Palaeorhincodon fialhoi, Hovestadt & Da Silva, 2025

Hovestadt, Dirk C. & Da Silva, Carlos M., 2025, A new chondrichthyan (Sharks and Rays) Fossil Assemblage from the Miocene Cacela Fm. at Albufeira (Algarve, Portugal) with two new species: Palaeoecology and Biogeography, Zootaxa 5724 (1), pp. 1-66 : 30-31

Palaeorhincodon fialhoi sp. nov.

Plate 5, Figs 47–48

Material. 2 teeth.

Type Material. Holotype NHMW 2025 /0177/0027, anterior tooth; paratype 1 NHMW 2025 /0177/0028; 6a. lateral tooth.

Etymology: Named after Pedro Fialho, Portuguese palaeontologist at the University of Évora, Portugal. Pedro represents the younger generation of Portuguese specialists working on Neogene chondrichthyan fishes.

Locus typicus: Leixão dos Alhos site ( Fig. 1 ), near de locality of Oura, Albufeira municipality, Algarve, southern Portugal.

Stratum typicum: Cacela Fábrica Middle Member of the Cacela Formation outcropping along the coast of Albufeira, western Algarve, basal fine micaceous sandstone, “Bed 3” in Cachão et al. (2009: fig. 2). Upper Miocene, Tortonian.

Diagnosis. Gradient monognathic heterodont. High anterior tooth lacking any ornamentation without mesial and distal cusplets, lateral teeth with small mesial and distal cusplets at the lower end of the cutting edges that are lost in posterior teeth. Teeth up to 2.5 mm wide, anterior teeth higher than wide. Main cusp triangular, elongate and lingually directed. Cusps of lateral and posterior teeth inclined towards commissure. Basal edge of the apron convex. Root holaulacorhizid and divided into two root lobes by a deep central groove with wide mediocentral foramen.

Description. Although the apex is rounded by wear the principal cusp of the anterior tooth is high, approximately three times as high as its base width ( Pl. 5, fig. 47a) and a tiny mesial and distal cusplet is present at the mesial and basal end of the hardly distinguishable cutting edges that are convex, blunt and rounded ( Pl. 5, figs 47c, d). Principal cusp is strongly lingually directed at an angle of 35°. The base of the principal cusp is concave. The smooth labial surface is slightly convex. The also smooth lingual surface is concave and ends in a small uvula. The holaulacorhizid root is divided into two equal sized root lobes by a deep central groove that run parallel to each other. A large central foramen is present in the median groove and one or two smaller ones are present near the crown-root junction at the mesial and distal part of the root lobes ( Pl. 5, figs 47b, c). The lateral tooth ( Pl. 5, figs. 48a–d) has similar features as the anterior one, but with a strongly distally inclined principal cusp and two mesial and one distal cusplet at the base of the also hardly distinguishable cutting edges.

Discussion. The genus Palaeorhincodon comprises three species: P. wardi Herman, 1974 from the Lutetian of Belgium, P. daouii Noubhani & Cappetta, 1997 from the Thanetian of Morocco and P. dartevellei ( Arambourg, 1952) from the Ypresian of Morocco. No occurrences had been reported from Miocene deposits so far.

The teeth of Palaeorhincodon fialhoi sp. nov. can be distinguished from those of P. wardi Herman (1974) and P. daouii Noubhani & Cappetta (1997) by the presence of sharp cutting edges, which are blunt and rounded in the new species. Very minute mesial and distal cusplets are also present, which are better developed in P. wardi and P. daouii . Palaeorhincodon dartevellei can be distinguised by sharp mesial and distal cutting edges, blunt in P. fialhoi sp. nov. and well developed mesial and distal cusplets that are hardly developed in P. fialhoi sp. nov.

Palaeoecology: Palaeorhincodon is an extinct genus of sharks originally reported from the Eocene of the North Sea Basin, from Belgium (Herman 1974). In the Tortonian of southwestern Iberia, Palaeorhincodon fialhoi sp. nov. could be found in subtropical to probably tropical neritic waters with an estimated depth of about 20 to 30 m over sandy bottoms. The only extant rhincodontid, Rhincodon typus Smith, 1828 , the Whale Shark, is a neritic to pelagic circumglobal species that occurs in warm temperate to tropical seas, except in the Mediterranean. The whale shark is not found today off the Algarve ( Ebert et al. 2021).

Distribution: Miocene Eastern Atlantic, southwestern Iberian coast; Algarve Basin ( Portugal), Tortonian (this paper).

Figures

FIGURE 1. Location of thestudy site, Leixão dosAlhos,Oura region,Albufeira municipality,southern Portugal, thegeographical coordinates: 37° 4'58.60"N, 8°14'0.39"W. H—Location of the Auramar Beach Resort Hotel.