Fig 1.
Geographical and geological contexts of the plant-bearing fossil locality.
(A) The Hunan Province locates in the South China. (B) The Devonian sediments distribution in Hunnan Province. I: Central-Southern Region; I1: Jiangyong-Laiyang Unit, I2: Shaoyang-Liling Unit, I3: Anhua-Liuyang Unit; II: Northwestern Region. (C) The fossil locality of Wangxianqiao Reservoir is close to the Liling City, Hunana Province. Notes: G, National highway; S, Province highway.
Fig 2.
Axes of Lilingostrobus chaloneri gen. et sp. nov. (I).
(A) Gross lateral view of the holotype. An unbranched stem bearing a distal strobilus. Sterile leaves borne on the stem in a low helix or pseudowhorl. Strobilus with densely arranged long sporophylls. Specimen n° 0901. Scale bar = 1 cm. (B) Lateral view of several stems, more or less parallel to each other. Two strobili are visible. Specimen n° 0902. Scale bar = 1 cm. (C) Lateral view of a stem with well-preserved leaves. Leaf base slightly decurrent. Leaf midvein preserved as a deeply sunken groove. Specimen n° 0907b. Scale bar = 2mm. (D) Detail of C. Vegetative leaf showing trichomes. Specimen n° 0907b. Scale bar = 2 mm. (E) Detail of Fig B. Sporophyll with trichomes. Specimen n° 0902. Scale bar = 2 mm. (F) Gross lateral view of a dichotomous axis. Specimen n° 0906. Scale bar = 1 mm.
Fig 3.
Axes of Lilingostrobus chaloneri gen. et sp. nov. (II).
(A) Stem with proximal and distal extremities broken. Vegetative leaves borne on the stem in a low helix or pseudowhorl. Specimen n° 0903P. Scale bar = 1 cm. (B) Detail of pseudowhorls showing more than 5 leaves per pseudowhorl. Deeply sunken grooves indicating leaf midveins. Specimen n° 0903CP. Scale bar = 5 mm. (C) Enlargement of Fig 3A showing the leaves and a partially petrified stem. Specimen n° 0903P. Scale bar = 5 mm.
Fig 4.
Anatomy of the vascular strand of Lilingostrobus chaloneri gen. et sp. nov. (I).
Figs A–D. Specimen n° 0903. (A) SEM of a transverse section of primary xylem bundle preserved in three-dimension. Scale bar = 100 μm. (B) Enlargement of Fig A. SEM of the protoxylem strands at the margin of primary xylem cylinder, with possible oval leaf traces (an arrow) separating from the primary xylem cylinder halfway between two protoxylem strands. Scale bar = 100 μm. (C) Enlargement of Fig B. SEM of a leaf trace preserved in three-dimension. Scale bar = 20 μm (D) Enlargement of Fig B. SEM of three tracheids. Scale bar = 10 μm (E) LM of the primary and secondary xylem preserved in three-dimension, seen in transverse section. Primary xylem is located in the central portion of xylem cylinder while the secondary xylem is arranged radially in the peripheral region. Specimen n° 0910. Scale bar = 1 mm. (F) LM of the primary and secondary xylem is preserved in three-dimension in transverse section. Primary xylem is located in the central portion of xylem cylinder while the secondary xylem is arranged radially in the peripheral region. Specimen n° 0915. Scale bar = 1 mm.
Fig 5.
Anatomy of the vascular strand of Lilingostrobus chaloneri gen. et sp. nov. (II).
Figs A–G. Specimen n° 0914. (A) LM of a portion of a stem showing leaves broken distally and a vascular strand (upper part). Scale bar = 5mm. (B) SEM of a longitudinal view of vascular strand. Primary xylem is in the central portion while secondary xylem is located laterally. Scale bar = 1 mm. (C) Enlargement of Fig B. SEM of the protoxylem tracheids (central part of the picture) and the metaxylem tracheids (left and right), as well as probable vertical parenchyma. Scale bar = 100 μm. (D) Enlargement of Fig B. SEM of the annular/helical thickening of protoxylem tracheids (central part of the picture) and scalariform thickenings of the metaxylem tracheids in the adjacent areas. Scale bar = 50 μm. (E–G) Enlargement of Fig A. SEM of tracheids showing the scalariform pitting, pit aperture and Williamson’s striations (vertical and narrow fibrils connecting two successive scalariform thickening bars) of the metaxylem tracheids. Scale bar = 10 μm in E and F; 20 μm in G. Note: the horizontal thickening bars appear completely filled with amorphous material. Some horizontals bars are branched.
Fig 6.
Anatomy of the vascular strand of Lilingostrobus chaloneri gen. et sp. nov. (III).
(A–E) SEM of specimen n° 0914 in longitudinal views. Enlargment of Fig 5A and 5B. (A) Tracheids of the metaxylem (left) and secondary xylem (right). Scale bar = 500 μm. (B) Metaxylem tracheid (right) and secondary xylem tracheid (left), the latter partly covered by ray(s). The rays consist of horizontally disposed, rectangular, thin-walled, parenchymatous cells. Scale bar = 100 μm. (C) Scalariform bars of tracheids of the secondary xylem and the Williamson’s striations. Note that the horizontal thickening bars are hollow. Scale bar = 10 μm. (D–E) Cross-field (tracheid/ray) pitting including numerous oval to rounded pitlets. In E, the outlines of the ray parenchymatous cells are visible. Scale bar = 10 μm in D and 20 μm in E.
Fig 7.
Reproductive structures of Lilingostrobus chaloneri gen. et sp. nov. (I).
(A) Gross view of several parallel-sided stems suggesting that they are preserved nearly in situ with several strobili are visible. Specimen n° 0904. Scale bar = 1 cm. (B) Isolated fertile specimen showing the densely placed, parallel subvertical laminae of sporophylls. Specimen n° 0906. Scale bar = 1 cm. (C) Detail of Fig A. showing the arrangement of sporophylls on the fertile axis and the base of sporophyll lamina. Specimen n° 0904. Scale bar = 2 mm.
Fig 8.
Reproductive structures of Lilingostrobus chaloneri gen. et sp. nov. (II).
(A) Strobilus preserved as a three-dimensional cast. The pedicels of the sporophylls are inserted on fertile axis at an angle of 90 degrees and sporangia are located in between pedicels. Specimen n° 0919. Scale bar = 5 mm. (B) Enlargement of the middle part of Fig A showing the rounded bodies interpreted as sporangia. Specimen n° 0919. Scale bar = 2 mm. (C) Enlargement of the lower part of Fig A. Arrow indicates a possible rounded sporangium with a short stalk attached at the angle between pedicel and sporophyll lamina. Specimen n° 0919. Scale bar = 1 mm.
Fig 9.
Reproductive structures of Lilingostrobus chaloneri gen. et sp. nov. (III).
(A) Strobilus with microspores. Specimen n° 0907a. Scale bar = 1 cm. (B) Enlargement of Fig A. showing the strobilus with numerous microspores (white cast). Specimen n° 0907a. Scale bar = 5 mm. (C) Enlargement of Fig B. showing the three-dimensional microspore casts. Specimen n° 0907a. Scale bar = 1 mm. (D) Strobilus preserved as a three-dimensional cast showing putative megaspores at the left top. Pedicels of sporophylls inserted on the fertile axis at an angle of 90 degrees. Specimen n° 0916. Scale bar = 2 mm. (E) Strobilus preserved as a three-dimensional cast. The pedicels of sporophylls are inserted on the fertile axis at an acute angle. Specimen n° 0918. Scale bar = 2 mm. (F) Strobilus preserved as a three-dimensional cast. Specimen n° 0917. Scale bar = 2 mm.
Fig 10.
Micro- and putative megaspore morphologies of Lilingostrobus chaloneri gen. et sp. nov.
Figs. A–F. Specimen n° 0907a viewed under SEM. (A) Gross view of microspores preserved in situ. Scale bar = 1 mm. (B) Tetrads of microspores preserved as cast. Scale bar = 100 μm. (C) Microspores preserved as casts (?). Scale bar = 10 μm. (D) Enlargement of Fig B showing tetrads of microspores. Scale bar = 100 μm. (E) Mass of microspores preserved in situ. Scale bar = 100 μm. (F) Enlargement of Fig E showing a spore trilete mark. Scale bar = 10 μm. Figs. G–I. Specimen n° 0916. (G) Portion of the strobilus from Fig 9D showing putative megaspores, which are preserved in between the pedicels in situ in three-dimension. Scale bar = 500 μm. (H) Enlargement of Fig G, showing the putative megaspores. Scale bar = 100 μm. (I) Enlargement of Fig H, showing the surface of a putative megaspore. Scale bar = 10 μm.
Table 1.
Comparison among related Middle-Upper Devonian lycopsids from China.
Fig 11.
Time-scaled phylogeny of the earliest evolutionary relationships of lycopsids.
Tree topology obtained from PAUP* 4.0. Time-scaled phylogeny plotted against stratigraphy via strap. Major clades are in bold. Black box indicates the temporal distribution of involved taxa. Raw data available from Supporting Information.