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The Foot and Ankle of Australopithecus sediba

Science  09 Sep 2011:
Vol. 333, Issue 6048, pp. 1417-1420
DOI: 10.1126/science.1202703

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  1. Fig. 1

    Partial foot and leg elements of Au. sediba. (A) U.W. 88-97, 98, and 99 right distal tibia, talus, and calcaneus (MH2) in a near anatomical relationship, cemented together with calcified sediment. Lateral view, left; posterior view, right. (B) U.W. 88-21 right distal tibia. Lateral view, left; posterior view, right. (C) U.W. 88-22 right fourth metatarsal. Medial view, left; dorsal view, right. (D) U.W. 88-33 right proximal fifth metatarsal. Medial view, left; dorsal view, right. A calcaneal apophysis (not illustrated in this figure; see Fig. 4A) was recently discovered and appears to be associated with MH1.

  2. Fig. 2

    Virtual reconstruction of the right distal tibia, talus, and calcaneus of MH2. Separation of elements: (A) Distal tibia, top; talus, middle; calcaneus, bottom. All anterior views. (B) Tibia views from left to right: inferior, medial, posterior. (C) Talus views from left to right: superior, inferior, lateral, medial, posterior. (D) Calcaneus views from left to right: superior, inferior, lateral (top), medial (bottom), posterior.

  3. Fig. 3

    Discriminant function analysis of the tibiae U.W. 88-21 and U.W. 88-97. These analyses were carried out using 11 measurements of the distal tibia (SOM text S2 and table S1). Function one is being driven in part by the anterior width of the tibial plafond and thickness of the medial malleolus (greater dimensions to right), as well as the anteroposterior expansion of the metaphysis (to the left). The Malapa hominins cluster with humans, australopiths, and fossil Homo.

  4. Fig. 4

    (A) Right calcanei illustrating the salient features discussed in the text. The peroneal trochlea is indicated with a dashed circle; black arrows point toward the retrotrochlear eminence connecting the peroneal trochlea and the LPP. MPP, medial plantar process. As demonstrated elsewhere (20), humans have an obliquely oriented retrotrochlear eminence and a plantarly positioned LPP, such that in lateral view, the MPP is often not visible at all. This general pattern is also found in Au. afarensis (A.L. 333-8) and is present already in juvenile humans (bottom right). In contrast, Au. sediba (U.W. 88-99) possesses a more apelike orientation of the retrotrochlear eminence and a superiorly positioned, non–weight-bearing LPP such that the MPP is clearly visible in lateral view. An elevated structure homologous to the LPP can be found in both adult and juvenile apes (bottom left) and is visible in the juvenile Au. sediba apophysis (U.W. 88-113 reversed image). However, Au. sediba has a humanlike angled cuboid facet (denoted by brackets), which is suggestive of foot arching, and a flat, smooth surface of the calcaneal tuber, perhaps for a retrocalcaneal bursa underlying an elongated Achilles tendon (asterisks). (B) Canonical variates analysis of the calcaneus using eight indices (SOM text S3 and tables S4 and S6). The plot of canonical means along canonical variates 1 and 2 (great apes, humans, and fossil) shows a discrimination of U.W. 88-99 between humans and African apes but shows the greatest affinity to female African apes. Homo, Pan, and Gorilla (n = 20 males, 20 females) and Pongo (n = 10 males, 17 females) are represented here.