Reyispermum parvum, 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 : 144-147

Reyispermum parvum gen. et sp. nov.

Text-figs 5 , 6

H o l o t y p e. Designated here, S174178 (Vale de Água sample 141; illustrated here on Text-figs 5a–c, i , 6a, 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.

PFN000094 (for new species).

P a r a t y p e s. Designated here, S174179, S175111 (Vale de Água sample 141), S174495 (Vale de Água sample 300).

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. From Latin: parvus, small relating to the small size of the seeds.

T y p e l o c a l i t y. Vale de Água , Portugal (39°37′15″N,

08°51′30″W).

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

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: 0.44–0.52 mm; width of seeds: 0.28–0.5 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 about eight isolated seeds of which three (S174178, S174179, S174495) were studied using SRXTM. All seeds are isolated and there is no information on the fruit in which they were borne. The seeds are tiny, anatropous, bitegmic and exotestal. They are broadly ovate in lateral view, bilaterally symmetrical with dorsiventral plane of symmetry, and sometimes slightly compressed laterally ( Text-fig. 5a– h ). The raphal region is seen on the outside as a slightly raised rounded ridge ( Text-fig. 5c, g, h ).

The hilum and micropyle are separated by a zone of testal tissue. The hilum lacks a rim and is seen as a small rounded depression ( Text-fig. 5b, c ). The hilar tissue is slightly expanded inside. The micropyle is formed by the inner integument (tegmen) and marked on the seed surface by a transverse slit through the outer integument (testa) ( Text-figs 5c, f , 6b ). Internally the micropylar slit is lined on all sides by testal cells.

The testa consists of an outer layer of palisade-shaped sclerenchyma cells and an inner layer of thin-walled parenchyma cells ( Text-figs 5b, e , 6a–e ). The palisadeshaped cells of the exotesta are about 45 µm tall over most of the seed but gradually become shorter towards the micropyle and hilum; in the hilar region the thin exotesta is sometimes loosened forming a slightly bulging structure ( Text-figs 5b, d–h , 6a, c ). The anticlinal cell walls of the exotesta cells are evenly thickened walls and the lumen is more or less straight ( Text-fig. 6a, b, d ). The outer and inner parts of the anticlinal walls are strongly undulate and slightly raised resulting in stellate-undulate facets and a jigsaw puzzle-like pattern on the seed surface ( Text-fig. 5a, d, f–i ) except in the micropylar region where the anticlinal walls are straight and the outer facets polygonal ( Text-fig. 5f ). The lobes of the exotestal walls are deep and sometimes bifurcated. The tegmen is thin, but thickened around the micropyle and composed of rectangular epidermal cells with a striate wrinkled surface that are often collapsed ( Text-fig. 6e ).

None of the specimens observed using SRXTM had an embryo preserved, but the irregular cavity in the nutritive tissue, which is in the appropriate position for the embryo, suggests that the embryo was tiny. The nutritive tissue consists of thin-walled and equiaxial cells, about 45 µm in diameter ( Text-fig. 6d ).

Figures

Text-fig. 5. Reyispermum parvum gen. et sp. nov. seeds from the Early Cretaceous Vale de Água locality, Portugal; Synchrotron radiation X-ray tomographic microscopy (SRXTM, volume renderings). a) Holotype (S174178; Vale de Agua sample 141) in lateral view showing shape and cell pattern; remains of mounting media (¤). b) Cut volume rendering of seed (cut at yz0553) showing the slightly raised tissue immediately adjacent to the lower edge of the hilum (arrow head) and palisade-shaped cells of exotesta. c) Apical view of seed showing hilar depression (hi), position of micropylar slit (mi) and the slightly raised raphal ridge (ra). d) Seed in lateral view showing raised tissue immediately adjacent to the lower edge of the hilum (arrow head) (S174495, Vale de Água sample 300). e) Cut volume rendering (cut at yz0500) of the seed in (5d) showing the raised tissue (arrow head) immediately adjacent to the lower edge of the hilum and sclerenchyma cells of exotesta. f) Detail of seed in (5d) showing micropylar slit (mi), hilum (hi) and raised tissue (arrow head) immediately adjacent to the lower edge of the hilum. g, h) Seed in lateral view (g) and view towards raphe (h) showing seed shape, the raised tissue below hilum (arrow head) and the raphal ridge (ra); note pointed micropylar area (S174179, Vale de Água sample 141). i) Seed surface of seed in (5d) showing the raised outlines of the undulate anticlinal walls of the exotestal cells. Scale bars = 250 µm (a–e, g, h); 125 µm (f, i).

Text-fig. 6. Reyispermum parvum gen. et sp. nov. seeds from the Early Cretaceous Vale de Água locality, Portugal (a, b, d, e: sample 141, c: sample 300); Synchrotron radiation X-ray tomographic microscopy (SRXTM, orthoslices). a) Longitudinal orthoslice (yz0563) through the median plane of the seed (holotype, S174178) showing the palisade-shaped cells of exotesta and collapsed inner parts of seed coat, raised exotestal tissue (arrow head) immediately adjacent to the lower edge of the hilum (hi), micropyle (mi) and remains of cellular nutritive tissue. b) Longitudinal orthoslice (xz0659) through the micropylar region perpendicular to the median plane showing the exotestal tissue surrounding the transverse micropyle slit (mi). c) Longitudinal orthoslice (yz0500) through the median plane of the seed (S175095) showing raised tissue (arrow head) immediately adjacent to the lower edge of the hilum (hi), micropyle (mi) and poorly preserved cells of the seed coat. d) Longitudinal orthoslice (xz0810) through middle part of seed perpendicular to the median plane (S174178) showing seed coat and remains of cellular nutritive tissue. e) Tangential and longitudinal orthoslice (xz0162) through the seed coat of holotype (S174178) showing thickened, undulate cell walls of exotesta (ex) and the short, thin-walled cells of tegmen (te) with a finely striate wrinkled surface. Scale bars = 250 µm (a, c, d); 125 µm (b, e).