Onosma L. (Boraginaceae tribe Lithospermeae) is a genus comprising about 240 species (He et al., 2020) mainly distributed in xeric habitats. The main centers of diversity are the Irano-Turanian and Mediterranean regions, especially Iran and Turkey (Meusel et al., 1978; Mehrabian et al., 2013; Cecchi et al., 2016). Systematics is complex because species show wide variability (Kolarčik et al., 2010), creating challenges to their identification (Ball, 1972; Mehrabian et al., 2014, Mehrabian, 2015). De Candolle (1846) provided the first classification of Onosma based on calyx characteristics which led to two sections: Onosma. sect. (Eu)Onosma DC. and Onosma. sect. Aponosma DC. Later, Schur (1866) as well as Borbás (1877) emphasized the importance of trichomes. Boissier (1875) also divided the genus into the three groups based on the trichome characteristics of leaves: Haplotricha Boiss. in Boissier (1875: 179), Heterotricha Boiss. in Boissier (1875: 180) [described as Diplotrichae in Borbás (1877: 418)], and Asterotricha Boiss. Stroth (1939) considered Boissier’s groups as subsections. Recently, Peruzzi & Passalacqua (2008) referred to them as natural groups. Nevertheless, Cecchi et al. (2011), Cohen (2011), Chacón et al. (2016) and Weigend et al. (2016), believed that they are integrative sections and representatives of the Echium-clade (Cecchi et al., 2016). Recent molecular studies have not confirmed their monophyly (Kolarčik et al., 2010; Cecchi et al., 2011). Several systematic studies have been done on Onosma L., including morphological and micro-morphological (Bigazzi & Selvi, 2000; Akçin & Engin, 2001, 2005; Akçin, 2007a , b ; Peruzzi & Passalacqua, 2008; Teppner, 2008; Akçin, 2009; Binzet & Akçin, 2009; Akçin & Binzet, 2011; Akçin et al., 2013; Martonfi et al., 2014; Mehrabian et al., 2014), karyological (Teppner, 1972, 1991, 1996, 2008, 2011, 2012; Vouillamoz, 2001; Martonfi & Kolarčik, 2008), palynological (Qureshi & Qaiser, 1987; Zemskova & Popov, 1991; Binzet & Orcan, 2003; Maggi et al., 2008; Binzet et al., 2010; Binzet, 2011; Kolarčik et al., 2015), phytogeographical and ecological (Kolačik & Martonfi, 2006), and molecular (Vouillamoz, 2001; Mengoni et al., 2006; Cecchi & Selvi, 2009; Weigend et al., 2009, 2013, 2016; Kolarčik et al., 2010, 2014; Cohen, 2011; Chen & Zhang, 2019; Nasrollahi et al., 2019, 2020) studies. Riedl (1967) pioneered the research on Onosma L. from the Iranian Plateau and described 59 species from the three sections including Onosma L., Podonosma (Boiss.) Gürke. and Protonosma Popov. Afterward, Khatamsaz (2002) provided taxonomic notes on the Flora of Iran with a similar classification to that of Riedl. Several other studies on Onosma L., including systematic (Mehrabian et al., 2011a , b ; Sheidai et al., 2015; Sayadi et al., 2017), palynological (Mehrabian et al., 2012), micro-morphological (Azizian et al., 2000; Arab Ameri et al., 2014; Mehrabian et al., 2014), ecological and geobotanical research (Mehrabian, 2015; Moradi et al., 2019; Khajoei Nasab et al., 2020a ; Naghizadeh et al., 2020) as well as the identification of new species (Mehrabian et al., 2013; Mehrabian & Amini Rad, 2018; Mehrabian & Mozaffarian, 2018), have been done by the Onosma studies team at Shahid Beheshti University as well Research Institute of Forests and Rangelands of Iran. During field excursions in the northwestern and northern geomorphologic zones of Iran and herbarium assessments, some unidentified species of Onosma were collected and evaluated through the examination of their valuable taxonomic traits and comparisons with similar species.

The current study aimed to evaluate the most important diagnostic characteristics of unidentified species compared to their related species, justify them as new species, and provide taxonomic as well as ecological descriptions of the new taxa.

During field studies in various regions of the country, some unknown samples were collected. They were also collected by the authors during their scientific excursions in the Azerbaijan, Ilam and Alborz provinces. The new taxa were compared with fundamental diagnostic keys, including Boissier (1875), Flora of USSR (Popov, 1953), Johnston (1954), Post (1966), Riedl (1967), Polunin (1969), Ball (1972), Riedl (1979) Nasir & Ali (1979), and Khatamsaz (2002). Additionally, the results of several studies on the newly introduced species of Onosma (Mehrabian & Mozaffarian, 2018, Mehrabian et al., 2022) were assessed and compared with the new taxa. More than 2800 herbarium accessions of Onosma, were examined, including type specimens and image types, in several European herbaria (W!, WU!, LE, BG!, JE!, C!, B!, G!, and K) and Iranian herbaria (HSBU, TARI, IRAN) (acronyms follow Thiers, 2019) to reinforce the taxonomic reasons for introducing the mentioned new species (Appendix). Furthermore, morphological characters including trichome type (cauline and basal leaves and nectary ring), shape and size of the calyx, shape and size of the corolla, nutlet morphology, anther length and connection as well as their exertion and the type and size of pollen grains were studied and compared with closely related species.

Holotypes and isotypes were deposited and preserved in the Herbarium of Shahid Beheshti University (HSBU) as well Herbarium of Research Institute of Forests and Rangelands of Iran (TARI) with the collector and acronyms of herbariums in parentheses, according to Index Herbariorum (Thiers, 2019). In addition, the author’s names are included in accordance with IPNI.

The upper and lower surfaces of basal and cauline dried leaves as well as pollen grains were mounted on stubs using double-sided adhesive tape and coated with gold by a DC magnetron sputtering desktop machine. Afterward, the samples were photographed by a scanning electron microscope (Cam Scan Hitachi SU3500). In addition, 15–30 pollen grains were assessed through analysis, and mature dried nutlets were photographed by a dinolite microscope. The morphological terminology follows that of Riedl (1967), Harris & Harris (2001), Simpson (2006), Punt et al. (2007), Halbritter et al. (2008), and Hesse et al. (2009). Lastly, morphological and micro-morphological evidence was provided to compare new introduced taxa with other asterotrichous and heterotrichous species of Onosma (Tables 1 and 2). A synoptic key to nearest taxa to new taxa was provided for decision making (Appendix).

Iran and particularly a segment of the prominent natural plateau of Iran featuring several mountainous barriers (Zagros, Alborz, Kopet Dagh, and Makran mountain ranges) and scattered internal mountains is considered one of the main centers of diversity and endemism for angiosperms in the world (Hedge & Wendelbo, 1978; Jalili & Jamzad, 1999) because of the area’s variability in paleo-biogeographical events (Takhtajan, 1986) and climatic and geomorphologic heterogeneity (Khalili, 2005; Stöklin, 1968).

The Zagros as well as the northwest geomorphologic unit of Iran are reported to be the main centers of diversity and endemism for Onosma in Iran (Mehrabian, 2015; Moradi, 2017; Naghizadeh, 2017; Khajoei Nasab et al., 2020a ). Accordingly, the mentioned zones were evaluated by our team through several field studies, which led to the discovery and identification of numerous new species of Onosma (Mehrabian et al., 2013; Mehrabian & Amini Rad, 2018; Mehrabian & Mozaffarian, 2018, Mehrabian et al., 2022). Moreover, this area is one of the main targets for scientific field work in the region, leading to the collection and determination of unknown species. Accordingly, a comprehensive literature review and the evaluation of numerous Iranian and European herbaria led to the identification of these novelties. Our argument for these novelties is based on the prominent divergence in the most important morphological characteristics (e.g. trichome type, shape and size of the calyx, shape and size of cauline and basal leaves, annulus hairs, shape and size of the corolla, anther length, and connection as well as their exertion, nutlet morphology, and pollen type and size) compared with their closest allied species that were highlighted by literature (Boissier, 1875; Popov, 1953; Johnston, 1954; Riedl, 1967; Polunin, 1969; Ball, 1972; Nasir & Ali, 1979; Post, 1986; Khatamsaz, 2002; Mehrabian et al., 2013; Sayadi et al., 2017; Mehrabian & Amini Rad, 2018; Mehrabian & Mozaffarian, 2018). In addition, these new species have been confirmed by the noticeable geobotanical divergence emphasized in recent studies (Cecchi et al., 2011; Mehrabian, 2015; Moradi, 2017; Nikjouyan, 2018; Nemati, 2019; Naghizadeh et al., 2020). Thus, the new species represent a significant differentiation compared with the species last introduced from the area under study as well as neighboring regions and improve our arguments that these unknown specimens can be considered as new species.

Onosma madjnoniani Mehrabian & Naghizadeh, sp. nov. (Fig. 1)

Type: Iran. Eastern Azerbaijan province: Oscoo, Kord Abad to Gonbarf Village, 2200 m a.s.l., 37º 43’ 13” N, 46º 12’ 40” E, 28 May 2017, Naghizadeh 2018658 (Holotype: HSBU).

Diagnosis: Onosma madjnoniani is closest to O. armena DC. Nevertheless, it is distinguished by its rosette leaf size, lanceolate to lanceolate-linear leaves, short and sparse dense rays, and shorter calyx and bracts. In addition, it is similar to O. rascheyana Boiss., but O. madjnoniani is differentiated by its lanceolate to lanceolate-linear leaves, long rosettes, long bracts, short and sparse trichomes, and sparse hairs. Additionally, it is similar to O. kurdica Teppner, a restricted endemic species found in western Iran; however, it differs from O. kurdica in having lanceolate to lanceolate-linear cauline leaves, long basal leaves, short pedicels, nearly dense tuberculate rays, and sub-dense hairs. Moreover, it is apparently close to O. moussavi Mehrabian & Amini Rad, a restricted endemic species found in western Iran, but distinguished by long rosettes, lanceolate to lanceolate-linear rosette and cauline leaves, short and sub-dense tubercles of setae, nearly dense hairs and longer corolla, bracts, and calyx (Table 1).

Description: Perennial, with woody rootstock. Stems branched at the base, partly diffuse, flowering stems up to 20(25) cm tall. Indumentum asterotrichous (Fig. 2 A–L). Rosette leaves lanceolate to lanceolate-linear, 90–140(150) × 4–9 mm, attenuate at the base into a short petiole, obtuse to acute at apex, involute, covered by nearly dense monomorphic hairs, each consisting of an antrorsely appressed central seta, 1.2–1.8 mm long inserted on a multicellular tubercle with 8–10 asterosetulae, ca. 5–6 times shorter than the central seta. Basal leaves similar to rosette leaves, 25–45 × 4–7 mm. Cauline leaves sessile, lanceolate to lanceolate-linear, 25–90 × 5–9(10) mm, tapering into a short petiole, obtuse to acute at apex involute, setae similar to rosette leaves. Inflorescence simple to bifurcate, with 2–3 apical cymes, each cyme up to 8(9) flowers, pedicel ca. 1.5 mm long; bracts lanceolate, 15–20(22) mm. Flowering calyx 16–18(19) mm long, divided to base in linear to oblanceolate lobes, covered with short hairs mixed to yellowish setae, sparse near the margins and along the central vein, dense at the base and on the pedicel. Corolla clavate, up to 25 mm long and 1 mm wide, puberulent outside. Stamens included, inserted at the upper 3/4 of the corolla tube, anthers connate at the base, ca. 8 mm, apically bifid. Style protruding outside the corolla limb, up to 29 mm. Stigma bilobed. Nutlet not seen.

Pollen: Heteropolar, tricolporate, prolate, polar axis 13.8–16.8 µm, mean: 14.3µm, equatorial axis 11.1–12.8 µm, mean: 11.8µm, exine granulate 0.15–0.28 µm wide (Fig. 2 M–P).

Phenology: These plants flower from May to June and fruit from June to July.

Etymology: This plant was named in honor of Professor Henric Madjnonian, a pioneering, outstanding as well famous environmental conservationist of Iran, who has made extensive efforts and several scientific references to protecting Iran’s nature as well Protected areas.

Distribution and habitat: Onosma madjnoniani is a sub-alpine species confined to the NW geomorphologic unit of Iran in volcano-sedimentary rocks and brown soils (lithosols) as well as the Mediterranean xeric-continental (Mxc) global bioclimatic unit. Additionally, it is distributed in the steppes as cushion-shaped plant formations on the western slopes of the Sahand Mountains in the Irano-Armenian province of the Irano-Turanian region (Fig. 3).

Conservation status: The estimated area of occupancy is less than 5000 km². The number of mature individuals in the population is less than 20. The status of critically endangered (CR) is suggested based upon the IUCN criteria (Bland et al., 2017) because of its restricted distribution range and existing threatening issues in its habitats (e.g. over-grazing, land-use change, etc.).

Onosma riahii Mehrabian, sp. nov. (Fig. 4)

Type: Iran. Alborz, Taleghan, North of Taleghan Dam, 2140–2250 m a.s.l., 36º 11’ 23” N, 50º 39’ 12” E, 13 June 2018, Mehrabian 2018981 (Holotype: HSBU).

Diagnosis: Onosma riahii is similar to O. rascheyana but, it is characterized by linear to linear-lanceolate, cauline leaf size, dense hairs, longer calyx, and denser inflorescences. It is similar to O. armena, but, it is distinguished by its shorter rosette leaves, linear to linear-lanceolate leaves, oblong cauline leaves, sparse hairs, and longer calyx. Also similar to O. kurdica, it is nonetheless differentiated from it by its lanceolate-linear basal leaves, shorter cauline leaves, sparse hairs and pedicels, and long calyx. It is apparently also similar to O. moussavi, a restricted endemic species in northwestern Iran, but distinct in its rosette leaf size, linear to linear-lanceolate leaves, nearly dense hairs, and long corolla and pedicels (Table 1).

Description: Perennial, with woody rootstock and long narrow rhizomes. Stems partly erect, the flowering ones up to 35(40) cm, covered at the base with scaly remains of the pervious years shoots. Indumentum asteritericous (Fig. 5 A–L). Rosette leaves linear to linear-lanceolate, 30–40 × 2–3 mm, acute to acute-acuminate at apex, involute, tapering into a long petiole, hispid, white to yellowish white, upper surface coverd by dense as well monomorphic setae, each consisting of an antrorsely appressed, central setae 1.2–1.5 mm long, inserted on a multicellular tubercle with 10–12 asterosetulae, ca. 4–5 times shorter than the central seta. Basal leaves, sessile, other characters similar to rosette leaves. Cauline leaves linear-lnceolate, sessile, 50–90 × 4–4.5(5.5) mm. Inflorescence, bifurcate, 2–3 apical cymes, each cymes with 3–4 flowers, Pedicel ca. 2 mm long in fruit. Bracts linear-lanceolate, pubescent, 18–20(25) × 2–3 mm. Flowering and fruiting calyx divided to base, 15–17 mm long, linear lobes, covered with short yellow hairs very dense at the base and on the pedicel. Corolla tubular to clavate, yellow, with very reflexed lobes short, up to 24 mm long yellow, glabrous to puberulent outside. Nectary ring glabrous. Stamens excluded, inserted, connate at base, inserted upper 4/5 corolla tube, anthers up to 8 mm, apically bifid, Style protruding outside the corolla limb, up to 26 mm long. Stigma bilobed. Nutlets unknown.

Pollen: Heteropolar, tricolporate, prolate, polar axis 12.9–15.2 µm, mean: 13.8 µm, equatorial axis 8.5–10.8 µm, mean: 9.8 µm, exine granulate 0.14–0.26 µm wide (Fig. 5 M–P).

Phenology: This species flowers from May to June and fruits from June to July.

Etymology: The specific epithet is based on in honor of the eminent Phycologist-Mycologist Prof. Dr. Hossein Riahi in Iran, who has played a prominent role in improving our knowledge in this field in Iran.

Distribution and habitat: Onosma riahii is known only from the restricted zone in igneous formations in the lithosol (from igneous rocks), brown soils, and seirozome zone of Taleghan (Alborz). It is distributed in the Mediterranean xeric-continental (Mxc) global bioclimatic units of Iran (Fig. 3).

Conservation status: Onosma riahii is known only from the restricted zone on the southern slopes of the Western Alborz Mountains with an estimated area of occupancy less than 5000 km². Critically endangered status (CR) is proposed based on IUCN criteria (Bland et al., 2017).

Onosma pseudohebebulba Mozaffarian & Mehrabian, sp. nov. (Fig. 6)

Type: Iran. Charvar to Ivan, Tange Dalab 1374 m a.s.l., 33º 42’ 24” N, 46º 28’ 28” E, 5 May 2005, Mozaffarian 92841 (Holotype: TARI).

Diagnosis: Onosma pseudohebebulba is similar to O. hebebulba DC., found in western and northwestern Iran, though it is differentiated by its spathulate and shorter rosette leaves, shorter cauline leaves, and shorter pedicels and bracts. Onosma pseudohebebulba is similar to O. iranshahri Ghahr. & Attar, a restricted species endemic to western Iran. Regardless of its similarities, it differs in having shorter cauline leaves, sub-dense and sub-adpressed setae, shorter pedicels, and dense hairs. In addition, it is apparently close to O. bilabiata Boiss., a species endemic to western and northwestern Iran, yet distinguished by shorter rosette and cauline leaves, spathulate rosette leaves, thinner cauline leaves, sparse tubercle rays, shorter corolla, longer pedicels, and shorter anthers (Table 2).

Description: Caespitose perennial, with woody rootstock, creeping rhizome. Stems partly diffuse, branched at the base, covered at base with scaly remains of the previous year’s shoots and bearing sterile leaf rosettes, the flowering stems up to 25 cm tall. Indumentum asterotrichous (Fig. 7 A–L). Rosette leaves spathulate, involute, obtuse to acute at apex, hispid, white to yellowish, 30–80(85) × 8–10(12) mm, upper surface covered by very dense and monomorphic seta and hairs, nearly dense setose, each consisting of an antrorsely appressed, central seta, 1.5–2 mm long, inserted on a multicellular tubercle with 14–16 asterosetulae, ca. 4–5 times shorter than the central seta. Basal leaves spathulate, 12–25 × 4–5 mm, obtuse to acute at apex, seta similar to rosette leaves. Cauline leaves sessile, spathulate, 18–35(40) × 7–9(10) mm acute to obtuse at apex. Inflorescence capaitate, with 5–6 apical cymes, each cyme with 8–12 flowers, fruiting pedicel ca. 7 mm long. Bracts lanceolate to lanceolate-linear, 14–25 × 1–1.2 mm. Flowering Calyx divided near to base in oblanceolate lobes, 14–16(18) mm long, ca. 1 mm wide, Fruiting calyx 18–20(22) mm long, ca. 2.5 mm wide, covered by very dense seta and hairs. Corolla tubular, clavate to tubular-clavate, yellow, 17–19(20) mm long, yellow, densely puberulent outside., lobes ca. 1.5 mm long, ca. 1.5 mm wide; annulus glabrous. Stamens included, inserted at the upper two-thirds corolla tube anthers connate at base, 6–7 mm, apically bifid. Style little out of corolla, stigma bilobed. Nutlet ovoid, 3.5–4 × 2.5–3 mm long, beak to 1 mm long, navicular, green.

Phenology: This plant flowers from May to June and fruits from June to July.

Etymology: The name of this species relates to its similarity to O. hebebulba.

Distribution and habitat: Onosma pseudohebebulba is distributed in open oak forests with well fertilized soils (Fig. 3).

Conservation status: Onosma pseudohebebulba is known only from Chavar (the restricted zone of Ilam province) to Ilam city and Tang Dalab on the western slopes of the Southern Zagros Mountains. It has an estimated area of occupancy less than 5000 km². The status of critically endangered (CR) is proposed based on IUCN criteria (Bland et al., 2017).

Onosma bozghushica Mozaffarian & Mehrabian, sp. nov. (Fig. 8)

Type: Iran. Eastern Azerbaijan, Bozghoosh Mountains, Neshagh top Mountains 2560 m a.s.l. 37º 45’ 54” N, 47º 41’ 43” E, 24 June 2010, Mozaffarian 94598 (Holotype: TARI).

Diagnosis: O. bozghushica is similar to O. iranshahri, but differing in its longer rosette leaves, shorter cauline leaves, dense and adpressed setae, dense hairs, and long corolla and bracts. It is also apparently similar to O. bilabiata. Nevertheless, it differs by having shorter and spathulate rosette leaves, sub-dense tubercle rays, longer pedicels, and shorter bracts and calyx. Moreover, it is similar to O. hebebulba, although differing by having longer rosette leaves and spathulate leaves (Table 2).

Description: Caespitose perennial, with woody rootstock as well long rhizome. Stems diffuse, the flowering stems 22–25 (30) cm tall. Indumentum asterotrichous (Fig. 9 A–L). Rosette leaves spathulate, 40–75 (85) × 7–10 (12) mm, acute at apex, involute, attenuate at the base to a long petiole, hispid, upper surface covered by very dense, monomorphic seta and hairs, each consisting of an antrosely appresse, central seta 1.5–2 mm long, inserted on a multicellular tubercle with 16–20 asterosetulae, 5–6 times shorter than the central seta. Basal leaves similar to rosette leaves, 15–32 × 2–4 mm. Cauline leaves sessile, 30–35 × 4–7 mm, spathulate, acute to obtuse at apex, involute Inflorescence 2–3 apical cymes, each cymes with 12–15 (17) flowers, pubescent. Bracts widely lanceolate, leaf like, pubescent, 18–24 × 5–6 (7) mm. Pedicel ca. 7 mm long. Calyx divided to base in oblanceolate lobes, 16–18 (20) mm long, covered with short and dense hairs mainly at the base. Corolla tubular to campanulate, yellow, ca. 22 mm long, glabrous to puberulent outside, lobes ca. 1mm long, ca. 1 mm wide; annulus glabrous. Stamens a little out of corolla, inserted at the upper 3/4 of corolla tube, connate at the base, ca. 10 mm, apically bifid. Style little out of corolla Limb. Stigma bilobed. Nutlet not found.

Pollen: Heteropolar, tricolporate, prolate, polar axis 11.7–12.9 µm, mean: 12.1 µm, equatorial axis 10.7–11.2 µm, mean: 10.9 µm, exine granulate 0.09–0.29 µm wide (Fig. 9 M–O).

Phenology: This plant flowers from May to June and fruits from June to July.

Etymology: The specific epithet is based on the geographical origin of the species (Bozghoosh Mountain) a prominent mountain range in northwestern Iran.

Distribution and habitat: Onosma bozghushica is known only from restricted zones in igneous formations in the lithosol (from igneous rocks), brown soils, and seirozome zone of Azerbaijan, on the southern slopes of the Bozghoosh Mountains. It is distributed in Mediterranean xeric-continental (Mxc) global bioclimatic units (Fig. 3).

Conservation status: Onosma bozghushica is known only from the restricted zone of Bozghoosh Mountains, Neshagh top mountains (Eastern Azerbaijan province) with an estimated area of occupancy less than 5000 km². Due to the narrow distribution range of the species, a status of critically endangered (CR) is proposed based on the IUCN criteria (Bland et al., 2017).