Bovidae

Brophy, Juliet K., de Ruiter, Darryl J., Fortelius, Mikael, Bamford, Marion & Berger, Lee R., 2016, Pleistocene Bovidae (Mammalia) from Malapa, Gauteng Province, South Africa, Palaeontologia Electronica 35 (8), pp. 1-22 : 11-16

Bovidae gen. et sp. indet.

Material. Cranial Specimens

UW 88-796 is a maxilla with right P 3, P 4, and M 1. The teeth are too heavily worn to identify them to the level of tribe with confidence, though the general morphology and lack of a basal pillar suggests this individual possibly belongs to the tribe Alcelaphini . UW 88-1314 is a partial mandible of a BSC II bovid consisting of the anterior portion with a broken incisor and the diastema of a mandible. A partial horn core, UW 88-555, was recovered from the site ( Figure 12 ). The width of the base is 27.35 mm and the height is 37.33. The horn core size identifies it as a bovid BSC II. UW 88-734 consists of a partial horn core of a BSC III bovid with a proximal width of 34.13 mm and height or 151.63 mm ( Figure 13 ). The morphology of this specimen, including slight torsion and a transverse ridge, is not inconsistent with Megalotragus though the specimen is not well enough preserved for taxonomic identification.

Material. Postcranial Specimens

The Malapa postcranial assemblage is noteworthy due to the extraordinary preservation, exemplified by the numerous complete skeletal

FIGURE 10. UW 88-869 right mandibular M 1.

elements and partially articulated limbs. This preservation contrasts with the long bone fragments more commonly seen at sites such as Swartkrans and Kromdraai. The best example of this postcranial preservation is seen in Malapa Block 848 ( Figure 13 ). This Block consists of portions of articulated/associated limbs including a diaphysis and epiphysis of a left femur ( UW 88-1181), right and left complete tibiae ( UW 88-1223a, b), right proximal metatarsal ( UW 88-1224), complete astragalus ( UW 88-1225), complete naviculo-cuboid ( UW 88-1226), and two complete distal phalanges ( UW 88-1221a, b) ( Figure 13 ). While not in articulation or encased in the same rock, a complementary right femur ( UW 88-748) matching the size and approximate age of the one in Block 848 was recovered. UW 88-748 consists of a distal epiphysis, diaphysis, and proximal epiphysis that refit making a complete specimen (210.3 mm). The incomplete left femur, UW 88-1181, measures 203 mm; estimates of a complete left femur overlap with the right femur, UW 88-748. The specimens in Block 848 and UW 88-748 represent an adult based on epiphyseal fusion. The estimated age for the individual in Block 848 is 12-18 months due to the fact that the proximal tibiae are fused while UW 88-748 is at least 10-18 months ( Davis, 1980). These fossils are consistent in size with a BSC II. According to Swanepoel and Steyn’s (2011) study on robusticity of Bovidae hindlimbs, a total femoral length of approximately 210 mm from UW 88-748 and UW 88-1181 (estimated) overlaps most closely with the femora of Antidorcas marsupialis (204.2 ±14.9) and Redunca fulvorufula (206.0±7.3). The total tibial length of 258.5 mm suggests that this individual’s body mass overlaps in range with Antidorcas marsupialis (258.1±19.1), Redunca fulvorufula (254.0±7.4), and Tragelaphus scriptus (249.9±13.8) ( Swanepoel and Steyn, 2011).

Block 051 contains a complete right humerus (209 mm), UW 88-1184, in articulation with a right, proximal and diaphysis shaft of a radius, UW 88- 1213. Both of the elements are adults based on the epiphyseal fusion, 12-18 months old, and are BSC III ( Davis, 1980).

Three articulated cervical vertebrae were recovered from Malapa. UW 88-720 , 88-721 , and 88-722 represent an adult, BSC II individual ( Figure 14 ). Block 081 also contains articulated vertebrae. UW 88-1235 from Block 081 includes two adult thoracic vertebrae from BSC III. An articulated BSC III proximal humerus and glenoid cavity of a scapula were also found in articulation. These specimens are adults, 12-18 months based on the fusion of the proximal humerus ( Davis, 1980) .

While the sample size is small, the skeletal part representation illustrates that the bovid postcranial remains are comprehensive; essentially the entire bovid skeleton is represented in some degree at the site ( Table 6). While minimal, this evidence supports the hypothesis that complete bovid individuals accumulated in the cave.

Phytolith Results

Unfortunately, very few phytolith fragments preserved on the Malapa bovid teeth and the ones that did were of very poor quality. The most common fragments are indeterminate, of no particular shape, and cannot be related to any phytolith morphotype. The second most common fragments are more or less geometric in shape (square, triangle, rectangle, etc.). These remains are probably siliceous but not related to any phytoliths. The samples frequently contained brown amorphous “blobs,” which may be a chemical residue. Some

BROPHY: BOVIDAE FROM MALAPA samples have fragments of hexagonal mesh, which have been interpreted as insect eye facets. Fungal hyphae also occur but their source is unknown. A few phytoliths were identified from three bovid specimens. Grass inflorescences, woody dicot and tracheid morphotypes were recovered from Megalotragus sp. specimens, UW 88- 746 and UW 88-1205, respectively. These results suggest Megalotragus sp. could have been a C 4 grazer with some browse in its diet. Makapania broomi ( UW 88-929) exhibit two very poorly preserved saddle morphotypes, which imply a diet that includes C 4 grasses.

Mesowear Results

Due to the preservation of the fossils and small sample size, a formal analysis of the mesowear could not be performed. Larger sample sizes can illustrate differences in the proportions of occlusal relief and cusp shapes that can be used to infer paleodiets. However, it is still informative to discuss the wear patterns of even single specimens that retain indications of occlusal relief and cusp shape. This data, coupled with other lines of research, can help identify the Malapa bovids and their diet.

The M 2 and M 3 of T. scriptus ( UW 88-518 and UW 88-519) have high relief ( Figure 15 ). While cusp damage makes identification of the outline difficult, the tips of the M 2 and M 3 appear sharp. This morphology coupled with taxonomic uniformitarianism suggests that T. scriptus was likely a browser or, possibly, a mixed feeder at the browsing end of the spectrum. In addition, the Sponheimer et al. (1999) isotope study found that T. scriptus was a browser.

The M 1 of M. broomi ( UW 88-929) is fairly worn for scoring, and the cusps of the M 2 are broken. Nevertheless, the relief appears high, and the cusp tip is rounded in both the upper and the lower molars. Based on mesowear, the specimen UW 88-929 was likely a mixed feeder or perhaps a fresh grass grazer. These results support the phytolith results above and Sponheimer et al. (1999) which suggest M. broomi was a mixed feeder that prefers grass.

The M 2 of Megalotragus ( UW 88-746) is also broken but the specimen exhibits high relief and rounded cusp tips. This morphotype possibly suggests a mixed feeder preferring grass. The Megalotragus ( UW 88-1205) M 1 has moderate wear and discernible morphology. The relief is high and the cusp tip is rounded. The analyses suggest that UW 88-1205 was possibly a mixed feeder though the overall appearance and weak facet development provides a stronger indication that it was a grazer. Both the M 1 and M 2 of Megalotragus ( UW 88-1251) show high relief and rounded cusp tips. The M 3 is unworn. This morphology suggests a mixed feeder towards the grazing end of the spectrum. These results correlate with Brink and Lee-Thorp (1992), which suggests Megalotragus was a grazer.

Taphonomy Results

Surface modification on the Malapa bovid limb bones includes cortical peeling, cracking, crushing, and erosion ( Figures 16 , 17 ). A significant portion (n=44), 86%, of the 51 limb fragments demonstrate

BSI BSII BSIII Humerus, complete 1/1/1 1/1/1 2/2/1 Proximal humerus 1/1/1 3/2/1 Distal humerus Femur, complete 1/1/1 2/2/2 Proximal femur 4/3/2 2/1/1 Distal femur Tibia, complete 2/2/1 2/2/2 1/1/1 Proximal tibia 1/1/1 1/1/1 Shaft tibia 2/2/1 Distal tibia Radius 1/1/1 Proximal radius 1/1/1 1/1/1 Shaft radius 1/1/1 1/1/1 Distal radius Ulna

3/3/2

Proximal ulna

1/1/1

Shaft ulna

1/1/1

Distal ulna

Metacarpal, complete 6/2/1 3/3/2

Proximal metacarpal

1/1/1

Shaft metacarpal

2/2/1

Distal metacarpal

Metatarsal

1/1/1 1/1/1

Proximal metatarsal

1/1/1 4/2/1

Shaft metatarsal

1/1/1 1/1/1

Distal metatarsal signs of cracking while ~24% of the assemblage reveal signs of being crushed (n=12). Twenty percent of the assemblage exhibit cortical peeling. According to Behrensmeyer (1978), longitudinal cracking in long bones is indicative of Stage 1 weathering, while cortical peeling and cracking denotes Stage 2 weathering ( Figure 16 ). Therefore, a majority of the assemblage was in Stage 2 weathering during fossilization. None of the bovid bones demonstrated any signs of weathering beyond Stage 2, as defined by Behrensmeyer (1978).

The breakage patterns of the limb bones include right, oblique, and intermediate fracture

Metapodial

1/1/1 2/2/1

Distal metatarsal Scapula 8/3/3 2/2/2

Atlas 1/1/1

Axis 1/1/1

Cervical vertebra 7/7/2 1/1/1

Thoracic vertebra 6/6/2 5/5/2

Lumbar vertebra 8/5/2

Caudal vertebra 1/1/1

Stenebra 1/1/1

Pelvis 1/1/1

Ribs 32/5/1 10/4/1

Sacrum 3/2/2

Proximal phalanx 4/3/1 10/10/3

Intermediate phalanx 1/1/1 4/4/2 7/7/2

Distal phalanx 2/2/1 2/2/1

Accessory carpal 1/1/1

Astragalus 3/3/2 1/1/1

Calcaneous 4/3/3 2/2/2 Internal cuneiform 1/1/1 Cuneiform 1/1/1 Lateral malleolus 1/1/1

Magnum 2/2/1 Naviculo-cuboid 2/2/1 1/1/1 Scaphoid 1/1/1

Unciform 1/1/1 1/1/1

Sesamoid 7/7/2

angles; each make up approximately one-third of the assemblage, 31%, 33%, and 36%, respectively. While approximately 32% of the long bone shaft fragments have transverse outlines, 34% have curved and 34% have intermediate fracture outlines in the morphology. Approximately 80% (n=36) of the long bones have a complete shaft circumference in at least a portion of the bone ( Figure 18 ). A majority, 71%, of the assemblage has ½ or less of its original shaft length ( Figure 19 ).

Age estimates for the Malapa specimens were determined in order to identify if the assemblage favors old or young individuals. The craniodental remains include young specimens with deciduous

BROPHY: BOVIDAE FROM MALAPA and erupting teeth (e.g., UW 88-1251, UW 88- 746), older individuals with fully erupted teeth (e.g., UW 88-929), and older, worn down teeth (e.g., UW 88-796, UW 88-1298). Age estimates for the Malapa Megalotragus sp. specimens are listed in Table 7 and range from 6-33 months. The ages are based on the occlusal rates of Connochaetes taurinus since eruptions rates for Megalotragus do not exist ( Talbot and Talbot, 1963). The postcranial elements range in age estimates from 10-18 months. Therefore, the ages of the bovids do not appear to follow any age patterns.

Figures

FIGURE 12. UW 88-555 horn core fragment of BSC II (left). UW 88-734 partial horn core of a BSC III (right).

FIGURE 13. Block 848 bovid BSC II in situ with femur and tibiae in articulation. Associated right metatarsal, astraga- lus, naviculocuboid, and distal phalanx are also in the Block.

FIGURE 14. Malapa blocks with articulated cervical (left) and thoracic (right) vertebrae.

FIGURE 15. Lingual view of Malapa UW 88-518 and UW 88-519 demonstrating high occlusal relief and sharp cusps.

FIGURE 16. Metapodial (left), UW 88-1247, demonstrating cracking and longitudinal fractures typical of Behrensmeyer (1975) Stage 1 weathering and diagenetic processes. UW 88-1224, (right) metatarsal exhibits longitudinal fractures, cracking, and cortical peeling.

FIGURE 17. Types of surface modification identified on Malapa bovid limb bones and number of specimens with that modification.

FIGURE 18. Results of the shaft circumference completeness in Malapa bovid limb bones.

FIGURE 19. Results of the shaft fragmentation in Malapa bovid limb bones.