Dictyozonia pusilla E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN, 2019

Friis, Else Marie, Crane, Peter R. & Pedersen, Kaj Raunsgaard, 2019, The Early Cretaceous Mesofossil Flora Of Torres Vedras (Ne Of Forte Da Forca), Portugal: A Palaeofloristic Analysis Of An Early Angiosperm Community, Fossil Imprint 75 (2), pp. 153-257 : 221-223

publication ID

https://doi.org/ 10.2478/if-2019-0013

persistent identifier

https://treatment.plazi.org/id/0396DC10-BF4B-C245-CEFC-B316E47819F2

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Diego

scientific name

Dictyozonia pusilla E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN
status

sp. nov.

Dictyozonia pusilla E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN sp. nov.

Text-fig. 44f–k View Text-fig

H o l o t y p e. Designated here. S105002 (Torres Vedras sample 144; figured Text-fig. 44f–k View Text-fig ).

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.

PFN000523 (for new species).

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

E t y m o l o g y. From Latin: pusillus, very small, referring to the very small size of the pollen grains.

T y p e l o c a l i t y. Torres Vedras (NE of Forte de

Forca; 39°06′13″ N, 9°14′47″ W).

T y p e s t r a t u m a n d a g e. Lower member of the Almargem Formation; Early Cretaceous (late Barremianearly Aptian).

D i a g n o s i s. As for the genus.

D i m e n s i o n s. Diameter of pollen grains: about

9–12 µm.

D e s c r i p t i o n a n d r e m a r k s. The species is based on a fragment of a tetrasporangiate stamen ( Text-fig. 44f View Text-fig ) with pollen in situ ( Text-fig. 44g –k View Text-fig ). The pollen grains were briefly described and illustrated earlier as pollen type “B.4 monocolpate, psilate-reticulate pollen” ( Friis et al. 1999), but the material was not formally named. The pollen grains are small, almost circular in equatorial outline, and monocolpate. The pollen wall is semitectate-reticulate in the equatorial region, and psilate to psilate-punctate in the polar regions ( Text-fig. 44g –k View Text-fig ). The reticulum forms a distinct band around the equator ( Text-fig. 44g, k View Text-fig ). The reticulum is heterobrochate with a narrow microreticulate to foveolate zone bordering the psilate regions of the distal and proximal poles. In the polar regions the tectum is psilate with a narrow punctate zone close to the colpus margin ( Text-fig. 44j View Text-fig ). Muri are smooth with slightly rounded profile, and are supported by short, scattered columellae. The colpus extends for the full length of the grains and has a distinct margin and verrucate membrane ( Text-fig. 44h–j View Text-fig ).

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. Dictyozonia pusilla is only known from the Torres Vedras mesofossil flora. A probably related pollen type with psilate polar regions and a semitectate equatorial region was observed in a small flower fragment from the Buarcos mesofossil flora (Pollen Type B. 3 in Friis et al. 1999). However, in the Buarcos specimen both monocolpate and trichotomocolpate pollen occur in the same anther and the tectum in the equatorial region is microreticulate to foveolate. Pollen grains with extended psilate polar regions and reticulate equatorial regions have been described from the Early Cretaceous of the Potomac Group by Walker and Walker (1986) who suggested an affinity for these grains with extant monocots, but so far we have been unable to place Dictyozonia pusilla in any modern taxon.

Very small pollen grains somewhat comparable to those of Dictyozonia pusilla with a graded reticulum and foveolate to psilate proximal face were also described from the Albian of Egypt as Reticoll-Smallpatch and Crochetret- Baldap ( Penny 1991), but none of these has a similar narrow reticulate equatorial band and psilate areas on the distal face.

R

Departamento de Geologia, Universidad de Chile

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