Meeting Abstract
The kidneys of extant sauropsids (birds, crocs, squamates, etc.) tend to be less efficient at removing excess salt from the blood, and sites of extrarenal salt excretion are common, such as the nasal gland in birds. The physiology of the hypertrophied nasal salt glands of many marine birds is well-understood, but the anatomy is poorly documented. We present the results of our survey of avian nasal gland structure to better resolve the osteological correlates (OCs) of the gland, its ducts, and its vascular supply. The resulting OCs allow an assessment of the presence, position, and size of the nasal gland in extinct birds, allowing rough assessments of salt loads and hence habitat preferences (e.g., marine vs. terrestrial). The extant studies emphasize marine and aquatic birds (e.g., albatrosses, gulls, cormorants, anseriforms) as well as non-marine outgroups (e.g., ostrich), drawing on (1) gross dissection, (2) diceCT and spiceCT (iodine enhanced microCT), and (3) radio-opaque vascular injection followed by microCT. These studies provide not only detailed anatomical information, but also permit quantification of gland volumes for comparative analysis. These extant studies shed new light on the interpretation of the nasal glands of extinct birds, such as the Cretaceous marine toothed birds Hesperornis and Ichthyornis. The flightless diver Hesperornis had enormous nasal glands, suggesting that it was forced to consume seawater, whereas the volant Ichthyornis had smaller salt glands suggesting that it perhaps also had access to fresh water sources. The Paleogene anseriform bird Presbyornis, typically regarded as inhabiting saline soda lakes, also was sampled and provides new evidence for a modest nasal salt gland.
