Phoebastria sp.

Mourer-Chauviré, Cécile & Geraads, Denis, 2010, The Upper Pliocene Avifauna of Ahl al Oughlam, Morocco. Systematics and Biogeography, Records of the Australian Museum 62 (1), pp. 157-184 : 159-161

Phoebastria sp. cf. P. albatrus (Pallas, 1769)

Fig. 2B–H

Material. Posterior part of cranium, AaO-2626; right quadrates, AaO-2627, 2628; right coracoid, almost complete, and right scapula, proximal part, AaO-892; right humeri, proximal part and shaft, AaO-2624, fragment of proximal part, AaO-717, and shaft possibly from the same bone, AaO-704, distal part, AaO-716, fragment of distal part, AaO-2633; left humeri, fragment of proximal part, AaO-720, distal parts, AaO-843, 4297; articulated bones including right humerus, distal part, right ulna, proximal part and shaft, right radius, proximal part and shaft, and two sesamoids, AaO-820; right radius, proximal part, AaO-418; right carpometacarpi, proximal part, juv., AaO-4796, distal parts and shaft, AaO-2629, 2630; left carpometacarpi, almost complete, AaO-4800, proximal part, AaO-845, distal part, AaO-824; phalanx 1 of right major digit of wing, AaO-2631; phalanx 1 of left major digit of wing, proximal part, AaO-823; phalanx 2 of left major digit of wing, AaO-2632; right femora, AaO-715, distal part, AaO-847; left femora, AaO-722, proximal part, AaO-846; left tibiotarsus, distal part, AaO-2634.

The Recent North Pacific albatrosses, which belong to the genus Phoebastria ( Nunn et al., 1996) , have some morphological characteristics that differ from those of the genera Diomedea , Phoebetria and Thalassarche , in particular in the shape of the tarsometatarsus and in its relative length compared to the ulna (Olson & Rasmussen, 2001; Dyke et al., 2007). Unfortunately the tarsometatarsi are absent from the Ahl al Oughlam material. The elements listed above have been designated as P. sp. cf. P. albatrus because they are more similar, morphologically and morphometrically to this species than to any other described taxa. Some of their dimensions, however, are slightly smaller than those of a population including recent forms and subfossil forms from middens ( Table 2 and Fig. 3 ).

Measurements of the posterior part of cranium (AaO- 2626) in mm: Greatest width of the posterior part at level of zygomatic processes: 55.6; width of the calvarium at level of temporal fossae: 44.9; least width of the frontal at level of indentation between the lacrimals and the postorbital processes: 17.5.

Measurements of the coracoid and scapula (AaO-892) in mm: (on the coracoid the ventralmost tip of the acrocoracoid of two osseous nodules, one rounded and one elongate, bound together by a supple tendon which is inserted on the dorsal side of the Processus supracondylaris dorsalis of the humerus. When the wing is flexed these two sesamoids position themselves in the space between the radius and the ulna, as in the fossil. It is possible to see these sesamoids when the skeletons still have some ligaments.

Greatest length of the elongate sesamoid on AaO-820: 17.5 mm; on a Recent P. albatrus ( USNM 576025): 18.3 mm.

Figures

Figure 2. (A) Phoebastria anglica, right humerus, shaft and distal part, AaO-3467, cranial view. Phoebastria sp. cf. P. albatrus, B–H: (B) posterior part of cranium, AaO-2626, dorsal view; (C) idem, ventral view; (D) right coracoid, AaO-892, dorsal view; (E) right humerus, distal part, right radius and right ulna, proximal parts, articulated, and two sesamoids, AaO-820, caudal view; (F) phalanx 1 of right major digit of wing,AaO-2631, dorsal view; (G) right humerus, distal part,AaO-716, cranial view; (H) left carpometacarpus,AaO-4800, ventral view. The scale bars represent 1 cm. Same scale bar for B–H.

Figure 3. Diagram showing the measurements on the distal part of the humerus (A, B), the proximal part of the ulna (C), and the distal part of the carpometacarpus (D, E) in the genera Phoebastria and Diomedea (Tables 1 and 2).