Calonectris 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 : 161-162

Calonectris sp. cf. C. diomedea (Scopoli, 1769)

Material. Right humerus, slightly incomplete proximal part, from a subadult individual, AaO-723; right femur, proximal part, AaO-2697.

This humerus differs from the similar-sized species of procellariid (genera Puffinus , Pterodroma , Bulweria ) by its morphological characteristics and it is in perfect agreement with the genus Calonectris . In Puffinus the Caput humeri is more developed both in proximo-distal and craniocaudal directions and is more projecting over the Fossa tricipitalis (sensu Ballmann, 1969) than in Calonectris . The Tuberculum dorsale is proximo-distally elongate in caudal view, and is projecting proximad, whereas in Calonectris it is more rounded and less projecting. The Tuberculum ventrale is proportionally more developed and more caudally projecting in Puffinus than in Calonectris . In Calonectris , as well as in Puffinus , there is a small protuberance, distally directed, on the Crus dorsale of the Fossa pneumoanconaea (sensu Ballmann, 1969), but this protuberance is more developed in Calonectris . On the caudal surface, the Margo caudalis goes vertically in proximal direction, then describes a curve which joins the humeral head in Calonectris whereas in Puffinus it does not make a curve and joins the distal border of the dorsal tubercle.

The shaft of the humerus is almost circular in Calonectris whereas it is flattened in Puffinus , but unfortunately this is not visible on the fossil the shaft of which is not preserved.

In the subgenus Thyellodroma (species Puffinus (Thyellodroma) pacificus ) the morphological characteristics of the proximal part of the humerus are slightly different from those of the subgenus Puffinus (species Puffinus (Puffinus) griseus ) but they are more similar to the subgenus Puffinus than to the genus Calonectris .

In the genera Pterodroma and Bulweria the ventral tubercle is more projecting ventrally and the Crista delto-pectoralis is more projecting dorsally than in the genus Calonectris . In Pterodroma the humeral head forms a well defined ledge, with a rounded lobe, above Fossa tricipitalis, and the dorsal tubercle is in the continuation of the humeral head, i.e. there is no space between the humeral head and the dorsal tubercle. Still in Pterodroma the Fossa pneumoanconaea has a lozengic shape, obliquely elongate both in proximodistal and dorsoventral directions, whereas in Calonectris this fossa is more rounded. Finally in Pterodroma there is no protuberance directed distally on the Crus dorsale fossa.

In the Recent species Calonectris diomedea there are great differences in size between the two subspecies. The largest one is C. diomedea borealis , which breeds on the Azores, the Canaries, the Berlengas, and Madeira (Jouanin & Mougin, 1979), and the smallest one is C. diomedea diomedea , which breeds on the Mediterranean islands. Calonectris edwardsii , which breeds on the Cape Verde islands, is now considered as a distinct species ( Olson, 2008) and it is smaller than the two subspecies of Calonectris diomedea . By its dimensions (prox. width of humerus, from tip of tuberculum ventrale to tuberculum dorsale 17.2 mm; depth of caput humeri, 4.7 mm; proximal width of the femur, 8.6 mm; proximal depth, 4.7 mm) the Ahl al Oughlam form is closer to C. d. diomedea . Its dimensions also correspond to those of C. leucomelas , which breeds on the offshore islands of the West Pacific. It is smaller than the extinct species Calonectris krantzi from the Pliocene of theYorktown Formation, North Carolina (Olson & Rasmussen, 2001).

An extinct species, Calonectris wingatei , has recently been described from the Middle Pleistocene of Bermuda ( Olson, 2008). In this species the total length of most of the bones is similar to that of C. diomedea diomedea , but the femur is longer and all the long bones are more robust. In the Ahl al Oughlam material the femur is similar in size to C. d. diomedea and it is smaller than the femur of C. wingatei .

The genus Calonectris has been reported from the lower Pliocene of Duinefontein (age 5 Ma), in South Africa ( Olson, 1985a), where it is represented by a carpometacarpus slightly larger and morphologically different from that of Calonectris diomedea , and Calonectris aff. diomedea is present in the deposits of Lee Creek Mine, North Carolina, probably from the Pliocene of the Yorktown Formation (Olson & Rasmussen, 2001).

Order Odontopterygiformes