Choffaticarpus compactus 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 : 229

Choffaticarpus compactus E.M.FRIIS, P.R.CRANE et K.R.PEDERSEN sp. nov.

Text-fig. 49d–j

H o l o t y p e. Designated here. S136725 (Torres Vedras sample 43; figured Text-fig. 49d–j ).

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.

PFN000490 (for new species).

P a r a t y p e. S137918 (Torres Vedras sample 44).

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: compactus referring to the compact structure of the fruit.

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. Length of fruit: 4.2 mm; width of fruit:

2.8 mm.

D e s c r i p t i o n a n d r e m a r k s. Choffaticarpus compactus is based on a single multicarpellate and apocarpous fruit that has been illustrated previously, but without formal description (Reproductive structure with many carpels in Friis et al. 2010a). There is also a single isolated fruitlet. Additional specimens assigned to this species are known from the Catefica and Buarcos mesofossil floras.

The fruit from Torres Vedras, as well as isolated fruitlets from Catefica, were studied using SEM and SRXTM. The Torres Vedras specimen consists of many fruitlets arranged helically along a long, slender receptacle to form a compact structure ( Text-fig. 49d, e ). The fruitlets are strongly compressed laterally and the only exposed regions in the compound fruit are the diamond-shaped faces of the fruitlets. The stigmatic region is indistinct and occurs towards the base in an elongated depression in the diamond-shaped surface of the fruitlets ( Text-fig. 49e ). This is more distinct in a specimen of Choffaticarpus from the Buarcos locality ( Friis et al. 2000a: fig. 3A, D). Stout, short trichomes are present along the borders of adjacent fruitlets and the stigmatic area ( Text-fig. 49f ). The lateral faces of the fruitlets are smooth. Each fruitlet contains a single seed ( Text-fig. 49h–j ). The cellular preservation as seen in SRXTM is good, but the fruits and seeds are crowded and have been compressed during fossilization making their structure and organization difficult to study. The micropyle points towards the central axis ( Text-fig. 49i, j ) and it is likely the seeds are anatropous. The seed coat is thin composed of narrow, longitudinally aligned cells ( Text-fig. 49j ).

The wall of each fruitlet consists of an inner layer of elongate sclerenchyma cells that line the locule. On the lateral faces of the fruitlets this layer of sclerenchyma cells is covered by a single layer of epidermal cells. The outer wall of the fruitlets is thicker and composed of thin-walled parenchyma cells covered by the epidermis ( Text-fig. 49h ).

Pollen attached to the surface of the fruitlets is circular in outline and about 11 µm in diameter. Only the nonapertural face is exposed and the grains were most likely monocolpate. The exine is semitectate-reticulate with a homobrochate reticulum, rounded muri, and broad, scattered columellae. The surface of the foot layer is finely granular ( Text-fig. 49g ).

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 tightly packed fruitlets borne on a long central receptacle resemble the gynoecium and fruits of extant Kadsura KAEMPF. ex JUSS. and Schisandra MICHX. (Schisandraceae) . However, the seeds of Choffaticarpus differ from those of Schisandraceae in their much thinner seed coat, and the systematic affinity of Choffaticarpus is currently uncertain. Fragments of a Choffaticarpus fruit and isolated fruitlets are also known from the Buarcos and Catefica localities.

Figures

Text-fig. 49. Scanning electron microscope (SEM) and synchrotron radiation X-ray tomographic microscopy (SRXTM) images of Vedresia elliptica gen. et sp. nov. (a–c) and a multicarpellate fruit of Choffaticarpus compactus gen. et sp. nov. and associated pollen (d–j); Torres Vedras locality, Portugal. a) Holotype; small fruit showing apical stigmatic region with attached pollen; b) Group of pollen grains from the stigmatic surface of the fruit in (a) showing the long colpus and reticulate tectum; c) Pollen grains from the stigmatic surface showing the long colpus and well developed reticulum, with smooth muri and short columellae