Dino-soars: Reptiles with feathers

Dinosaurs have long captured our hearts and our curiosity.  From our first field trips to museums where their fossilized skeletons towered over us, it was difficult not imaging what they looked like and how they lived.  How many species were there?  What did they eat?  Did they have social groups?  How did they die?  Science and paleontology have slowly been able to answer these and many other questions about their biology, ecology, and environment.

Until recently one of the hottest debates about dinosaurs were the mechanics behind such a successful species’ extinction.  Schulte et al. (2010) were able to definitively show that the Chicxulub asteroid was the cause of the dinosaurs’ demise.  When the 7.5 mile wide asteroid blanked the sun for a decade with debris from an impact a billion times more powerful the the Hiroshima nuclear strike, the dinosaurs (and many other forms of life) stood no chance.

With this issue finally laid to rest a new debate has surfaced; did dinosaurs have feathers? We’ve all seen the renditions of dinosaurs as scaly, drab colored creatures with skin similar to modern reptiles.  The recent evidence from McKellar et al. (2011) and Wogelius et al. (2011) indicate that this too is incorrect. Dinosaurs had feathers, colorful ones even (see images).  These amber entombed feathers were discovered in Late Cretaceous amber from Grassy Lake, Alberta, Canada.  These findings fill a large gap in feather evolution and coincide geologically with Chinese compression fossils of feathered non-avian dinosaurs.  The combined evidence strongly support the theory that dinosaurs possessed protofeathers and that feathers from a variety of developmental stages were present in the Late Cretaceous on both dinosaurs and birds (McKellar et al. 2011).

This is fascinating on two separate levels.  First, dinosaurs had feathers!   I’ve studied biology my entire life, I am constantly amazed at what we learn as science and technology progress.  Second, and more scientific, the implications this discovery has on the evolution of feathers is priceless.  As these feathers have been preserved in amber, structures that would be lost in any compression fossil are literally frozen in time.  Complex features of the (proto)feathers including the calamus, rachis, and barbules (see images) are clearly identifiable.  These findings have been able to fill in the missing stages in feather evolution and provide a clear picture of the development of extremely complex features.   To paraphrase a bit of Hollywood “Fifteen hundred years ago we knew the earth was the center of the universe, 500 years ago we knew the earth was flat [and 3 months ago we knew dinosaurs were scaly and dull] imagine what [we’ll] know tomorrow.” (Men in Black) Amazing.

Schulte, P., Alegret, L., Arenillas, I., Arz, J., Barton, P., Bown, P., Bralower, T., Christeson, G., Claeys, P., Cockell, C., Collins, G., Deutsch, A., Goldin, T., Goto, K., Grajales-Nishimura, J., Grieve, R., Gulick, S., Johnson, K., Kiessling, W., Koeberl, C., Kring, D., MacLeod, K., Matsui, T., Melosh, J., Montanari, A., Morgan, J., Neal, C., Nichols, D., Norris, R., Pierazzo, E., Ravizza, G., Rebolledo-Vieyra, M., Reimold, W., Robin, E., Salge, T., Speijer, R., Sweet, A., Urrutia-Fucugauchi, J., Vajda, V., Whalen, M., & Willumsen, P. (2010). The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary Science, 327 (5970), 1214-1218 DOI: 10.1126/science.1177265

McKellar RC, Chatterton BD, Wolfe AP, & Currie PJ (2011). A diverse assemblage of Late Cretaceous dinosaur and bird feathers from Canadian amber. Science (New York, N.Y.), 333 (6049), 1619-22 PMID: 21921196

Wogelius RA, Manning PL, Barden HE, Edwards NP, Webb SM, Sellers WI, Taylor KG, Larson PL, Dodson P, You H, Da-qing L, & Bergmann U (2011). Trace metals as biomarkers for eumelanin pigment in the fossil record. Science (New York, N.Y.), 333 (6049), 1622-6 PMID: 21719643

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