256


Journal of Paleontology 92(2):254–271


compares well with what he described immediately below the caprock, as does the abundance of bivalve fossils. Based on the specific locality information, the specimen was collected from the fossiliferous chalk no more than 1.5m below Marker Unit 10, and is of upper middle Santonian age. The specimen consists of the distal halves of the radius


(61mm) and ulna (50 mm), the carpus, and complete McIV (160mm) and WP1 (194mm). The bones were flattened by compression, as is typical of Smoky Hill Chalk Member pterosaur specimens, and some of the bone of WP1 in an area ~7.5cm x ~5mm near the distal end was lost and reconstructed with plaster painted to resemble the adjacent bone. The bones of the specimen are largely articulated and were presumably held in articulation by ligaments until arriving on the sea floor, but there are minor dislocations that probably resulted from gravity or currents after the ligaments decomposed. Thus, the radius, ulna, and carpus are preserved in close association, but are separated from McIV by ~6mm, and the individual carpal ele- ments exhibit dislocations. McIV and WP1 are articulated with the metacarpophalangeal joint extended as in flight. The radius and ulna halves exhibit irregular breaks with no


impressions of the missing portions in the chalk, and they are splayed apart proximally even though the distal ends are preserved nearly in contact with the proximal syncarpal. This indicates that the bones were broken or perhaps bitten off before preservation of the specimen. The carpus is shown in Figure 2. All carpal elements are


severely deformed by compression such that they preserve little of their original morphology, and all exhibit pitted surfaces indicative of incomplete ossification. The radiale and ulnare that would have fused to form the proximal syncarpal are preserved slightly disarticulated from one another and close to the distal radius and ulna and the distal row of carpals. Few details of the


radiale are discernable other than its wedge-shaped dorsal aspect and part of the intersyncarpal articular surface. The ulnare exhibits the articular surface for the dorsal articular facet of the ulna and its slender-waist dorsal aspect is pierced by an oval pneumatic foramen. Its intersyncarpal articular surface is not exposed. The three distal carpals that would have fused to form a distal syncarpal are preserved slightly disarticulated from one another and close to the proximal carpals, but well separated from the proximal end of McIV. Most prominent is the sub- rectangular dorsal aspect of distal carpal 3, which is pierced by an oval pneumatic foramen. Most of distal carpal 2 is hidden behind distal carpal 3, but its prominent preaxial carpal process is visible anterior to distal carpal 3, and distal carpal 4 is largely hidden behind distal carpal 3. The preaxial carpal is still articulated with the preaxial carpal process of distal carpal 2, and its fovea is directed upward with the pisiform (= Sesamoid Aof Bennett, 2001, 2008) articulated in it. The pteroid is preserved in dorsal view a short distance away from the carpals. It is shaped like an ice hockey stick and is ~42mm long as pre- served, although its non-articular end is missing. The articular end of the pteroid has a pitted articular surface indicative of incomplete ossification. There is a more or less straight section ~11mm long and ~4mm wide, a gentle bend of ~25°, and then the bone narrows to 2mm to form a long straight shaft extending proximally. A small bone fragment that does not seem to be related to the carpus lies ~8mm from the shaft of the pteroid. Metacarpal IV is crushed such that it seems to present a


posterolateral view, whereas WP1 is crushed such that it seems to present a fully dorsal view. The posterior margin of McIV is broken and some fragments presumably were lost. The extensor tendon process is articulated with the rest of WP1, but is unfused. The articular ends of both bones were poorly ossified


Figure 2. Pteranodon sp. indet. (FHSM 17956). Detailed photograph and interpretive drawing of right carpus in dorsal view. Individual carpal elements are indicated with different shades of gray. Abbreviations: dc, distal carpal; fr, indeterminate bone fragment; mciv, metacarpal IV; pc, preaxial carpal; pcp, preaxial carpal process of distal carpal 2; pis, pisiform; pt, pteroid; ra, radius; rae, radiale; ul, ulna; and ule, ulnare. Scale bar is 3 cm.


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