Zamites pateri J.KVAČEK, 2022

Kvaček, Jiří, 2022, New Species Of Zamites From The Cenomanian Of The Bohemian Cretaceous Basin, Fossil Imprint 78 (2), pp. 425-431 : 427-430

Zamites pateri J.KVAČEK sp. nov.

Text-figs 1 , 2

H o l o t y p e. NM-F 5185, Text-figs 1 , 2.

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.

PFN003021.

E t y m o l o g y. The species name is derived from pater, meaning father in Latin. It is devoted to my father and teacher Professor Zlatko Kvaček.

T y p e l o c a l i t y. Pecínov quarry, 50 km west of Prague, the Czech Republic.

T y p e h o r i z o n. Peruc-Korycany Formation.

A g e. Cenomanian, Late Cretaceous.

D i a g n o s i s. Leaf simply pinnate, pinnae linear to narrowly lanceolate, entire-margined. Base of pinna slightly contracted, apex unknown. Veins 2–3 per mm, simple or rarely dichotomising. Leaf hypostomatic. Adaxial cuticle very thin, bearing polygonal cells with tightly sinuous anticlinal walls. Mesophyll present, consisting of isodiametric cells. Abaxial cuticle thick, showing distinct marginal band bearing tetragonal ordinary cells. Inner part of leaf consists of costal ordinary cells forming zones typically narrower than intercostal zones, formed by 4–5 rows of syndetocheilic stomata (sometimes ill-defined). Subsidiary cells large, ellipsoidal, thickly cutinised, bearing one or several papillae. Ordinary cells of intercostal zone polygonal in shape with roughly straight anticlinal walls. Ordinary cells of costal zones quadrangular in shape with sinuous anticlinal walls. Epidermal cells of both costal and intercostal zones bearing 3–5 papillae.

D e s c r i p t i o n.The holotype corresponds to a fragment of a simply pinnate leaf ( Text-fig. 1a ). Leaves are attached to the upper part of the robust, longitudinally striated rachis, 7–9 mm broad. The holotype shows 5 incomplete pinnae arising from a common rachis. The pinnae are attached to the dorsal part of the rachis, where they seem to touch each other. Each pinna is linear to narrowly lanceolate, gradually widening from a contracted base to about 10 mm wide in the parallel-sided middle region ( Text-fig. 1a ). From the base, parallel, rarely dichotomising veins arise in density 2–3 per 1 mm ( Text-fig. 1c ).

The adaxial cuticle is very thin and thus difficult to prepare. It consists of polygonal ordinary cells (25–30 × 30–55 µm). Their anticlinal walls are thin and tightly sinuous ( Text-fig. 1e ). It is devoid of papillae. The tissue between the adaxial and abaxial cuticle is probably mesophyll, consisting of isodiametric cells (30–40 × 40–50 µm; Text-fig. 1f ). The abaxial cuticle shows costal and intercostal zones. The costal zones are narrower than the intercostal ones, typically 75–90 µm wide ( Text-fig. 1b, d ). They consist of basically quadrangular ordinary epidermal cells (25–38 × 50–125 µm) with sinuous anticlinal walls ( Text-fig. 2a, e ). Intercostal zones are 220–300 µm wide with syndetocheilic stomata (Textfig. 2b–d). Stomata are oriented perpendicularly to the leaf margin, typically arranged in 3–4 ill-defined rows ( Text-figs 1b , 2a ). Externally, they are sunken in pits, surrounded by 2–5 papillae ( Text-fig. 2f ). Their subsidiary cells are 27–35 × 55– 66 µm. Ordinary epidermal cells are isodiametric to elongate (15–25 × 28–40 µm), with straight anticlinal walls ( Text-fig. 2c ). The external side of the cuticle shows numerous papillae, typically 4–5 per ordinary epidermal cell ( Text-fig. 2i, h ). They are so dense that they are sometimes fused, forming united groups ( Text-fig. 2h ).

two better-preserved ordinary cells, LM micro-photograph, scale bar 50 µm. f: Abaxial cuticle showing perpendicularly arranged stomata and papillae per ordinary cell, LM micrography, scale bar 50 µm. g: Detail of mesophyll tissue consisting of isodiametric cells, LM micrography, scale bar 50 µm.

D i s c u s s i o n. Zamites pateri is reminiscent of Zamites bayeri J.KVAČEK, from the same Peruc-Korycany Formation in Praha Malá Chuchle ( Knobloch and Kvaček 1997). They are similar in morphology of the pinnae. Zamites pateri differs from Z. bayeri in having pinnae attached to the dorsal part of the rachis. Further differences are in epidermal structures. Abaxial ordinary epidermal cells in the intercostal zones of the newly described species are nearly straight, bearing 3–5 papillae, whereas Z. bayeri shows ordinary cells more sinuously waved, bearing typically one, rarely several papillae per ordinary epidermal cell. Stomata of Z. bayeri in the marginal parts are occasionally oriented longitudinally to the leaf margin, whereas in Z. pateri they are always perpendicularly oriented ( Tab. 1 ). Furthermore, Z. bayeri does not have preserved any mesophyll tissues. Additionally, Z. bayeri comes from calcareous substrates of Barrandian limestones, whereas Z. pateri comes from silicate substrates of Carboniferous clastic.

Discussion about other similar impression material, including Zamites bohemicus VELEN. described from the Peruc-Korycany Formation by earlier authors was published in detail by Knobloch and Kvaček (1997), and therefore not discussed here.

Z. pateri resembles some Zamites species described from the English Wealden by Watson and Sincock (1992). It particularly shares characters with Z. dowellii J.WATSON et SINCOCK, Z. corderi J.WATSON et SINCOCK and Z. nicolae J.WATSON et SINCOCK in having long and narrow pinnae. Zaimets dowellii is similar in possessing papillae on the abaxial cuticle, but differs from the present material in having stomata on the adaxial cuticle, thus being amphistomatic. Additionally, its abaxial cuticle shows stomata with clearly sinuous anticlinal walls. Zamites corderi differs from Z. pateri in lacking papillae on the abaxial side, while its cuticle shows ordinary epidermal cells with conical trichome bases and well-developed sinuous anticlinal walls. Zamites nicolae differs from Z. pateri in having abaxial ordinary cells with sinuous anticlinal walls, and with only one papilla per ordinary cell. Zamites decurrens C.A.MENÉNDEZ from the Early Cretaceous of Argentina ( Menéndez 1966) resembles Z. pateri in cuticle, having stomata perpendicularly oriented, forming rows and belts. It differs from Z. pateri in having spatulate pinnae. Its adaxial cuticle is thicker, consisting of uniform elongated cells. Its abaxial cuticle shows less dense stomata, forming regular rows ( Tab. 1 ).

Other Early Cretaceous species of Zamites from the English Wealden show more profound differences from Z. pateri : Z. carruthersii SEWARD and Z. manoniae J.WATSON et SINCOCK differ in having narrowly to broadly oval pinnae with rounded bases and bluntly rounded apex; Z. wendyellisae J.WATSON et SINCOCK differs in having pinnae triangular in outline; Z. notokenensis J.WATSON et SINCOCK and Z. tatianae J.WATSON et SINCOCK differ in having smooth or tuberate but not papillate external side of abaxial cuticle ( Watson and Sincock 1992). Further differential characters in epidermal micromorphology of the discussed species are shown in Table 1 .

Figures

Text-fig. 1. Zamites pateri J.KVAČEK sp. nov.; Pecínov locality, holotype, No. NM-F 5185. a: Holotype overview showing fragment of simply pinnate leaf, scale bar 20 mm. b: Abaxial cuticle showing costal and intercostal scale zones and stomata in ill-defined rows, LM micro-photograph, scale bar 100 µm. c: Pinnule detail showing venation pattern, scale bar 5 mm. d: Abaxial cuticle showing costal and intercostal zones, LM micro-photograph, scale bar 500 µm. e: Fragmentary preserved adaxial cuticle showing

Text-fig. 2. Zamites pateri J.KVAČEK sp. nov.; Pecínov locality, holotype, No. NM-F 5185. a: Abaxial cuticle showing costal and intercostal zones, SEM micro-photograph, scale bar 100 µm. b: Abaxial cuticle, detail of syndetocheilic stoma, SEM microphotograph, scale bar 10 µm. c: Abaxial cuticle showing transversely oriented stomata, SEM micro-photograph, scale bar 50 µm. d: Abaxial cuticle, detail of syndetocheilic stoma showing ledges of guard cells, SEM micro-photograph, scale bar 10 µm. e: Abaxial cuticle showing costal ordinary cells seen from inside, SEM micro-photograph, scale bar 50 µm. f: External side of abaxial cuticle showing stoma sunken in a stomatal pit surrounded by papillae, SEM micro-photograph, scale bar 10 µm. g: External side of abaxial cuticle showing papillae, SEM micro-photograph, scale bar 100 µm. h: External side of abaxial cuticle showing detail of fused papillae, SEM micro-photograph, scale bar 10 µm.