Breathing Life Into Dinosaurs: Tackling Challenges of Soft‐Tissue Restoration and Nasal Airflow in Extinct Species

Abstract

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.

Sensory Evolution and Ecology of Early Turtles Revealed by Digital Endocranial Reconstructions

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