Watsoniocladus

Mendes, Mário Miguel, Dinis, Pedro & Kvaček, Jiří, 2018, Some Conifers From The Early Cretaceous (Late Aptian - Early Albian) Of Catefica, Lusitanian Basin, Western Portugal, Fossil Imprint 74 (3 - 4), pp. 317-326 : 321

Watsoniocladus cf. virginiensis V.SRINIV., 1995

Text-fig. 4 a–g

D e s c r i p t i o n. These conifer twigs consist of unbranched stems bearing decussately or semi-decussately arranged leaves of Brachyphyllum - type. They are usually borne so tightly together along the stems that the latter are not visible ( Text-fig. 4a, e ). The apices are usually pointed and falcate in outline, but some specimens show the most distal leaves being rounded ( Text-fig. 4e, f ). The leaves are up to 2.5 mm long and 1.2 mm wide. The abaxial surfaces are convex and keeled, whilst the adaxial surfaces are concave and unkeeled. The leaves are amphistomatic. Ordinary cells of abaxial cuticle bear papillae, particularly in their terminal parts. The stomata are surrounded by a raised rim with finger-like outer papillae. The papillae form star-shaped stomatal apertures ( Text-fig. 4d , arrowed). The stomata are arranged in ill-defined rows ( Text-fig. 4c ).

D i s c u s s i o n. Based on the opposite decussate leaf arrangement and cuticle characters, the present fossil material is ascribed to the genus Watsoniocladus . Watsoniocladus consists of at least 6 species collected from the Early Jurassic – Albian of England, France, Germany, Israel, Iran, Japan, Spain and USA (e.g. Watson and Alvin 1999, Srinivasan 1995, Néraudeau et al. 2012, Buscalioni et al. 2018). Due to presence of elongate leaves and papillae borne rather outside then inside the stomatal pits, we compare the studied material with W. virginensis V.SRINIV. and W. florinii V.SRINIV. described from the Early Cretaceous (early to middle Albian) flora of the Potomac Group in eastern North America ( Srinivasan 1995). Both species have papillae and trichomes on their outer abaxial surfaces, papillate stomatal rims and stomata arranged in ill-defined stomatal rows. The present material shows separate leaves, and is therefore assigned to W. virginiensis rather than to W. florinii, in which adjacent leaves are fused ( Srinivasan 1995).

Figures

Text-fig. 4. SEM micrographs of two types of conifers from the Early Cretaceous mesofossil flora of Catefica, Portugal. (a) Leafy twig of Watsoniocladus cf. virginiensis with opposite-decussate leaves showing convex, keeled, abaxial surface and concave, unkeeled, adaxial surface (P0127, sample Catefica 316). (b), (c) Details of the leaf apex showing amphistomatic abaxial and adaxial surfaces (P0127, sample Catefica 316). (d) Detail of stomata surrounded by a raised rim with finger-like outer papillae showing star-shaped stomatal apertures (arrows) (P0127, sample Catefica 316). (e), (f) Leafy twig of Watsoniocladus cf. virginiensis showing hook-shaped leaves in outline (P0129, sample Catefica 317). (g) Detail of the abaxial surface showing stomata arranged in ill-defined rows (P0129, sample Catefica 317). (h) Leafy twig of Pagiophyllum sp. showing convex, keeled, abaxial surface and concave, unkeeled, adaxial surface (P0126, sample Catefica 318). (i) Detail of the abaxial leaf surface showing serrate margin and scattered stomata (P0126, sample Catefica 318). Scale bars = 1 mm (a, e, f, h); 100 μm (b, c, g, i); 50 μm (d).