Croton claussenianus Baillon 1864
Creators: name: Rossine, Yuri
name: Melo, André Laurênio De
name: Athiê-Souza, Sarah Maria
name: Sales, Margareth Ferreira De
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malpighiales
Euphorbiaceae
Croton
Croton claussenianus

description: 3. Croton claussenianus Baillon (1864: 291).
— Oxydectes clausseniana (Baillon) Kuntze (1891: 611).
Lectotype (designated by Rossine et al. 2020b):— BRAZIL. Minas Gerais, without further locality, 1841, P.C.D. Claussen 1574 (P [P00623106!]; isolectotypes: P [P00623108!, P00623107!], A [A00257907!], NY [NY0046528!]). Fig. 4 (k–o), 6 (a)
Croton pentandrus M ̧ller Argoviensis (1865: 97). Holotype:— BRAZIL. Minas Gerais: without further locality, 1840, P.C. D. Claussen s.n. (G [G00311205!]).
Description: —Monoecious shrub, 1–2 m tall; latex not seen; monopodial branching, branches cylindrical, brown to ferruginous; trichomes dentate-lepidote to lepidote. Leaves alternate; stipules narrowly lanceolate or 3-lobed, 0.3–0.5 × 0.1–0.2 cm, usually persistent, with stellate-lepidote trichomes; petiole cylindrical, 0.4–1 cm long, with lepidote trichomes; leaf blade chartaceous, elliptic to oval, 3–6.5 × 1.5–3 cm, strongly bifacial, adaxial face green to dark green with simple trichomes 2–5-radiate and dentate-lepidote, abaxial surface shiny, silver to ferruginous with dentatelepidote trichomes, base rounded to obtuse, margins entire, apex acute to rounded, venation brochidodromous, with 6–9 secondary veins. Thyrse 4–8 cm long, terminal or axillary, trichomes dentate-lepidote to lepidote, peduncle ca. 1 cm long; cymules unisexual, congested, reduced to solitary flowers; bracts persistent, 3-lobed, with two smaller and inconspicuous lateral lobes, 2–2.2 × 0.5 mm, margins entire, apex acute, trichomes stellate-lepidote to dentatelepidote. Staminate flower with pedicel ca. 1 mm long; sepals silver to ferruginous, united for ⅓ of their length, lobes triangular to ovate, 1–1.3 × 1 mm, margins entire, apex acute, trichomes stellate-lepidote externally, simple internally; petals white, oblong, ca. 1 × 0.4 mm, margins entire, apex rounded, trichomes simple; stamens 5–6, filament up to 1.3 mm long, anther elliptic, ca. 0.5 × 0.3 mm; nectary disk of 5 free segments, ovate, glabrous. Pistillate flower with pedicel up to 2 mm long; sepals silver to ferruginous, free, oboval, slightly unequal in size, 3–5.5 × 1.3–3 mm, reduplicated vertically, margins entire, apex rounded to acute, with lepidote trichomes externally, glabrous internally; petals white to yellowish, transformed into filiform glands, ca. 0.8 mm long, margins entire, apex rounded, glabrous; ovary spheroid, 2.5–2.8 mm diam., trichomes lepidote; styles ascending, free, 2-partite, 6 stigmatic tips, trichomes lepidote; nectary disk 5-lobed, apex of lobes rounded, glabrous. Capsule yellow to orangish, spheroid, 4–4.5 mm diam., not lobed, surface non-muricate, trichomes dentate-lepidote to lepidote; columella ca. 3 mm long, striated, apex flattened. Seed brown, ellipsoid, ca. 4.0 × 2.8 mm, rugose, caruncle reniform.
Vernacular names:— not found.
Distribution and habitat, conservation status, and phenology: — Croton claussenianus is a rupicolous species, restricted to the Cerrado (Rossine et al. 2020b), and found only in the municipalities of Pedro Leopoldo and Matozinhos, Minas Gerais (Fig. 6, a). It is found growing on limestone outcrops (Rossine et al. 2020b). This species is classified here as endangered (EN), based on its restricted EOO (2,085 km 2) and AOO (12 km 2), applying in the criteria B1, B2a, B2c (ii, iii) (IUCN 2022). Only two recent collected specimens were found during this study, and none individual were found during our field expeditions. Flowering and fruiting in January and February.
Notes: — Croton claussenianus can be confused with C. tricolor by the general appearance of its leaves and branches, but they can be easily distinguished, as discussed by Rossine et al. (2020b). C. claussenianus is also morphologically close to C. suassunae, sharing strongly bifacial leaves, a silvery to ferruginous indumentum, axillary inflorescences, capsule spheroid, and styles with 6 stigmatic tips. C. claussenianus, however, can be distinguished from C. suassunae by having simple to radiate or dentate-lepidote trichomes on the adaxial leaf surface (vs. trichomes stellate to stellate-lepidote in C. suassunae), brochidodromous venation (vs. eucamptodromous), 5–6 stamens (vs. 10–15), nectary disk with 5 free segments in the staminate flower (vs. 5-lobed), sepals of the pistillate flower oboval and slightly unequal in size (vs. spatulate and equal), yellow to orangish capsule (vs. silver to ferruginous), and seeds with a rugose surface, with a reniform caruncle (vs. smooth surface with an elliptic caruncle).
Representative specimens: — BRAZIL. Minas Gerais: Pedro Leopoldo, Lapa do Baú, 19º32’53” S, 43º59’20” W, 12 February 2015, N. C. Moreira et al. 177 (BHCB, HEPH); ibid, Matozinhos, Haras Veredas, proximidades do povoado S „ o Bento. Morro com afloramentos de calcário em paredıes, grandes fendas e campos de lapiás, 19º43’05” S, 44º03’52” W, 20 January 2017, P. H. A. Melo et al. 6026 (HUEFS).
description: Published as part of Rossine, Yuri, Melo, André Laurênio De, Athiê-Souza, Sarah Maria & Sales, Margareth Ferreira De, 2023, Understanding the " Marmeleiros ": a taxonomic treatment of Croton sect. Lasiogyne (Euphorbiaceae) in Brazil, pp. 219-250 in Phytotaxa 584 (4) on pages 232-233, DOI: 10.11646/phytotaxa.584.4.1, http://zenodo.org/record/7663429