Esox nogaicus Kovalchuk & Wilson & Grande 2017, sp. nov.
Creators: name: Kovalchuk, Oleksandr M.
name: Wilson, Mark V. H.
name: Grande, Terry
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Esociformes
Esocidae
Esox
Esox nogaicus

description: Esox nogaicus sp. nov.
Fig. 4.
Etymology: Derived from the name of the type locality.
Type material: Holotype: NMNHU-P 27/1697, almost complete right dentary (Fig. 4A). Paratypes: NMNHU-P 27/1001, right dentary, NMNHU-P 27/998, left dentary.
Type locality: Nogaisk, Zaporozhye region, Ukraine (Fig. 1).
Type horizon: Calabrian (early Pleistocene).
Material.—NMNHU-P 27/1088–1092, vomers; NMNHU-P 27/1124–1128, frontals; NMNHU-P 27/1129, parietal; NMNHU-P 27/1047–1054, parasphenoids; NMNHU-P 27/1036–1046, maxillae; NMNHU-P 27/1102–1106, 1108, 1110–1115, 1117–1121, palatines; NMNHU-P 27/1012–1021, 1040, quadrates; NMNHU-P 27/1022–1033, 1038, articular bones; NMNHU-P 27/992–995, 997, 1000, 1006, 1007, left dentaries; NMNHU-P 27/1004, 1005, 1008, 1009, 1463, right dentaries; NMNHU-P 27/1093–1096, 1099, hyomandibulars; NMNHU-P 27/1056–1069, ceratohyals; NMNHU-P 27/986–989, 1097, opercular bones; NMNHU-P 27/1035, 1071–1076, 1614, cleithra. All material from the type locality and horizon.
Diagnosis.— Esox nogaicus sp. nov. differs from other esocids in the following combination of characters: (i) massive dentary with wide dental shelf and high symphysis; (ii) well-developed antero-ventral crest on frontal; (iii) large angle between horizontal crest and preopercular process of opercle and wide foramen on hyomandibula; (iv) low anguloarticular with wide retroarticular process; (v) long and flat dentigerous surface on palatine; (vi) wide articular crest on cleithrum.
Description.—The dentary (Fig. 4A) is massive, with a well-developed wide dental shelf, a deep symphysis, and uniserial dentition. The anterior (toothed) edge of the dentary is straight and thickened near the symphysis. The oral margin is relatively high. C-shaped tooth bases occupy the anterior two-thirds of the tooth row, with bases of fixed teeth and large replacement pits in the posterior third. A shallow lateral groove divides the anterior edge of the dentary and forms a ventral bulge in the symphysis. On the lateral surface, four pores for the mandibular sensory canal (Nelson 1972) are clearly visible near the ventral edge while, near the tooth row, the trigeminal foramen opens toward the posterior (see Wilson et al. 1992). Measurements of dentaries of the new species are as follows: height of dentary symphysis, 6.6–9.1 mm; width of the dentary near the symphysis, 3.9–5.0 mm; width of tooth row, 4.2–4.5 mm.
The posterior part of the medial suture edge of the frontal (Fig. 4B) is slightly thickened, with a wide sphenotic ledge, a clearly expressed antero-ventral crest, and a narrow side branch of the supraorbital canal. The dorsal surface of the bone is sculptured by radial smooth plates.
The parietal (Fig. 4C) is massive, with a wide posterolateral process and a well-developed ventral crest.
The front edge of the vomer (Fig. 4D) is smooth. The anterior premaxillary process of the vomer forms an angle of 115° with the longitudinal axis of the bone. The elongate dental field on the shaft of the vomer is relatively wide (WDF 5.1–6.8 mm) and has numerous very small C-shaped tooth bases. The dental field tapers anteriorly, and connects at a small neck to the triangular anterior dental field on the vomerine head (WCV 11.1–14.3 mm). There are several larger, medial C-shaped tooth bases (DDC 2.3–2.4 mm) on the vomerine head, their sizes increase laterally. A single pair of even larger replacement pits suggests the presence of fixed teeth (Fig. 4D). Similar replacement pits can be seen in several other vomers of E. nogaicus sp. nov.
Both anterior and posterior parts of the parasphenoid (Fig. 4E) are long: WPSa 7.3–9.5 mm, WPSp 6.9–8.6 mm. The narrow anterior median crest passes without a neck into the posteriorly extended dorsal medial crest. Carotid grooves are clearly expressed and deepened anteromedially. The angle between the postcarotid crests is about 110–120°.
The upper edge of the hyomandibula (Fig. 4F 1, F 2) and the horizontal crest on the medial surface are almost parallel. The angle between the horizontal crest and the preopercular process is about 120°. There is a deep notch between the wall and the upper edge of the preopercular process.
The maxilla (Fig. 4G) is highly elongated (LM 50.3– 61.5 mm), with wider posterior and narrower anterior parts. The short medial process has a rounded tip.
The articular (Fig. 4H) is characterized by a low wall (the anguloarticular angle is 40–45°), an uvular notch of the articular facet (LAF 4.9–5.6 mm), and a wide and elevated retroarticular process. There is an elongated keel at the posteroventral edge of the bone.
The palatine (Fig. 4I) has a large maxillary process with a wide fossa articularis and a small notch beside it. The dentigerous surface is long and flat. There are C-shaped bases from six rows of small, depressible teeth on the ventral surface, the largest bases located anteriorly in the medial row. The width of the bone is in the range 5.7–7.2 mm, DFA 3.2–4.8 mm.
The opercular (Fig. 4J) is flat and almost rectangular, with smooth edges. The articular facet is lenticular.
The massive barbell-shaped ceratohyals (Fig. 4K) are mostly represented by their medial parts with broken ends; they have weekly expressed branchiostegal pits and a wide main shaft.
The quadrate (Fig. 4L) is more or less triangular. The articular condyle is doubled, with medial and lateral lobes, and forms an oblique articulation with the articular bone. In lateral view, the angle between the articular condyle and the body of the quadrate is about 80°. The notch of the anterior edge just above the condyle is narrow and elongated.
The cleithrum (Fig. 4M) is massive and characterized by a wide and well-developed, medially bending articular crest. The width of the main plate is 10.2–12.1 mm.
Remarks.— Esox nogaicus sp. nov. is similar to E. lucius in the uniserial dentition of the dentary, the well-developed anteroventral crest of the frontal, and in the structure of parietal, vomer, parasphenoid and opercular, but differs in its wider dental shelf and higher dentary symphysis, as well as its lower anguloarticular angle, flat dentigerous surface on palatine, and wider articular crest of the cleithrum. Esox moldavicus is close to E. nogaicus sp. nov. in the structure of the dentary, but it differs in its weakly visible carotid grooves on parasphenoid, higher anguloarticular angle, and short toothed surface on the palatine. As compared to those in E. nogaicus sp. nov. the dentaries of Esox sibiricus and E. reichertii are characterized by a small and weakly developed dental shelf, two-row dentition, a larger anguloarticular, a relatively short dentigerous surface on the palatine, and a wider articular crest on the quadrate; on the other hand, these species resemble E. nogaicus sp. nov. in the structure of the frontal and parasphenoid.
Stratigraphic and geographic range.— Type locality and horizon only.
description: Published as part of 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, pp. 121-135 in Acta Palaeontologica Polonica 62 (1) on pages 127-129, DOI: 10.4202/app.00311.2016, http://zenodo.org/record/10980766