Archaeotetraodon winterbottomi TYLER et BANNIKOV, 1994

Přikryl, Tomáš, Kovalchuk, Oleksandr, Carnevale, Giorgio & Barkaszi, Zoltán, 2022, New Material Of The Puffer Fish Archaeotetraodon Winterbottomi Tyler Et Bannikov, 1994 (Tetraodontidae) From The Oligocene Of The Eastern Paratethys, Fossil Imprint 78 (2), pp. 513-518 : 514-516

Archaeotetraodon winterbottomi TYLER et BANNIKOV, 1994

Text-figs 2–3

1994 Archaeotetraodon winterbottomi new species; Tyler and Bannikov, p. 103, figs 1–4.

2010 Archaeotetraodon winterbottomi TYLER et BANNIKOV, 1994 ; Bannikov, p. 170, pl. XXIX, fig. 3.

2010 Archaeotetraodon winterbottomi TYLER and BANNIKOV, 1994 ; Carnevale and Tyler, p. 295, fig. 13.

M a t e r i a l. The specimen NMNHU-P PI 1995 is deposited in the Department of Palaeontology of the National Museum of Natural History, National Academy of Sciences of Ukraine in Kyiv.

D e s c r i p t i o n. The specimen is preserved in left lateral view ( Text-fig. 2 ), with the neurocranium exposed in dorso-lateral view.

The skull roof is almost hourglass-shaped. Although the anterior portion of the neurocranium is not completely clear, it is possible to recognize the crescent-shaped mesethmoid posteriorly articulated with the poorly preserved lateral ethmoids.The frontals have concave lateral margins, widened posteriorly and contact the sphenotics posterolaterally. The outline of the pterotic is partially recognizable. The ventral part of the neurocranium is extensively fragmented and partially covered by overlying bones.

The beak-like jaws are massive. The premaxillae are more or less triangular. Remains of the left maxilla suggest the presence of a relatively large, dorsally oriented process forming a right angle with the main shaft of the bone. The left mandible is triangular in outline and anteroposteriorly elongate; the bone in its postero-ventral corner is articulated with the quadrate. There is a distinctive notch with a rounded profile along the posterior margin of the mandible. Bony fragments located just below the ethmoid region of the skull probably represent what remains of the palatine.

The ceratohyal is rod-like anteriorly and broadly expanded posteriorly. Along the ventral margin of its expanded portion, it is possible to observe five partially complete branchiostegal rays, possibly representing the second to sixth rays of the series. The first ray was probably enlarged, as in other tetraodontids, and it is poorly preserved, displaced behind the hyoid arch. Remains of three other contralateral branchiostegal rays are preserved below the neurocranium. The left hyomandibula is displaced from its original position; it has a straight vertical shaft and a gently concave anterior margin.

Several isolated fragments of the branchial skeleton (pharyngobranchials and, possibly, a portion of an epibranchial) are disarticulated and dispersed above the ceratohyal.

The cleithrum is sigmoid in outline and bears a posterodorsally-directed spine and a relatively large posterior lamina, partially covering the remains of a single pectoralfin radial, while a second one is exposed just below it. The supracleithra are extensively fragmented. There are two welldeveloped postcleithra, of which the ventral one is thin, riblike and slightly bent. Its length slightly exceeds 20 % of SL, while the dorsal one is slightly more massive than the ventral one and its length is about half of the ventral one. Remains of the scapula, coracoid and pectoral fins are not recognizable.

The vertebral column consists of 17 vertebrae (eight abdominal plus nine caudal). The first three abdominal vertebrae bear shortened neural spines. Neural spines of the three successive vertebrae are much longer and posteriorly inclined. The neural spines of the seventh to eleventh vertebrae are not completely recognizable, while the twelfth to penultimate vertebrae have wide and relatively short neural spines. The first centrum seems to be slightly thinner compared to the following ones, but that part of the fossil is not completely preserved, suggesting that this condition may represent a preservation artifact. The subsequent centra are rectangular in outline, longer than high. The terminal section of the vertebral column comprises anteroposteriorly compact centra. Ribs and intermuscular bones are not present.

The caudal skeleton is characterized by an autogenous parhypural and haemal spine of the second preural vertebra fused to the centrum. The hypural plate and the dorsal portion of the caudal skeleton is not completely clear. The truncate caudal fin is only partially preserved; its preserved portion is characterized by nine or ten elongates rays (preserved portion represent 18.3 % of SL).

The dorsal fin is located in the posterior third of the body (predorsal length represents 79.9 % of SL) and consists of about ten rays. Its endoskeleton is partially preserved, but clearly shows relatively large pterygiophores with the anterior-most one, the so-called “rayless pterygiophore”, that inserts in the fifth interneural space.

The anal fin is not completely preserved, having at least six preserved rays. The anal fin is located just below the posterior part of the dorsal fin and was probably supported by eight pterygiophores, of which the anterior is the longest.

The body is covered with bifid spinules ( Text-fig. 3 ). The spinules apparently lack stellate basal plates.

M e a s u r e m e n t s. Standard length: 71.2 mm; total measurable length: 86.2 mm; head length (from premaxilla to posterior wall of the basioccipital): 27.1 mm (38.1 % of SL); height/length ratio of the posteriormost abdominal centrum 0.63; rayless pterygiophore length: 12 mm (18 % of SL); predorsal length: 56.9 mm (79.9 % of SL); measurable caudal fin: 13 mm (18.3 % of SL); ventral postcleithrum length: 15.1 mm (21.2 % of SL).

Figures

Text-fig. 2. Archaeotetraodon winterbottomi. Specimen NMNHU-P PI 1995. Sheshory locality, Ukraine (Rybnytsia Member, lowermost part of the Menilite Series, Oligocene). a: photo of the specimen; b: interpretative drawing of the (a).

Text-fig. 3. Archaeotetraodon winterbottomi. Specimen NMN- HU-P PI 1995. Details of dermal bifid spinules.