed that the NLL was attached from C2–C7 in the Yonaguni ponies.