Fossil Provenance and Ethical Statement
The material described herein originates from two amber mines, Tanaing and Hkamti, located in the Hukawng Valley, Kachin State in northern Myanmar11. The mines are introduced in Supplementary Text 1.1. The amber has been radiometrically dated to the earliest Cenomanian, ~99 Ma, and was not produced earlier than the late Albian12,13. Our study was initiated in 2015 and all amber specimens were acquired from local sellers before December 2016, prior to the escalation of the humanitarian crisis in the region (https://doi.org/10.6084/m9.figshare.13317890.v1). The present fossils were briefly introduced in a lecture and poster presentation at the XIX International Botanical Congress (IBC) in ShenZhen, China, July 2017 (lecture title ‘Mid-Cretaceous Seed Plant Diversity in Burmese Amber’, presented by Shuo Wang).
Authenticity of the 21 amber pieces studied herein was verified by the National Gemstone Testing Center (NGTC) of China with Certificate Numbers XCXNo20200903 to XCXNo20200923. These tests included examination of physical and chemical properties of the specimen such as colour, density, optical character, refractive index, amber flow characteristics, and absorption spectrum.
All 21 pieces of amber pieces, preserving 22 fossils, are curated at the Qingdao University of Science and Technology under the collection numbers QUST-AM20501–12, QUST-AM32413–17 and QUST-AM33310 for E. priscastellata sp. nov., and QUST-AM32127, QUST-AM33311, QUST-AM20513–14 for P. piloburmensis sp. nov. (Supplementary Fig. 6). Of the 21 pieces of amber in this study, 19 originate from the ‘Tanaing’ amber mine in Hukawng Valley, except for QUST-AM20511 and QUST-AM32414 which originate from the nearby ‘Hkamti’ mine, which is further shown in (Supplementary Figs. 1–3 and 6).
Fossils were photographed with a digital camera (Fujifilm GFX 50 R with Laowa C11625 2.6 X, Cambo Actar 105 hr or Mitutoyo 5-10 X lens) fitted to a macro rail (Cognisys). For every photograph, 30 to 200 images were stacked with Combine ZP and Photoshop CS4. Some specimens were also photographed using Leica DVM6 and M205FA microscopes (Leica AG, Heerbrugg, Switzerland).
To examine internal structures of the flowers, fossils were scanned with Xradia Versa Micro-XCT 620 (Carl Zeiss X-ray Microscopy Inc., Pleasanton, USA) housed in the Advanced Materials Research Institute of Yangtze Delta. All specimens were scanned with the same beam energy of 40 kV, 3 W, and the LE1 filter, but with different exposure times and pixel sizes that depended on the sample size and condition. Of the 22 fossil specimens, clear scanned images were obtained for 20, but the other 2 samples lack sufficient contrast for scanning. The obtained image stacks were reconstructed with Dragonfly (Ors, Montreal, Canada). Final figures were prepared with Photoshop CS5 and Illustrator CS5 (Adobe, San Jose, USA).
Family Rhamnaceae Jussieu 1789
Tribe Phyliceae Reissek ex Endl. 1840
Genus Eophylica Shi, Wang, et Engel gen. nov.
Type species: Eophylica priscastellata Shi, Wang, et Engel sp. nov.
Etymology: The generic name is a combination of the Greek words, Ēṓs (Ἠώς, meaning “dawn”) and the extant genus Phylica L. (itself derived from Greek: phyllikos, meaning, “leafy”). The gender of the name is feminine.
Generic diagnosis: Identical to Phylica except with eight sepals (2 × 4-merious) (versus five in Phylica), lacking petals (present in most Phylica, although secondarily reversed independently in several crown species), and indumentum composed of stellate Rhamnaceous hairs (simple in Phylica). Additionally: Ovary inferior, fused to receptacle. Style columnar, simple. Fruit a typical capsule, obovoid, about 5.0 mm long, crowned with persistent base of calyx with a convex calyx-area. A complete description is provided in the Supplementary Material.
Species Eophylica priscastellata Shi, Wang, et Engel sp. nov.
Holotype (hic designatus): No. QUST-AM32413 (Fig. 2a–b, l, n–v and Supplementary Fig. 21, deposited in the collection of the Qingdao University of Science and Technology, Qingdao, China.
Paratypes (17 specimens): No. QUST-AM20501–QUST-AM20512, QUST-AM32414–QUST-AM32417 and QUST-AM33310, same repository as holotype.
Type locality and age: No. QUST-AM20501–QUST-AM20510, QUST-AM20512, QUST-AM32413, QUST-AM32415–QUST-AM32417 and QUST-AM33310 are from Tanaing mines, earliest Cenomanian, 98.79 Ma ± 0.62 (ca. 99) Ma. QUST-AM20511 and QUST-AM32414 are from ‘Hkamti’ mines, early Albian, 109.7 ± 0.4 (ca. 110) Ma.
Etymology: The specific epithet is a combination of the Latin terms priscus (meaning, “ancient”) and stellatus (meaning, “starry”).
Species diagnosis: Plants covered in stellate and linear hairs. Leaves long linear, spirally arranged. Head of flower terminal surrounded by interior spreading, sub-incurved, linear leafy bracts. Bracts about twice as long as flower. Flower single on twig tip. Disc epigynous and covering inside of calyx tube. Sepals 8 (2 × 4-merious). Petals absent. A complete description is provided in the Supplementary Material.
Genus Phylica L. 1753
Species Phylica piloburmensis Shi, Wang, et Engel sp. nov.
Etymology: The specific epithet is a combination of the Greek term pîlos (πῖλος, meaning, “hair”) and burmensis (itself a combination of Burma and the Latin suffix –ensis, denoting place).
Holotype (hic designatus): No. QUST-AM32127 (Fig. 4a–g and Supplementary Fig. 26, deposited in the collection of the Qingdao University of Science and Technology, Qingdao, China.
Paratypes (3 specimens): No. QUST-AM33311, QUST-AM20513–QUST-AM20514, same repository as holotype.
Type locality and age: Tanaing mines, earliest Cenomanian, 98.79 Ma ± 0.62 (ca. 99) Ma.
Species diagnosis: Leaves slightly wider (1.5–2.0 mm wide, 4.5–8.0 mm long) and both ad- and abaxial sides covered with simple linear hairs. Flowers not single but forming a corymb. Petals present. Fruit covered with dense indumentum. A complete description is provided in the Supplementary Material.
Character scoring and phylogenetic analysis
Morphological characters scored from leaf, habit, flower, fruit, and pollen were compiled from previous studies29,30,89 and are described in the Supplementary notes. The combined phylogenetic tree was reconstruction based on morphological characters and molecular data following the method of Wilf et al.90; the procedure is further described in the Supplementary notes.