Chainandra zeugostylus gen. et sp. nov., a mid-Cretaceous amber fossil with sagittate anthers opening widely at maturity
A flower preserved in 100 Ma amber from Myanmar is described here as Chainandra zeugostylus, a new genus and species of fossil angiosperms. The anthers in Chainandra are sagittate at the base and have only a short connective. They dehisce by means of a circumferential stomium, the dorsal and ventral sides of each locule forming flaps that become widely separated. The style of Chainandra is columnar and two-branched above the middle, and the fully inferior ovary bears an epigynous nectar disc but lacks well-defined ribs or veins. In Tropidogyne, Lacknociona, and Strombothelya, similar genera described earlier from the same am-ber deposits, the styles are either unbranched or are 3–5-branched to near the base, and the ovary is half-inferior to inferior, its lower portion often being dis-tinctly veined and ribbed. Morphology of the stamens and gynoecium of the three genera suggests that they are early members of the eudotyledons.
Chambers, K.L., G.O. Poinar, Jr., & R. Buckley. 2010. Tropidogyne, a new genus of Early Cretaceous eudicots (Angiospermae) from Burmese amber. Novon 20:23–29.
Chambers, K.L. & G.O. Poinar, Jr. 2020. Thymolepis toxandra gen. et sp. nov., a mid-Cretaceous fossil flower with horseshoeshaped anthers. J. Bot. Res. Inst. Texas 14:57–64.
Cohen, K.M., S. Finney, & P.L. Gibbard. 2013. International Chronostratigraphic Chart. International Commission on Stratigraphy. www.stratigraphy.org
Cruickshank, R.D. & K. Ko. 2003. Geology of an amber locality in the Hukawng Valley, northern Myanmar. J. Asian Earth Sci. 21:441–445.
Endress, P.K. & S. Stumpf. 1990. Non-tetrasporangiate stamens in the angiosperms: Structure, systematic distribution and evolutionary aspects. Bot. Jahrb. Syst. 112:193–240.
Endress, P.K. & S. Stumpf . 1991. The diversity of stamen structures in “Lower” Rosidae (Rosales, Fabales, Proteales, Sapindales). Bot. J. Linn. Soc. 107:217–293.
Liu, Z-J., D. Huang, C. Cai, & X. Wang. 2018. The core eudicot boom registered in Myanmar amber. Sci. Rep. 8:16765. www.nature.com/scientificreports
Manchester, S.R., D.K. Dilcher, W.B. Judd, B. Corder, & J.F. Basinger. 2018. Early Eudicot flower and fruit: Dakotanthus gen. nov. from the Cretaceous Dakota Formation of Kansas and Nebraska, U.S.A. Acta Palaeobot. 58:27–40.
Perkins, J. & E. Gilg. 1901. Monimiaceae. In: A. Engler, ed. Das Pflanzenreich. Verlag Wilhelm Engelmann, Leipzig, Germany. IV. 101:1–122.
Poinar, G.O., Jr. & K.L. Chambers. 2017. Tropidogyne pentaptera sp. nov., a new mid-Cretaceous fossil angiosperm flower in Burmese amber. Paleodiversity 10:135–140.
Poinar, G.O., JR. & K.L. Chambers. 2018. Fossil flowers of Lachnociona camptostylus sp. nov., a second record for the genus in mid-Cretaceous Myanmar amber. J. Bot. Res. Inst. Texas 12:655–666.
Poinar, G.O., Jr. & K.L. Chambers. 2019a. Strombothelya gen. nov., a fossil angiosperm with two species in mid-Cretaceous Myanmar amber. J. Bot. Res. Inst. Texas 13:451–460.
Poinar, G.O., Jr. & K.L. Chambers. 2019b. Tropidogyne lobodisca sp. nov., a third species of the genus from mid-Cretaceous Myanmar amber. J. Bot. Res. Inst. Texas 13:461–466.
Poinar, G.O., Jr. & K.L. Chambers. 2020. Phantophlebia dicycle gen. et sp. nov., a five-merous fossil flower in mid-Cretaceous Myanmar amber. J. Bot. Res. Inst. Texas 14:73–80.
Poinar, G.O., Jr., K.L. Chambers, & R. Buckley. 2008. An Early Cretaceous angiosperm fossil of possible significance in Rosid floral diversification. J. Bot. Res. Inst. Texas 2:1183–1192.
Poinar, G.O., Jr., K.L. Chambers, U.T. Iwaniec, & F.E. Vega. 2020. Valviloculus pleristaminis gen. et sp. nov., a fossil Lauralean flower with valvate anthers from mid-Cretaceous Myanmar amber. J. Bot. Res. Inst. Texas 14:xxx–xxx.
Poinar, G.O., Jr., G.J.B. Lambert, & Y. Wu. 2007. Araucarian source of fossiliferous Burmese amber: Spectroscopic and anatomical evidence. J. Bot. Res. Inst. Texas 1:449–455.
Rohwer, J.G. 1993. Lauraceae. In: K. Kubitzki, J.G. Rohwer, & V. Bittrich, eds. The families and genera of vascular plants. Springer-Verlag, Berlin, Germany. 2:366–391.
Shi, G., D.A. Grimaldi, G.E. Harlow, J. Wang, M. Yang. W. Lu, Q. Li, & X. Li. 2012. Age constraint on Burmese amber based on U-Pb dating of zircons. Cretaceous Res. 37:155–163.
Sokol, J. 2019. Troubled treasure. Science 364:722–729.