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

The study investigates a rare breed of pony, Yonaguni, which could provide insights into equine biology that are no longer observed in modern domestic horses. By examining the ponies, it was discovered that they maintained attachment of the nuchal ligament lamellae (NLL) from the second to seventh cervical vertebrae, a trait lost in most domestic horses.

Introduction

• The research focuses on a unique breed of pony called Yonaguni, native to the westernmost island of Japan and isolated from other breeds.
• This isolation has resulted in certain distinctive traits being preserved, notably the morphology of the nuchal ligament lamellae (NLL), specifically its attachment to the second to seventh cervical vertebrae (C2-C7).
• The NLL is no longer attached at the sixth and seventh cervical vertebrae (C6 and C7) in most contemporary breeds of domestic horses.

Methodology

• The research was conducted on three Yonaguni ponies. Two ponies were deceased and their physical structures were studied in situ, i.e., in their original place. The third pony was alive and its structure was examined using ultrasound imaging.
• The goal of the study was to confirm the attachment of the NLL from C2 to C7 in the Yonaguni ponies, and then compare the shape and structure (morphology) to those of horses in prior studies.

Findings

• The study confirmed that the NLL in Yonaguni ponies is attached from the second to the seventh cervical vertebrae. This is the case with both ponies observed in situ and the one examined by ultrasound.
• This finding provides interesting evidence of biological diversity and possible historical evolution in pony and horse physiology, since this feature is missing from most domesticated horses.