Leptoptilos robustus, Meijer & Due, 2010

Meijer, Hanneke J. M. & Due, Rokus Awe, 2010, A new species of giant marabou stork (Aves: Ciconiiformes) from the Pleistocene of Liang Bua, Flores (Indonesia), Zoological Journal of the Linnean Society 160 (4), pp. 707-724 : 714-716

LEPTOPTILOS ROBUSTUS SP. NOV.

Holotype: Associated partial skeleton with wing and leg bones ( Figs 3 , 5 , 7 , 9 ), consisting of the proximal half of a left carpometacarpus (preliminary registration nr LBA-XI-01) and the distal part of a left ulna (LBA-XI-02), an almost complete left femur (LBA-XI- 03), and the distal part of a left tibiotarsus (LBA-XI-

04). The bones are stored at the National Centre for Archaeology in Jakarta ( Indonesia).

Etymology: From the Latin robustus meaning ‘strong, robust’, and referring to the large tibiotarsus and the thickness of its cortex.

Type locality: Liang Bua cave , Manggarai Province, Flores, Indonesia at 08°31′50.4″S, 120°26′36.9″E .

Type horizon and age: Sector XI at Liang Bua ( Fig. 1 ) at a depth of 425–470 cm in layers of brown clayey silts (Layer O in Fig. 2 ) and Late Pleistocene in age ( Morwood et al., 2005).

Diagnosis: A large species of extinct Leptoptilos resembling L. dubius in dimensions of the femur, carpometacarpus, and ulna, but with a tibiotarsus wider and deeper than any living Leptoptilos and yet smaller than L. falconeri , and with the following unique combination of characters: pneumatized carpometacarpus with a distinct foramen in the fossa infratrochlearis; femur with well-pronounced muscle scars on proximocranial surface; linea intermuscularis cranialis and linea intermuscularis caudalis with a more lateral and medial location on the shaft, respectively, than extant Leptoptilini ; condylus ventralis ulnae pointed, elevated, and projecting distally; tuberculum carpale rectangular in ventral view; foramen in incisura tuberculi carpalis; tibiotarsus with straight shaft and bone wall thicker than any species of Leptoptilos ; sulcus extensorius shallow, narrow, and located on medial half of bone.

Apomorphies for the genus Leptoptilos are the pneumatized carpometacarpus with a distinct foramen in the fossa infratrochlearis and the pointed condylus ventralis ulnae. Autapomorphic characters for L. robustus sp. nov. are its large size, the thickening of the cortical bone wall of the tibiotarsus, the absence of a rotation in the tibiotarsal shaft, the elevated and distal projection of the pointed condylus ventralis ulnae, pronounced muscle scars on the proximocranial surface of the femur, and a more lateral and medial location of the linea intermuscularis cranialis and linea intermuscularis caudalis on the femur shaft.

Figures

Figure 1. Map of South-East Asia, showing (A) the location of Flores within Indonesia and (B) the location of Liang Bua Cave in western Flores. (C) is a map of the excavated sectors within Liang Bua. Sector VII/XI is located against the eastern wall of the cave. A and B adapted from van den Hoek Ostende et al. (2007), C is taken from Morwood et al. (2005) and reprinted with permission.

Figure 2. Stratigraphical sequence of the Sector VII/XI trench. Remains from Leptoptilos robustus sp. nov. were retrieved from Sector XI, spits 43–47, which correspond to Layers O–P. The white tuffaceous layer is indicated by Na-d and has been dated at 11–17 kya. From Morwood et al. (2005), reprinted with permission.

Figure 3. Leptoptilos robustus sp. nov., proximal left carpometacarpus (LBA-XI-01). A, ventral view; B, dorsal view. Abbreviations: fccd, fovea carpalis caudalis; fi, fossa infratrochlearis; fs, fossa supratrochlearis; pp, processus pisiformis; tc, trochlea carpalis. Scale bar = 50 mm. Photographs by E. Kruidenier.

Figure 5. Leptoptilos robustus sp. nov., distal part of left ulna (LBA-XI-02). A, ventral view; B, dorsal view. Abbreviations: cdu, condylus dorsalis ulnae; cvu, condylus ventralis ulnae; dr, depression radialis; f, foramen; itc, incisura tuberculi carpalis; pr, papillae remigales; si, sulcus intercondylaris; tc, tuberculum carpale. Scale bar = 50 mm. Photographs by E. Kruidenier.

Figure 7. Leptoptilos robustus sp. nov., left femur (LBA-XI-03). A, caudal view; B, cranial view. Abbreviations: cl, condylus lateralis; cm, condylus medialis; ct, crista trochanteris; faa, facies articularis antitrochanterica; fcd, facies caudalis; fcr, facies cranialis; fp, fossa poplitea; ii, incisura intercondylaris; licd, linea intermuscularis caudalis; licr, linea intermuscularis cranialis; pf, pneumatic foramen; sp, sulcus patellaris; tf, trochanter femoris; tfi, trochlea fibularis. Scale bar = 50 mm. Photographs by E. Kruidenier.

Figure 9. Leptoptilos robustus sp. nov., distal left tibiotarsus (LBA-XI-04). A, anterior view of specimen; B, anterior view of distal fragment; C, posterior view of distal fragment. Abbreviations: cs, location of natural fracture at which cross-section is visible; dce, distal opening of canalis extensorius; fcd, facies caudalis; fcr, facies cranialis; gm, gnawing marks; pce, proximal opening of canalis extensorius; pst, pons supratendineus; se, sulcus extensorius; tub, tubercle laterodistal of the pons supratendineus. Scale bars = 50 mm. Photographs by E. Kruidenier.