Unidentified Cretaceous Granules Discovered in Myanmar Amber

Myanmar amber has long been famous for preserving a wide variety of fossils, and fossil flowers in particular have often attracted the attention of researchers. This time, two pieces of Myanmar amber from the Hukawng Valley in Kachin State, Myanmar, were found to contain a large number of well-preserved granules, including both winged and wingless forms. These amber specimens date to the early Cenomanian of the Cretaceous, approximately 98.79 million years ago.

Two pieces of amber, (a) specimen number PB206074 and (b) specimen number PB206075 （Image source：Huang W and Wang X. (2025)， CC BY-NC-ND 4.0 ）

In one amber specimen (catalog number PB206074), 33 granules representing 14 Morphotypes were recognized. These structures are extremely small, measuring only about 30 to 260 μm in length and 15 to 210 μm in width, with many so minute that they can be observed only under a microscope. As shown in the figures, some of these granules are almost completely surrounded by a wing, some possess an eccentric wing, and others bear bilobate, trilobate, or even irregularly margined wings. Through exclusion, the researchers inferred that these granules may represent angiosperm seeds, potentially reflecting a remarkably high morphological diversity of local angiosperms.

Winged granules in amber specimen PB206074（Image source：Huang W and Wang X. (2025)， CC BY-NC-ND 4.0 ）

In the other amber specimen (catalog number PB206075), at least 66 wingless granules were found concentrated within an area of less than 1 mm². Their forms are not uniform: some are more rounded, whereas others are rectangular or nearly square. The rounded granules measure about 43 to 55 μm long and 21 to 27 μm wide, whereas the more common square or rectangular granules are about 34 to 43 μm long and 28 to 39 μm wide. If these structures are indeed seeds, their extreme concentration suggests that they may all have originated from a single fruit and were later embedded together in resin. This would imply that some angiosperms at that time may already have produced very large numbers of seeds within a single fruit.

Wingless granules in amber specimen PB206075（Image source：Huang W and Wang X. (2025)， CC BY-NC-ND 4.0 ）

How Cretaceous angiosperms rapidly expanded, diversified, and occupied new environments has long been a central question in plant evolution, and these granules—if they are indeed seeds—may provide part of the answer. When plants reduce their seeds to such a minute size, they may be able to produce offspring at very low cost and disperse them over greater distances by wind, thereby promoting both genetic diversity within populations and speciation driven by geographic separation.

Several features of these granules invite comparison with the seeds of extant orchids (Orchidaceae), including their extremely small size, the poor development of the seed coat, and, in some cases, the presence of wing-like structures that may facilitate aerial dispersal. However, extant orchid seeds are usually more elongate, whereas the granules in this amber are often discoid, oval, or even rectangular. For this reason, they cannot currently be identified directly as seeds of true orchids.

In addition, the researchers also raised another possibility: could these tiny structures instead represent certain algae? The study compared them with some green algae previously reported from amber, including forms generally similar to the extant alga Myrmecia, although those fossil algae have not yet been formally classified and named. Although these granules may superficially resemble green algae, they contain a distinct dark body of organic material and differ in size from the observed algal forms, meaning that they cannot be confidently identified as algae.

Although this study did not provide a definitive identification for these granules preserved in amber, the fossils themselves remain highly intriguing and are very likely to represent angiosperm seeds. Their abundance in a very limited space, their morphological variation, and the presence of wing-like structures in some of them all suggest that these are not random microscopic fragments, but rather biologically meaningful dispersal units.

Author: Shui-Ye You

Reference:

Huang W and Wang X. (2025). Fossil evidence of orchid-like dust seeds in Myanmar amber featuring early angiosperm radiation. Scientific Reports.