Gnatholepis gunae, Schwarzhans & Aguilera, 2024

Gnatholepis gunae n. sp.

Figure 44k–k View Fig

Holotype NMB P15833 View Materials ( Fig. 44k View Fig ), Tortonian , Gatun FM, Atlantic Panama, PPP 2168 .

Paratypes 6 specimens Tortonian: 4 specimens same data as holotype ( NMB P15834-37 View Materials ) ; 2 specimens Tuira FM , Pacific Panama, Darien, PPP 1137 ( NMB P15838-39 View Materials ) .

Referred specimens 12 specimens Tortonian: 2 specimens Tuira FM , Pacific Panama, Darien, PPP 1137 ; 1 specimen Yaviza FM , Pacific Panama, Darien, PPP 1553 ; 9 specimens same data as holotype .

Etymology Named after the Guna, the indigenous Indians inhabiting the region of the type location.

Diagnosis Otolith size up to 1.05 mm in length. OL:OH = 0.85–0.92. Otolith high-bodied, with expanded, angular middorsal angle. Preventral angle pointed, postventral angle orthogonal; postdorsal projection rounded, slightly protruding. Sulcus large, with moderate ostial lobe; OL:SuL = 1.65–1.8; sulcus inclination angle 9–14°. No subcaudal iugum. Ventral furrow distinct, regularly curved in specimens below 1 mm in length; anteriorly and posteriorly open in larger specimens.

Description Otolith size up to 1.05 mm in length (holotype). OH:OT = 3.3. Otolith high-bodied; dorsal rim high, with angular, relatively high predorsal angle, per- and postdorsal rims ascending to elevated to relatively sharp middorsal angle in straight lines; postdorsal projection broad, high, slightly protruding. Anterior rim slightly inclined towards dorsal, with weak concavity at level of ostium. Posterior rim inclined towards ventral, with weak concavity below postdorsal projection. Ventral rim straight to slightly bent and horizontal, with sharp preventral and orthogonal postventral angles. All rims smooth.

Inner face only bent in horizontal direction. Sulcus wide, relatively large, slightly deepened, sole-shaped with moderate ostial lobe, its ostial tip tapering; sulcus margins at ostial-caudal joint broadly but not strongly ingressing, thereby narrowing sulcus; cauda with rounded tip; sulcus inclination angle 9–14°; OL:SuL = 1.65–1.8. No subcaudal iugum. Dorsal depression wide, with indistinct margins; ventral furrow distinct, relatively close to ventral rim of otolith, anteriorly and posteriorly opening to ventral portions of anterior and posterior rims in large specimens

( Fig. 44k View Fig ), curving upward behind cauda in smaller specimens ( Fig. 44l–q View Fig ). Outer face slightly convex, smooth.

Discussion Otoliths of G. gunae are smaller than those of the extant G. thompsoni , but the development of the ventral furrow touching the anterior and posterior rims in morphologically mature specimens indicates that specimens larger than 1 mm in length are mature, and hence G. gunae is indeed a relatively small species. Gnatholepis gunae resembles the extant G. thompsoni in many aspects but differs in the smaller size, the lower OL:OH ratio (0.85–0.92 vs 0.8–0.88), and the smooth otolith rims. Te occurrence of G. gunae in the Tortonian of tropical America confirms the long presence of this genus in the region.