Microgobius praeglaber, Schwarzhans & Aguilera, 2024

Microgobius praeglaber n. sp.

Figure 31q–v View Fig

Holotype NMB P15729 View Materials ( Fig. 31q View Fig ), Langhian to Serravallian, upper Brasso FM, Trinidad, KR-9244 .

Paratypes 7 specimens: 4 specimens Langhian to Serravallian, same data as holotype ( NMB P15730-33 View Materials ) . 3 specimens Tortonian , Gatun FM , Atlantic Panama, PPP 2167 ( NMB P15734-36 View Materials ) .

Referred specimen 6 specimens Langhian to Serravallian, same data as holotype .

Etymology A combination of prae (Latin) = before, earlier and the species-name glaber of Microgobius glaber indicating its possible relationship to that species and its earlier occurrence.

Diagnosis Otolith size up to 0.85 mm in length. OL:OH = 0.79–0.83. Otolith shape high-bodied; dorsal rim elevated, with rounded postdorsal angle. Anterior rim slightly curved; posterior rim vertical, straight. Ventral rim curved. Sulcus short, anteriorly widened, posteriorly tapering, eccentrically forward positioned; OL:SuL = 2.0–2.2; sulcus inclination angle 12–16°. Subcaudal iugum long, wide, ingressing into rear part of cauda. Ventral furrow close and parallel to ventral rim of otolith, regularly curved.

Description Otolith size up to 0.85 mm in length (holotype). OH:OT = 3.3–4.0. Otolith shape high-bodied. Dorsal rim high, rounded or with rounded postdorsal angle; predorsal angle indistinct, postdorsal projection indistinct. Anterior rim slightly curved, posterior rim nearly vertical, straight. Ventral rim distinctly curved. Preventral and postventral angles broadly rounded. All rims smooth.

Inner face completely flat. Sulcus short, droplet-shaped, eccentrically positioned towards anterior, with rounded, widened anterior tip and rounded ostial lobe, and short cauda, with tapering, often pointed tip; sulcus inclination angle 12–16°; OL:SuL = 2.0–2.2. Subcaudal iugum long, wide, broadly extending around caudal tip and ingressing into cauda from ventral and posterior. Dorsal depression distinct. Ventral furrow distinct, close and parallel to ventral rim of otolith and regularly curved. Outer face evenly convex, smooth.

Discussion Microgobius praeglaber is characterized by small otoliths that at first sight could be taken as stemming from juvenile specimens of some other gobiid species. It does, however, show a number of unique features that exclude such explanation, including the droplet-shaped forward-positioned sulcus and the massive ingression of the wide subcaudal iugum into the cauda. We therefore postulate that M. praeglaber and M. aphioides represented small, possibly hemipelagic gobies similar to the extant Aphia minuta .