Paisia, 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 : 388-390

Paisia -like follicles

Text-figs 34a–h , 35a–e , 36a–e

D e s c r i p t i o n a n d r e m a r k s. The material includes several isolated follicles probably derived from apocarpous gynoecia. The follicles vary considerably in size and shape, and range from narrow elongated-ellipsoidal to obovate. Follicles are 0.7–1.7 mm long, 0.35–0.7 mm broad in the dorsi-ventral direction, and 0.3–6.2 mm wide (Textfigs 34a–h, 35a–e, 36a–e).

The follicles have a distinct ventral suture with a decurrent stigma that extends along the full length of the follicle. In some specimens there is a distinct papillate zone that extends along both sides of the ventral suture from the follicle base to the apex ( Text-fig. 34a–d ). This papillate zone is possibly stigmatic. In many specimens the follicles have a distinct apical cleft ( Text-figs 34d , 35a, d , 36b, d ).

The follicles contain many anatropous ovules/seeds that are borne on placentae that extend on either side of the ventral suture for the full length of the follicle. In most specimens the ovules/seeds are arranged in two distinct rows ( Text-figs 34e–h , 35e ), but in one specimen ( Text-fig. 36a–e ) this is less distinct and the ovules/seeds are more crowded. This specimen is larger than the other follicles and clearly more mature. There are smaller undeveloped ovules in its lower part ( Text-fig. 36c ) but there are larger, probably mature, seeds in the upper part ( Text-fig. 36c ). Whether the crowding of the seeds is due to the stage of maturity of the follicles, or because this larger specimen represents another species, is uncertain. The epidermal cells of the ovules/seeds have slightly raised anticlinal walls that give the surface a striate-reticulate appearance ( Text-figs 34e, f , 36c ).

The follicle wall is thick. It consists of an inner layer of transversely aligned fibres ( Text-fig. 34e ), a middle layer that is one to two cell layers deep and an outer epidermis of smaller, thin-walled cells ( Text-figs 34g , 35e ). The mesocarp is composed of large, isodiametric, thick-walled cells that have a rounded cell lumen ( Text-figs 34e, f, h , 35e ). The follicle is supplied by one dorsal and two ventral bundles ( Text-figs 34g, h , 35e , 36e ).

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. The follicles are closely similar to the follicles seen in flowers of Paisia pantoporata in their elongate shape and in the anatomical details of the follicle wall. However, the carpels in the Paisia flowers are immature and the stigmatic zone is indistinct. Other features seen in the isolated follicles, such as the apical cleft, and a papillate zone extending along the margins of the ventral suture, are also not seen in Paisia pantoporata . It is possible that the isolated follicles represent different developmental stages of a single species, perhaps Paisia pantoporata . However, it is also possible that they represent additional species of Paisia or a closely related genus.

Isolated follicular fruits occur in other mesofossil floras from Portugal, but Paisia -like follicles like those described here are known only from Catefica.

Isolated eudicot stamens and pollen clumps with tricolpate pollen in situ

Five different kinds of eudicot have been identified from the Catefica mesofossil flora based on isolated stamens and pollen clumps with different kinds of tricolpate pollen. Dispersed tricolpate pollen grains are typically assigned to species of dispersed pollen genera such as Foveotricolpites R.L.PIERCE , Psilatricolpites HAMMEN ex HAMMEN et WYMSTRA , Retitricolpites HAMMEN ex HAMMEN et WYMSTRA , Rhoipites WODEHOUSE , Rousea SAT.K.SRIVAST. , or Striatopollis KRUTZSCH and Tricolpites COOKSON ex COUPER. However , the application of these pollen genera is typically very broad and their type specimens have been studied and illustrated mainly using light microscopy. Light microscope resolution is insufficient for detailed comparison with specimens studied using scanning electron microscopy, including the specimens described here from Catefica. New genera are probably warranted for the Catefica material, but for present purposes we simply refer to the five different taxa as “Stamen/pollen clump with tricolpate pollen sp. 1 – sp. 5”.

Stamen with tricolpate pollen sp. 1

Text-fig. 37a–f

D e s c r i p t i o n a n d r e m a r k s. The material comprises a single fragmentary stamen, about 2.3 mm long and 0.5 mm wide. The anther is tetrasporangiate and dithecate with long narrow pollen sacs ( Text-fig. 37a ). Pollen grains in situ are small, almost spherical, about 21 µm in diameter and tricolpate ( Text-fig. 37b–d ). The colpi are long, reaching almost to the poles, and have a distinct margin ( Text-fig. 37b– d ). The grains are semitectate-reticulate with a heterobrochate reticulum that is coarse in the mesocolpium zones but finer over the poles and along the margins of the colpi (Textfig. 37b–d). The muri are smooth, about 0.4 µm wide, with a rounded to flattened profile. Columellae supporting the muri are short and densely spaced ( Text-fig. 37f ).

Orbicules are densely-scattered on the inner surface of the anther wall and over the surface of the pollen grains ( Text-fig. 37e ). Orbicules are up to about 1 µm long, irregular in shape and have a solid base of laterally fused spheres with rod-like projections ( Text-fig. 37e ).

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. The triaperturate pollen grains clearly indicate a relationship to eudicots, but relationships to extant taxa within the group are uncertain.

In the mesofossil floras from Portugal this taxon is currently known only from Catefica. The in situ pollen grains are identical in size, shape and most features of the reticulum to the dispersed pollen Retitri-Liliret described by Penny (1991) from the Aptian of Egypt, but in that material the polar regions are foveolate to psilate rather than finely reticulate.

Figures

Text-fig. 34. Synchrotron radiation X-ray tomographic microscopy (SRXTM, a–h) images of “Paisia-like follicle”; Catefica locality, Portugal. a–d) Volume rendering of follicles in lateral (a, c) and ventral (b, d) views showing the decurrent stigmatic region that extends from base of the follicle to the apex; note papillate zone forming a probable stigma along the full length of the ventral suture; e) Longitudinal section (volume rendering cut at orthoslice yz0326) near the base of the follicle showing two ovules with a striate-reticulate surface (asterisks); note transverse fibers lining the inner follicle wall and large cells of the mesocarp; f) Transverse section (volume rendering cut at orthoslice xy2475) of follicle showing two rows of ovules borne on placentae on

Text-fig. 35. Scanning electron microscope (SEM, a, b, d) and synchrotron radiation X-ray tomographic microscopy (SRXTM, c, e) images of “Paisia-like follicle”; Catefica locality, Portugal. a) Lateral view of slender follicle with an almost straight ventral margin and a slightly curved dorsal margin; b) Lateral view of small, broad follicle with slightly sinuous ventral margin and rounded dorsal margin; c) Lateral view of small, broad follicle with slightly sinuous ventral margin and rounded dorsal margin; d) Apical part of follicle in (a) showing the slight apical cleft in the probable stigmatic region; e) Transverse section (orthoslice xy0407) of follicle showing ovules and distinct follicle wall with small, thin-walled cells of the outer epidermis (arrow), larger, isodiametric cells of the mesocarp and an inner layer of smaller, thin-walled cells. Specimens, Catefica 50-S171523 (a, d), Catefica 343-S171515 (b), Catefica 49-S174929 (c, e). Scale bars = 300 Μm (a–c), 100 Μm (d, e).

Text-fig. 36. Synchrotron radiation X-ray tomographic microscopy (SRXTM, a–e) images of “Paisia-like follicle”; Catefica locality, Portugal. a, b) Volume rendering of follicle in lateral (a) and ventral (b) views showing the decurrent stigmatic region that extends from the follicle base to the apex but lacks a distinct papillate zone; c) Longitudinal section (volume rendering cut at orthoslice yz0341) of follicle showing under-developed ovules towards the base and numerous well-developed ovules/seeds in the upper part suggesting that the follicle is probably mature; d) Dorsal view of follicle apex showing the cleft in the presumed stigmatic apical region; e) Transverse section (orthoslice xy1294) of follicle with one dorsal and two ventral bundles and two placentae bulging into the locule, one on either side of the ventral suture; note the strongly compressed outer epidermis and the homogenized cells of the mesocarp. Specimen, Catefica 49-S174915 (a–e). Scale bars = 300 Μm (a–d), 100 Μm (e).

Text-fig. 37. Scanning electron microscope (SEM) images of “Stamen with tricolpate pollen sp. 1”; Catefica locality, Portugal. a) Stamen fragment showing the elongate, tetrasporangiate anther but with the base and apex poorly preserved; b–d) Pollen grains from stamen fragment in equatorial view showing the long colpi and well-developed, heterobrochate reticulum with very distinct large and small lumina; e) Detail of pollen wall showing orbicules with irregular projections; f) Detail of pollen wall showing smooth muri supported by short, densely spaced columellae. Specimen, Catefica 50-S170419 (a–f). Scale bars = 600 Μm (a), 6 Μm (b–d), 1.5 Μm (e, f).