# Evolutionary Specializations in the Venous Anatomy of the Two-Toed Sloth (Choloepus didactylus): Insights from CT-scan 3D Reconstructions

## TL;DR

This study uses CT scans to reveal unique venous structures in live two-toed sloths, offering new insights into their anatomy.

## Contribution

The study presents non-invasive 3D reconstructions of venous anatomy in live two-toed sloths, revealing previously undocumented features.

## Key findings

- A significant intravertebral vein was identified in Choloepus didactylus.
- Complex venous connections were observed through ventral sacral and vertebral foramina.
- The findings challenge existing literature on sloth venous anatomy.

## Abstract

There are few available data on the venous anatomy of Choloepus didactylus, particularly in living subjects. This study highlights the unique venous anatomy of this species in a non-invasive, retrospective, and reproducible manner, to enhance our understanding of this understudied species.

The venous anatomy of the two-toed sloth (Choloepus didactylus) remains poorly understood, particularly in living specimens due to the limitations of traditional cadaveric studies. This study aims to describe the unique venous structures of Choloepus didactylus using computed tomography, enhancing our understanding of this species in a live setting. Three living Choloepus didactylus underwent CT scans as part of routine clinical assessments. The images were reconstructed using 3D Slicer software (version 5.6.2), focusing on the caudal vena cava anatomy. The reconstructions confirmed the presence of a significant intravertebral vein, showing complex venous connections through the ventral sacral foramen and vertebral foramina. These findings highlight notable anatomical variations and challenge existing literature on the species’ venous architecture. By employing modern imaging technologies, this research provides new insights into the venous anatomy of Choloepus didactylus, demonstrating the value of non-invasive techniques in studying the anatomical features of live animals, thereby offering a foundation for further comparative and evolutionary studies.