Gastonispermum, 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 : 138

Genus Gastonispermum gen. nov.

T y p e. Designated here, Gastonispermum portugallicum 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.

PFN000088 (for new genus).

E t y m o l o g y. In recognition of Gaston de Saporta (*1823, †1895) for his pioneering contributions to studies of the Mesozoic floras of Portugal.

D i a g n o s i s. Isolated seeds occurring singly. Seeds small, anatropous, bitegmic and exotestal. Seeds bilaterally symmetrical with a dorsiventral plane of symmetry. Seed surface smooth without longitudinal ridges. Raphe distinct, seen externally as a slightly raised rounded ridge that extends from hilum to the chalazal end opposite the micropyle. Hilum and micropyle separated by a narrow zone of sclerenchyma. Hilar scar small, slightly raised without a hilar rim. Micropyle formed by the inner integument (tegmen) and marked on the seed surface by a Y-shaped slit through the outer integument (testa) adjacent to the hilar scar. Testa formed from an outer layer (exotesta) of palisade-shaped sclerenchyma cells and an inner thin layer of thin-walled parenchyma cells (mesotesta/endotesta). Palisade-shaped cells of exotesta with evenly thickened anticlinal walls and a straight lumen. Anticlinal walls of palisade-shaped sclerenchyma strongly undulate toward the inside and toward the outside, resulting in stellateundulate facets and a jigsaw puzzle-like pattern on the seed surface. 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. Details of the seed coat in Gastonispermum are similar to those of Nitaspermum ( Friis et al. 2018c), a genus established for Early Cretaceous seeds from eastern North America. However, there are also important differences, including the shape of the micropylar slit, which is Y-shaped in Gastonispermum but transversely elongate in Nitaspermum. Many features of Gastonispermum seeds, including the Y-shaped micropyle and the strongly undulate anticlinal walls of the exotesta cells, are very similar to seeds of some species of extant Illicium L. ( Illiciaceae , Austrobaileyales ), but Gastonispermum lacks the pronounced zone of expanded testal tissue between hilum and micropyle (strophiole) that characterizes extant Illicium species ( Oh et al. 2003). Similar seeds with strongly undulate anticlinal walls of the exotesta cells and a Y-shaped micropylar slit also occur in Victoria LINDL. ( Nymphaeaceae ; Takahashi et al. 2007), but Victoria is distinguished from Gastonispermum by its much thicker mesotesta and the greater separation between the circular hilar scar and the micropylar slit.