Osmeridae

Osmeridae View in CoL View at ENA ( Osmeriformes ) ( Fig. 9 View Figure 9 )

There are two CMCs in Osmerus eperlanus . Both have about the same size, width and shape: they are crescent-shaped and have about double to triple the width of the hypural plates ( Fig. 9A–G View Figure 9 ). The lower CMC might be slightly larger than the upper ( Fig. 9G View Figure 9 ). However, the anatomical orientation differs: the upper CMC, lying inside the diastema on the lower distal edge of hypural 3, is almost parallel to the body axis with its tips pointing anteriorly. The lower CMC, on the distal edge of hypural 2, also lying in the diastema, is oblique to the body axis with its tips pointing anteriorventrally. The upper CMC is associated with the lowest ray of the upper caudal lobe and the lower CMC with the uppermost ray of the lower lobe. Both rays are placed directly or ventrally on the CMCs and none of the rays possess medially directed pegs ( Fig. 9E View Figure 9 ). In shape, position, orientation and fin-ray association, the situation in Hypomesus olidus ( Fig. 9H–I View Figure 9 ) is very similar to that in Osmerus .

In contrast to Osmerus and Hypomesus , the cartilage did not stain well in Mallotus villosus . Nevertheless, it is clearly visible that there is a single, large CMC over the complete height of the diastema ( Fig. 9J View Figure 9 ). Together with the neighbouring hypural plates, this CMC supports the lowest ray of the upper lobe and the uppermost ray of the ventral lobe. The CMC is clearly wider than the hypural plates with anterodorsal and anteroventral grooves for fitting on the neighbouring hypural plates. Medially directed pegs on the articulating fin rays are absent.