Cuon sp.

Suraprasit, Kantapon, Jaeger, Jean-Jacques, Chaimanee, Yaowalak, Chavasseau, Olivier, Yamee, Chotima, Tian, Pannipa & Panha, Somsak, 2016, The Middle Pleistocene vertebrate fauna from Khok Sung (Nakhon Ratchasima, Thailand): biochronological and paleobiogeographical implications, ZooKeys 613, pp. 1-157 : 8-10

Taxon classification Animalia Carnivora Canidae

Cuon sp.

Referred material.

A right ulna, DMR-KS-05-04-11-34; a right femur, DMR-KS-05-04-28-13.

Material description.

DMR-KS-05-04-11-34 is a half proximal ulna preserving complete parts from the olecranon to the midshaft (Fig. 6E, F). The olecranon tuber is well-developed. The upper margin of the olecranon is concave and possesses a slightly higher posterior part that extends laterally. The anconeal process is distinct. The medial and lateral coronoid processes diverge laterally (Fig. 6F). The trochlear notch is deep, forming nearly a semicircular surface for articulation (Fig. 6E).

The right femur preserves a complete proximal part and broken shaft (Fig. 6G, H). The greater trochanter is as high as the upper surface of the rounded femoral head. The intertrochanteric crest is straight and nearly oriented vertically (Fig. 6H). The upper border of the neck is flat. The lesser trochanter projects anteriorly and is situated at about 1.5 cm below the femoral head.

Taxonomic remarks and comparisons.

The proximal ulna of canids is characterized by a bilobed and laterally compressed olecranon process, well-developed anconeal and lateral coronoid processes, and a laterally compressed shaft. The proximal crest of the olecranon is grooved anteriorly, but enlarged and rounded posteriorly ( Tong et al. 2012). Pionnier-Capitan et al. (2011) suggested that in medial view the posteroproximal tuberosity of the olecranon of Canis is more proximally developed than in Cuon . The posteroproximal tuberosity of the Khok Sung ulna is as developed as that of Cuon . Furthermore, based on our comparisons with extant specimens, the Khok Sung canid ulna resembles that of Cuon alpinus because the olecranon bends more medially and the posterior border of the olecranon is straighter than those observed in Canis lupus . The Khok Sung specimen is slightly smaller than the recent Cuon alpinus (Tab. 3). However, it is much smaller than recent and fossil Canis lupus , as well as the paleosubspecies Cuon alpinus caucasicus (Tab. 3).

Living canids generally show a typical morphology of the proximal femur, characterized by their relatively vertical intertrochanteric crests, prominent lesser trochanter with the sharp crest extending downward along the shaft, moderately-sized greater trochanter, and slender shaft ( France 2009, Tong et al. 2012). In Canis lupus , the lateral side of the caput femoris is obliquely prolonged towards the trochanteric fossa. The upper border of the neck is concave and shorter than those in Cuon alpinus ( Ripoll et al. 2010). The femur DMR-KS-05-04-28-13 is canid-sized (Tab. 3) and is comparable in morphology to Cuon alpinus . For instance, the intertrochanteric crest is more oblique and straighter (nearly vertical and curved in Canis lupus ), the caput femoris is round, and the upper border of the neck is long and flat ( Ripoll et al. 2010).

Because the Khok Sung ulna and femur morphologically match better Cuon alpinus than Canis lupus , we identify these two postcranial specimens as belonging to Cuon sp.