Sycon quadrangulatum

Sycon quadrangulatum (Schmidt, 1868) (Figure 6) Sycandra quadrangulata Schmidt, 1868: 29, pl. V, fig. 9. Sycon guadrangulatum, Longo and Pronzato, 2011: 202, fig. 102. Material examined: ESFM-POR / 2017-434, S19, 20 m, on stone, 3 specimens. Description: It is usually elongated and cylindrical in shape. It reaches 5 cm in length and 1.5 cm in width (Figure 6a). The body is white, greyish in color and has a hard structure. The osculum is not surrounded by spicules. Its calcareous spicules are composed of equiangular and uniangular triactines and diactines. The tubar skeleton is composed of non-congruent triactine rows (actins of equal length: 50–70 µm × 8–10 µm, actin of unequal length: 90–120 µm × 10–12 µm) (Figure 6b 1, c), and the atrial skeleton is composed of equiangular triactine rows (100–150 µm × 10–15 µm). Diactines are 250–400 µm long and 18–25 µm in diameter. Habitat and distribution: It was previously reported from rocks and crevices in the shallow sublittoral zone (Van Soest & Weinberg 1980). In this study, only 3 individuals were found on rocks at a depth of 20 m. This species was previously reported from the eastern Atlantic Ocean and the western Mediterranean Sea (de Voogd et al. 2024). This is a new record for the Eastern Mediterranean fauna.