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Confuciusornis growth patterns

From: Ben Creisler

Not exactly a partridge in a pear tree, but here's a new 
paper to unwrap:

Jesus Marugan-Lobon; Luis M. Chiappe; Shu'an Ji; Zhonghe 
Zhou; Gao Chunling; Dongyu Hu; Qinjing Meng (2010)
Quantitative patterns of morphological variation in the 
appendicular skeleton of the Early Cretaceous bird 
Journal of Systematic Palaeontology (advance online 
DOI: 10.1080/14772019.2010.517786 

Confuciusornis sanctus stands out among the remarkable 
diversity of birds of the Jehol biota (Lower Cretaceous, 
Liaoning Province, China). Its basal position in the 
phylogenetic tree of birds, combined with the exceptional 
number of well-preserved, largely complete and 
articulated specimens, makes it a perfect model system 
for studying the variation, development and life history 
of early Mesozoic birds. A comprehensive morphometric 
study (measurements of humerus, ulna, radius, femur and 
tibia) previously identified two distinct size classes of 
C. sanctus, while demonstrating the lack of statistical 
support of the association between this size dimorphism 
and the characteristic pair of long tail feathers present 
in some specimens. Four plausible explanations were 
discussed to account for the resultant size classes: the 
existence of more than one species in the sample; sexual 
size dimorphism; two size classes corresponding to 
attritional death assemblages; and/or a particular growth 
pattern similar to that inferred for non-avian dinosaurs. 
Here we present an expanded statistical analysis based on 
a larger sample of C. sanctus that substantiates previous 
interpretations, but also addresses the statistical 
association between the presence/absence of tail feathers 
and fore- and hind-limb allometry. We discuss the 
implication of the resulting quantitative patterns of 
morphological variation to understand better 
confuciusornithid taxonomy and the life history of C.