Manumia japonica Legrand, Pons, Nishida & Yamada 2011, n. sp.

Manumia japonica Legrand, Pons, Nishida & Yamada n. sp. (Fig. 6 A-F, I, J) Manumia sp. A, Legrand, Palynologie des dépôts Jurassique supérieur et Crétacé inférieur du Japon, et provinces paléofloristiques du sud-est asiatique: 138, 139, pl. III, figs 8-10 (2009). TYPE MATERIAL. — Site II, horizon 2, slides b, g; slide SEM-b; holotype (II2 g-O68; Fig. 6C, F), paratypes (SEM-II2 b, SEM-II2 b, II2b-N21/4, II2c-K 65g; Fig. 6A, B, D, E, I, J). Collection de Paléobotanique - UPMC, Paris, France. ETYMOLOGY. — The species name is after Japan, where the Choshi Group is located. OCCURRENCE. — Ashikajima and Kimigahama Fm. TYPE LOCALITY. — Hatoyama, SE Choshi Peninsula, Chiba Prefecture, Japan. STRATIGRAPHIC HORIZON. — Ashikajima Fm (Barremian). DIAGNOSIS Trilete microspore. Amb rounded triangular. The laesurae are straight and extend to the 3/4 of the spore radius. They are bordered by raised lips with irregular margins (3 to 7 µm wide) that can be continuous in the apices areas. The ornamentation of the exine is scabrate to granulate, with isolated verrucae (3-7 µm in diameter) irregularly distributed along the laesurae of the proximal face, wider (3-7 µm) in the interradial areas. At the equator, some circular or elongated verrucae are randomly distributed near the angles or between the laesurae. On the distal face, verrucae are more or less densely distributed. The exine is thick (about 2-3 µm). Equatorial diameter = 50-55 µm. REMARKS A wide range is noted in the ornamentation of this new species. The laesurae can extend to the 3/4 of the spore radius or nearly to the equator. On the proximal face of the largest specimens (Fig. 6A, D), verrucae can sometimes be coalescent in the interradial areas to form ridges parallel to the equator. At the equator also, the elongated verrucae can gather to form an equatorial thickening (Fig. 6D, I). On the distal face, depending of the specimen, verrucae or tubercules can be isolated (Fig. 6F) or more or less densely distributed and coalescent (Fig. 6B, J). The equatorial diameter ranges from 40 to 55 µm. The genus Manumia is generally characterized by strong equatorial thickenings and/or coarse tubercules more or less fused into ridges. The faces are unequal, with different ornamentations. Four species have been defined for the genus Manumia: M. delcourtii (Pocock, 1970) Dybkjaer, 1991, M. irregularis Pocock, 1970, M. variverrucata (Couper, 1958) Hoelstad, 1985, and M. verrucata Pocock, 1970. The Japanese species can be distinguished from the other species of the genus by the shape and distribution of its verrucae. Concerning M. variverrucata, Hoelstad (1985) defined it on the basis of an emendation and new combination of Concavisporites variverrucatus Couper, 1958. However, as the diagnosis made by Couper (1958) does not fit that made by Pocock (1970) for the genus Manumia, particularly about the ornamentation, we can suggest that the definition of a new species would have been more suitable than the new combination proposed by Hoelstad (1985). This spore genus was previously reported from the Jurassic of Canada (Pocock 1970), Greenland (Lund & Pedersen 1984; Koppelhus & Hansen 2003), Alaska (Bjaerke 1993), and northern Europe (Couper 1958; Schulz 1967; Guy 1971; Herngreen & de Boer 1974; Hoelstad 1985; Dybkjaer 1991; Koppelhus 1992; Seidenkrantz et al. 1993; Koppelhus & Nielsen 1994; Koppelhus & Dam 2003; BØe et al. 2005; Lindström & Erlström 2007; Stefanowicz 2008), and the Lower Cretaceous of Norway (BØe et al. 2005). It was also reported from the Lower to Middle Jurassic of Afghanistan (Schweitzer et al. 1987). It seems to characterize the South Laurasian Province of Brenner (1976). Legrand (2009: 139, pl. III, fig. 11) distinguished a second form, morphologically similar but smaller (30-35 µm) and with a thinner exine, that could correspond to a variation of M. japonica. BOTANICAL AFFINITIES Even if the ornamentation suggests an affinity with the present Polypodiales (Pteridaceae), particularly Pteris Linnaeus or Pityrogramma Link figured by Tryon & Lugardon (1991), the absence of any cingulum should distinguish them.

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.