Esox sibiricus Sytchevskaya, 1974

Kovalchuk, Oleksandr M., Wilson, Mark V. H. & Grande, Terry, 2017, A review of Neogene and Quaternary pikes of southeastern Europe and a new species from the early Pleistocene of Nogaisk, Ukraine, Acta Palaeontologica Polonica 62 (1), pp. 121-135 : 125-126

Esox sibiricus Sytchevskaya, 1974

Fig. 2 .

1959 Esox ( lucius ?); Lebedev 1959: 50, fig. 25.

1971 Esox sp. ; Sytchevskaya and Lebedev 1971: 49, pl. 1, pl. 2: 5b.

1974 Esox sibiricus sp. nov.; Sytchevskaya 1974: 227, pl. 1: 8, pl. 2: 12, pl. 3: 1–4, pl. 4: 1–8.

1976 Esox sibiricus Sytchevskaya, 1974 ; Sytchevskaya 1976: 107, pl. 6: 6–9; 108, figs. 1–11; 109, fig. 8; 110, fig. 1.

1980 Esox sibiricus Sytchevskaya, 1974 ; Sytchevskaya 1980: 201, 202, pl. 9: 8, pl. 10: 1–5.

1989 Esox sibiricus Sytchevskaya, 1974 ; Sytchevskaya 1989: 22–23, pl. 1: 3–11.

Material.—Late Miocene: one left and two right dentaries (NMNHU-P 29/1678–1680, Popovo 3); one left dentary (NMNHU-P 29/3965, Lobkovo); one left dentary (NMNH-P 45/5690, Cherevichne 3); one parasphenoid, three dentary fragments (NMNHU-P 29/1033–1036, Verkhnya Krynitsya 2); one left and three right dentaries, one right articular (NMNHU-P 41/4323–4326, 4525, Egorovka 2); one left dentary (NMNHU-P 41/2847, Orekhovka); one right dentary (NMNHU-P 41/2741, Vinogradovka 1). Early Pliocene: one left dentary (NMNHU-P 37/2554, Novopetrovka); one left dentary (NMNHU-P 29/1583, Popovo 2).

Emended diagnosis.— Esox sibiricus differs from other Eurasian taxa by a number of characters: (i) predominance of double tooth row at symphysis of dentary; (ii) narrow and weak dental shelf; (iii) absence of symphysial notch; (iv) very large articular angle (nearly or more than 70°); (v) clearly visible grooves of carotid arteries on parasphenoid; (vi) short and flat facet of maxillar process on palatine.

Description.—The parasphenoid from the Verkhnya Krynitsya 2 locality is presented by caudally extended anterior part ( Fig. 2E ). The bone is massive; grooves of the carotid arteries are clearly visible. Measurements of the medial part of the parasphenoid are width 5.9 mm, height 3.5 mm, width of anterior medial crest 1.2 mm.

The dentary, which is not deep, has a moderately developed dental shelf, which smoothly rises into the medial wall ( Fig. 2A–D, F–H, J–L ). Teeth at the symphysis are arranged in two rows, and internal one being better developed. Teeth are completely broken in the fossils, but C-shaped crown bases are visible. There is a gradual increase in their diameter in the direction towards the symphysis. A clear lateral groove separates the anterior edge of the dentary and forms a ventral bulge in the symphysis. The anterior edge of the dentary is straight and thickened at the symphysis. Pores for the sensory canal ( Nelson 1972) are clearly visible at the ventral edge. Two small hook-shaped teeth with rounded crowns are preserved on one dentary from Popovo 3. Measurements of dentaries of Esox sibiricus from late Miocene and Pliocene strata of Ukraine are presented in the Table 2 .

The articular bone is massive ( Fig. 2I ), with a high wall anguloarticular angle is 67°). The posterior process of the bone is elongated, laterally compressed and has a narrow ventral keel. The articular facet is wide (W 4.5 mm; L 6.1 mm), with a thick raised edge. The anteroventral angle is smooth. The height of the bone at the front edge of the articular facet is 7.3 mm.

Remarks.—The described remains from the late Miocene and Pliocene localities of southeastern Europe correspond closely in morphology to those of Esox sibiricus from Kazakhstan Sytchevskaya 1976) and Mongolia (Sytchevskaya 1989). This species is similar to Esox reichertii in the structure of the anterior median crest of the parasphenoid. As compared to that in Esox aralensis , the dentary of the described species has a smaller dental shelf, a two-row dentition, and lacks a symphysial notch (Sytchevskaya 1976). The limited variety of skeletal elements of Esox sibiricus from the described localities (i.e., dentary, parasphenoid and articular bone only) does not allow comparison with some other extinct species. The presence of Esox sibiricus in the early Pleistocene strata of Popovo 2 could have been caused by the redeposition of these remains from an older layer (probably Popovo 3).

Stratigraphic and geographic range.—Early Miocene–late Pliocene of Western Siberia; late Miocene–early Pliocene of southeastern Europe.

Figures

Fig. 2. Isolated elements assigned to a pike Esox sibiricus Sytchevskaya, 1976 from Southeastern Europe; late Miocene (A–J), Pliocene (K), and Pleistocene (L). A. Right dentary (NMNHU-P 29/1679), Popovo 3, occlusal view. B. Dentary fragment with teeth (NMNHU-P 29/1680), Popovo 3, medial view. C. Left dentary (NMNHU-P 29/3965), Lobkovo, occlusal view. D. Left dentary (NMNHU-P 45/5690), Cherevichne 3, occlusal view. E. Parasphenoid (NMNHU-P 29/1033), Verkhnya Krynitsya 2, dorsal view. F. Dentary fragment (NMNHU-P 29/1034), Verkhnya Krynitsya 2, lateral view. G. Right dentary (NMNHU-P 41/4324), Egorovka 2, occlusal view. H. Left dentary (NMNHU-P 41/2847), Orekhovka, occlusal view. I. Right articular (NMNHU-P 41/4525), Egorovka 2, lateral view. J. Right dentary (NMNHU-P 41/2741), Vinogradovka 1, occlusal view. K. Left dentary (NMNHU-P 37/2554), Novopetrovka, occlusal view. L. Left dentary (NMNHU-P 29/1583), Popovo 2, occlusal view. C, D, H, I, K, L, anterior to right; A, B, F, G, J, anterior to left; E, anterior towards top. Scale bars 5 mm.