Gillichthys caribbaeus, Schwarzhans & Aguilera, 2024

Gillichthys caribbaeus n. sp.

Figure 46e View Fig

Holotype NMB P15846 View Materials ( Fig. 46e View Fig ), Tortonian , Manzanilla FM, San José Member, Trinidad, PPP 2670 .

Etymology Named after the occurrence of this species in the Caribbean while the genus today is strictly East Pacific.

Diagnosis Otolith size 1.65 mm in length. OL:OH = 1.15. Otolith oval, with regularly curved dorsal rim and expanded postdorsal region. Preventral and postventral angles rounded, recessed; postdorsal projection broad, rounded, protruding. Sulcus large, wide, shallow, with low ostial lobe; OL:SuL = 1.8; sulcus inclination angle 15°. No subcaudal iugum. Ventral furrow narrow, distant from ventral rim of otolith, curving around sulcus to join narrow, furrow-like dorsal depression.

Description Otolith size 1.65 mm in length (holotype). OH:OT = 3.5. Otolith with a generally rounded, more or less oval shape. Dorsal rim high, regularly curved, broadly expanded postdorsal region, slightly depressed rounded and slightly protruding predorsal angle; postdorsal projection broad, rounded, protruding. Anterior rim slightly curved, slightly inclined toward ventral, without concavity. Posterior rim with mild concavity below postdorsal projection followed towards ventral by slight bulge. Ventral rim straight, horizontal, with broadly rounded and recessed preventral and postventral angles. All rims relatively sharp in lateral view, slightly undulating.

Inner face convex, particularly bent in horizontal direction, relatively smooth but area outside of central field defined by circular ventral furrow and dorsal depression somewhat undulating. Sulcus large, wide, shallow, sole-shaped with low, rounded ostial lobe, its ostial tip rounded; cauda with rounded tip; sulcus inclination angle 15°; OL:SuL = 1.8. No subcaudal iugum. Dorsal depression narrow, close to sulcus and distant from dorsal rim of otolith, relatively distinct but not deep; ventral furrow narrow, relatively close to sulcus and distant from ventral rim of otolith, turning around sulcus posteriorly and joining up to dorsal depression; curvature anteriorly interrupted by tip of sulcus. Outer face slightly concave, relatively smooth.

Discussion Te single, superbly preserved but thin and fragile otolith bears all the typical hallmarks of otoliths of the extant Gillichthys mirabilis ( Fig. 46a–b View Fig ), including the general shape of the otolith and the sulcus and the pattern of the ventral furrow and its connection to the dorsal depression, which is distant from the dorsal rim of the otolith. Gillichthys caribbaeus differs from G. mirabilis in being slightly more compressed (OL:OH = 1.15 vs 1.2–1.25), the relatively large sulcus (OL:SuL = 1.8 vs 2.0–2.2), and the ventral furrow running more distant from the ventral rim of the otolith. Clearly, G. caribbaeus represents an extinct species of the lineage that today is strictly East Pacific but was in the Atlantic during the Late Miocene. In fact the otolith suggests that G. caribbaeus is more closely related to G. mirabilis than the latter is to the second extant species, G. seta ( Fig. 46d View Fig ). Most of the fishes in the Gillichthys clade inhabit shallow coastal to estuarine environments. Gillichthys mirabilis inhabits shallow coastal environments such as mudflats and bays and is well known for its facultative air-breathing ( Todd & Ebeling, 1966).