Silutanispermum, 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 : 149-150

Genus Silutanispermum gen. nov.

T y p e. Designated here, Silutanispermum kvacekiorum 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.

PFN000098 (for new genus).

E t y m o l o g y. Silutanispermum is an anagram of Lusitanispermum described above to indicate the similarity of the seeds of the two fossil genera.

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 separated by a narrow zone of testal sclerenchyma. Hilar scar small, triangular without a rim. Micropyle formed by the inner integument (tegmen) and marked on the seed surface by a transverse, slightly wavy slit through the outer integument (testa) adjacent to hilar scar. Testa formed from an outer layer (exotesta) of palisade-shaped sclerenchyma cells and an inner thick layer of large parenchyma cells (mesotesta/endotesta), that is particularly well-developed close to hilum. Palisade-shaped cells of exotesta with unevenly thickened walls that are thick towards the outside, slightly thinner towards the inside, but with an almost straight lumen. Anticlinal walls of palisadeshaped sclerenchyma strongly undulate towards the inside and towards the outside, resulting in stellate-undulate facets and a jigsaw puzzle-like pattern on the seed surface except over the raphe 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. Seeds assigned to Silutanispermum are similar to those of Lusitanispermum , and are distinguished from seeds of Gastonispermum , Pazlia , Pazliopsis and Reyispermum by their well-developed mesotesta. Silutanispermum seeds are distinguished from those of Lusitanispermum by the shape of the micropyle. In Silutanispermum the micropyle is lined by tall testal cells and is seen on the surface as a prominent, slightly wavy, slit. In Lusitanispermum the micropyle is less distinct. There are also differences in details of the seed coat, including especially the absence of any significant expansion in the thickness of the exotesta below the hilum in Silutanispermum .