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Chiappe, L.M., Marugán-Lobón, J., Ji, S., and Zhou, Z. 2008. Life history of
a basal bird: morphometrics of the Early Cretaceous Confuciusornis. Biology
Letters. doi: 10.1098/rsbl.2008.0409.

ABSTRACT: Confuciusornis sanctus stands out among the remarkable diversity
of Mesozoic birds recently unearthed from China. Not only is this primitive
beaked pygostylian (birds with abbreviated caudal vertebrae fused into a
pygostyle) much more abundant than other avian taxa of this age but
differences in plumage between specimens?some having a pair of long stiff
tail feathers?have been interpreted as evidence for the earliest example of
sexual dimorphism in birds. We report the results of a multivariate
morphometric study involving measurements of more than 100 skeletons of C.
sanctus. Our analyses do not show any correlation between size distribution
and the presence or absence of blade-like rectrices (tail feathers), thus
implying, that if these feathers are sexual characters, they are not
correlated with sexual size dimorphism. Our results also provide insights
into the taxonomy and life history of confuciusornithids, suggesting that
these birds may have retained ancestral dinosaurian growth patterns
characterized by a midlife exponential growth stage.

     (The supplementary info for this one synonymizes _Jinzhouornis_ with
_Confuciusornis_.)



Lombardo, M.P., Thorpe, P.A., Brown, B.M., and Sian, K. 2008. Digit ratio in
birds. Anatomical Record. doi: 10.1002/ar.20769.

ABSTRACT: The Homeobox (Hox) genes direct the development of tetrapod
digits. The expression of Hox genes may be influenced by endogenous sex
steroids during development. Manning (Digit ratio. New Brunswick, NJ:
Rutgers University Press, 2002) predicted that the ratio between the lengths
of digits 2 (2D) and 4 (4D) should be sexually dimorphic because prenatal
exposure to estrogens and androgens positively influence the lengths of 2D
and 4D, respectively. We measured digits and other morphological traits of
birds from three orders (Passeriformes, house sparrow, Passer domesticus;
tree swallow, Tachycineta bicolor; Pscittaciformes, budgerigar,
Melopsittacus undulates; Galliformes, chicken, Gallus domesticus) to test
this prediction. None were sexually dimorphic for 2D:4D and there were no
associations between 2D:4D and other sexually dimorphic traits. When we
pooled data from all four species after we averaged right and left side
digits from each individual and z-transformed the resulting digit ratios, we
found that males had significantly larger 2D:4D than did females. Tetrapods
appear to be sexually dimorphic for 2D:4D with 2D:4D larger in males as in
some birds and reptiles and 2D:4D smaller in males as in some mammals. The
differences between the reptile and mammal lineages in the directionality of
2D:4D may be related to the differences between them in chromosomal sex
determination. We suggest that (a) natural selection for a perching foot in
the first birds may have overridden the effects of hormones on the
development of digit ratio in this group of vertebrates and (b) caution be
used in making inferences about prenatal exposure to hormones and digit
ratio in birds.





~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Jerry D. Harris
Director of Paleontology
Dixie State College
Science Building
225 South 700 East
St. George, UT  84770   USA
Phone: (435) 652-7758
Fax: (435) 656-4022
E-mail: jharris@dixie.edu
 and     dinogami@gmail.com
http://cactus.dixie.edu/jharris/

"I have made this letter longer
than usual because I lack the
time to make it shorter."
                      -- Blaise Pascal