THEODOR, J. M.; VAN VALKENBURGH, B. ; FRISCIA, A.; ROWE, T.: CT scan based quantitative comparison of respiratory turbinates in the Canidae and Felidae

The maxilloturbinates, bony scrolls within the anterior nasal chamber of most mammals, function to warm inspired air and conserve water during ventilation. Variation in maxilloturbinate structure among species is poorly understood, because their location and fine-scale structure has made them inaccessible to study. High resolution CT scanning allows visualization of the fine detail in the bones, and thus quantitative analysis of turbinate morphology. We compared canid and felid species from arid and mesic environments, which might be expected to differ in respiratory turbinate structure. Based on scaling, we predicted that turbinate volume relative to respiratory chamber volume should decrease with increasing body size. Instead, turbinate volume increases isometrically with body size. Similarly, we expected that arid species with greater need for water conservation would have higher turbinate volumes, but there is no evidence for any difference in volumes. Because of their shorter snouts, we expected to find more densely packed turbinates in felids than in canids. While larger felids show more open, less tightly packed scrolls than smaller ones, there is no evidence for denser packing of turbinates in felids. However, architectural differences exist among canid and felid species that may reflect different aerobic capacity. African wild dogs, Lycaon pictus, have an expanded nasal chamber that may be a lower resistance pathway for air during intense activity.