SYSTEMATIC PALEONTOLOGY
(continued)

Coracoid. The left coracoid (Mal-235; Figure 19C) is slightly damaged. Typical of titanosaurians, the bone is roughly quadrangular (301 mm by 230 mm) and thickens towards the glenoid fossa. The glenoid fossa is rugose. The lateral surface is convex, and the medial surface is concave as in Apatosaurus (Gilmore 1936), Camarasaurus (Osborn and Mook 1921), and in Isisaurus colberti (Jain and Bandyopadhyay 1997). The coracoid foramen is elliptical and restricted to the dorsal portion of the element penetrating diagonally from the lateral surface through the bone.

Humerus. Four humeri (left, Mal-221, Figure 20A-D; right, Mal-289, Figure 20E; right, Mal-316; and left, Mal-317; Table 7) of possibly three individuals (different sizes and quarries) are well preserved and complete. The proximal end is slightly more expanded than the distal end. The head is rugose and placed more medially than laterally and directed posteriorly as in Alamosaurus (Gilmore 1946), Opisthocoelicaudia (Borsuk-Bialynicka 1977), and Saltasaurus (Powell 1986). The anterior surface is hollowed out and has a strongly marked facet proximally, below which is a well-marked depression for muscular attachment. The deltopectoral crest overhangs the center of the shaft on the proximal anterolateral margin. The shaft is straight and rounded. The ulna and radial condyles are strongly pronounced. The ulnar condyle is more prominent than the radial condyle.

Ulna. Three ulnae (Mal-190, Mal-218, Figure 21A-C, left; Mal-309; Table 7) of at least two different individuals are present. Mal-218 is well preserved, but Mal-190 and Mal-309 are less well preserved. The olecranon process is strongly developed and protrudes above the articular surface. The articular surface is concave medially, convex laterally. The shaft is triangular in section and has a deep radial fossa proximally, and is quadrangular distally. A strong posterior tuberosity for muscle attachment emerges about 240 mm down and extends to the distal end. The distal end has a medially concave reniform outline.

Radius. A complete right radius (Mal-41; Figure 21D-G, Table 7) was found with a distal fragment (Mal-160) of a right humerus. The proximal and distal ends are about equally expanded and rugose. The proximal end is slightly concave and semicircular, whereas the distal end is slightly convex and ovoid. A longitudinal groove occurs on the posterior surface.

Manus. Four complete, associated metacarpals, and two fragmentary metacarpals are preserved. Based on comparison with Alamosaurus (Gilmore 1946), Opisthocoelicaudia (Borsuk-Bialynicka 1977), and Neuquensaurus (von Huene 1929; Powell 1986) the associated metacarpals pertain to Mc I to IV. The proximal end of right metacarpal I (Mal-196; Figure 22A-D, Table 7) is roughly triangular and rugose. The shaft is rounded proximally and becomes mediolaterally compressed distally. The lateral surface has a triangular roughened surface proximally to articulate with metacarpal II. A ridge occurs midshaft on the lateral surface. The distal end is rectangular.

Metacarpal II (Mal-208-2, right, Mal-214, left distal fragment; Figure 22E-H, Table 7) has an oval proximal end. The proximal surface is rugose and generally convex. The shaft is transversely compressed and somewhat constricted medially. The medial surface of the shaft has a well-developed ridge proximally and a depression distally. The distal surface is subrectangular, convex, and rugose.

Metacarpal III (Mal-209 right, Figure 22I-J, Table 7) has a triangular proximal end with a posterior acute angle. In lateral view, about one third of the proximal portion is paddle shaped while the distal portion is more rounded. The lateral surface is flat and rugose, broad proximally and narrow distally. The distal end is rectangular and is widest anteromedio-posterolaterally. Mal-209 is shorter and more slender than metacarpal II.

Metacarpal IV (Mal-208-1, right, Mal-144, left proximal fragment; Figure 22K-N, Table 7) has a strongly twisted shaft. The proximal end is expanded and subrectangular. The proximal surface is slightly convex. The shaft is medially constricted and slightly twisted. About 20 mm from the distal end is a well-defined broad triangular tuberosity on the anterior surface. This is similar to Alamosaurus. The distal end is expanded mediolaterally, and the articular surface is convex.

In Alamosaurus, the lengths of the metacarpals decrease laterally (Gilmore 1946). The manus is reported but not illustrated in Saltasaurus and Aeolosaurus (Powell 1986). In Opisthocoelicaudia, metacarpal I is the longest, whereas metacarpals II and III are approximately the same length. In Camarasaurus (McIntosh et al. 1996a, 1996b) and in Apatosaurus (Gilmore 1936, p. 226, top table) the third metacarpal is the longest and the two lateral metacarpals are the shortest. In Malawisaurus, the length of metacarpals decreases laterally.

There is no direct evidence of phalanges although the distal ends of metacarpals have articular surfaces that suggest the presence of phalanges. Titanosaurians are said to have no manual phalanges. If manual phalanges were present in Malawisaurus, this would suggest that basal titanosaurians had manual phalanges that were lost in more derived species.

Ischium. Three ischia (left, Mal-42, length = 400 mm; width = 125 mm at the widest point, and = 90 mm at the narrowest point, Figure 23A, [Jacobs et al. 1993, figure 1g]; Mal-184; right, Mal-183-1, length = 382 mm; width = 114 mm at the widest point and = 100 mm at the narrowest point, Figure 23B) have dorsoventrally broad pubic articular facets. Opposite the pubic peduncle is a small, well-defined tubercle on the lateral surface for muscle attachment. The posterior blade is plate-like and short (Jacobs et al. 1993). The angle between the posterior surface of the ischium and the ischium-ischium articular surface is steep as in Alamosaurus (Gilmore 1946) and Opisthocoelicaudia (Borsuk-Bialynicka 1977), suggesting that the cross section of the ischium shaft is nearly coplanar.

Femur. The femur (Figure 24, Table 8) is represented by a right proximal fragment (Mal-201; length of the preserved portion = 0.745 m). The anterior and posterior surfaces of the proximal end are damaged. The proximal portion is medially deflected and has a lateral bulge. The shaft of the femur is flattened anteroposteriorly and widened transversely so that it has an elliptical cross section with the long axis oriented mediolaterally. The humerus/femoral ratio is 0.72 in Opisthocoelicaudia (Borsuk-Bialynicka 1977), 0.74 in Titanosaurus (McIntosh 1990), 0.78 in Aegyptosaurus (McIntosh 1990), and 0.80 in Rapetosaurus (Curry Rogers and Forster 2001) with an average of 0.76. The larger humerus of Malawisaurus (Mal-221) is 0.722 m. Thus, the estimated length of Mal-201 is 0.950 m.

Tibia. The surface of the right tibia (Mal-207; Figure 25, Table 8) is weathered. The tibia has a prominent and anteriorly projecting cnemial crest. The shaft is slightly twisted and medially constricted. A lateral groove occurs at the distal end of the shaft. The distal posteroventral process is broad transversely.

Fibula. The proximal end of the right fibula (Mal-189; Figure 25E-H, Table 8) is expanded anteroposteriorly. The proximal surface is crescent shaped. The proximal tibial scar on the medial surface is triangular and well marked. The shaft is flattened medially and convex laterally. About 230 mm downshaft on the lateral surface is an elongate lateral trochanter for muscle attachment (flexors of digits; Borsuk-Bialynicka 1977) beyond which the bone becomes more cylindrical. The distal end is triangular in cross section.

Pes. Metatarsal III? (Mal-145) is represented by a small fragment. The articular surface is subrectangular in outline and is concave as in the proximal surface of metatarsal III of Opisthocoelicaudia that articulates with the astragalus. Based on these observations, Mal-145 is interpreted as the proximal fragment of metatarsal III of Malawisaurus.

Metatarsal V (right; Mal-210; Figure 26A-B, Table 8) is flattened mediolaterally. The proximal end is semicircular, convex, and expanded. The shaft is laterally compressed. The medial surface is more concave proximally than distally. The distal end is convex and ellipsoidal.

A proximal right pedal phalanx, probably of digit I (Mal-213; Figure 26C-D), is conical proximally with the apex of the cone being placed laterally. The ventral surface is shallowly depressed medially.

The left ungual (Mal-211; Figure 26E-G, Table 8) probably of digit I, is compressed laterally. The proximal surface is concave while the distal end is pointed. Longitudinal grooves occur on the interpreted lateral surface as in Apatosaurus (Gilmore 1936) and in Camarasaurus (BYU 9047; McIntosh et al. 1996b). Although shallow grooves occur, the medial surface is relatively smooth compared to the lateral surface. The ventral surface has a proximal medial tuberosity. In lateral view, it arcs ventrally to the point.

Another left ungual (Mal-212; Figure 26H-J) is smaller than Mal-211. In Apatosaurus, the shapes of the ungual phalanges are similar in the first, second, and third digits. The sizes decrease laterally. Thus, Mal-212 is likely a more lateral phalanx than Mal-211, probably from the second digit.

Armor. Previously it was reported that Malawisaurus lacked direct evidence of dermal armour, but calcite pseudomorphs shaped like dermal scutes were found associated with the bones in the same quarry (Jacobs et al. 1993, figure 2e). A large dermal scute was more recently discovered (Mal-204; Figure 27). It is 190 mm long and 95 mm wide. The morphology of this dermal armour is similar to the large dermal scutes associated with Saltasaurus (PVL 4017-112), whereas the pseudomorphs are similar to the small dermal scutes of Saltasaurus (PVL 6017-118) and small dermal scutes of the titanosaurian from Madagascar (FMNH PR 2021; Dodson et al. 1998).