Silutanispermum kvacekiorum, Friis & Crane & Pedersen, 2018

Friis, Else Marie, Crane, Peter R. & Pedersen, Kaj Raunsgaard, 2018, Extinct Taxa Of Exotestal Seeds Close To Austrobaileyales And Nymphaeales From The Early Cretaceous Of Portugal, Fossil Imprint 74 (1 - 2), pp. 135-158 : 151

Silutanispermum kvacekiorum gen. et sp. nov.

Text-figs 11–12

H o l o t y p e. Designated here, S170238 (Famalicão sample 025; illustrated here on Text-figs 11a, b, d, e , 12a, b ).

P l a n t F o s s i l N a m e s R e g i s t r y N u m b e r.

PFN000099 (for new species).

P a r a t y p e s. Designated here, S174352 (Famalicão sample 025).

R e p o s i t o r y. Palaeobotanical Collections , Department of Palaeobiology, the Swedish Museum of Natural History, Stockholm, Sweden .

E t y m o l o g y. In recognition of Zlatko and Jiří Kvaček for their many contributions to angiosperm palaeobotany.

T y p e l o c a l i t y. Famalicão , Portugal (39°42′16″N;

8°46′12″W).

T y p e s t r a t u m a n d a g e. Below the Figueira da Foz Formation; Early Cretaceous (late Aptian – early Albian or older).

D i a g n o s i s. As for the genus.

D i m e n s i o n s. Length of seeds: 1.6–2.0 mm; width of seeds: 1.2–1.9 mm.

D e s c r i p t i o n a n d r e m a r k s. The species is based on two isolated seeds that were studied using SRXTM (S170238, 174352). There is no information on the fruits in which the seeds were borne. The seeds are small, anatropous, bitegmic and exotestal with bilateral symmetry. They are elliptic in lateral view ( Text-fig. 11a–c ) and elliptical to circular in transverse section ( Text-fig. 12c, d ). The seed surface is smooth with a jigsaw puzzle-shaped pattern formed from the slightly raised undulate anticlinal walls of the exotesta cells.

The micropyle and hilum are very close together and slightly displaced towards the raphal side of the seed (Textfig. 11a–d). The hilum is rounded triangular in outline without a hilar rim ( Text-fig. 11d ). The course of the raphe is seen on the seed surface as a slightly raised ridge that is also distinctive in its transversely aligned cells. The micropyle is formed from the inner integument and is marked on the outside by a transverse, slightly undulate slit in the testa ( Text-figs 11d , 12b ). Internally the micropylar slit is lined by tall cells of the exotesta ( Text-fig. 12a, b ) and there is a tendency towards a Y-shaped branching internally.

The seed coat is composed of a thick exotesta, a thick mesotesta/endotesta, and a thin tegmen. The exotesta consists of a single layer of tall, columnar sclerenchyma cells that are about 65 µm tall over most of the seed (Textfig. 12a, c–e) but taper out in the micropylar region ( Text-fig. 12a ). The anticlinal walls of the exotestal cells are thickened, and of almost even thickness from the outside to the inside, resulting in an almost straight lumen ( Text-fig. 12c–e ). The anticlinal walls are strongly undulate towards the outside and the inside forming stellate-undulate facets and a jigsaw puzzle-like pattern with rounded, undivided lobes on the seed surface; except over the raphe where the cell walls are straight and the facets are polygonal. The mesotesta/ endotesta is as thick as the exotesta, about 65 µm over most of the seed, and consists of up to five layers of large rectangular, tangentially elongated parenchyma cells, (Textfig. 12c–e). The mesotesta/endotesta is thickest around the raphe and close to the hilar region it is up to about 180 µm thick ( Text-fig. 12c ). The tegmen is thin.

Nutritive tissue is well preserved in one of the specimens studied using SRXTM (S174352). It is cellular, consisting of isodiametric cells, about 55 µm in diameter, with thin, straight, cell walls ( Text-fig. 12d ).

Figures

Text-fig. 11. Silutanispermum kvacekiorum gen. et sp. nov. seeds from the Early Cretaceous Famalicão locality (sample 025), Portugal; Synchrotron radiation X-ray tomographic microscopy (SRXTM, volume renderings). a, b) Holotype (S170238), seed in oblique (a) and lateral (b) view showing large triangular hilar scar (hi) and transverse micropylar slit (mi). c) Oblique view of seed showing slightly raised raphal area (S174352); remains of mounting media (¤). d) Details of holotype showing triangular hilum (hi) and transverse micropylar slit in the exotesta (mi). e) Cut volume rendering of holotype (cut at yz1170) through the median plane showing hilum (hi) and micropylar slit (mi) lined by radially expanded exotestal cells. Scale bars = 500 µm (a–c); 250 µm (d, e).

Text-fig. 12. Silutanispermum kvacekiorum gen. et sp. nov. seeds from the Early Cretaceous Famalicão locality (sample 025), Portugal; Synchrotron radiation X-ray tomographic microscopy (SRXTM, orthoslices). a) Longitudinal orthoslice (yz1170) through the median plane of the seed (S170238) in the micropylar region showing exotestal cells lining the micropylar slit (mi) and hilum (hi); note the well-preserved mesotestal cells (me). b) Longitudinal orthoslice (xz0805) of seed perpendicular to the median plane through the micropylar region showing the transverse micropylar slit (mi) lined by radiating exotestal cells; note abundant mesotestal cells (me). c) Transverse orthoslice (xy0768) through seed below hilum and micropyle showing exotesta (ex) and mesotesta (me) that is strongly developed along the raphe (ra) (S174352). d) Transverse orthoslice (xy2113) through middle of the seed showing well-preserved cellular nutritive tissue with empty cells; note that the raphe (ra) is enclosed in mesotestal tissue (S174352). e) Longitudinal orthoslice (yz0970) through seed coat showing exotesta (ex) of tall palisade-shaped cells and thick mesotesta (me) of low cells (S174352). Scale bars = 500 µm (a, c, d); 250 µm (b); 125 µm (e).