Sinosauropteryx feathers?

Jeff Poling

In the April 12 edition of New Scientist, a short news article appeared called "Feathered Fallacy." The article states that Dr. John Ostrom has declared that the structures present along the back of the famous "feathered" fossil Sinosauropteryx prima are not true feathers. This characterization is not quite accurate and, unfortunately, the article does not go into the details that would make this fact clear. Indeed, the later qualification that they are not like modern feathers may be missed by many even though this is a very important fact.

Alan Brush, John Ostrom, Larry Martin and Peter Wellnhofer ("the group") spent nearly 3 weeks in China. The trip was sponsored by the Philadelphia Academy of Natural Science, and the group had invitations from various Chinese institutions and the CAS. They were given unlimited access to the three known specimens of Sinosauropteryx by the Beijing Geological Museum and the Nanjing Institute of Geology and Paleontology. Each organization possesses one half of the first specimen plus a larger specimen acquired later.

The findings of the trip will be announced at a press conference at the Academy on Thursday, April 24th. Additional questions may be answered, and further details revealed. One of the Chinese scientists may attend the press conference. At this time the group does not plan a lengthy report, but that can change.

A few details have been released by Alan Brush prior to the news conference to clear up the sketchiness of the New Scientist article:

1. Brush writes "In our opinion the structures on Sinosauropteryx are not feathers in the sense of any modern feather morphology. They might represent some sort of protofeather, but homology can only be established by internal and perhaps molecular evidence. Microscopic work, both SEM and perhaps TEM of thin sections would help." The structures could also be true feathers of a different morphology than is known today.

2. If the structures are not some sort of feather, the scientists feel that they could be a support structure for some sort of a crest (a news story that reported the structures covering the entire surface of one of the later fossils was in error). If so, the structures would be derived from alpha-keratin and therefore not be feather homologues. Another possibility is that they were a dermal (internal to the skin) collagen structure used to maintain body shape.

3. "The skeleton is certainly dinosaurian," Brush writes. "We felt it was very close to Compsognathus and was so named by the Nanjing group."

All the specimens need much more preparation work and study. The group hopes the two Chinese institutions will work together and give the specimens the attention that such important discoveries deserve.

The group was also able to visit the site in Liaoning Province where Sinosauropteryx, Liaoningornis, Confuciusornis, Protarchaeopteryx, and many other extremely well preserved and important fossils have been found. Brush describes the site as "mind-blowing." There are an abundance of insect, fish and plant fossils, and in some spots "literally dozens of Confuciusornis fossils." There are many isolated feather fossils as well. The Chinese workers date the site to the late Jurassic, which is disputed by western workers who date it instead to the early Cretaceous. As yet there is not a widely accepted, accurate dating of the site. Brush commented that it was a "thrill for me was have more Mesozoic feather fossils in my hand, picked up rather causally in the field, than exist in most U.S. museums combined!" Brush characterizes Liaoning as a spectacular a site, truly a paleontological treasure.

Papers describing Sinosauropteryx and Protarchaeopteryx have been submitted to western journals and are currently in the editing or re-write phases. The group therefore will not elaborate further on the specimens than what has been revealed here, and what will be revealed in the April 24th press conference, in order not to compromise these papers. The world will have to wait a little longer for information about Sinosauropteryx, but hopefully not much longer. For myself, if these structures are indeed protofeathers, fossils of which have never before been found, I wonder how they compare to pterosaur "hair." Perhaps feathers will turn out to be an archosaurian trait after all...

1. Brush, Alan. Sinosauropteryx. Public e-mail to the Dinosaur Mailing List, 15 April 1997.
2. Brush, Alan. Re: Sinosauropteryx. Private e-mail to the author, 17 April 1997.
3. uncredited. 1997. Feathered Fallacy, http://www.newscientist.com/ns/970412/inbrief.html#feathers. New Scientist 12 April 1997.