Hexactinellida Schmidt, 1870
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publication ID |
https://doi.org/ 10.4202/app.00612.2019 |
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persistent identifier |
https://treatment.plazi.org/id/AE74871F-B86C-B73B-FF48-FE7FFD35F95F |
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treatment provided by |
Felipe |
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scientific name |
Hexactinellida Schmidt, 1870 |
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Class Hexactinellida Schmidt, 1870 View in CoL Hexactinellida indet.
Figs. 8B–E View Fig , 10A, B, D, E–G, I–L View Fig .
Material.—Middle, middle–upper Eocene, south-central Ukraine.
Remarks. —The hexactines illustrated on Fig. 10C, E, F, I, H View Fig are most probably dermal spicules of rosselid sponges (compare Tabachnick 2002b: figs. 18, 19). However, similar spicules can be found also in other hexactinellid groups, e.g., Euretidae Zittel, 1877 (order Sceptrulophora ), Aphrocallistidae Gray, 1867 (order Hexactinosida ), or even in the amphidiscosid family Pheronematidae Gray, 1870 (see Reiswig 2002a; Reiswig and Wheeler 2002; Tabachnick and Menshenina 2002b). Yet, their rossellid affinity seems most likely because another spicule illustrated on the same figure ( Fig. 10J View Fig ), called dermal triactine, is also noted in the rossellid sponges (compare Tabachnick 2002b: fig. 40d). Besides, a fragment of the sparsely tuberculated pentactine ( Fig. 10A View Fig ) can be attributed to rossellids as well. It resembles especially the hypodermal pentactines of Crateromorpha (Neopsacas) Tabachnick, 2002b (see Menshenina et al. 2007: figs. 2k, 7h; as well as Tabachnick 2002b: fig. 18e).
In turn, the hexactine with a rough, weakly tuberous surface, slightly bent rays, and one ray fusing with a fragment of another spicule ( Fig. 10K View Fig ) seems to be a part of dictyonal framework of hexasterophorid sponges (see Reiswig 2002b: figs. 2b, 3c; 2002c: fig. 2b–d; Reiswig and Wheeler 2002: fig. 8B).
Some anchorate basalia ( Fig. 10J View Fig ) may belong to pheronematid sponges (compare Lévi and Lévi 1989: fig. 2).
Some pentactines ( Figs. 8B View Fig , 10B View Fig ) and stauractines ( Fig. 10M View Fig ) resemble dermalia of Symplectella Dendy, 1924 ( Lyssacinosida , Euplectellidae ) (see Tabachnick 2002a: fig. 27f–h).
The oxyhexactines ( Figs. 8C View Fig , 10L View Fig ) show some affinity to choanosomal spicules of Hyalonema Gray, 1832 ( Amphidiscosida , Hyalonematidae ) (see Tabachnick and Menshenina 2002a: fig. 1l). Amongst the spicules of unquestionable hexactinellid affinity are also those illustrated on Figs. 8B, D, E View Fig , 10K View Fig , but their more accurate attribution is impossible.
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