Paisia pantoporata E.M.FRIIS, M.M.MENDES et K.R.PEDERSEN, 2018

Friis, Else Marie, Crane, Peter R., Pedersen, Kaj Raunsgaard, Mendes, Mário Miguel & Kvaček, Jiří, 2022, The Early Cretaceous Mesofossil Flora Of Catefica, Portugal: Angiosperms, Fossil Imprint 78 (2), pp. 341-424 : 388

Paisia pantoporata E.M.FRIIS, M.M.MENDES et K.R.PEDERSEN, 2018

Text-fig. 33a–c

D e s c r i p t i o n a n d r e m a r k s. Paisia pantoporata is based on about 60 specimens of fossil flowers and isolated floral parts recovered from the Catefica mesofossil flora (for a full description and discussion see Friis et al. 2018a). Flowers are small, about 1 mm long and 1.2 mm in diameter, actinomorphic and pentamerous with a perianth consisting of a single whorl of five tepals, an androecium consisting of a single whorl of stamens, and a gynoecium of five free carpels ( Text-fig. 33a, c ). The organs of the three whorls are arranged on the same radius with the incurved margins of each tepal embracing a stamen ( Text-fig. 33c ). Stamens have a short, stout filament that merges above into the anther. Anthers are tetrasporangiate with two pairs of pollen sacs borne laterally and separated by a massive connective.

Pollen grains are small, spheroidal, about 11–14 µm in diameter and pantoporate with six to eight pores. The pollen wall is tectate-punctate with spiny supratectal ornamentation ( Text-fig. 33b ). The carpels are follicular, narrowly elliptical to obovate with a ventral slit that extends for the full length of the carpel. Each carpel has one dorsal and two ventral bundles and contains about 20–30 seeds borne in two rows along the full length of the ventral suture.

A f f i n i t y a n d o t h e r o c c u r r e n c e s. Pantoporate pollen occurs scattered among all major groups of angiosperms. However, the characters of the pollen combined with the pentamerous organisation indicate that Paisia pantoporata is most likely an extinct lineage of basal eudicots, probably most closely related to extant Ranunculales.

Flowers of Paisia pantoporata have so far been recovered only from the Catefica locality. Pollen of Paisia pantoporata is also encountered in the palynological strew preparations from Catefica, where it occurs in clumps of several grains. Pantoporate pollen grains of the kind produced by Paisia pantoporata have not been reported from other palynofloras. Pantoporate pollen grains are not uncommon in Early Cretaceous palynofloras (for references see Ibrahim et al. 2015, Friis et al. 2018a), but grains similar to pollen of Paisia pantoporata have not been reported from other mesofossil floras or dispersed palynofloras.

Figures

Text-fig. 33. Synchrotron radiation X-ray tomographic microscopy (SRXTM, a, c) and scanning electron microscope (SEM, b, d) images of Paisia pantoporata (a–c) and?Paisia sp. (d); Catefica locality, Portugal. a) Lateral view (volume rendering) of flower showing the carpels (c) and the fleshy tepals (t) that have a slightly bulge near the base; b) Pollen grains in situ from stamen showing scattered pores and spiny supratectal ornamentation; c) Transverse section (orthoslice xz1024) through flower showing the pentamerous organization with five tepals (green) five stamens (yellow) and five carpels (red) all on the same radii; d) Lateral view of floral structure with three free carpels borne on the swollen receptacle that has poorly defined facets at the apex indicating the former presence of perianth parts. Specimens, Catefica 49-S101214 (a, c), Catefica 50-S170188 (b), Catefica MM125-P0292 (d). Scale bars = 300 Μm (a, c, d), 6 Μm (b).