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The New Papers Walk Among Us

Hi All -

   A few that I don't think have been mentioned yet:

Fajardo, R.J., Hernandez, E., and O'Connor, P.M. 2007. Postcranial skeletal pneumaticity: a case study in the use of quantitative microCT to assess vertebral structure in birds. Journal of Anatomy 211(1):138-147. doi: 10.1111/j.1469-7580.2007.00749.x.

ABSTRACT: Limb elements in birds have been characterized as exhibiting a reduction in trabecular bone, thinner cortices and decreased bending strength when pneumatized, yet it is unclear if these characteristics generalize to the axial skeleton. Thin section techniques, the traditional gold standard for bone structure studies, have most commonly been applied to the study of avian bone. This destructive technique, however, makes it subsequently impossible to use the same samples in experimental testing systems that allow researchers to correlate structure with the mechanical properties of the bone. Micro-computed tomography (µCT), a non-destructive X-ray imaging technique, can be used to assess the effect of pneumatization on vertebral cortical and trabecular bone through virtual extraction and structural quantification of each tissue type. We conducted a preliminary investigation of the application of µCT methods to the study of cortical and trabecular bone structure in a small sample of pneumatic and apneumatic thoracic vertebrae. The sample consisted of two similar-sized anatids, Aix sponsa (n = 7) and Oxyura jamaicensis (n = 5). Volumes of interest were created that contoured (outlined) the boundaries of the ventral cortical bone shell, the trabecular compartment and the whole centrum (cortical bone + trabecular bone), and allowed independent structural analysis of each volume of interest. Results indicated that bone volume fraction of the whole centrum was significantly higher in the apneumatic O. jamaicensis than in the pneumatized A. sponsa (A. sponsa = 36%, O. jamaicensis = 48%, P < 0.05). In contrast, trabecular bone volume fraction was similar between the two species. The ventral cortical bone shell was approximately 23% thinner (P < 0.05) in A. sponsa (0.133 mm) compared with apneumatic O. jamaicensis (0.172 mm). This case study demonstrates that µCT is a powerful non-destructive imaging technique that may be applied to the three-dimensional study of avian bone. The preliminary results suggest that pneumatic and apneumatic vertebrae of comparably sized avian species differ in relative bone volume, with the largest difference apparent at the level of the cortex, and not within trabecular bone. The presence of relatively thin cortices in pneumatic vertebrae is consistent with previous studies contrasting diaphyseal cortical bone between pneumatic and apneumatic long bones. Methodological issues related to this and any comparative µCT study of bone structure are discussed.

Nudds, R.L., Dyke, G.J., and Rayner, J.M.V. 2007. Avian brachial index and wing kinematics: putting movement back into bones. Journal of Zoology 272(2):218-226. doi: 10.1111/j.1469-7998.2006.00261.x.

ABSTRACT: The relationship between wing kinematics, wing morphology and the brachial index of birds (BI=humerus length/ulna length) was examined. BI was found to differ between three groups of birds, which were classified on the basis of similar wing kinematics. In addition, a comparative analysis of a large dataset, using phylogenetically independent contrasts, suggested a significant, albeit weak, correlation between BI and four measures of wing morphology (wing loading, wing area, wing length and aspect ratio). Although wing kinematics and wing morphology are both correlated with BI in birds, the dominant selective pressure upon this ratio is probably wing kinematics. The previously identified clade specificity of BI within Neornithes is most likely because birds with similar BIs fly with kinematic similarity and closely related birds have similar flight styles. A correlation between BI and wing kinematics means that it may be possible to characterize the wing beat of fossil birds. A more robust relationship between wing morphology and BI may emerge, but only after the relationship between wing kinematics and BI is quantified. A comparative and quantitative study of wing-bone anatomy and wing kinematics is a priority for future studies of avian wing-skeleton evolution and functional morphology.

Nudds, R.L. 2007. Wing-bone length allometry in birds. Journal of Avian Biology 38(4):515-519. doi: 10.1111/j.2007.0908-8857.03913.x.

ABSTRACT: A comparative analysis using both independent contrasts (CAIC) and a species level analysis was used to investigate the allometric scaling of avian wing-bone lengths. Total arm (ta=humerus+ulna+manus) scaled with positive allometry as body mass (M)0.37-0.39. Similarly, and in accordance with previous studies, wing-span (b) was positively allometric, but CAIC suggested a lower allometric exponent (M0.35) than found using species as independent data points (M0.39). Contrary to previous studies, individual wing-bones appear to scale with similar exponents against M and scale isometrically with ta. In addition to a general trend for larger birds to have longer wings, wing-bones and ta, their ta was a larger proportion of their b. A detailed study of primary feather length and elbow joint angle across a wide range of bird species and bird size, however, is required before a conclusive explanation for this increase in ta relative to b in larger birds can be established. Scaling equations are presented that can be used to predict M, ta and b from individual wing-bone lengths, which may be of use to palaeontologists wishing to reconstruct whole animals from single bones.

Senter, P. 2007. A method for distinguishing dromaeosaurid manual unguals from pedal 'sickle claws'. Bulletin of the Gunma Museum of Natural History 11:1-6.

ABSTRACT: The manual unguals and pedal "sickle claws" of dromaeosaurid dinosaurs are easily confused. To find a method for distinguishing them. I compared the manual and pedal unguals of the dromaeosaurids Microraptor zhaoianus, Bambiraptor feinbergi, Velociraptor mongoliensis and Deinonychus antirrhopus. I found that the dorsal edge of a dromaeosaurid manual ungual arches higher than the articular facet when the latter is held vertically, whereas the same does not occur in a pedal "sickle claw". Also. the flexor tubercle of a dromaeosaurid manual ungual is much more pendant than that of a pedal "sickle claw". Application of these findings shows that disarticulated unguals of Utahraptor and Pyroraptor pertain to the foot, as does an ungual referred to Dromaeosaurus, whereas disarticulated unguals of Achillobator and Unenlagia pertain to the hand. This method is applicable only to Dromaeosauridae. because the unguals of other theropod taxa exhibit different morphologies.

Tumarkin-Deratzian, A.R. 2007. Fibrolamellar bone in wild adult Alligator mississippiensis. Journal of Herpetology 41(2):341-345. doi: 10.1670/0022-1511(2007)41[341:FBIWAA]2.0.CO;2.

ABSTRACT: Histological examination of long bones from wild American Alligators (Alligator mississippiensis) reveals weakly defined growth zones and extensive fibrolamellar bone formation in both healthy and stressed adult individuals. The discovery of this tissue in wild adults of variable health status challenges three current assumptions concerning fibrolamellar bone in crocodylians: first, that it can only be formed in juveniles; second, that it occurs only in captive animals; and third, that it occurs only in individuals experiencing optimal physiological conditions. This highlights the need for further detailed study of bone microstructural diversity among modern crocodylians. Moreover, these results have potentially far-reaching implications for studies of fossil archosaurs, which often draw on extant crocodylian models, and for the phylogenetic significance of fibrolamellar bone within Archosauria as a whole.

Zelenkov, N.V. 2007. The structure and probable mechanism of evolutionary formation of the foot in piciform birds (Aves: Piciformes). Paleontological Journal 41(3):290-297. doi: 10.1134/S0031030107030082.

ABSTRACT: The foot structure of piciform and coraciiform birds is examined in detail. Certain similarity in foot structure between woodpeckers and woodhoopoes is shown and provides the basis for the model of the evolutionary formation of the zygodactyl foot. It is shown that African mousebirds and the Madagascan Leptosomus discolor are probably the closest relatives of piciforms. A brief review of fossil groups presumably belonging to the piciform stem is provided.

Candeiro, C.R.A. 2007. Paleogeographic distribution of the terrestrial squamate reptiles from the Cretaceous of Brazil. Bioscience Journal 23(1):65-74.

ABSTRACT: The terrestrial squamates from Brazil are the Early Cretaceous Olindalacerta brasiliensis and Tijubina pontei from Ceará State; the Late Cretaceous Pristiguana brasiliensis from Minas Gerais State, Ophidia indet. and Aniloidea from São Paulo State. Squamates were widespread in western Gondwana and Laurasia landmasses, and iguanids and mainly snakes widely distributed in southern South America.

Lastly, I haven't seen this one, but it's out:

Veldmeijer, A.J., Signore, M., and Bucci, E. 2007. Predator-prey interaction
of Brazilian Cretaceous toothed pterosaurs: a case example, pp. 295-308 in:
A.M.T. Elewa, ed., Predation in organisms: a distinct phenomenon. Berlin,

ABSTRACT. This chapter presents an overview of evidence of predator-prey relationships in pterosaurs, with a focus on the Cretaceous (Santana Formation) pterosaurs from Chapado do Araripe, northeastern Brazil. The examples from the fossil record of pterosaurs as prey is scanty; the situation of pterosaurs as predators is not much better. However, especially for pterosaurs as predator, secondary evidence provides much insight in the life of these extinct predators. Here, we present a simple geometric model that proves the suggested way of predations of the toothed and crested taxa of the Anhangueridae.

This book (http://www.springer.com/west/home/geosciences?SGWID=4-10006-22-173679911-detailsPage=ppmmedia|toc) also has in it a chapter entitled "Predation tactics in flightless birds and non-avian dinosaurs," but I've been unable to determine the author or page numbers (though it looks like the last article in the book). If anyone has access to the book, please let us know!

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

"Trying to estimate the divergence times
of fungal, algal or prokaryotic groups on
the basis of a partial reptilian fossil and
protein sequences from mice and humans
is like trying to decipher Demotic Egyptian with
the help of an odometer and the Oxford
English Dictionary."
-- D. Graur & W. Martin (_Trends
in Genetics_ 20[2], 2004)