Endressistemon cateficensis 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 : 381-383

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

Text-fig. 28a–g

Holotype. S107778 (Catefica sample 49; figured Text-fig. 28a, b, e, f ).

Plant Fossil Names Registry Number.

PFN002797 (for new species).

Paratypes. S107751, S107768, S107769, S266022 (Catefica sample 49).

Repository. Palaeobotanical Collections, Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden (S).

Etymology. From the Catefica locality where the fossils were collected.

Type locality. Catefica (39° 03ʹ30ʺ N; 09°14ʹ 30ʺ W), between the villages of Catefica and Mugideira, about 4 km south of Torres Vedras, Portugal .

Type stratum and age. Almargem Formation, Early Cretaceous (Aptian-early Albian).

Specific diagnosis.As for the genus.

Dimensions. Stamens up to about 0.9 mm long and 0.2 mm in broad.

Description and remarks. The material includes isolated staminal structures each consisting of two lateral stamens and in some specimens a median axislike structure. The two stamens and axis-like structure are borne on a short, common stalk ( Text-fig. 28a–e ). The anthers are basifixed, tetrasporangiate and dithecate ( Text-fig. 28a, b ).

The stamens are up to about 0.9 mm long including the common stalk and the apical projection, and the anther is about 0.2 mm broad. The stamen base is short, about 0.1 mm long ( Text-fig. 28a, b, d, e ). Apically the two stamens have a prominent peltate to wing-like projection that is coriaceous and sometimes leaf-like ( Text-fig. 28a–e ). A similar projection is also present at the tip of the median axis-like structure in the holotype ( Text-fig. 28a, b, e, f ). In another specimen ( S 107769) the median axis-like structure is seen between the two stamens ( Text-fig. 28c ) in the same position as in the holotype, but in this specimen the axis-like structure is broken and has no apical projection. In the holotype three distinct ribs, which probably reflect the position of vascular bundles, extend from the common stalk into the apical projections ( Text-fig. 28b, e ). It is possible that these bundles are in an abaxial position, but the orientation of the staminal structure and which side is adaxial and which side is dorsal is unknown. Dehiscence of the anthers is longitudinal and in dehisced stamens, the anther wall is rolled back indicating valvate dehiscence ( Text-fig. 28a, c ).

Pollen grains were observed in situ in one specimen (Textfig. 28g). They are monocolpate, semitectate-reticulate, circular in equatorial view, 10–11 µm in diameter, with a homobrochate reticulum. The aperture is long, reaching almost to the equator.

Affinity and other occurrences. The monocolpate pollen indicates that Endressistemon is a non-eudicot, most likely related to the basal grade of early angiosperm lineages (see discussion above). While it is not possible to place the fossils in any extant family or order a relationship to Chloranthaceae seems most likely. Currently Endressistemon has only been recovered from the Catefica mesofossil flora, where it is restricted to the basal part of the exposure.

Figures

Text-fig. 28. Scanning electron microscope (SEM) images of stamens and pollen of Endressistemon cateficensis gen. et sp. nov.; Catefica locality, Portugal. a, b) Staminal structure with two lateral stamens and one median structure seen in ventral and dorsal view (orientation unknown) showing that each stamen has a prominent apical extension and two pairs of pollen sacs separated by a narrow connective; both stamens are borne on a common base together with the median structure and their anthers are sessile on the common stalk; note the apical projection of the median structure (asterisk) between the two stamens and the ribs over probable vascular bundles that extend from the common base into the apical projections of both stamens and the median structure (arrows); c) Staminal structure showing two stamens with prominent apical projections and median axis-like structure between the two stamens (arrow); d) Staminal structure showing two stamens with prominent apical projections borne on a common base; e) Staminal structure in (a) and (b), from the same orientation as (b), showing the ribs over probable vascular bundles (yellow) that extend into the apical projections; f) Detail of staminal structure in (a) and (b) showing the fused or strongly adhering apical projections of the two lateral stamens and the median structure (asterisk); g) Monocolpate, reticulate pollen grains from the pollen sacs of stamen in (d). Specimens, Catefica 49-S107778 (holotype, a, b, e, f), Catefica 49-S107769 (c), Catefica 49-S107751 (d, g). Scale bars = 600 Μm (a–d), 300 Μm (e), 100 Μm (f), 6 Μm (g).