(2892) Dennstaedtia Bernh. in J. Bot. (Schrader) 1800(2): 124. Oct–Dec 1801, nom. cons. prop. Typus: D. dissecta (Sw.) T. Moore (Dicksonia dissecta Sw.), typ. cons. prop. Dennstaedtia Bernh. and Microlepia C. Presl are two sub-cosmopolitan genera belonging to the bracken fern family, Dennstaedtiaceae. As currently circumscribed, they are the second- and third-richest genera in the family, with respective estimates of 70 and 60 species (Yan & al. in Wu & al., Fl. China 2–3: 147–168. 2013; PPG I in J. Syst. Evol. 54: 563–603. 2016). The circumscription of these genera has remained stable since the middle of the 19th century (Moore, Index Fil.: xcii–xcvii, cxlvii–cxlviii. 1859; Christensen in Verdoorn, Man. Pteridol.: 522–550. 1938; Copeland, Gen. Fil.: 50–51. 1947; Holttum in Biol. Rev. (London) 24: 267–269. 1949; Alston in Taxon 5: 23–25. 1956; Nayar in Taxon 19: 229–236. 1970; Tryon & Tryon, Ferns Allied Pl.: 377–383. 1982; Kramer in Kubitzki, Fam. Gen. Vasc. Pl. 1: 81–94. 1990), and they have been largely accounted for in floras worldwide (Mickel & Smith, Pterid. Mexico: 245–248. 2004; Roux in Strelitzia 23: 111–112. 2009; Schwartsburd in Forzza & al., Cat. Pl. Fungi Bras. 1: 530. 2010; Yan & al., l.c.; Murillo-P. & al. in Bernal & al., Cat. Pl. Liq. Colombia: 469–470. 2016; Cámara-Leret & al. in Nature 584: 579–583, suppl. 1. 2020). They are morphologically close, and their delimitation and differentiation have traditionally relied on the sorus shape and position: Dennstaedtia had marginal sori protected by the inner and outer indusia fused into a specialized purse- or cup-shaped structure; whereas Microlepia had abaxial sori protected only by the modified inner indusium (Tryon & Tryon, l.c. 1982; Kramer, l.c.). When Tryon & Tryon (in Taxon 29: 512–513. 1980) added spore morphology to differentiate these two genera, they realized that the original type of Dennstaedtia (D. flaccida (Forst.) Bernh.) had delicately tuberculate spores, similar to Microlepia spp., whereas the remaining Dennstaedtia species had verrucate-tuberculate, reticulate, or ridged spores. Tryon & Tryon (l.c. 1980) believed the spore ornamentation to be more taxonomically reliable than sorus shape and position, and they predicted considerable nomenclatural change among these two genera, with: (1) the synonymization of Microlepia under Dennstaedtia; (2) all Microlepia species combined into Dennstaedtia; and (3) most Dennstaedtia species combined into Sitobolium Desv., except for D. flaccida. Tryon & Tryon (l.c. 1980) estimated that these changes would require about 90 new combinations – at that time, the estimates of Dennstaedtia and Microlepia were about 45 species each. In order to maintain nomenclatural stability, Tryon & Tryon (l.c. 1980) presented what today seems like an unusual conservation proposal (although still permitted – Art. 14.9(b)) but which was necessary at the time as only after 1981 did the Code provide for conservation with a different type that might not have been included in the protologue. In this, they proposed to alter the original place of publication of Dennstaedtia and hence its authorship and type from Dennstaedtia Bernh. (in Schrader, l.c.; type: D. flaccida), to Dennstaedtia T. Moore (l.c.; type: D. cicutaria (Sw.) T. Moore), since, in their view, the “modern” circumscription of Dennstaedtia was initiated by Moore (l.c.). Acceptance of their proposal would have meant that both Dennstaedtia and Microlepia would retain their circumscriptions in use (i.e., from the 1850s to 1980s) and 90 name changes would be avoided. Tryon & Tryon's (l.c. 1980) proposal was, however, rejected by the Nomenclature Committee for Pteridophyta (Voss in Taxon 31: 314–315. 1982): Holttum argued that their prediction was taxonomically premature, and Pichi-Sermolli argued that Moore (l.c.) never intended to describe a new genus Dennstaedtia – he was adopting Bernhardi's genus and expanding upon it. Even with the rejection by the Committee, Tryon & Tryon (l.c. 1982), in their comprehensive monograph of Neotropical pteridophytes, pursued this idea, and cited Dennstaedtia as authored by Moore and with D. cicutaria as type. With the advent of molecular phylogenetics, Perrie & al. (in Austral. Syst. Bot. 28: 256–264. 2015), Schneider & al. (in Perspect. Pl. Ecol. Evol. Syst. 18: 70–78. 2016), Shang & al. (in Molec. Phylogen. Evol. 127: 449–458. 2018), Schwartsburd & al. (in Molec. Phylogen. Evol. 150: 106881. 2020), and Wang & al. (in Taxonomy 1: 256–265. 2021) demonstrated the paraphyly (or polyphyly) of Dennstaedtia, with Microlepia and small segregates (Leptolepia Prantl, Oenotrichia Copel.) nested within it. These papers also proposed that sorus position in Dennstaedtiaceae is a homoplastic character, evolving from marginal to abaxial (sub-marginal for the authors) at least five times in the family, and reversing again to marginal at least two times (Schwartsburd & al., l.c.: fig. 5C; Wang & al., l.c.). Some taxonomic solutions have been suggested (e.g., Schneider & al., l.c.; Schwartsburd & al., l.c.), but these were made without a clear understanding of the phylogenetic position of Dennstaedtia flaccida, which has only recently been included in a phylogenetic analysis (Triana-Moreno & al. [the same authors of this proposal], submitted to Taxon). We now confirm the inference by Tryon & Tryon (l.c. 1980) of D. flaccida, the current type of Dennstaedtia, as nested within Microlepia spp. (37 species in our sampling, but probably representing ca. 60 spp.). Three other major clades are formed: one with five north-temperate species currently classified in Dennstaedtia (with alternative names in Sitobolium and Coptidipteris Nakai & Momose); another clade with only two Neotropical species, currently classified in Dennstaedtia (with no other generic name available); and another, a more distant clade, representing the main core of “Dennstaedtia”, with 26 pantropical species in our sampling (but probably representing ca. 50–60 spp.), currently classified in Dennstaedtia (along with Leptolepia and Oenotrichia, with one species each), with alternative names in Patania. In order to reach a natural, monophyletic classification, nomenclatural changes will be necessary. One solution is to merge these four clades into Dennstaedtia s.l., synonymizing all those generic names, including Microlepia. In doing so, the ca. 60 species of Microlepia will need to be combined into Dennstaedtia, and the circumscription of Dennstaedtia will be expanded to comprise a large and morphologically diverse clade. A second solution is to merge the three first mentioned clades in Dennstaedtia s. medio and classify the other one as Patania (which has been the main core of Dennstaedtia sensu 1850s until 2020s). This solution will also require that the ca. 60 species of Microlepia be combined into Dennstaedtia, and the circumscription of Dennstaedtia altered significantly, to a broader and unfamiliar concept, and that the majority of Dennstaedtia, as currently recognized, be transferred to the unfamiliar Patania. There seems to be little value in this solution; concepts are changed but the resulting genera are not necessarily more useful. The third solution is to consider the four clades as four distinct genera. This solution is the best in our judgment, since the resulting genera are morphologically distinct and geographically coherent (Triana-Moreno, l.c.). In doing so, following priority of names and type placement in the phylogeny, Dennstaedtia as we know it would drastically change its circumscription, keeping its current type and those ca. 60 species of Microlepia; ca. 5–10 north-temperate species will become (or return to) Sitobolium; a new genus will be described to accommodate two Neotropical species; and the ca. 50–60 pantropical species of “Dennstaedtia” will become (or return to) Patania. “Microlepia” and “Dennstaedtia” in the traditional sense (1850s to 2020s) will drastically change their circumscription, and at least 100 combinations are needed. Therefore, in order to reduce the number of new combinations associated with this option, we propose the conservation of Dennstaedtia with D. dissecta (Sw.) T. Moore (Index Fil.: 305. 1861) (≡ Dicksonia dissecta Sw. in J. Bot. (Schrader) 1800(2): 91. 1801) – a core member of the clade as currently circumscribed – as conserved type. In doing so, the circumscription of both Dennstaedtia and Microlepia will be largely maintained (the latter altered by the inclusion D. flaccida and D. smithii (Hook.) T. Moore): the other 70 species of Dennstaedtia and the 60 species of Microlepia will retain their name. As complementary information to support this proposal, we should mention that Microlepia is already in the process of becoming a conserved name. Schwartsburd (in Taxon 66: 216. 2017) uncovered that Scyphofilix Thouars (Gen. Nov. Madagasc.: 1. 1806), has priority over Microlepia and proposed conservation of the latter against Scyphofilix in order to prevent 60 name changes. This conservation was recommended for approval by the Nomenclature Committee for Vascular Plants (Applequist in Taxon 68: 850. 2019), a recommendation confirmed by the General Committee (Wilson in Taxon 71: 217. 2022). Thus, retention of Microlepia (1836) against the much older name Scyphofilix (1806) is already authorized (Art, 14.15 of the ICN; Turland & al. in Regnum Veg. 159. 2018). In summary, acceptance of this modern equivalent of Tryon & Tryon's (l.c. 1980) unsuccessful conservation proposal, will ensure continued application of Dennstaedtia and Microlepia to the vast majority of species traditionally assigned to those genera. LATM, https://orcid.org/0000-0002-5344-0697 PBS, https://orcid.org/0000-0002-5305-9300 AY, https://orcid.org/0000-0002-4508-2148 NTLP, https://orcid.org/0000-0002-3145-8183 LYK, https://orcid.org/0000-0002-3388-3757 CR, https://orcid.org/0000-0002-6605-1770 MS, https://orcid.org/0000-0003-1568-150X We thank John McNeill (E) and Jefferson Prado (SP) for their thoughtful help in the development of this manuscript. LATM was partially supported by a grant from Universidad Nacional de Colombia (HERMES-40890). NTLP thanks FAPEMIG (for the Doctoral grant) and IAPT (research grant 2020).