Olfactory receptor repertoire size in dinosaurs

Area of Science:

• Paleogenomics
• Comparative Genomics
• Evolutionary Biology

Background:

• The olfactory bulb (OB) ratio, a measure of the olfactory bulb's size relative to the cerebral hemisphere, serves as a proxy for olfactory acuity in birds.
• This ratio correlates with the number of olfactory receptor (OR) genes, providing a basis for inferring sensory capabilities.
• Understanding OB ratios in extinct taxa can illuminate their sensory world and evolutionary trajectories.

Purpose of the Study:

• To infer minimum olfactory receptor gene repertoire sizes for extinct taxa, including non-avian dinosaurs.
• To investigate the evolutionary history of olfactory acuity and sensory adaptations in avian and dinosaur lineages.
• To explore the ancestral sensory space and potential ecological niche adaptations of extinct animals.

Main Methods:

• Coupling OB ratios with known avian OR gene repertoires.
• Utilizing phylogenetic modeling and ancestral state reconstruction.
• Applying comparative genomics and integrating morphological data.

Main Results:

• Inferred minimum OR repertoire sizes for extinct taxa, including non-avian dinosaurs.
• Identified a shift in the scaling of OB ratio to body size along the lineage leading to modern birds.
• Demonstrated variable OR repertoires across different dinosaur and bird lineages, suggesting diverse sensory evolution in theropods.

Conclusions:

• Olfactory bulb ratios and genomic data can be combined to investigate evolutionary trajectories of sensory systems in extinct species.
• The study highlights potential adaptations to specific ecological niches based on inferred sensory capabilities.
• While direct genetic data is lost, evolutionary insights into extinct genomes are potentially feasible.