Plesiogulo crassa TEILHARD DE CHARDIN

Plesiogulo crassa TEILHARD DE CHARDIN in TEILHARD DE CHARDIN et LEROY, 1945

Text-figs 15, 16

L o c a l i t y. Thermopigi.

M a t e r i a l. Cranium with right I1–I3, C and left, P1,

P2, P3, P4 SIT 1494.

D e s c r i p t i o n. The skull is deformed and compressed due to neotectonic activity in the area, but bears most of the teeth in good condition. It shows a short rostrum, and preserves the nasal and frontal bones, the anterior part of the zygomatic arch, the right orbit, and the small infraorbital foramen located above the anterior root of P4 and the protocone ( Text-fig. 15a, d, e). There is a small diastema (ca. 3 mm) between I3 and C. The posterior part of the skull is missing, as well as the sagittal crest. The almost unworn dentition and the half-raised right P3 suggest a young individual. All incisors are well-preserved and show V-shaped palatal cingula. In addition, the much larger I3s exhibit slight torsion. The robust canines may indicate a male individual. They show wrinkled enamel at their base, and two well-defined anterior and posterior longitudinal crests. The P1 is a small, single-rooted tooth with the main cusp, and a distinct basal cingulum well-developed. The P2 is doublerooted, has a single main cusp and a crest extending along its midline, weaker anteriorly and more distinct posteriorly, terminating on a small tubercle on the posterior margin of the low, relatively distinct cingulum ( Text-fig. 15b). The P3 is half-raised, with a strong main cusp and a basal cingulum. The upper carnassial, P4, is typically robust and three-

a: palatal view, b: details of teeth – occlusal view, c: details of P4, M1, d: cranial view, e: right lateral view. Scale bars 20 mm.

rooted. The parastyle is weak but distinct, and includes a small, conical parastylar cusp. The paracone is broad and bears a pair of low crests along the anterior surface; the medial crest terminates just to the parastylar cusp, posterior to the parastyle. There is a relatively deep inflection of the anterior portion of the P4, located between the parastyle and protocone. The protocone is low and extends anteromedially from the base of the paracone, projecting nearly as far forward as the parastyle. The metastyle is mesially broad, but tapers distally. As regards the cingulum, the condition of the specimen does not allow any description. The paracone on the M1 is externally rounded, large (5.8 mm × 6.4 mm) and dominates over the metacone (3.8 mm × 4.3 mm). Both paracone and metacone are relatively short. The inner lobe is broad, expanding posterolingually to form a broad talon, with a slight constriction. Protocone and paraconule are joined by a pronounced crest. A cingulum surrounds the entire lingual part of the molar, and buccally there is a platform, more developed in the paracone area. It is further bounded by a well-developed cingulum, which in its union with the paracone forms a rudimentary parastyle ( Text-fig. 15c). Dimensions of skull are in Table 8.

D i s c u s s i o n. Many studies have described the expansion, evolution and extinction of Plesiogulo . The giant wolverine was the largest terrestrial mustelid, originating in Asia and migrating to North America between 7.0 and 6.5 Ma ago ( Kurtén 1970, Hendey 1978, Harrison 1981, Alcalá et al. 1994, Haile-Selassie et al. 2004, Samuels et al. 2018 and references therein). It is known from several Middle to Late Miocene and Pliocene sites across Eurasia, North America, and Africa, and has long been discussed as a possible relative of Gulo . The earliest occurrence in Europe is from the Middle Miocene (MN 6, ca. 15.2–12.5 Ma) ( Samuels et al. 2018). There is a question if Plesiogulo crassa was ecologically replaced in the Pliocene by the leopard-sized wolverine Plesiogulo monspessulanus VIRET, 1939 (Montpellier, MN 13), as some of its characters are intermediate between those of the Late Miocene form and * Koufos 2006c, ** Kurtén 1970, Alcalá et al. 1994

modern Gulo ( Kurtén 1970) View in CoL . Gulo View in CoL has a distinct P4 parastyle. A weak parastyle appears in Plesiogulo SIT1494 , contrary to the indication that the parastyle is absent in Plesiogulo ( Harrison 1981, Samuels et al. 2018). The Thermopigi Plesiogulo displays robust anterior premolars with strong cingula, a P4 with a large protocone and relatively broad metastyle, and a large M1 with a posterolingually expanding inner lobe to form a broad talon. Ecologically, Plesiogulo as related to Gulo View in CoL has traditionally been interpreted as a forestdweller, and thus its presence may indicate a forest area near the deposition site. However considering its size and its abundance in faunas associated with hypsodont grazers and cursorial ungulates, it might have been a hunter in open grassland as well. Therefore, this genus was not a strictly woodland inhabitant. Harrison (1981) notes that most of the fossil localities with Plesiogulo have not produced a sample of significant statistical size, often no more than one individual, as is the case at Thermopigi.

As shown in Text-fig. 16 and in Table 7, the measurements of the SIT specimen are closer to Plesiogulo crassa . In Greece, Plesiogulo crassa is rather rare and besides Thermopigi, only a mandible fragment from Vathylakkos-3 (lower Axios valley, Northern Greece) ( Koufos 1982), and an almost complete skull with mandible from Perivolaki (Thessaly) are reported. All are from the middle Turolian biozone MN 12, ~7.3 Ma ( Koufos 2000, 2006b, c, 2022c). The southernmost occurrence of Plesiogulo in Europe, represented by humeral remains of Plesiogulo sp. , is reported from Pikermi, Attika ( Symeonidis 1975).