Mammalian maxilloturbinal evolution does not reflect thermal biology

Area of Science:

• Vertebrate Paleontology
• Evolutionary Biology
• Mammalian Anatomy

Background:

• Endothermy, the ability to maintain a high body temperature, is a key mammalian adaptation.
• The anterior nasal cavity's maxilloturbinal bone has been hypothesized to be crucial for thermoregulation and moisture conservation.
• Maxilloturbinal size has been proposed as an indicator of endothermy and metabolic rate in extinct vertebrates.

Purpose of the Study:

• To investigate the relationship between maxilloturbinal morphology and endothermy in mammals.
• To determine if maxilloturbinal surface area correlates with basal metabolic rate or body temperature.
• To explore variations in maxilloturbinal structure across mammalian phylogeny and ecology.

Main Methods:

• Utilized a comprehensive dataset of micro-computed tomography (µCT)-derived maxilloturbinals from diverse mammalian orders.
• Analyzed the relative surface area, morpho-anatomy, and complexity of maxilloturbinals.
• Correlated maxilloturbinal traits with corrected basal metabolic rate and body temperature data.

Main Results:

• Found no significant correlation between maxilloturbinal relative surface area and corrected basal metabolic rate or body temperature.
• Demonstrated that the presence and development of turbinal bones are not linked to the origin of endothermy.
• Identified significant variations in maxilloturbinal relative surface area, morpho-anatomy, and complexity across mammalian phylogeny and species ecology.

Conclusions:

• The maxilloturbinal's role in heat and moisture conservation does not directly reflect endothermy or metabolic rate in mammals.
• Maxilloturbinal morphology is shaped by mammalian evolutionary history and ecological adaptations rather than solely by thermoregulatory demands.
• This study challenges previous hypotheses linking turbinal bone development to the evolution of endothermy.