Lusitanispermum, 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

Genus Lusitanispermum gen. nov.

T y p e. Designated here, Lusitanispermum choffatii gen. et sp. nov.

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.

PFN000096 (for new genus).

E t y m o l o g y. From the Roman province Lusitania that included the part of Portugal where the fossils were collected.

D i a g n o s i s. Isolated seeds occurring singly. Seeds small, anatropous, bitegmic and exotestal. Seeds bilaterally symmetrical with dorsiventral plane of symmetry. Seed surface smooth without longitudinal ridges. Raphe indistinct externally. Hilum and micropyle close together separated by a narrow zone of testal sclerenchyma. Hilar scar small without a hilar rim. Micropyle formed by the inner integument (tegmen) and marked on the seed surface by a transverse slit through the outer integument (testa) adjacent to the hilar scar. Testa formed from an outer layer (exotesta) of palisadeshaped sclerenchyma cells, and an inner thick layer of large parenchyma cells (mesotesta/endotesta). Palisade-shaped cells of exotesta with unevenly thickened walls that are thick towards the outside, thin towards the inside, and have a conical lumen. Exotesta thick adjacent to the hilum forming a bulging zone that may be two-parted. Anticlinal walls of palisade-shaped sclerenchyma strongly undulate toward the inside and toward the outside, resulting in stellate-undulate facets and a jigsaw puzzle-like pattern on the seed surface except over the raphe and around the micropyle where the cell walls are straight and facets polygonal. Tegmen thin. Embryo tiny, with two rudimentary cotyledons.

C o m m e n t s o n t h e g e n u s. In their general organization and the structure of the seed coat seeds assigned to Lusitanispermum are similar to the other exotestal seeds described here, and to the two extinct exotestal seeds, Nitaspermum and Tanispermum, however, they are distinguished from these other fossil seeds, except Silutanispermum , by the much thicker mesotesta/ endotesta and in details of the exotestal cells. Among extant angiosperms comparable seeds occur in Illicium and in members of the Nymphaeales . Illicium is, however, distinguished by its strophiole and thinner mesotesta, while seeds of Nymphaeales have an operculum, formed from the inner integument, which has not been seen in the fossil seeds.