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Flattened dinosaur and basal bird feathers reinterpreted

From: Ben Creisler

New paper online:

Christian Foth (2011)
On the identification of feather structures in stem-line representatives of
birds: evidence from fossils and actuopalaeontology. 
Paläontologische Zeitschrift (advance publication)
DOI: 10.1007/s12542-011-0111-3

Dinosaurs with fossilized filamentous integument structures are usually
preserved in a highly flattened state. Several different feather types have
been described on this basis, but the two-dimensional preservation of
specimens during fossilization makes the identification of single feather
structures difficult due to overlapping feather structures in vivo.
Morphological comparison with the diversity of recent feather types is
therefore absolutely vital to avoid misinterpretation. To simulate the
preservation process, a cadaver of recent Carduelis spinus (European
siskin) was flattened in a printing press. Afterwards, the structure of the
plumage was compared with the morphology of a single body feather from the
same specimen. In comparison with the single feather, the body plumage of
the flattened bird looked rather filamentous. It was almost impossible to
identify single structures, and in their place, various artefacts were
produced. The investigation of plumage in a specimen of the Mesozoic bird
Confuciusornis sanctus reveals similar structures. This indicates that
flattening of specimens during fossilization amplifies the effect of
overlapping among feathers and also causes a loss of morphological detail
which can lead to misinterpretations. The results are discussed in
connection with some dubious feather morphologies in recently described
theropods and basal birds. Based on recent feather morphology, the
structure of so-called proximal ribbon-like pennaceous feathers (PRPFs)
found in many basal birds is reinterpreted. Furthermore, the morphology of
a very similar-looking feather type found in the forelimb and tail of an
early juvenile oviraptorosaur is discussed and diagnosed as the first
feather generation growing out of the feather sheath. Thus, the whole
plumage of this theropod might represent neoptile plumage. 

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