Photoluminescent visual displays: an additional function of integumentary structures in extinct archosaurs?

ABSTRACT

Many extant invertebrate and vertebrate taxa possess osteological, keratinous, or chitinous structures that are photoluminescent: that is, variably coloured and patterned when observed under ultraviolet light. These features are frequently associated with inter- and/or intraspecific display. Among terrestrial vertebrates, keratinous photoluminescent capabilities are especially well documented in birds. Inspired by recent discoveries, we consider whether non-bird dinosaurs, the evolutionary precursors to birds, might also have possessed photoluminescent display structures. Dinosaurs and other bird-line archosaurs (collectively ornithodirans) often possess extravagant structures that likely functioned in visual display. From a phylogenetic bracketing perspective, UV-sensitive visual capabilities in extant reptiles – including Aves – support the likelihood of tetrachromatic vision in extinct ornithodirans. The ability to perceive the ultraviolet, or near-ultraviolet, range of the visible light spectrum, combined with the presence of extravagant, keratinous-covered display structures, supports proposals that these features may have played an important role in inter- and intraspecific visual displays and communication in extinct Mesozoic bird-line archosaurs.

KEYWORDS:

• Photoluminescence
• keratin
• archosaur
• dinosaur
• pterosaur
• ultraviolet

Acknowledgments

Thanks to D. Evans, S. Claramunt, M. Peck, V. DiCecco, and K. Seymour of the Royal Ontario Museum for access to vertebrate palaeontology, avian, and osteology collections as well as the use of research-grade UV lights. C. Brown provided insightful conversation about Borealopelta markmitchelli and research. B. Engh provided the amazing artwork used in Figure 5 (dontmesswithdinosaurs.com). Thanks to T. Holtz, an anonymous reviewer, and a previous anonymous reviewer for valued feedback, insightful comments, and constructive discussions. Additionally, this project stemmed from the power of social media – sharing discoveries and connecting researchers around the globe to discuss new research, ask new questions, and spark new ideas.

Disclosure statement

No potential conflict of interest was reported by the authors.