Valvidistemon globiferus E.M.FRIIS, P.R.CRANE, K.R.PEDERSEN, M.M.MENDES et J.KVAČEK, 2022

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 : 379

Valvidistemon globiferus E.M.FRIIS, P.R.CRANE, K.R.PEDERSEN, M.M.MENDES et J.KVAČEK sp. nov.

Text-fig. 27a–d

H o l o t y p e. S107779 (Catefica sample 49; figured Text-fig. 27a–d ).

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.

PFN002795 (for new species).

R e p o s i t o r y. Palaeobotanical Collections, Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden (S).

E t y m o l o g y. From Latin in Greek combinations globifer, with spherical organ.

Ty p e l o c a l i t y. Catefica (39° 03ʹ30ʺ N; 09°14ʹ 30ʺ W), between the villages of Catefica and Mugideira, about 4 km south of Torres Vedras, Portugal .

T y p e s t r a t u m a n d a g e. Almargem Formation, Early Cretaceous (Aptian-early Albian).

S p e c i f i c d i a g n o s i s.As for the genus.

D i m e n s i o n s. Stamens up to about 0.9 mm long and 0.2 mm in broad.

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 stamen, about 0.6 mm long with semitectate-reticulate pollen in situ ( Text-fig. 27a–d ). The stamen consists of a short base that is poorly differentiated from the basifixed anther. The anther is tetrasporangiate and dithecate with an almost spherical apical extension of the connective that overhangs the thecae ( Text-fig. 27a, b ). Epidermal cells of the connective tissue between the thecae are slightly elongate and arranged in longitudinal rows (Textfig. 27c). The four pollen sacs are arranged in two pairs in a lateral position and are separated by a broad connective that is equally thick on both adaxial and abaxial sides (Textfig. 27a, b). Dehiscence is valvate by laterally hinged valves that result from a distal and proximal bifurcation of the stomium ( Text-fig. 27c ). Valves are preserved on one side of the stamen ( Text-fig. 27a, c ), but are broken off on the other side exposing the distinct, quadrangular cells of the endothecium ( Text-fig. 27b ).

The thecae are dehisced. Most pollen has been shed and only a few grains remain adhering to the inside of the anther wall ( Text-fig. 27d ). Pollen grains are about 15 µm in diameter. The grains are folded and while the apertures of all the grains are poorly exposed the pollen appears monoaperturate, probably monocolpate. The pollen wall is semitectate-reticulate with a homobrochate reticulum (Textfig. 27d). There is no trace of orbicules on the inside of the anther wall.

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. Detailed consideration of possible systematic affinities is not possible given the limited material and information available. Similar stamens have not been observed in other Early Cretaceous mesofossil floras from Portugal and North America.

Figures

Text-fig. 27. Scanning electron microscope (SEM) images of stamens and pollen of Valvidistemon globiferus gen. et sp. nov.; Catefica locality, Portugal. a) Stamen in oblique lateral view showing laterally hinged valves, massive connective between the thecae and prominent, globular, apical extension of the connective; b) Stamen in oblique lateral view on the opposite side from (a) showing broken laterally hinged valves and distinct endothecium cells; c) Detail of stamen showing the large, longitudinally aligned cells of the massive connective, broad, poorly defined stamen base, and the laterally hinged valves of one of the thecae; d) Reticulate pollen attached to the inside of the anther wall. Specimen, Catefica 49-S107779 (holotype, a–d). Scale bars = 600 Μm (a, b), 100 Μm (c), 20 Μm (d).