Lusitanispermum choffatii, 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 : 147-148

Lusitanispermum choffatii gen. et sp. nov.

Text-figs 7–10

H o l o t y p e. Designated here, S174345 (Famalicão sample 025; illustrated here on Text-figs 7a, b , 9a, 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.

PFN000097 (for new species).

P a r a t y p e s. Designated here, S105097, S105098, S170239, S174035, S174353, S174467 – S174470, S174472, S174474, S174811, S175113 – S175118 (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 Léon Paul Choffat (*1849, †1919) for his geological studies of Cretaceous deposits in Portugal.

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: 1.7–2.8 mm; width of seeds: 0.8–1.9 mm.

O t h e r m a t e r i a l. S175046 (Vale de Água sample

333).

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 120 isolated seeds of which 12 specimens were studied using SRXTM ( S105097 , S105098 , S170239 , S174035 , S174345 , S174353 , S174467 – S174470 , S174472 , S174474 ). 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-figs 7a, c , 8a–e ) and elliptical to circular in transverse section ( Text-figs 9d , 10e). The seed surface is smooth with a jigsaw puzzle-shaped pattern formed from the slightly raised undulate anticlinal walls of the exotesta cells ( Text-fig. 8g ). The seeds vary considerably in size and shape and they may belong to more than one natural species. However, there are transitional forms between the smaller more narrow type ( Text-fig. 8a–c ) and the larger more rounded type ( Text-figs 7a–c , 8d, e ) and all specimens are therefore included here in the same species .

The micropyle and hilum are very close together at the seed apex ( Text-figs 8b , 10a, d). The hilum is rounded triangular in outline without a hilar rim ( Text-fig. 8f ). The course of the raphe is not seen on the seed surface. The micropyle is formed from the inner integument and marked externally by a transverse slit in the testa ( Text-figs 8f , 10d).

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. In the bulging areas close to the hilum the exotestal cells are up to about 180 µm tall ( Text-figs 9a–d , 10a, c, e), but are about 95 µm tall laterally and on the antiraphal sides of the seed. These exotesta cells become gradually shorter towards the micropylar slit and in the micropylar region ( Text-fig. 10a, b). They have slightly raised anticlinal walls and towards the outside (Textfig. 8g) and inside ( Text-fig. 7d ) the cells of the exotesta are strongly undulate forming stellate-undulate facets and a jigsaw puzzle-like pattern with rounded, undivided lobes.

In the bulging portion of the seed coat around the micropylar area the cells of exotesta have slightly thinner walls ( Text-fig. 9c ) and this part of the seed is sometimes abraded or collapsed. Also in this part of the seed the cells of the exotesta have straight anticlinal walls and polygonal facets ( Text-fig. 8f ). The mesotesta/endotesta consists of at least three layers of large parenchyma cells ( Text-figs 9a, b, d , 10e), most prominent below the bulging hilar zone ( Text-fig. 9b ). The tegmen is thin over most of the seed, but thicker towards the micropyle.

Nutritive tissue is well preserved in most specimens studied using SRXTM and in seven specimens ( S170239 , S174345 , S174468 , S174469 , S174470 , S174472 , S174474 ) a complete or almost complete embryo was observed ( Text-figs 9a, b , 10f). In all cases the embryo is tiny, about 110 µm long and 180 µm broad, with two rudimentary cotyledons ( Text-figs 9b , 10f), and an embryo to seed ratio of about 0.016. The cells of the embryo are much smaller than those of the surrounding nutritive tissue and each cell has a dense central structure ,

which we interpret as the remains of a nucleus ( Text-figs 9b , 10f). The nutritive tissue is cellular consisting of isodiametric and thin-walled cells, about 40 µm in diameter, with thin, straight or slightly undulate cell walls ( Text-figs 9a–d , 10b, c, e). In most specimens the cells of the nutritive tissue are filled with small granular bodies that we interpret as the remains of protein or lipid bodies ( Text-figs 9b, d , 10c, d, f). The cells are rarely completely empty ( Text-fig. 10a, b, e).

Figures

Text-fig. 7. Lusitanispermum choffatii gen. et sp. nov. seeds from the Early Cretaceous Famalicão locality (sample 025), Portugal; Synchrotron radiation X-ray tomographic microscopy (SRXTM, volume renderings). a) Holotype; seed in lateral view showing seed shape; note that the seed is broken near the lower surface of the hilum (S174345). b) Oblique apical view of micropylar-hilar region of holotype showing slightly ruptured micropylar slit (mi) in the outer integument and two bulging and abraded areas (arrow heads) close to hilum. c) Seed in oblique lateral-raphal view showing the two bulging structures (arrow heads) immediately adjacent to the lower edge of the hilum (S174472). d) Tangential, longitudinal cut (cut at yz0131) through the seed coat of seed in (7c) showing the undulate anticlinal cell walls of the exotesta cells that are thickest towards the outside and thinner towards the inside. Scale bars = 500 µm (a–c); 250 µm (d).

Text-fig. 8. Lusitanispermum choffatii gen. et sp. nov. seeds from the Early Cretaceous Famalicão locality (sample 025) (a, b, d, e), and the Vale de Água locality (sample 333) (c, f, g), Portugal; Synchrotron radiation X-ray tomographic microscopy (SRXTM, volume renderings). a) Smaller seed in lateral view showing the bulging region (arrow head) close to hilum (S174467). b) Cut volume rending (cut at yz1032) of seed in (8a) showing the expanded cells of exotesta immediately adjacent to the lower edge of the hilum (hi), micropyle (mi) and the well preserved nutritive tissue. c) Small seed in lateral view showing the bulging exotesta (arrow head) close to hilum (S175046). d, e) Larger seed in lateral (d) and raphal (e) view (S174035). f) Detail of seed in (8c) showing the micropylar slit (mi) above the hilum (hi) and bulging exotestal tissue (arrow head) in which the walls of the exotestal cells have straight anticlinal walls. g) Surface of seed in (8c) showing the raised undulate anticlinal walls of the exotestal cells. Scale bars = 500 µm (a–e); 250 µm (f); 125 µm (g).

Text-fig. 9. Lusitanispermum choffatii 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 (yz0769) through the median plane of the seed (S174345) showing expanded exotestal cells (ex, arrow head) in the hilar region and well-preserved cellular nutritive tissue with an embedded tiny embryo (asterisk markes the margin of the embryo); note well-developed mesotesta (me) on the raphal side of seed. b) Longitudinal orthoslice (yz0750) in the median plane showing detail of micropylar part of seed with well-preserved exotesta (ex) and mesotesta (me) and tiny embryo with two rudimentary cotyledons (asterisks mark the margin of the cotyledons); note numerous granular bodies in the cellular nutritive tissue that are probably the remains of protein and lipid bodies. c) Transverse orthoslice (xy0311) through seed below hilum showing the bulging exotesta (arrow heads) (S174472); note that the exotestal cells in this region have thinner walls (arrows). d) Transverse orthoslice (xy0900) through the middle of a seed showing the uneven thickening of the anticlinal walls of the exotestal cells (ex), which are thicker towards the outside and very thin towards the inside; note also mesotesta (me) and the well-preserved cellular nutritive tissue (S174472). Scale bars = 500 µm (a, d); 250 µm (b, c).