Florigerminis jurassica, Cui & Hou & Yin & Wang, 2022

Cui, Da-Fang, Hou, Yemao, Yin, Pengfei & Wang, Xin, 2022, A Jurassic flower bud from China, Geological Society, London, Special Publications 521, pp. 1-13 : 4

Florigerminis jurassica gen. et sp. nov.

Etymology. jurassica for the Jurassic, the age of the fossil plant ( Figs 2 & 3 ).

Species diagnosis. In addition to the generic diagnosis, branch 21 mmlongand 2.6 mm wide, slightly tapering distally, internode 2.9–5.1 mm long. Leaf scars 0.4–0.6 mm wide and 0.23 mm thick. Flower bud pedicel straight, 4.6 mm long and 1 mm wide. Flower bud 3.8 mm long and 3.3 mm wide. Lower tepals 1.2 mmlongand>0.8 mm wide. Uppertepals 1.8–3.8 mmlongand 1.5–2.6 mm wide. Fruit approximately 11.5 mmlongand 7.7 mm wide, on a longitudinally striated 22 mm-long and 0.65 mmwide pedicel, with an apical invagination approximately 0.5 mm deep, and persistent foliar parts approximately 2.4 mmlongand 1.4 mm wide. Endocarp approximately 9 mm long and 6 mm wide.

Holotype. PB21737 .

Description. The holotype specimen is 42 mm long and 20 mm wide, preserved as a compression with some coalified residue and an impression ( Fig. 2a ). The plant tissues are embedded in yellowish volcanic tuff ( Fig. 2a–c ). When the coalified residue falls off, an exquisite morphological impression is left on the fine sediment matrix ( Figs 2d–i & 3a–g ). The preserved part of the fossil includes a leafy branch that is physically connected to a fruit and a flower bud ( Fig. 2a ). The branch is elongated, approximately 21 mm long and 2.6 mm wide, with longitudinal fine striations on its surface and at least five nodes, tapering distally ( Figs 2a, d, h & 3b, d, e ). The nodes are marked by several transversal wrinkles ( Figs 2h & 3b ). The lengths of the internodes increase from 2.9 mm at the proximal to 5.1 mm at the distal ( Fig. 2a, h ). Leaves with decurrent bases are helically arranged along the branch, more concentrated to the distal portion of each internode ( Figs 2h & 3d ). All of the leaves have been abscised and only have their scars left on the branch ( Figs 2a, h & 3d ). The leaf scars are 0.4–0.6 mm wide and 0.23 mm thick, with terminal abscission zones ( Fig. 3b, d & e ). Close to the terminal of the branch, fruit pedicel scars are subtended by bracts ( Fig. 3a– c ). The fruit pedicel with longitudinal fine striations is rounded in cross-view, branching into a pair ( Figs 2a–c, i, j & 3h–i ). The fruits are inserted subapically ( Figs 2a, b & 3a ). The flower bud (only one visible in full) is in pairs, on a straight pedicel approximately 4.6 mm long and 1 mm wide, oval in shape, approximately 3.8 mm long and 3.3 mm wide ( Fig. 2a, b, e– g, i, j ). Several layers of upper tepals enwrap the central part ( Figs 2e–g , 3g–i , 4 & 5a ). Micro-CT sections indicate that the tepals surround the bud centre (gynoecium?) ( Fig. 3h, i ). Uppertepals vary from 1.8 to 3.8 mm in length and from 1.5 to 2.6 mm in width ( Figs 2e–g , 3g & 5a ), distinguishing from each other by differently orientated sculpture ( Figs 2e–g , 3g , 4 & 5a ). The fruit is approximately 11.5 mm long and 7.7 mm wide, on a pedicel 22 mm long and only 0.65 mm wide, subtended by four (only three visible in the fossil) foliar parts approximately 2.4 mmlongand 1.4 mm wide, with an apical invagination approximately 0.5 mm deep ( Figs 2a, c, k, l & 3j ). Only the mesocarp and endocarp of the fruits are visible, while the exocarp (epidermis) is too thin to see ( Figs 2a, c, k & 5b ). The mesocarp is approximately 0.34–1.1 mm thick, much thinner near the fruit tip ( Figs 2a, c, k & 5b ). The endocarp is approximately 9 mm long and 6 mm wide, with a pointed tip ( Figs 2a, c & 5b ).

Depository. The Nanjing Institute of Geologyand Palaeontology, Nanjing, China.

Remarks. Only one flower bud and one fruit are preserved in entirety in this fossil. However, there is one extra slender pedicel that is identical to that of the preserved fruit ( Fig. 2a, b, i ), and there seems to be another pedicel of a flower bud embedded in the sediments ( Fig. 2i, j ). Considering the morphology of the fruit pedicel, we assume that it is another fruit, which, unfortunately, is not visible in this specimen. Furthermore, several fruit pedicel scars ( Fig. 3a–c ) strongly imply the existence of fallen fruits in Florigerminis . Therefore, we assume that this fossil originally bore two fruits and two flower buds.

Figures

Fig. 2. Florigerminis jurassica gen. et sp. nov and its details. Stereomicroscopy. (a) Holotype of Florigerminis jurassica, showing the physically connected parts. Two (one missing to the left) fruits and a flower bud are on the branch terminal. Arrows point to the nodes on the branch. PB21737. The scale bar is 10 mm. (b) Close-up of the branch terminal showing a physical connection between two fruit pedicels (1 and 2) and a pedicel of flower bud (3). The scale bar is 2 mm. (c) Close-up of the fruit in (a). Note the mesocarp (m), endocarp (e), three persistent foliar parts visible (arrows) and connected pedicel (lower right). The scale bar is 2 mm. (d) Longitudinal fine striations on the branch surface. The scale bar is 0.25 mm. (e) The flower bud in (b). Note a foliar part at the bottom (arrow). The scale bar is 1 mm. (f) Close-up of (e) showing overlapping distinct tepals (1–4). The scale bar is 0.2 mm. (g) Close-up of (e) showing distinct overlapping tepals in the top portion of the flower bud. The scale bar is 0.5 mm. (h) Nodes (black arrows) with transversal wrinkles and helically arranged decurrent leaf scars (white arrows) on the branch. The scale bar is 1 mm. (i) Pedicels of the fruits (1 and 2) and flower bud (3). The scale bar is 1 mm. (j) Close-up of the rectangular area in (i), showing a pedicel (arrow) embedded in the sediments. The scale bar is 0.5 mm. (k) Tip of the fruit in (c), showing apical invagination (black line), mesocarp (m) and endocarp (e). The scale bar is 1 mm. (l) Three persistent foliar parts (black line) at the fruit bottom in (c). The scale bar is 1 mm.

Fig. 3. SEM and micro-CT details of Florigerminis jurassica gen. et sp. nov. (a) Detailed view of the fruit/flower pedicels and leaf scar near the branch apex. Note the fruit pedicels (1 and 2), flower bud pedicel (3), two additional fruit pedicel scars (black arrows) and a leaf scar (white arrow). Labelled as in Figure 2b. The scale bar is 1 mm. (b) Details near a node, showing a leaf scar (white arrow), transversal wrinkles (black arrow) at the node and two possible fruit pedicel scars (outlined) subtended by scales. The scale bar is 0.2 mm. (c) Elliptical fruit pedicel scar enlarged from (a), subtended by a scale (arrows). The scale bar is 0.1 mm. (d) Branch with helically arranged decurrent leaf scars (arrows). The scale bar is 1 mm. (e) Decurrent leaf base (arrow) with abscission zone at the tip. The scale bar is 0.1 mm. (f) Subtending scale (below the line) and an axillary primordium (arrow), enlarged from the rectangle in (a). The scale bar is 0.1 mm. (g) Fragments of three overlapping tepals (1–3) with differently orientated surface textures. The scale bar is 0.1 mm. (h) Longitudinal micro-CT view of the flower bud with tepals (white arrow) surrounding gynoecium (?) (right arrow) in the centre. The fruit pedicel has obvious longitudinal fine striations (lower arrow). The scale bar is 1 mm. (i) Longitudinal micro-CT view of the flower bud with gynoecium (?) (arrow) in the centre and tips of the tepals at the top. The scale bar is 1 mm. (j) Longitudinal micro-CT view of the fruit with an apical invagination (arrow). The scale bar is 2 mm.

Fig. 4. SEM view of the flower bud of Florigerminis jurassica gen. et sp. nov., showing tepals with sculptures

Fig. 5. Details of Florigerminis jurassica gen. et sp. nov. (a) Sketch showing the arrangement of patches of overlapping tepals. There are at least four layers of tepals (1–4), one over the other. The scale bar is 1 mm. (b) Sketch showing the organization of the fruit, showing the endocarp (black) inside the mesocarp (yellow) supported by a carpopodium (grey) subtended by foliar parts (blue). Refer to Figure 2c, g and h. The scale bar is 2 mm.