Marine benthic diatoms of Guam: new records, Dictyoneis apapae sp. nov., and updates to the checklist Author Lobban, Christopher S. Division of Natural Sciences, University of Guam, Mangilao, GU 96923, USA clobban @ triton. uog. edu clobban@triton.uog.edu Author Witkowski, Andrzej University of Szczecin, Institute of Marine and Environmental Sciences Mickiewicza 16 a, PL 70 - 383 Szczecin, Poland text Micronesica 2023 2024-06-06 2023 2 1 75 journal article 299061 10.5281/zenodo.12118784 2b921c3c-8618-439e-96da-1de9c66a90f9 0026-279X 12118784 Serratifera andersonii Chunlian Li, Dąbek & Wachnika Figs 94, 95 Ref. illus.: C. Li et al. 2018 , p. 63, figs 360–373 Sample: GU26A Dimensions: Length 5.5–9.2 µm, width 2.3 µm, striae 15 in 10 µm Diagnostics: Small, clavate (heteropolar), with a clear pore field at one pole, simple, stick-like spines arising from areolae, whereas in S. rhombica there are “accessory” spines flanking the larger central spines (C. Li et al. 2018 ). Comments: Many small Fragilariaceae have been studied recently, incorporating much debate on generic boundaries. Serratifera Ashworth, Chunlian Li & Witkowski (in C. Li et al. 2016 ) was established largely on molecular grounds and emended on morphological grounds by the same authors (in C. Li et al. 2018 ). Morales et al. (2019: 274) argued against the new genus and for inclusion of its species in the older genus Pseudostaurosira D.M.Williams & Round. Witkowski did not accept the argument (personal communication during ms. preparation), so we have presented this and the next species under their original names. Morales et al. transferred them to Pseudostaurosira andersonii (S.Sato, Chunlian Li & Witkowski) E.A.Morales, Novais & C.E.Wetzel , and P. rhombica (S.Sato, Chunlian Li & Witkowski) E.A.Morales, Novais & C.E.Wetzel , respectively. The senior author cannot contribute to this debate. All small Fragillariaceae are rare in our Guam samples to date, probably because the frustules are washing in from their primary habitats (mostly sediments and biofilms).