852


Journal of Paleontology 89(5):845–869


distance one can see the bones of the wing skeleton and a series of undulations and occasional prominent folds in the dactylo- patagium, but on closer examination the most abundant features are the raised longitudinal strips. Also visible are gouges and tool marks, the retrophalangeal wedge, and blood vessel traces. These features will be described below, and with the exception of the undulations, gouges, and tool marks, they were mapped and are shown in Figure 1.1.


Medial part of the impression.—The medial part of the soft tissue impression consists of traces of the propatagium, the plagiopatagium, and probably some of the skin of the lateral trunk. The margins of the impression were cleaned up by the specimen’s finder, who scraped and smoothed the limestone, but only the trailing edge of the plagiopatagium near the humerus can be accepted as the actual margin of the wing in life. The area of the propatagium in the angle between the humerus and antebrachium is irregularly textured and provides no informa- tion as to the structure or extent of the propatagium. Those parts medial to digits I–III and anterior and medial to the pteroid are stained with iron oxide, and a tongue-shaped flap preserves traces of integumentary hairs highlighted with iron oxide. Therefore, that part may pertain to the skin of the trunk. The area of the plagiopatagium lies behind the forelimb and


extends laterally to contact the dactylopatagium posterior to the MCP joint of digit IV. Comparing the area of the preserved plagiopatagium with that of reconstructions of the skeleton with the wing spread as in flight (e.g., Wellnhofer, 1975, fig. 41; Bennett, 2000, fig. 1) shows that the plagiopatagium, if essentially complete, must have been strongly contracted and/or folded. There are a few ridges within the area that may be overlapping folds, and it is possible that some of the plagiopatagium was folded under the humerus. The texture of most of the plagiopatagium’s area differs from that typical of bedding planes of the Solnhofen Limestone and seems to preserve a trace of the patagium though in most places it is indecipherable. Immediately behind the lateral four-fifths of the antebrachium there is a raised area with a loose linear texture and a curving posterior margin that is part of the retrophalangeal wedge. It continues into the angle between the metacarpus and WP1 where the regularity of the texture disappears. The lateralmost parts of the plagiopatagium exhibit some short raised longitudinal strips immediately behind the retrophalangealwedge and anterior to the trailing edge, but the area between the two has an irregular texture lacking distinct raised strips. Medial to the raised longitudinal strips along the trailing edge, the texture has a distinct linearity with the lines roughly perpendicular to the trailing edge and the shaft of the humerus, but the texture lacks the regularity of raised longitudinal strips. Farther posteromedially and behind a prominent ridge that probably is an overlapping fold, the texture has a pattern of faint regular lineations more or less parallel to the trailing edge continuing posteromedially toward the hindlimb. The lineations are finer and more closely spaced than the raised longitudinal strips of the dactylopatagium.


Undulations and folds.—There are undulations and prominent folds in various places on the dactylopatagium, which in most cases are parallel to the raised longitudinal strips. There is a series of gentle undulations behind WP2 and 3, which have a


wavelength of ~3mm and fade away medially, laterally, and posteriorly, and there are gentle undulations with a wavelength of 3–4mm along the trailing edge of the brachiopatagium behind WP1. There are also several prominent posterolaterally oriented folds indicated by heavy lines in Figure 1.2. They are best seen in the posterior half of the dactylopatagium but the lines along which the patagium is folded presumably continued anteromedially paralleling the raised longitudinal strips. Five of the folds seem to be prominent enough that they are lettered A through E for identification. Note that it is argued below that the folds occurred along genetically controlled fold lines in the dactylopatagium. Folds A and C–E are visible as long, promi- nent raised linear features, whereas Fold B is shorter and fainter, but it is roughly midway between Folds A and C, and with it included and assuming that the fold lines extended proximally and distally parallel to the raised longitudinal strips the five fold lines divide the dactylopatagium into five sections of roughly equal width. The positions of the fold lines can be described in terms of positions along the wing phalanges and the trailing edge behind the phalanges. Fold LineAextends posterolaterally for some distance from the MCP joint before arcing posteriorly to the middle of the curve where the trailing edge bends toward the hindlimb behind the first IP joint, Fold Line B extends from roughly one-third of the distance along WP1 from its proximal end to the trailing edge behind the mid-point of WP2, Fold Line C extends from roughly the mid-point of WP1 to the trailing edge behind the second IP joint, Fold Line D extends from a point one-fifth along WP2 to the trailing edge behind the


mid-point of WP3, and Fold Line E extends from a point three- fifths along WP3 to the trailing edge behind the distal third of WP4. There is also a prominent fold in the retrophalangeal wedge that is highlighted by iron oxide and extends poster- olaterally from a point one-third along WP1 to the intersection of the trailing edge of the wedge and Fold Line C. In addition to the undulations and folds, in the lateral part of the dactylopata- gium there are features that can be best described as creases where two sections of the dactylopatagium that exhibit concave- up curves meet in a sharp edged convex-up crease.


Gouges and tool marks.—There are several prominent gouges (~2.5 × ~5mm) into the patagium impression near the trailing edge behind the middle third of WP2, the proximal third of WP3, and the proximal third of WP4. None of them shows any evidence of internal structure or permineralized soft tissues, rather they merely expose matrix that has taken the impression. There are also several tool marks gouged into the matrix just behind the distal third of WP4. The matrix near the wing tip has a slightly different character than elsewhere in the area of the dactylopatagium, and I suspect that the finder in preparing the specimen had difficulty identifying and following a separation between the wing impression and the overlying matrix, and made the tool marks in his attempt to do so.


Raised longitudinal strips.—The raised longitudinal strips are present across most of the dactylopatagium and a small part of the lateralmost plagiopatagium and lie roughly parallel to the wingfinger in the lateral parts of the dactylopatagium but are angled progressively more anteroposteriorly in the more medial parts. Their shape, spacing, and length are variable across the


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