Prototetrapturus courcelli ( Arambourg, 1927 ) Gracia & Correa-Metrio & Carvalho & Velez-Juarbe & P̆rik & & Kri, 2022

Gracia, Carlos De, Correa-Metrio, Alex, Carvalho, Monica, Velez-Juarbe, Jorge, P ̆ rik, Tom ́ a ̆ s, , Carlos Jarami & Kri, nd Jurgen, 2022, Towards a unifying systematic scheme of fossil and living billfishes (Teleostei, Istiophoridae), Journal of Systematic Palaeontology (2091959) 20 (1), pp. 1-36 : 20

† Prototetrapturus courcelli ( Arambourg, 1927) comb. nov.

( Figs 7B, 8C, 9A–E, Supplemental material Fig. S4)

1927 † Xiphiorhynchus courcelli Arambourg : 173, pl. 36/ 6, fig. 40.

1978 † Istiophorus courcelli (Arambourg) ; Fierstine: 8.

1987 † Makaira courcelli (Arambourg) ; Schultz: 120, 140, 148, 172, tabs. 2, 3, figs 6A, 7C, 8A–E, S1, S4.

Diagnosis. † Prototetrapturus courcelli comb. nov. is differentiated from all other istiophorids in the following combination of morphological traits (an asterisk indicates autapomorphic traits): very slender rostrum with acute distal tip; an oval to angularly obtuse cross-section$; two additional, small and dorsolaterally positioned internal canals in dorsal position and laterally distributed$; denticles on the lateral sides that are distinctly large, conical and pointed$ (Supplemental material Fig. S4).

Holotype. MNHNP 250 ( Fig. 8C), a nearly complete rostrum without nasals.

Occurrence. Late Miocene (Messinian), pre-evaporitic period of the Tripoli Unit, locality of ‘Les Planteurs’, Algeria ( Landini & Menesini 1984; Carnevale et al. 2002; Gaudant 2008).

Remarks. The preserved rostrum is 295 mm long, rather slender, with a generally elliptical cross-section (wider than tall) ( Fig. 8C). In cross-section, two continuous and large internal internal canals are visible ( Table 3 ; Fig. 8C). In lateral view, the rostrum is straight dorsally, but slightly curved upwards ventrally ( Fig. 8C). It is covered partly by conical denticles that are restricted to the ventral and lateral surfaces of the specimen. The denticles located on the lateral sides are the largest, while those located on the ventral surface are smaller (Supplemental material Fig. S4).

The cross-sections of the rostrum change along its length and each section is described here in the same sequence as in Arambourg (1927). The first section is represented by the fracture at the proximal end of the rostrum and is equivalent to the 0.5 L distance ( Fig. 9A). At this distance, the rostrum is oval in cross-section but with an angularly obtuse ventral surface. The shape for the second section ( Fig. 9B) is similar to the first section. The obtuse ventral angle forms a convex surface along the ventral surface of the rostrum that decreases gradually as it advances distally up to approximately 139 mm (if measured from the proximal end) ( Fig. 9A, B). At this distance, the third section is located and is equivalent to that at 0.25 L ( Fig. 9C). Here the rostrum is oval and two smaller canals located dorsolateral to the centre of the bone are visible ( Fig. 9C). These small canals are visible for about 62 mm from this point extending dorsally before they gradually disappear distally. The fourth section is located at 200 mm ( Fig. 9D). It is oval but with a planar ventral margin and the second pair of internal canals are visible ( Fig. 9D). From this point (at 200 mm) to the distal tip, the ventral planar surface extends for about 46 mm, until the rostrum acquires an oval shape anew in cross-section. The last section is located at 260 mm ( Fig. 9E). Here the lateral sides (when observed in cross-section) are compressed and the distal tip acquires a slender and very pointed shape ( Figs 7A, 8C).