# Morphological Investigation of the Roe Deer (Capreolus capreolus) Os Hyoideum and Creating a 3D Model

## TL;DR

This study provides the first detailed analysis of the hyoid bone in roe deer, including its structure, measurements, and a 3D model.

## Contribution

The first morphological and 3D modeling study of the roe deer hyoid bone, revealing its unique structure and comparison with other species.

## Key findings

- The roe deer hyoid bone consists of six parts, with distinct bone composition and joint types.
- The stylohyoideum is the longest part, while the tympanohyoideum is the smallest.
- The 3D printed model maintained structural integrity, and the hyoid showed morphological similarities to carnivores.

## Abstract

The os hyoideum, located at the intersection of the respiratory and digestive tracts, holds strategic importance due to its role in breathing, swallowing and vocalisation. The morphological structure of the os hyoideum varies among species. Since no research has been found on the hyoid bone in the roe deer (Capreolus capreolus), this study was planned. Six roe deer os hyoideum were used. The bones forming the os hyoideum were examined macroscopically and histologically, with morphometric measurements taken from 28 parameters. Additionally, the roe deer os hyoideum was 3D modelled and printed using TPU filament. The hyoid bone, connected to the skull by syndesmosis, consists of six parts: basihyoideum, thyrohyoideum, ceratohyoideum, epihyoideum, stylohyoideum and tympanohyoideum. While the tympanohyoideum is entirely compact bone, the middle of the other parts is compact bone and the ends are spongy bone. Among the joints between the parts, the tympanohyoideum—stylohyoideum and basihyoideum—thyrohyoideum joints are synchondrotic, while the others are synovial. In the roe deer, stylohyoideum was the longest part at 42.56 mm, while tympanohyoideum was the smallest at 6.92 mm. When the os hyoideum was printed using TPU filament, each bone part maintained its structural integrity. This study provided detailed morphological and morphometric data on the roe deer os hyoideum for the first time. The absence of proc. lingualis in the basihyoideum and the general morphological resemblance to carnivora in roe deer were noteworthy.

With this study, detailed morphological, morphometric and 3D printing data of the roe deer os hyoideum were obtained for the first time and its similarities and differences with other animal species were compared. The os hyoideum consisted of six parts, but the processus lingualis, which is found in ruminants, was not present in the roe deer. When the general morphological structures and morphometric values of the os hyoideum were examined, their similarities with carnivorous species were striking.