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Journal of Paleontology 89(5):845–869
point about one-fifth along the antebrachium to a point about three-quarters along WP3 (Fig. 1.2). Its posterior margin is somewhat irregular and the chordwise width of the trace increases evenly to ~8mm at mid-antebrachium before follow- ing an arcing path toward the distal half ofWP1 where it is again ~8mm. The trace continues behind WP2 and 3 with the width varying between ~7–11mm until it ends or disappears at a point about two-thirds along WP3. The appearance of the trace’send suggests that the wedge continued farther distally but its trace broke away fromthe slabwith the overlyingmatrix. The texture of the trace is that of loose, coarse fibers, but what can be seen of individual fibers suggests that they were rather short and followed sinuous paths, thus quite different from the adjacent long and parallel raised longitudinal strips. The orientation of the fibers is more or less perpendicular to the antebrachium in the medial part of the trace but parallel to the wing phalanges in the lateral part. Thewedge appears to be a distinct structure that lay on top of
the raised longitudinal strips rather than merely being raised longitudinal strips becoming indistinct near the bones of the wing spar because in places, particularly behind the antebrachium and the first IP joint, the posterior margin of the trace forms a step down fromthe plane of thewedge to that of the raised longitudinal
strips posterior to the wedge, and because the orientation of the fibers of thewedge behindWP2and 3 is not parallel to the slightly oblique posterolateral orientation of the raised longitudinal strips. The prominent fold in the wedge, which extends from a point approximately one-third along WP1 to where Fold Line C intersects the trailing edge of the wedge, supports the interpreta- tion that the wedge tissues were distinct fromthose that produced the raised longitudinal strips. In the more lateral parts of the trace, there appear to be patches of small raised longitudinal stripswithin the area of the retrophalangeal wedge, which suggest that the wedge tissue was not particularly substantial.
Blood vessel traces.—Within 1 cm of the dactylopatagium’s trailing edge behind WP2 and the proximal half of WP3 there are raised features, which have widths that are more variable than the adjacent raised longitudinal strips, are sinuous rather than straight, are sometimes branched, and often cut across the raised longitudinal strips and appear to be superimposed on top of the strips (Fig. 5). These are the features that Padian and Rayner (1993) thought were bifurcating structural fibers and interpreted as structural fibers that had been detached from
the underlying membrane and were displaced laterally to expose the grooves in which they had lain. That interpretation is rejec- ted here because some of the raised features are wider than the raised longitudinal strips anteriorly and taper to be narrower than the strips posteriorly, because the raised features cut across the strips at steep angles and nowhere appear to connect to them, and because no grooves in which the supposed cylindrical fibers had formerly lain can be seen. The raised features are interpreted as positive impressions of blood vessels, an interpretation consistent with their branching and variable widths. Note that although Frey et al. (2003, fig. 7A) found traces of the large vessel subparallel to the wing phalanges and its branches under UV illumination in the Zittel wing, no traces of large vessels are apparent under daylight illumination.
Description of the Marsh specimen
The Marsh specimen (YPM 1778; Fig. 2) is a nearly complete, articulated specimen preserved with soft tissue traces of both wings and the tail vane on the underside of an upper slab consisting of two subrectangular pieces mounted in plaster in a wooden frame. The bedding plane preserves large numbers of small dark calcareous nodules that may be Saccoma debris and also exhibits large numbers of light scratches and small shallow gouges that probably resulted from removal of a thin counterpart slab in small pieces. The neck is strongly bent to the left such that the skull is exposed in right lateral view, lying to the trunk’s left and roughly parallel to it. The trunk is preserved in ventral view with the sternum, the ventral ends of dorsal ribs, gastralia, prepubes, and the ventral parts of the paired puboischiadic plates of the pelvis exposed. The dorsal, sacral, and anterior caudal vertebrae cannot be seen and are presumably buried in matrix, and the tail is first visible immediately behind the right WP2. The tail is preserved in a nearly straight line and despite some damage from splitting off the counterpart from the part slab and subsequent preparation exhibits the hyperelongate pre- and postzygapophyses and hemal arches well. The tail vane is preserved at an angle to the plane of the slabs so that its left side is exposed to view. The right wing is complete and flexed such that the wing-
finger extends posteriorly along the right side of the trunk before curving to the left and crossing over the proximal caudal vertebrae. The left wing is folded such that the head and
Figure 5. Zittel wing of Rhamphorhynchus muensteri, BSP 1880 II 8. (1) Photograph of blood vessel traces near the trailing edge behind the second interphalangeal joint; (2) interpretive drawing with raised longitudinal strips indicated by thin black lines, the trailing edge of the dactylopatagium indicated by medium black lines, Folds C (left) and D (right) indicated by heavy black lines, and blood vessel traces indicated by gray lines. Note the gouge near the trailing edge. Abbreviations: bvt, blood vessel traces; and te, trailing edge. Scale bar represents 5mm.
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