The nasal region plays a key role in sensory, thermal, and respiratory physiology, but exploring its evolution is hampered by a lack of preservation of soft-tissue structures in extinct vertebrates. As a test case, we investigated members of the "bony-headed" ornithischian dinosaur clade Pachycephalosauridae (particularly Stegoceras validum) because of their small body size (which mitigated allometric concerns) and their tendency to preserve nasal soft tissues within their hypermineralized skulls. Hypermineralization directly preserved portions of the olfactory turbinates along with an internal nasal ridge that we regard as potentially an osteological correlate for respiratory conchae. Fossil specimens were CT-scanned, and nasal cavities were segmented and restored. Soft-tissue reconstruction of the nasal capsule was functionally tested in a virtual environment using computational fluid dynamics by running air through multiple models differing in nasal softtissue conformation: a bony-bounded model (i.e., skull without soft tissue) Abbreviations used: acPM 5 anastomotic canal in premaxilla; aEth 5 ethmoid artery; air 5 airway; anas 5 anastomosis between palatine, lateral nasal, and dorsal alveolar vessels; aSO 1 LN 5 anastomosis between supraorbital and lateral nasal vessels; aSph 5 sphenopalatine artery; at 5 potential accessory turbinate; bch 5 bony choana (fenestra exochoanalis); bLN 5 branches of lateral nasal vessels; bMN 5 branches of medial nasal vessels; cap 5 cartilaginous nasal capsule; caud co 5 caudal concha; cDA 5 dorsal alveolar canal; ch 5 choana (fenestra endochoanalis); cLN 5 canal for lateral nasal vessels; cMN 5 canal for medial nasal vessels; co 5 concha; cPM 5 canal in premaxilla; cSO 1 LN 5 canal for anastomosis between supraorbital and lateral nasal vessels; cSO 5 canal for supraorbital vessels; DA 5 dorsal alveolar vessels; f 5 frontal; fSO 5 suborbital fenestra; gLN 5 groove for lateral nasal vessels; j 5 jugal; lac 5 lacrimal; Lc 5 lacrimal canal; LN 5 lateral nasal vessels; max 5 maxilla; mid co 5 middle concha; MN 5 medial nasal vessels; mu 5 mucosa; nar 5 naris; nas 5 nasal; nc 5 nasal capsule; ng 5 nasal gland; npd 5 ductus nasopharyngeus; ns 5 nasal septum; ob 5 olfactory bulb; OfC 5 olfactory conchal vessels; olf e 5 olfactory epithelium; om 5 olfactory meatus; ot 5 olfactory turbinate; p 5 parietal; PA 5 palatine vessels; pl 5 palatine; pm 5 premaxilla; po 5 postorbital; post 5 postvestibular ridge; preco 5 preconcha; preco rec 5 preconchal recess; prf 5 prefrontal; ps 5 parasphenoid rostrum; pt 5 pterygoid; q 5 quadrate; qj 5 quadratojugal; RC 5 respiratory conchal vessels; res e 5 respiratory epithelium; sDS 5 dorsal sagittal sinus; so1 5 supraorbital 1; so2 5 supraorbital 2; som 5 supraorbital bone (mineralized supraorbital membrane); sOf 5 olfactory sinus; SO 5 supraorbital vessels; sq 5 squamosal; t 5 tongue; turb 5 turbinate; v 5 vomer; vest 5 vestibulum nasi; vp 5 ventromedian process.

The general anatomy of avian cephalic blood vessels is well known and there are published details of their role in physiological thermoregulation. Unfortunately, the finer details of vascular pathways to and from sites of thermal exchange are not well known. Additionally, the role of the rete ophthalmicum (RO), a vascular heat exchanger in the temporal region, has been investigated in terms of brain temperature regulation, yet only the arteries have received substantial attention. Without anatomical details of both the arterial and venous pathways, the role of blood vessels in physiological thermoregulation is incomplete. Cephalic vascular anatomy of multiple avian taxa was investigated using a differential-contrast, dual-vascular injection technique and high-resolution X-ray microcomputed tomography. Sites of thermal exchange (oral, nasal, and orbital regions) and the RO were given special attention due to their known roles in cephalic thermoregulation. Blood vessels to and from sites of thermal exchange were investigated to detect conserved vascular patterns and their ability to deliver cooled blood to the RO and dural venous sinus. Sites of thermal exchange were supplied by arteries directly and through collateral pathways. Veins were found to offer multiple pathways that could influence the temperature of neurosensory tissues, as well as pathways that would bypass neurosensory tissues. These results question the paradigm that arterial blood from the RO is the primary method of brain cooling in birds. A shift in the primary role of the RO from brain cooling to regulating and maintaining the temperature of the avian eye should be further investigated. Anat Rec, 299:1461-1486, 2016. © 2016 Wiley Periodicals, Inc.

Convoluted nasal passages are an enigmatic hallmark of Ankylosauria. Previous research suggested that these convoluted nasal passages functioned as heat exchangers analogous to the respiratory turbinates of mammals and birds. We tested this hypothesis by performing a computational fluid dynamic analysis on the nasal passages of two ankylosaurs: Panoplosaurus mirus and Euoplocephalus tutus. Our models predicted that Panoplosaurus and Euoplocephalus would have required 833 and 1568 thermal calories, respectively, to warm a single breath of air by 20°C. Heat recovery during exhalation resulted in energy savings of 65% for Panoplosaurus and 84% for Euoplocephalus. Our results fell well within the range of values for heat and water savings observed in extant terrestrial amniotes. We further tested alternate airway reconstructions that removed nasal passage convolutions or reduced nasal vestibule length. Our results revealed that the extensive elaboration observed in the nasal vestibules of ankylosaurs was a viable alternative to respiratory turbinates with regards to air conditioning. Of the two dinosaurs tested, Euoplocephalus repeatedly exhibited a more efficient nasal passage than Panoplosaurus. We suggest that the higher heat loads associated with the larger body mass of Euoplocephalus necessitated these more efficient nasal passages. Our findings further indicate that the evolution of complicated airways in dinosaurs may have been driven by the thermal requirements of maintaining cerebral thermal homeostasis.

The treatment of vertebrate specimens with radio‐opaque substances to enhance soft‐tissue contrast in CT scans has revolutionized morphological analysis. DiceCT has produced spectacular results and involves immersing specimens in Lugol's iodine. A shortcoming of diceCT is that diffusion (the “d” in “diceCT”) can take days, weeks, or months in large, intact, unskinned specimens. Moreover, long diffusion times can cause marked shrinkage. Alternatively, our team has developed spiceCT, which involves perfusing specimens with Lugol's iodine, yielding excellent results—literally within hours. The vascular system of thawed, unfixed, unskinned specimens (mostly birds and reptiles thus far) is cannulated, and then hypertonic (2.5 or 5%) aqueous Lugol's iodine is injected with a syringe. The solution perfuses well, easily filling capillary beds. Perfusion can be visually monitored in key areas, as well as tactilely via syringe pressure. Staining is rapid, and specimens can be scanned immediately, yielding same‐day results. There is no time for shrinkage, which is a well‐known problem for diceCT specimens immersed in iodine for long periods. The absence of prior fixation shortens processing time and also opens new avenues for final storage in that the specimen can be fixed, refrozen, or even skeletonized. Perfusion rather than diffusion also allows targeting of tissues—selective perfusion (the “sp” of “spiceCT”)—by injecting their vascular supply. One shortcoming of spiceCT is that iodine is too large to cross the blood‐brain barrier (BBB), even in cadaveric specimens. Our team is currently exploring ways to overcome this problem, experimenting with adding EDTA to the Lugol's injection medium to disrupt the cadherins forming the tight junctions of the endothelial cells of the cerebral vasculature. Initial results are promising. SpiceCT is intended to supplement, not replace, diceCT in the toolkit of morphologists.Support or Funding InformationUS National Science Foundation (IOB‐0517257, IOS‐1050154, IOS‐1456503)This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Vertebrates use the blood vascular system to moderate the temperature of specific anatomical regions. However, in many groups, such as birds, fundamental thermoregulatory mechanisms—the actual link between physiological function (heating and cooling) and the underlying vascular “plumbing”—have largely remained obscure, challenging our understanding of issues ranging from organismal responses to climate change to the human health consequences of vascular disease. In vivo physiological testing typically involves highly invasive procedures that may impose confounding artifacts due to stress responses mediated by the sympathetic nervous system. Fortunately, high‐resolution infrared (IR) thermal imaging provides a non‐invasive means of in vivo physiological measurement of surface temperatures in free‐ranging, normally behaving animals. In our study, thermal imaging was used to document heat maps of freely ranging birds (e.g., vultures, pelicans) in South Carolina and Florida. Quantitative thermographic data were analyzed to assess sites of heat exchange. Thermal data were compared to existing and new anatomical data based on microCT scanning of radio‐opaque (barium‐latex) vascular injections on legally obtained cadaveric bird specimens. Specific regions of the head where vascular devices in birds are suspected to be important for shedding heat as well as for cooling venous blood destined for the brain and eye were analyzed for anatomical and physiological correlations. This study seeks to establish the mechanistic links that ultimately allow birds to manage thermal stressors. Thermal images of investigated sites of thermal exchange indicated heat flow was found to correspond to the location of known blood vessels. These blood vessels were discernable in times of both heating and cooling. For example, in pelicans, the location of the ophthalmic rete corresponds to the location of a cool spot located behind the eye. Blood vessels in the pelican's pouch correspond to a streak of high temperature in the pouch. These results indicate that blood vessels play an active role in the thermophysiology of free‐ranging and unstressed birds and that the details of thermoregulatory mechanisms are discernable with non‐invasive methods.Support or Funding InformationUnited States National Science Foundation (IOB‐0517257, IOS‐1050154), Ohio University Heritage College of Osteopathic Medicine, Ohio University Research Committee, Natural Sciences and Engineering Research Council of Canada, and the National Geographic Society.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.