First European Neogene record of true pheasants from Gorna Sushitsa (SW Bulgaria)

A late Miocene (Middle Turolian) ulna is described as a holotype of Phasianus bulgaricus sp. n.. This find is the first record of Neogene true pheasants in Europe.


Material and methods
The examined find represents an incomplete left ulna bone. All measurements are given in millimetres (Table 1). The taxonomy follows Mlíkovský (2002) and Dickinson & Remsen (2013). The osteological terminology is after Baumel & Witmer (1993) and Livezey & Zusi (2006 Etymology: The name bulgaricus is given after the name of Bulgaria, the country where the specimen originates from. Measurements: Table 1; Fig. 2. Differential diagnosis: A medium-sized fossil species in the genus Phasianus, differing from the recent Phasianus colchicus by: (1) the wider depressio m. brachialis; (2) the more approached medial edge of depressio m. brachialis to the medial linea intermuscularis on the medial side of the bone; (3) wider impressio m. scapulotricipitis; (4) the blunt instead sharp, ending of depressio m. brachialis at its proximal end; (5) more straight, instead bent lateral edge of the profile of the bone in dorsal view; (6) blunt instead sharp, ending of depressio m. brachialis at its proximal end.
Preservation: The holotype represents a proximal bone fragment, which is almost 2/3 of the total length of the bone (Fig. 1).
Locality: Vicinity of Gorna Sushitsa Village ( Description: The specimen is of good preservation. The distal third is missing and the total length of the bone fragment is 47.1 mm. All morphological details of an ulna bone are excellently preserved, incl. lineae intermusculares, foramina nutritia, specific edges, papilae remigiales caudales, etc.

Comparisons
The specimen shows all the features of mediumsized gallinaceous birds -medium or even short ulna, well-developed (wide and relatively short) impressio brachialis and shallow relief on the facies articularis proximalis. Its morphological characteristic suggest the find belongs to Phasianidae (i.e. Phasianinae), see below. Both osteometrically and osteomorphologically the examined specimen approaches to genus Pha sianus. Relatively blunt olecranon, crescent-shaped bent diaphysis, well-developed sharp proximal edge of depressio brachialis and the thicker proximal half First European Neogene record of true pheasants from Gorna Sushitsa (SW Bulgaria) Historia naturalis bulgarica 41 (2020) of the bone suggest a pheasant of Phasianus. In addition, the specimen NMNHS 15143 was compared with 38 phasianid species (23 recent and 15 fossil) to confirm it belongs to Phasianidae and to identify its genus.      Janossy, 1974 andT. partium (Kretzoi, 1961) are known from the early Pliocene to Late Pleistocene, while T. macropus Janossy, 1976 andT. praeurogallus Janossy, 1969 are Late Pliocene to Middle Pleistocene species (Janossy,196). Tetrao rhodopensis Boev, 1998 Kurochkin, 1982 andPirortyx Brodkorb, 1964 are significantly smaller than the compared specimen is. Lophogallus naran bulakensis Zelenkov & Kurochkin, 2010 is known with its humerus and femur from the Middle Miocene of Mongolia (Zelenkov & Kurochkin, 2010), while Syrmaticus kozlovae Kurochkin, 1985 is known with its humerus and coracoid from the Middle Pliocene of Mongolia (Kurochkin, 1985). Thus, both are incomparable. The Miocene Linquornis gigantis Yeh, 1980 from China was a large pheasant, similar in size to Pavo (Zelenkov & Kurochkin, 2010). Phasianus sp.: acording Mlikovsky (2002), the only Neogene re-cord of g. Phasianus in Europe came from the Early Pleistocene (formerly Late Pliocene; MN 17) locality of Varshets (NW Bulgaria). Boev (2002) listed a find of Phasianus sp. This specimen (NMNHS 256) represents a distal half of coracoid dex. Its age is Middle Villafranchian (MN 17) and could not be compared.

Discussion
The above-presented comparison shows that the NM-NHS 15143 find could not be referred to any of the recent and fossil species belonging to the genus. The Pleistocene Palaearctic pheasants are of considerable chronostratigraphic differences. The Neogene Palaearctic record of true pheasants consists of finds of only "Phasianus sp.". Thus the Middle Turolian specimen of Gorna Sushitsa should be distinguished under a separate name as a new species. Phasianus bulgaricus sp. n. is the oldest known true pheasant in Europe.
The dominating semi-open-land grass/forested savannah habitat in the region, dating back to ca. 7.36 Mya, indicates the more open-habitat preferences of Ph. bulgaricus sp. n. This completely agrees with the habitats of the large mammals fauna (Spassov et al., 2019).