# Sensory Reconstruction of the Fossil Lorisid Mioeuoticus: Systematic and Evolutionary Implications

## TL;DR

This study reconstructs the sensory anatomy of a fossil lorisid, Mioeuoticus, to understand its behavior and evolutionary position.

## Contribution

The study provides new insights into the sensory evolution and phylogenetic placement of Mioeuoticus within lorisids.

## Key findings

- Mioeuoticus exhibited modern lorisid behaviors like slow locomotion and nocturnal activity.
- Its nasal turbinal arrangement suggests a basal position within Lorisidae or Lorisoidea.
- Olfactory abilities of Mioeuoticus align with those of modern lorisids.

## Abstract

We reconstructed the internal sensory system anatomy of the lorisid, Mioeuoticus shipmani (KNM-RU 2052), from the early Miocene of Rusinga Island, Kenya. Results suggest that Mioeuoticus developed typical modern lorisid behaviour (i.e., slow locomotion, nocturnal activity pattern) and olfactory abilities consistent with modern representatives.

The fossil record of lorises and pottos (family Lorisidae) potentially dates back to the late Oligocene of Namibia, but a later moderate diversification of this family occurred during the Miocene of Africa and Asia. In the African Miocene, the family Lorisidae is represented solely by one genus: Mioeuoticus. The phyletic position of Mioeuoticus has been a source of debate, as it has been suggested to belong to either the stem of the family Lorisidae or to be further nested within lorisids, as a sister to the African potto clade (subfamily Perodicticinae). Reconstructing the internal sensory anatomy of Mioeuoticus shipmani (KNM-RU 2052) could shed some light on this debate and possibly clarify how modern lorisoid olfactory and visual sensitivity and locomotor abilities evolved. Here, we collected data from the nasal turbinals, bony labyrinths, and orbits of Mioeuoticus shipmani from the early Miocene of Rusinga Island, Kenya. These results are consistent with Mioeuoticus, having developed typical modern lorisid behaviour (i.e., slow locomotion, nocturnal activity pattern) and olfactory abilities consistent with modern representatives. However, the arrangement of the nasal turbinals shows an intermediate state between lemuroids and lorisoids that is most consistent with a basal position of Mioeuoticus within the family Lorisidae or even the superfamily Lorisoidea.