Kvacekispermum rugosum E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN
Friis, Else Marie, Crane, Peter R. & Pedersen, Kaj Raunsgaard, 2018, Rightcania And Kvacekispermum: Early Cretaceous Seeds From Eastern North America And Portugal Provide Further Evidence Of The Early Chloranthoid Diversification, Fossil Imprint 74 (1 - 2), pp. 65-76: 72-73
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|Kvacekispermum rugosum E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN|
H o l o t y p e. Designated here, S174951 (Vale de Água
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.
PFN000107 (for new species).
R e p o s i t o r y. Palaeobotanical Collections, Department of Palaeobiology, Swedish Museum of Natural History (S).
E t y m o l o g y. The specific epithet is from Latin rugosus: wrinkled.
T y p e l o c a l i t y. Vale de Água locality, Portugal
(39° 37′ 15″ N, 08° 51′ 30″ W).
T y p e h o r i z o n a n d a g e. Early Cretaceous (late Aptian – early Albian; basal part of the Figueira da Foz Formation).
D i a g n o s i s. As for the genus.
D i s t i n g u i s h i n g f e a t u r e s f o r K v a c e k i s p e r m u m
r u g o s u m. As for the genus.
D i m e n s i o n s. Length of seed: 1.14 mm; width of seed: 1.04 mm.
D e s c r i p t i o n a n d r e m a r k s. Kvacekispermum rugosum is known from a single well-preserved seed. The seed is abraded, and the fruit wall is missing except near the apex where stigma is preserved. There is no information on organization of the flower, but synchrotron radiation X-ray microtomographic microscopy ( SRXMT) of the seed (Holotype, S174951) has revealed fine details of the endotesta and nutritive tissue .
The seed is broadly obovate in lateral view, almost circular in transverse section, about 1.14 mm long and 1.04 mm in diameter, with rounded (apical) chalazal region and slightly pointed (basal) micropylar region ( Text-figs 3a–f View Text-fig , 4a–e View Text-fig ). The stigma, at the seed apex is sessile, slightly raised and hemispherical ( Text-fig. 3a–d View Text-fig ). The position of the stigma and the shape of the seed, as well as comparison to fruits and seeds of Canrightiopsis , suggest that the fruits of Kvacekispermum were one-seeded.
The seed is orthotropous and pendent, bitegmic and endotestal. The seed surface is coarsely rugulate to reticulate due to differences in the size of the cells comprising the endotesta with the resulting depressions arranged in poorly defined grooves. The endotesta is 60–125 µm thick consisting of a single layer of palisade-shaped crystal cells with endoreticulate infillings of fibres and imprints of small cubic crystals ( Text-figs 3c–e View Text-fig , 4a, c View Text-fig ). The crystals appear to be more densely packed close to the outer surface of the irregular grooves in the coarsely rugulate to reticulate surface ( Text-fig. 4c, d View Text-fig ). The exotesta consists of small, thinwalled cells that are preserved only in small patches in the grooves of the endotesta. The tegmen is collapsed in the mature seed, but the narrow, longitudinally arranged cells of the exotegmen are well preserved ( Text-fig. 4 a–d, f View Text-fig ).
The embryo is not preserved, but there is a very small well-defined embryo cavity ( Text-figs 3c, f View Text-fig , 4a, e View Text-fig ) indicating that the embryo was tiny. The surrounding nutritive tissue consists of thin-walled cells that do not show signs of shrinkage ( Text-fig. 4a, b, d, e View Text-fig ). Based on comparison with extant angiosperms the nutritive tissue is interpreted as endosperm.
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