Plioperdix africana, Mourer-Chauviré & Geraads, 2010

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 : 168-172

Plioperdix africana n.sp.

Fig. 4M–U

Holotype. Complete right humerus AaO-755.

Horizon and locality. Late Pliocene, age about 2.5 Ma, Ahl al Oughlam, southeast boundary of the city of Casablanca, Morocco.

Paratypes. Right humeri, almost complete, AaO-753, shaft, AaO-2687, distal parts, AaO-761, 769, 857; left humeri, distal parts, AaO-760, 762, 763, 4809.

Referred material. Left coracoids, almost complete, AaO-754, omal part, AaO-2688, shaft, subadult, AaO-757; left ulna, proximal part, AaO-4810; radius, almost complete, AaO-2689; right carpometacarpi, almost complete,AaO-756, 758, 858; left carpometacarpi, proximal part, AaO-759, proximal part and shaft, AaO-4811; right tibiotarsus, distal part, AaO-764; right tarsometatarsus, AaO-856.

Diagnosis. Species showing the morphological characteristics of the genus Plioperdix but larger than the only species known so far, Plioperdix ponticus ( Tugarinov, 1940) , from the Pliocene of Europe and Central Asia.

Measurements. See Table 6.

Etymology. africana , for Africa, because the only other species of this genus, Plioperdix ponticus , was described from Eastern Europe and Asia.

Curation of the material. The material will be deposited at the Institut National des Sciences de l’Archéologie et du Patrimoine (INSAP), in Rabat, Morocco.

Description and comparisons. This small galliform from

Ahl al Oughlam has been compared with all the Recent African genera present in the USNM collection but it cannot be referred to any of them

The humeri have a double pneumotricipital fossa. The Fossa pneumoanconaea is widely open and penetrates up to the proximal end of the bone, under the humeral head. The Fossa tricipitalis penetrates only 1 to 2 mm under the humeral head. The tricipital fossa is continued on the caudal face of the shaft by a shallow groove, that goes distally and obliquely onto the ventral border of the shaft. This groove is very elongated distally. It is bordered on the dorsal side by a ridge, the Margo caudalis, which keeps to the Eminentia musculi latissimi dorsi posterioris ( Ballmann, 1969). On the cranial side, the Sulcus transversus is very shallow and indistinctly outlined proximally.

In their description of the material referred to the genus Plioperdix Bocheński and Kurochkin (1987) gave three morphological characteristics for the humerus. One was this groove. Another was that the distal part of the Crista pectoralis humeri ends with a sharp step. This is not very visible on the Ahl al Oughlam humeri but it is similar to what can be seen on the cranial face of the humerus of P. ponticus illustrated by them (Bocheński & Kurochkin, 1987, pl. XVIII, fig. 11–12). The third feature was that the Epicondylus ventralis is sharpened distally, which is also the case on the Ahl al Oughlam humeri.

The Ahl al Oughlam humeri have been compared with the humeri of the genus Palaeortyx . This genus is known in many European localities, from the beginning of the Late Oligocene and generally to the Middle Miocene ( Göhlich & Mourer-Chauviré, 2005), but also in the Late Miocene of Hungary ( Janossy, 1976), Spain ( Villalta, 1963; Cheneval & Adrover, 1993), and is present until the Early Pliocene in Gargano, in Southern Italy ( Ballmann, 1973, 1976; Göhlich & Pavia, 2008). A form referred to the genus Palaeortyx is also present in southwestern Africa, in the lower Miocene of Elisabethfeld and in the middle Miocene of Arrisdrift, both in Namibia ( Mourer-Chauviré, 2003; 2008). Palaeortyx differs from the Ahl al Oughlam form in that the Fossa tricipitalis penetrates very deeply under the humeral head, to the end of the bone, and consequently the Fossa pneumoanconaea penetrates less deeply than the tricipital fossa. In addition the tricipital fossa continues in the disto-ventral direction as a groove which is more oblique and shorter than in the genus Plioperdix .

Two other genera of small galliforms, Palaeocryptonyx and Chauvireria , are present in the European Pliocene. The Ahl al Oughlam humeri have been compared with those of the type-species of Palaeocryptonyx , P. donnezani , from the lower Pliocene of Perpignan (MN 15) ( Depéret, 1892, 1897). On the humerus of P. donnezani , the tricipital fossa penetrates under the humeral head, but not deeply, and is not continued as a groove crossing the shaft obliquely, in the disto-ventral direction. The humerus of P. donnezani is smaller than that of P. africana , but its deltopectoral crest is proportionally longer. The pneumatic foramen situated in the Fossa pneumoanconaea is smaller in P. donnezani . In P. africana , the distal part of the humerus is more elongate ventrad and the ventral epicondyle projects more ventrad than in P. donnezani .

In Chauvireria balcanica Boev, 1997 , from the upper Pliocene of Varshets (MN 17), Bulgaria, the humerus is straighter, whereas in P. africana both proximal and distal parts are ventrally incurved. In Chauvireria , the tricipital fossa penetrates deeply under the humeral head, but it is not prolonged as a groove. The humeral head is more swollen in the proximo-distal direction than in the genera Plioperdix and Palaeocryptonyx , and the distal part is relatively narrower than in the other two genera.

The genus Plioperdix , with the species P. ponticus ( Tugarinov, 1940) , has been reported in the Early Pliocene of Ukraine and Moldova, and in the Late Pliocene of Transbaikalia and northern Mongolia (Bocheński & Kurochkin, 1987; Zelenkov & Kurochkin 2009). A phasianid similar to Plioperdix ponticus has also been reported in the Late Miocene of Southern European Russia ( Titov et al., 2006). Mlíkovský (1995) placed Francolinus minor Janossy, 1974 , in synonymy with Plioperdix ponticus ( Tugarinov, 1940) , and reported this species in the locality of Stránská Skála, Musil’s Talus Cone, in the Czech Republic, dated from the Early Middle Pleistocene ( Tyrberg, 1998). But subsequently Mlíkovský (2002) placed the genus Plioperdix in synonymy with the Recent genus Alectoris , and the species Plioperdix ponticus in synonymy with Alectoris donnezani ( Depéret, 1892) . The species donnezani is the type-species of the genus Palaeocryptonyx and we have shown above that the genus Plioperdix differs from the genus Palaeocryptonyx . Therefore the occurrence of the species Plioperdix ponticus in the Early Middle Pleistocene relies on the correction refused of F. minor Janossy, 1974 to Plioperdix and so cannot be confirmed.

The carpometacarpi of P. ponticus are characterized by a Processus intermetacarpalis weakly developed, and a minor metacarpal narrow, not projecting caudally as angle, and not extending distally beyond level of Facies articularis digitalis major. Distinct fossae are located at base and in distal part of the minor metacarpal, one fossa on each side (Bocheński & Kurochkin, 1987; Zelenkov & Kurochkin, 2009). In P. africana the carpometacarpus is relatively shorter than in P. ponticus . The Processus intermetacarpalis is small and is situated very close to the proximal symphysis of the major and minor metacarpals, but it is relatively more developed than in P. ponticus . The minor metacarpal is only preserved on one specimen and it is very thin. The fossa which is situated on the ventral side of the distal symphysis of P. ponticus (Zelenkov & Kurochkin, 2009, pl. 9, figs 7b and 10b) is absent in P. africana .

In P. africana , the carpometacarpus differs from that of Palaeortyx because the Processus pisiformis is globular and does not extend cranially, and the Depressio muscularis interna (sensu Ballmann, 1969) is shallow, unlike that in the genus Palaeortyx (see Mourer-Chauviré et al., 2004, pl. 1, fig. 5). It differs from the genus Palaeocryptonyx as in this genus the Processus intermetacarpalis is situated farther from the proximal synostosis of the two metacarpals. Chauvireria is distinguished from P. africana by a very robust major metacarpal, and its minor metacarpal is more robust and more distant from the major metacarpal. In Chauvireria the Processus intermetacarpalis is well developed, the minor metacarpal protrudes very slightly distally beyond the level of the facies articularis digitalis major, and there is a fossa on the ventral side of the distal symphysis.

Bocheński & Kurochkin (1987) then Zelenkov & Kurochkin (2009) give the morphological characteristics of the coracoid of Plioperdix . In P. africana the Pars omalis of the coracoids is incomplete but the coracoid AaO-754 agrees with P. ponticus in having a sternal facet very short and very curved and it lacks a pneumatic foramen in the Impressio m. sternocoracoidei. Coracoids of Palaeocryptonyx have a longer and less curved sternal facet and the Angulus medialis projects less mediad. AaO-754 differs also from the genus Chauvireria , the sternal facet of which is also longer and less curved, but the Angulus medialis more projecting. In these two genera, there is no pneumatic foramen in the Impressio m. sternocoracoidei. On the ventral face, the Ahl al Oughlam coracoid shows a strong longitudinal ridge which causes a bulge of the sternal facet, while in Palaeocryptonyx and Chauvireria the sternal part is flatter.

The tarsometatarsus AaO-856 shows the principal characteristic of the genus Plioperdix : the trochleae are constricted rather than splayed, causing a relatively narrow distal end. Trochlea met. II is strongly pushed back plantarly and both Trochleae met. II and IV do not project significantly on the medial and lateral sides. This tarsometatarsus is subadult. The Sulcus extensorius is very deep at its proximal part. The two proximal vascular foramina are situated at the bottom of a fossa. The medial border of the Cotyla medialis projects significantly proximad as can be seen also in Plioperdix ponticus (see Bocheński & Kurochkin, 1987, pl. XVIII, fig. 3–4). In the two specimens of P. ponticus the hypotarsus is not completely preserved. There are two ridges, a medial one, and a lateral one, separated by a canal. On the Ahl al Oughlam specimen there is a roofed canal, situated approximately in the sagittal plane, and another roofed canal, narrower, situated plantarly compared to the first one. Both canals open distally by a single orifice, situated on the medial side of the hypotarsus. On the plantar face of the hypotarsus there are two smooth ridges, separated by a shallow groove. The hypotarsus is prolonged, along the plantar face, by a short median ridge. On each side of the hypotarsus there are the Fossae parahypotarsales medialis and lateralis. The Fossa parahypotarsalis lateralis is bordered by a ridge on its lateral side. The Fossa met. I is hardly visible.As Bocheński & Kurochkin (1987) have indicated, the tarsometatarsus of Plioperdix is very different from that of Ammoperdix . The most striking characteristic of the P. africana tarsometatarsus is that its distal width is less than its proximal width.

The measurements of P. africana are given in Table 6. On average, the dimensions of P. africana are 30% larger than those of P. ponticus .

Order Gruiformes

Figures

Figure 4. (A) Phoebastria sp. cf. P. nigripes, left humerus, distal part, AaO-718, cranial view. Morus peninsularis, B–D: (B) left coracoid, AaO-2108, ventral view; (C) right carpometacarpus, AaO-2643, ventral view; (D) left femur, AaO-724, caudal view. Morus sp. cf. M. bassanus, E–F: (E) right humerus, distal part, AaO-4801, cranial view; (F) left ulna, proximal part and shaft, AaO-2640, craniodorsal view.Geronticus olsoni n.sp., G–K: (G) right humerus, distal part and shaft,AaO-838, cranial view; (H) left coracoid,AaO-741, holotype, dorsal view; (I) idem, ventral view; (J) left tibiotarsus, distal part, AaO-2654, cranial view; … [caption continued on facing page]