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The men who stare at dinosaurs

A Jerry Harris' style mail to announce the next release of the following papers in Acta Palaeontologica Polonica:

Dermal armor histology of Saltasaurus loricatus, an Upper Cretaceous sauropod dinosaur from Northwest Argentina
Ignacio A. Cerda and Jaime E. Powell
Acta Palaeontologica Polonica in press
available online 24 Mar 2010

The first unambiguous evidence of the presence of osteoderms in sauropod dinosaurs came from the discovery of Saltasaurus loricatus, a titanosaur from the Upper Cretaceous of Argentina. The dermal armor of Saltasaurus is composed of bony plates and small dermal ossicles. Here, we analyze the bone microstructure of these elements and provide information regarding its origin and development. The bony plates are composed almost entirely of reconstructed cancellous bone. Remains of primary bone consist of coarse bundles of mineralized collagenous fibers towards the external surface. Also, woven fibered bone tissue appears in the basal and lateral regions. Dermal ossicles lack secondary remodeling, and their matrix is formed by three orthogonal systems of collagenous fiber bundles. Growth lines are present in both bony plates and ossicles. Bone histology reveals that osteoderms mainly originated through direct mineralization (metaplasia) of the dermis, although other mechanisms are also involved (at least in the origin of dermal plates). The common features of development and integumental location of the osteoderms of Saltasaurus and other non-related vertebrates (e.g., lepidosaurs, crocodylomorphs) are linked to the intrinsic skeletogenic properties of the dermis.


Evidence for a sauropod-like metacarpal configuration in stegosaurian dinosaurs
Phil Senter
Acta Palaeontologica Polonica in press
available online 24 Mar 2010

The stegosaurian forelimb is usually portrayed with the metacarpals slanted and distally spread. However, manual manipulation of stegosaurian metacarpals reveals that in that configuration they do not articulate with each other nor with the rest of the forelimb. Rather, they do articulate with each other and with the rest of the forelimb when posed vertically and arranged in a compact, semi-tubular configuration, as in sauropods. This configuration agrees with data from articulated specimens and trackways. As with sauropods, this metacarpal configuration makes retention of phalanges awkward for locomotion and may be functionally related to the vestigiality of the manual phalanges of the outer digits.


The digital Plateosaurus II: an assessment of the range of motion of the limbs and vertebral column and of previous reconstructions using a digital skeletal mount
Heinrich Mallison
Acta Palaeontologica Polonica in press
available online 08 Mar 2010

Scientific literature and museum exhibits are full of explicit and implicit claims about the possible postures and motion ranges of dinosaurs. For the example of the prosauropod Plateosaurus engelhardti Meyer, 1837 I assessed the motion range of limbs and vertebral column in a CAD program using a 3D virtual skeletal mount. The range of motion of the forelimb is very limited, allowing the grasping of objects placed directly ventrally and ventrolaterally of the anterior torso. The manus is adapted for grasping. The powerful fore limb can barely reach in front of the shoulder, making a quadrupedal walking cycle impractical. Only a digitigrade pose of the pes with a steeply held metatarsus is feasible, and the morphology of the stylopodium and zeugopodium indicates a slightly flexed limb posture. Hind limb protraction and retraction are limited by the pelvic architecture. The neck has significant mobility both dorsoventrally and laterally, but blocks torsion. The dorsal vertebral column is flexible to a degree similar to the neck, mainly in the anterior half, but blocks torsion totally in the anterior and posterior thirds. The anterior dorsals are similar in shape to the posterior cervicals and significantly increase the motion range of the neck. The tail is highly flexible due to its large number of elements, showing more lateral than dorsoventral mobility. These results are compared to reconstruction drawings and museum skeletal mounts, highlighting a pattern of errors specific to certain widely used reconstruction methods.