Alca ausonia ( Portis, 1889 )

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 : 174-175

Alca ausonia ( Portis, 1889)

Fig. 5J–M

Material. Right humerus, proximal part, AaO-781; left humerus, shaft and distal part, AaO-2666; left scapula, cranial part, AaO-2665; left ulna, distal part, AaO-2667; left radius, shaft and distal part, AaO-841; left carpometacarpus, distal part, AaO-2668; right femur, distal part, AaO-2661; left tibiotarsus, proximal part and shaft, AaO-2693.

This material shows the morphological characteristics of the genus Alca and differs from the other members of Alcidae . Alcids are very numerous in the Pliocene of the Yorktown Formation and include, from the smaller to the larger, Alca aff. torda , A. ausonia , Alca grandis and Alca stewarti ( Olson, 2007; Wijnker & Olson, 2009). There are no detailed measurements, but it is possible to see that the distal width of the humerus is comprised between ca. 11.8 and 12.8 mm for Alca ausonia , and between ca. 13.5 and 14.5 mm for A. grandis (Olson & Rasmussen, 2001, fig. 9). In the Ahl al Oughlam specimen the distal part of humerus is incomplete, but it is possible to estimate the distal width (from the cranial face of the Condylus dorsalis to the caudal face of the Epicondylus ventralis) at ca. 11.9 mm. On a cast of the holotype of Alca ausonia ( IGF 14875), this distal width is 12.3 mm. The Ahl al Oughlam Alcidae is therefore attributed to the extinct species Alca ausonia . The measurements are given in Table 9. Compared to a Recent specimen of Alca torda islandica , the dimensions of the specimens referred to Alca ausonia here from Ahl al Oughlam are on average 24% larger.

In addition to the fossil forms from the Yorktown Formation, alcids belonging to the genus Alca have also been reported on the coasts of the Old World. Alca ausonia has been described from the Middle Pliocene of Orciano Pisano, in Tuscany, close to the Mediterranean ( Delle Cave, 1996). Alca sp. has been reported from the Pliocene of El Alamillo, southeast Spain, in marine deposits ( Sánchez-Marco, 2003). This form is slightly larger than Alca torda and could belong to Alca ausonia . Alca ausonia has been reported in the lower Pliocene of the Kattendijk Sands Formation at Kallo, Belgium (Dyke & Walker, 2005). However the total length given for a complete ulna (55 mm) seems too small for this species. Four different species of Alca (including probably A. ausonia ) are present in the Early Pliocene (age 3.5 Ma) of the Netherlands (E. Wijnker, pers. comm.).

At the present time alcids still occur on the Moroccan coasts ( Urban et al., 1986).

Order Columbiformes

Figures

Figure 5. Otis sp. size Otis tarda, A–B: (A) right ulna, proximal part, AaO-766, cranial view: (B) right ulna, distal part, AaO-767, ventral view.Chlamydotis sp. cf. C. mesetaria, C–E: (C) right tarsometatarsus, proximal part and shaft,AaO-2644, caudal view; (D) idem, cranial view; (E) idem, proximal view. cf. Lophotis sp., F–G: (F) right coracoid, almost complete,AaO-768, dorsal view; (G) idem, ventral view. (H) Columba sp. cf. C. pisana, right humerus, distal part and shaft,AaO-2672, cranial view. (I) Catharacta sp. cf. C. skua, right humerus, distal part and shaft, AaO-4793, cranial view. … [caption continued on facing page]