Aruma atlantica, Schwarzhans & Aguilera, 2024

Aruma atlantica n. sp.

Figure 32c–g View Fig

Holotype NMB P15739 View Materials ( Fig. 32c View Fig ), Gelasian , Bastimentos FM, Ground Creek Unit , Atlantic Panama, PPP 1256 .

Paratypes 7 specimens: 2 specimens Piacenzian, Escudo de Veraguas FM , Atlantic Panama, PPP 1241 ( NMB P15745-46 View Materials ) . 5 specimens Calabrian, Swan Cay FM , Atlantic Panama, PPP 2221 ( NMB P15740-44 View Materials ) .

Referred specimen 7 specimens Gelasian: 4 specimens Escudo de Veraguas FM , Atlantic Panama, PPP 2170 ; 3 specimens Bastimentos FM , Ground Creek Unit, Atlantic Panama , 1 specimen PPP 3202 , 2 specimens PPP 1256 .

Etymology Named after its occurrence in the West Atlantic.

Diagnosis Otolith size up to 1.65 mm in length. OL:OH = 1.25–1.3. Otolith shape nearly rectangular with orthogonal predorsal, preventral and postventral angles and not protruding postdorsal projection. Dorsal rim highest at obtuse postdorsal angle; ventral rim straight to slightly bent, horizontal. Sulcus small, without ostial lobe; OL:SuL = 2.15–2.55; sulcus inclination angle 10–15°. No subcaudal iugum. Dorsal depression connected to ventral furrow forming continuous circumsulcal furrow.

Description Otolith size up to 1.65 mm in length (holotype). OH:OT = 2.3–2.6. Otolith shape nearly rectangular. Dorsal rim low, anteriorly straight and slightly inclined, with broad, obtuse postdorsal angle as highest point, and short, not protruding postdorsal projection. Predorsal and preventral angles nearly orthogonal and anterior rim almost vertical. Postventral angle rounded orthogonal and as strongly developed as postdorsal projection; posterior rim near vertical, with moderate concavity at about level of caudal tip. Ventral rim flat or slightly curved, horizontal to slightly inclined. All rims smooth.

Inner face flat but area around sulcus somewhat bulged. Sulcus small, somewhat deepened, evenly wide, without ostial lobe, and rounded caudal tip; sulcus inclination angle 10–15°; OL:SuL = 2.15–2.55. No subcaudal iugum. Dorsal depression distinct, narrow, curved, close to dorsal rim of otolith, continuously connected around sulcus with distinct ventral furrow. Resulting circumsulcal furrow almost oval, clipping otolith angles. Outer face evenly and relatively strongly convex, smooth.

Discussion Te genus Aruma today is known from a single species, Aruma histrio ( Jordan, 1844) ( Fig. 32a–b View Fig ), a secretive species inhabiting rocky crevices and tide pools in the Gulf of California ( Robertson & Allen, 2015). Its otoliths are characterized by the elongate rectangular outline and the small sulcus without clear differentiation of ostium and cauda and no ostial lobe. Aruma otoliths differ from those of the other genus in the clade, Barbulifer , in the absence of a protruding postdorsal projection. It is of interest to note that, from the Late Pliocene to the late Early Pleistocene, a presumably vicariant species existed in the tropical West Atlantic. Aruma atlantica differs from otoliths of the Pacific A. histrio in the shorter sulcus (OL:SuL = 2.15–2.55 vs 1.8–2.0) and the obtuse postdorsal angle (vs flat dorsal rim). Aruma atlantica seems also to have grown to larger sizes than its extant counterpart in the East Pacific. Aruma atlantica has been found in only a few localities, which may indicate a specific environmental adaptation. Of particular interest is its relatively common occurrence in the Swan Cay FM in locality PPP 2221, which represents a carbonatic sand layer in a cavity in a fossil reef bioherm.