Evolutionary drivers of the unique directional asymmetry of the odontocete skull

• Grant number: 25/12714-5
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: September 30, 2025
• End date: September 29, 2026
• Field of knowledge: Biological Sciences - Genetics - Animal Genetics
• Principal Investigator: Gabriel Henrique Marroig Zambonato
• Grantee: Maíra Laeta de Brito
• Supervisor: Anders Galatius-Jorgensen
• Host Institution: Instituto de Biociências (IB). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Aarhus University, Denmark
• Associated to the scholarship: 23/11843-0 - Evolution of modularity and morphological integration in skulls of Odontoceti (Mammalia, Cetacea) as full-time swimmers and sound-dependent mammals, BP.PD

Abstract

Odontocetes are aquatic mammals showing profound differences in cranial anatomy from all other mammals, including their terrestrial cetacean ancestor Pakicetus from the early Eocene (~54 Mya). Among their unique and ubiquitous cranial adaptations are the 'telescoping', directional asymmetry and feeding specializations. Directional cranial asymmetry in odontocetes is likely associated with sound production for echolocation. Despite advances in knowledge about cranial asymmetry, its association with skull modularity during the taxon's evolutionary historyand the driving forces behind this remain unclear. A modular structure of the odontocete skull, with rostrum/face and neurocranium modules is broadly recognised in odontocetes. Other modules, including palate, nasal, pterygoid, zygomatic, orbital and basicranium have also been proposed. Similarity of these modules to other mammals breaks down when directional cranial asymmetry is added to the picture, the asymmetry seems to work as an important evolutionary driver of changes in modularity. Cranial modules in odontocetes have been related to habitat use, prey preferences, and sound production. Here, we aim to understand the role directional asymmetry plays in the evolution of cranial modules in odontocetes - patterns, magnitudes and integration, evaluating selective pressures related to being fully aquatic, including insights into changes throughout ontogeny. Our material comprises ¿1,250 skulls belonging to c. 73 species of odontocetes held in 20 collections. Linear measurements derived from ¿121 three-dimensional anatomical landmarks will be used in analyses of asymmetrical form as it relates to phylogeneticsand potential evolutionary drivers affecting skull modularity, ontogeny and functionality. (AU)