[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

New feather-like fossil from the Jurassic of Kazakhstan, Dzik et al 2010

Dzik, J., T. Sulej & G. Niedwiedzki, 2010. Possible link connecting reptilian 
scales with avian feathers from the early Late Jurassic of Kazakstan.  
Historical Biology 22 (4): 394-402.  

Abstract: "Organic tissue of a recently found second specimen of feather-like 
*Praeornis* from the Karabastau Formation of the Great Karatau Range in 
southern Kazakstan, has a stable carbon isotope composition indicative of its 
animal affinity. Three-dimensional preservation of its robust carbonised shaft 
indicates original high contents of sclerotic organic matter, which makes the 
originally proposed interpretation of *Praeornis* as a keratinous integumental 
structure likely. The new specimen is similar to the holotype of *Praeornis* in 
the presence of three 'vanes' on a massive shaft not decreasing in  width up to 
near its tip. Unlike it, the vanes are not subdivided into  barbs and the 
pennate structure is expressed only in the distribution of organic-matter-rich 
rays. Similar continuous blades border the 'barbs' in the holotype, but the 
organic matter was removed from them by  weathering. It is proposed that the 
three-vaned structure is a remnant of the ancestral location of scales along 
the dorsum and their original function in sexual display, similar to that 
proposed for the Late Triassic probable megalancosaurid *Longisquama*. Perhaps 
subsequent rotation around the shaft, in the course of evolution from an 
ancestral status similar to *Praeornis* towards the present aerodynamic and 
protective function of feathers, resulted in the tubular appearance of their 

Unfortunately Dzik et al. do not compare their *Praeornis* fossil with any 
known stage of dinosaur feathers, so it is not clear from their paper how, if 
at all, their findings can be incorporated into the current mainstream model of 
feather evolution.  *Anchiornis* is referenced as "the oldest unquestionable 
bird".  *Longisquama* is variously called a "megalancosaurid" or a 
"prolacertid" in this paper, and there is really no discussion about when 
feathers are supposed to first appear in archosauromorph phylogeny (or indeed 
if birds are dinosaurs in their view).  The acknowledgements mention that new 
specimens of *Longisquama* have been collected, which should be exciting if 
they are not merely additional plumes.  All in all a rather unusual and 
surprising paper, what do the fossil feather experts on the list think of it?