Endressistemon sp. 3

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 : 383

cf. Endressistemon sp. 3

Text-fig. 29e–g

Description and remarks. The material comprises a single stamen from which the stamen base is missing. The anthers are basifixed, tetrasporangiate and dithecate ( Text-fig. 29e ). The stamens are up to about 0.7 mm long, including the apical projection, and about 0.3 mm broad over the anther. Apically the stamen has a prominent, coriaceous projection that is peltate to wing-like ( Text-fig. 29e ). Dehiscence is longitudinal and the anther wall is rolled back indicating valvate dehiscence ( Text-fig. 29e ).

Pollen grains in situ are monocolpate, semitectatereticulate, circular in equatorial view, 13 µm in diameter, with a homobrochate reticulum ( Text-fig. 29f, g ). The grains are folded and the extent of the aperture is not fully exposed.

Affinity and other occurrences. The stamen is similar to stamens of some extant Annonaceae (see comments on Endressistemon above), but also to the individual stamens of Endressistemon cateficensis and it is possible that it was originally part of a similar staminate structure. The pollen grains in situ are also similar to those of Endressistemon cateficensis , but are larger and the two taxa are probably not conspecific.

Figures

Text-fig. 29. Scanning electron microscope (SEM) images of stamens and pollen grains of cf. Endressistemon sp. 1 (a, b), cf. Endressistemon sp. 2 (c, d) and cf. Endressistemon sp. 3 (e–g); Catefica locality, Portugal. a) Two adhering stamens, each with a long, pointed extension of the connective; b) Monocolpate, reticulate pollen in situ in stamen from stamen pair in (a); c) Fragment of stamen with prominent apical extension of the connective; d) Reticulate, apparently monocolpate, pollen in situ in stamen fragment in (c); e) Stamen with basifixed anther, perhaps sessile, and with prominent, wing-like apical extensions of the connective; note the dehisced thecae with the anther wall curved back; f, g) Monocolpate, reticulate pollen in situ in stamen in (e). Specimens, Catefica 49-S107780 (a, b), Catefica 49-S107784 (c, d), Catefica 49-S107781 (e–g). Scale bars = 600 Μm (a, c, e), 6 Μm (b, d, f, g).