Carcharhinus acuarius ( Probst, 1879 )

Carcharhinus acuarius ( Probst, 1879)

Plate 4, Figs 14–29

* Alopecias acuarius Probst 1879: 140 , pl. 2, figs 76, 77.

Carcharhinus ( Aprionodon) Lerichei [ sic] (Dartevelle & Casier)— Zbyszewski & Almeida 1950: 340 ( partim), pl. 6, figs 79–97, 99, 101, 104.

Isurus View in CoL cf. novus (Winkler)— Serralheiro 1954: 49, pl. 1, figs 14, 16,?15.

Carcharhinus ( Aprionodon) lerichei (Dartevelle & Casier) — Serralheiro 1954: 58, pl. 2, figs 38–40.

Carcharhinus ( Aprionodon) lerichei Dartevelle & Casier [ sic] var. minuta Jonet 1966: 69 , pl. 2, figs 1–13.

Carcharhinus ( Aprionodon) gracilis Jonet 1966: 70 , pl. 2, figs 14–21.

Aprionodon acuarius ( Probst, 1879) — Antunes & Jonet 1970: 182, pl. 14, figs 93–96, pl. 15, figs 97–99.

Aprionodon acuarius ( Probst, 1879) — Cappetta 1970: 57, pl. 17, figs 1–20.

Aprionodon acuarius ( Probst, 1879) — Jonet 1978: 32, pl. 1, figs 13, 16, 17, 19, 20.

Carcharhinus acuarius ( Probst, 1879) — Kruckow & Thies 1990: 52.

Isogomphodon acuarius ( Probst, 1879) — Laurito 1999: 77, pl. 21 figs 1–8, pl. 22, figs 1, 2.

Isogomphodon acuarius ( Probst, 1879) — Müller 1999: 51, pl. 7, fig. 9.

Isogomphodon acuarius ( Probst, 1879) — Cappetta 2012: 301, figs 284a–l.

Carcharhinus acuarius ( Probst, 1879) — Höltke et al. 2024: 169, figs 8.14, 9.1–9.3.

Material. 607 isolated teeth. NHMW 2025 View Materials /0177/0007 ( 17 specimens) .

Description. The dentition comprises teeth with a narrow, high principal cusp with smooth mesially and distally extended cutting edges. The upper and lower teeth are distinguishable by a labiolingually flattened cusp and root in the upper teeth that are more strongly convex, and the principal cusp is often directed lingually in lower teeth. The upper teeth ( Pl. 4, figs 14–20) possess a relatively high, narrow, upright principal cusp that is four times higher than its base width and are constricted near the base, resulting in mesial and distal extensions of the smooth cutting edges. The root is divided into two root lobes by a relatively deep central groove, of which the mesial one is narrower than the distal one. The principal cusp of more lateral teeth becomes lower with wider extensions of the cutting edges and the root lobes wider and diverge at an angle of approximately 120°. The lower teeth ( Pl. 4, figs 21–29) have a convex principal cusp with mesial and distal extensions of the smooth cutting edges. The root is lingually protruding in the center and divided into two root lobes that diverge at an angle of 90° in anterior teeth. The principal cusp of the lower teeth gradually lowers in more lateral teeth and mesial and distal cutting-edge extensions becomes wider, as well as the root lobes that diverge at an angle of up to 180°.

Discussion. After assignment to several genera by various authors Carcharhinus acuarius is the latest generic assignment of this species after Höltke et al. (2023).

Carcharhinus acuarius is one of the best represented species in the study assemblage. It is the second most abundant one in the bulk sample with 42 out of 319 specimens ( Fig. 5 View FIGURE 5 ) and the most abundant in the search sample with 565 out of 2260 specimens ( Fig. 4 View FIGURE 4 ). This extinct species was widly distributed in the Miocene northern Atlantic and the Mediterranean during the Miocene ( e.g., Vialle et al. 2011). According to Höltke et al. (2023: 35), its closest living congener is Carcharhinus oxyrhynchus ( Müller and Henle 1839) . This present-day species was until recently the type species of the monotypic genus Isogomphodon Gill, 1862 . However, based on molecular genetics, Rodrigues-Filho et al. (2023) reassigned I. oxyrhynchus ( Müller and Henle 1839) to the genus Carcharhinus . The present-day daggernose sharks inhabit estuaries, mangroves and river mouths, as well as marine neritic environments, 4 to 40 m deep ( Ebert et al. 2021). Therefore, the abundant presence of fossils of C. acuarius in the study assemblage strongly suggedsts a shallow marine neritic environment close to the coastal zone.

Distribution. Upper Oligocene (Chattian): Catahoula Fm. of Mississipi, USA ( Cicimurri et al. 2025). LowerMiddle Miocene: Caribbean, Venezuela ( Carrillo-Briceño et al. 2016) southern Germany. Middle–Upper Miocene Portugal, southern France, ( Cappetta 1987: 121), North Carolina, USA ( Müller 1999).

Distribution in Portugal. Lower Miocene: (Burdigalian) Lower Tagus Basin ( Serralheiro 1954). Middle Miocene: (Langhian–Serravallian) Lower Tagus Basin ( Serralheiro 1954; Antunes & Jonet 1970). Upper Miocene: (Tortonian) Lower Tagus Basin ( Serralheiro 1954); Algarve Basin, Cacela Fm. (this paper).