Gonostomatidae (Betancur, 2017)

Gonostomatidae View in CoL View at ENA ( Stomiiformes ) ( Fig. 12 View Figure 12 )

In Sigmops elongatus there are two large and prominent CMCs ( Fig. 12A View Figure 12 ). They almost contact each other within the diastema and are connected via a strong ligament ( Fig. 12B View Figure 12 ). In lateral view they are ovoid and the upper CMC is slightly larger than the lower CMC ( Fig. 12A View Figure 12 ). The lowermost fin ray of the upper lobe directly articulates on the ventral portion of the upper CMC; the penultimate fin ray of this lobe articulates at, or close to, the dorsal margin of the upper CMC. In posterior view the upper CMC is roughly quadrate in shape with two little pads, left and right, that seem to serve as articular facets for the fin rays. These pads are more pronounced on the lower CMC giving it an upside-down crown shape with a tip pointing upwards in posterior view. The uppermost ray of the lower lobe articulates with these downward-pointing pads ( Fig. 12B View Figure 12 ). The anterior side of the CMCs is concave, thus forming a cap on the diastemal edge of hypural 2 and 3, respectively, and they are only slightly wider than the hypural plates. In Cyclothone sp. there are two small CMCs, roundish in lateral ( Fig. 12C View Figure 12 ) and posterior views ( Fig. 12D View Figure 12 ). Their anterior facet is concave and therewith they sit like little caps at the diastemal corners of the dorsal and ventral hypural plates. The lowermost ray of the upper caudal fin lobe articulates directly with the upper CMC. The uppermost ray of the lower lobe articulates only with the ventral edge of the lower CMC. The CMCs are about the same width as the hypural plates.

In Manducus maderensis , Diplophos sp. and Triplophos hemingi no CMCs have been observed.