Fig 3

Selected polylobate sub-morphotypes retrieved from the studied grasses. Light microscopic images (1-13) and scanning electron microscopic images (14-22). (Tri-regular-small - 1. a. Oplismenus compositus, 1.b. Paspalum conjugatum, 1.c. Echinochloa picia, 14.a Brachiaria reptans, 14.b Echinochloa crus-pavonis), (Tri-irregular-small - 2.a Setaria pallide-fusca, 2.a Zea mays), (Tetra-regular-small - 3.a Oplismenus burmanni, 3.b Setaria verticillata), (Tetra-irregular-small - 4. Paspalum scrobiculatum, 15.a Setaria pallide-fusca, 15.b Oplismenus compositus), (Penta-irregular-small - 5.a Oplismenus burmanni, 5.b Apluda mutica), (Hexa-irregular-small – 6, 16.a Themeda arundinacea, 16.b – 16.c Apluda mutica), (Hepta-irregular small - 7.a and 7.c Apluda mutica, 7.b - 7.d Themeda arundinacea), (Octa-irregular small 8.a - 8.b, 17. Themeda arundinacea, (Tri-regular-medium - 9.Porteresia coarctata, 18.a Echinochloa stagnina, 18.b Digitaria setigera), (Tri-irregular-medium - 19.Setaria viridis), (Tetra-regular-medium - 20. Panicum flavidium), (Tetra-irregular-medium - 10. Paspalum distichum), (Penta-irregular-medium 11. Dichanthium annulatum, 22. Dichanthium caricosum), (Hexa-regular-medium - 12. Oplismenus burmanni), (Tri-regular-large - 13. Digitaria abscendens, 21. Echinochloa frumentacea)

Fig 5

Selected rondel/tower sub-morphotypes retrieved from the studied grasses. Light microscopic images (1-11) and scanning electron microscopic images (12-19). (Flat tower – 1.a Sporobolus spicatus, 1.b Paspalum vaginatum, 12.a Aeluropus lagopoides, 12.b Zoysia matrella), (Two-horned rondel – 2.a-e, 13.a-e), (Three-horned rondel – 3.a-c Porteresia coarctata, 3.d-e Paspalum vaginatum, 3.f Eragrostis gangetica, 3.g Dichanthium caricosum -14.a Paspalum conjugatum, 14.b Porteresia coarctata), (Four-horned rondel – 4.a-g Porteresia coarctata), (Pyramidal rondel – 5. Coix lacryma-jobi), (Ellipsoid rondel – 6.a Digitaria bicornis, 6.b Sporobolus wallichii, 6.c Porteresia coarctata ), (Keeled rondel – 7.a Eragrostis unioloides, 7.b Eragrostis nutans, 15.a Paspalum distichum, 15.b Chrysopogon aciculatus 15.c Leersia hexandra), (Spool/horned tower – 8.a Paspalum vaginatum, 8.b Porteresia coarctata, 18.a Eragrostis viscosa, 18.b Leptochloa chinensis, 18.c Aeluropus lagopoides ), (Oval rondel – 9.a Thysanolaena maxima, 9.b Arundo donax, 9.c Eragrostis viscosa, 16 Sporobolus diander), (Wavy top rondel – 10 Aeluropus lagopoides, 17 Oryza rufipogon), (Complex tower – 11.a Bambusa ventricosa, 11.b Desmostachya bipinata, 11.c Chloris montana, 19. Bambusa wamin

Supplementary Table 1

List of studied grass taxa along with their taxonomic position (After Soreng et al. 2015), collection areas, habitats, and principal phytolith assemblages

Fig 7

Selected sub-morphotypes of elongate, bulliform, and ‘others’ groups, retrieved from the studied grasses. Light microscopic images (1-13) and scanning electron microscopic images (14-24). (Elongate psilate/smooth long cells – 1.a Echinochloa stagnina, 1.b Panicum paludosum, 1.c Setaria palmifolia, 14. Eragrostis japonica), (Elongate papilate/sinuate long cells 2.a Digitaria bicornis, 2.b Phragmites karka, 2.c Echinochloa crusgalli 15. Setaria barbata), (Elongate echinate long cells – 3.a Brachiaria milliformis, 3.b Panicum paludosum, 3.c Setaria viridis, 16.a Dendrocalamus giganteus, 16.b Bambusa wamin), (Elongate dendritic long cells – 4. Panicum repens, 17. Apluda mutica), (Elongate crenate long cell – 5. Triticum aestivum), (Elongate angular long cells – 6.a Digitaria setigera, 6.b Panicum repens, 6.c Cymbopogon citratus, 18. Bambusa oliveriana), (Parallepipedal bulliform – 7.a Brachiaria sp., 7.b Imperata cylindrica, 23. Leptochloa chinensis), (Cuniform bulliform 8.a Oryza rufipogon, 8.b Bambusa vulgaris var. vittata, 8.c Dinochloa maclellandii, 24.a Imperata cylindrica, 24.b Pennisetum typhoides, 24.c Oryza sativa), (Stomate – 9.a Cynodon dactylon, 9.b Paspalum longifolium, 9.c Eragrostis atrovirens, 21. Eleusine indica), (Silicified epidermal tissue – 10 Eragrostis japonica), (Prickle – 11.a Digitaria ciliaris, 11.b Eragrostis atrovirens, 19. Leptochloa chinensis), (Hair – 12. Digitaria abludens, 20. Dinochloa maclellandii), (Broken bilobate – 13.a Saccharum spontaneum, 13.b Aristida adscensionis, 22. Saccharum spontaneum

Table 2

Morphotypes and sub-morphotypes of studied phytoliths with hand drawn illustrations. (Modified after Twiss et al. 1969, Sase and Kondo 1974, Brown 1984, Kondo and Sase 1986, Piperno 1988, Mulholland 1989, Pearsall 1989, Pearsall and Piperno 1990, Mulholland and Rapp 1992, Twiss 1992, Fredlund and Tieszen 1994, Kondo et al. 1994, Piperno and Pearsall 1998, Pearsall 2000, Lu and Liu 2003a, Lu and Liu 2003b, Stromberg 2003, Gallego and Distel 2004, Blinnikov 2005, Madella et al. 2005, Honaine et al. 2006, Piperno 2006, Fahmy 2008, Barboni and Bremond 2009, Mercader et al. 2010, Ghosh et al. 2011, Gu et al. 2013, Biswas et al. 2016, Naskar and Bera 2016, Neumann et al. 2017

Fig 2

Selected bilobate sub-morphotypes retrieved from the studied grasses. Light microscopic images (1-33) and scanning electron microscopic images (64-61). (Small bilobate with short shank and convex-convex ends – 1. Panicum paludosum), (Small bilobate with medium shank and convex-convex ends – 2. Brachiaria milliformis, 34. Leersia hexandra), (Small bilobate with long shank and convex-convex ends – 3. Digitaria setigera, 35. Chrysopogon aciculatus), (Small bilobate with nodular shank and convex-convex ends – 4. Oplismenus burmanni, 36. Setaria verticillata), (Small bilobate with short shank and concave-concave ends 5. Arundo donax, 37. Digitaria compacta), (Small bilobate with medium shank and concave-concave ends – 38. Oryza sativa), (Small bilobate with long shank and concave-concave ends – 6. Paspalidium geminatum, 39. Digitaria ciliaris), (Small bilobate with nodular shank and concave-concave ends – 7. Setaria barbata, 40. Themeda arundinacea), (Small bilobate with short shank straight-straight ends – 41. Setaria glauca), (Small bilobate with short shank and concave-convex ends – 8, (Small bilobate with medium shank and concave-convex ends – 9. Panicum repens), (Small bilobate with spiny shank and concave-convex ends – 10. Setaria verticillata), (Small bilobate with medium shank and convex-straight ends – 11. Setaria palmifolia), (Small bilobate with long shank and convex-straight ends – 12, Digitaria bicornis, 43. Chrysopogon aciculatus, ), (Small bilobate with short shank and concave-straight ends – 42. Eriochloa procera), (Small bilobate with long shank and concave-straight ends – 13. Digitaria compacta), (Medium bilobate with short shank and convex-convex ends – 14. Panicum flavidium ), (Medium bilobate with medium shank and convex-convex ends – 15. Leptochloa chinensis, (Medium bilobate with long shank and convex-convex ends 16. Imperata cylindrica var. major, 44. Setaria palmifolia), (Medium bilobate with spiny shank and convex-convex ends – 17. Paspalum longifolium), (Medium bilobate with short shank and concave-concave ends – 46. Paspalidium punctatum), (Medium bilobate with medium shank and concave-concave ends – 18.Oryza sativa, 48. Thysanolaena maxima), (Medium bilobate with nodular shank and convex-convex ends – 47. Echinochloa stagnina), (Medium bilobate with short shank and concave-convex ends – 20. Setaria pallide-fusca), (Medium bilobate with medium shank and concave-convex ends – 45. Digitaria violascens), (Medium bilobate with long shank and concave-convex ends 21. Digitaria ciliaris), (Medium bilobate with nodular shank and concave-convex ends – 22. Oplismenus burmanni), (Medium bilobate with medium shank and straight-straight ends – 49. Heteropogon contortus), (Medium bilobate with short shank and convex-straight ends – 50. Saccharum officinarum), (Medium bilobate with medium shank and scooped ends 51. Oryza sativa), (Large bilobate with short shank and convex-convex ends – 23. Panicum flavidium), (Large bilobate with medium shank convex-convex ends – 52. Hymenachne amplexicaulis), (Large bilobate with long shank convex-convex ends – 25. Aristida adscensionis, 53. Heteropogon contortus), (Large bilobate with spiny shank and convex-convex ends – 24. Digitaria timorensis), (Large bilobate with medium shank and concave-concave ends – 26. Tritichum aestivum), (Large bilobate with medium shank and convex-concave ends – 54. Hymenachne amplexicaulis), (Large bilobate with long shank and convex-concave ends – 27. Saccharum spontaneum), (Large bilobate with nodular shank and concave-concave ends – 55. Brachiaria subquadripara), Large bilobate with long shank and convex-straight ends – 28. Heteropogon sp.), (Large bilobate with medium shank and concave-straight ends – 29. Setaria glauca), (Large bilobate with long shank and concave-straight ends – 56. Leptochloa filiformis), (Large bilobate with short shank and scooped ends– 57. Oryza rufipogon), (Very large bilobate with short shank and convex-convex ends – 30. Setaria palmifolia, (Very large bilobate with medium shank and convex-convex ends – 58. Echinochloa crus-galli), Very large bilobate with long shank and convex-convex ends – 31. Heteropogon sp., 59. Digitaria abludens), (Very large bilobate with short shank and concave-concave ends – 32. Echinochloa frumentacea), (Very large bilobate with medium shank and concave-concave ends – 61. Brachiaria milliformis), (Very large bilobate with nodular shank and concave-concave ends – 60. Echinochloa frumentacea), (Very large bilobate with medium shank and convex-concave ends – 33. Eriochloa procera

Fig 6

Selected sub-morphotypes of cross, trapeziform, and pooidae class groups, retrieved from the studied grasses. Light microscopic images (1-13) and scanning electron microscopic images (14-22). (Small cross with thin lobes – 2.a Leersia hexandra, 2.b Dichanthium caricosum, 2.c Paspalum distichum, 2.d Porteresia coarctata, 15.a Echinochloa crusgalli, 15.b Panicum repens, (Small cross with thick lobes – 1.a Echinochloa crus-pavonis, 1.b Brachiaria mutica, 1.c Panicum sp., 14.a Pennisetum typhoides, 14.b Setaria glauca, (Medium cross with thick lobes – 3.a Echinochloa stagnina, 3.b Brachiaria subquadripara, 3.c. Saccharum officinarum 16. Echinochloa colonum), (Medium cross with thin lobes – 4.a Paspalum distichum, 4.b Brachiaria distachya, 4.c Paspalidium geminatum, 17. Imperata cylindrica), (Large cross with thick lobes – 5.a Coix lacryma-jobi, 5.b Paspalidium sp., 18. Coix gigantea), (Large cross with thin lobes – 6.a Brachiaria milliformis, 6.b Porteresia coarctata, 19.a Echinochloa frumentacea, 19.b Paspalum distichum), (Trapeziform rectangular short cell – 7.a Pennisetum pedicellatum, 7.b Bambusa tulda, 7.c Desmostachya bipinata, 20.a Eragrostis tenuifolia, 20.b Heteropogon contortus), (Trapeziform square short cell –8.a Vetiveria zizanioides, 8.b Sporobolus diander, 8.c Paspalum scrobiculatum), (Trapeziform sinuate 9.a, 9.b Triticum aestivum, (Trapeziform polylobate –10a, 21 Triticum aestivum, 10.b Brachiaria subquadripara, 10.c Aeluropus lagopoides), (Circular/Round – 11.a Echinochloa picia, 11.b Paspalum longifolium, 11.c Sporobolus diander, 11.d Zoysia matrella, 21. Eragrostis coarctata), (Crescent moon – 12.a Sporobolus spicatus, 12.b Eleusine indica, 12.c Sporobolus diander, (13. Biconvex - Aeluropus lagopoides

Percentage frequency of principal phytolith morphotypes

Percentage frequency of principal phytolith morphotype