Fig. 4 Acanthochaetetes fischeri n in Acanthochaetetes Fischeri N. Sp. (Coralline Demosponge) From The Upper Paleocene (Thanetian) Of Iraq (Kurdistan Region) And Iran (Sistan Suture Zone)

Fig. 4 Acanthochaetetes fischeri n. sp. from the upper Paleocene of northeastern Iraq. a Longitudinal (left) and cross (right) sections. Note the thick double walls (black arrows). Thin-section 18. b–c cross sections, where spines inside calicles (black arrows) and thick double walls (white arrows in c) can be seen. Thin-sections 24 and 17. d Oblique section, showing scarce tabulae (black arrows). Thin-section 17. e Cross section. Note the round/oval to elliptical shape of calicles, as well as two fissiparous division processes (black arrows). Thin-section 24. f Longitudinal section, where tabulae (black arrows) and subsequent fissiparous division processes (grey arrows) can be observed. Thin-section 17. g Cross-to-oblique section, showing massive thickenings (square; common for all Acanthochaetetidae; compare Reitner, 1991; Sánchez-Beristain et al., 2019, 2021). Thin-section 16. h Oblique section, with abundant lamellae (black arrows), common for all Acanthochaetetidae (compare Reitner, 1991). Thin-section 24. i Cross-oblique section, showing round to elliptical shape of calicles, as well as multiple lamellae (right side of the picture). See text and table 1 for further details. Thin-section 24.