OSU fossil research leads to first description of grass in Baltic amber

CORVALLIS, Ore. (KTVZ) — Research on amber by the Oregon State University College of Science has produced the first definitive identification of the grass in fossilized tree resin from the Baltic region, home to the deposits of the most famous amber in the world.

The specimen studied by George Poinar Jr., named Eograminis balticus, also represents the earliest fossil member of the Arundinoideae, a subfamily of the widespread family Poaceae that includes cereal grasses, bamboos, and many species found in lawns and gardens. natural meadows.

The results, currently in preprint, will be published in the International Journal of Plant Sciences.

Blown or pushed against a resin tree, the fossil grass lost one of its spikelets 40 or 50 million years ago, along with an accompanying insect that fed on it.

A spikelet is a unit of inflorescence, or floral arrangement, and consists of two glumes and one or more florets. A glume is a leaf-like structure below the flower cluster, and a floret is one of the small flowers in the cluster.

The fossil spikelet is the first definitive evidence that grasses were among the various plants of the Baltic Amber Forest.

“The discovery not only adds a new group of plants to the vast flora that has been described from Baltic amber, but provides new insights into the forest habitat where amber originated, a controversial topic. in this area of ​​study,” said Poinar, an international expert. to use plant and animal life forms preserved in amber to learn about the biology and ecology of the distant past.

Poinar says that some scientists have proposed that fossiliferous amber from the Baltic region formed in tropical and subtropical woods, and others say it came from humid, swampy, warm temperate forest.

“Our new grass suggests that for at least a time the habitat was warm temperate, as you see today in mixed deciduous and coniferous forests,” said Poinar, who collaborated on the study with Roberg Soreng. of the Smithsonian Institution. “Present on the spikelet are an immature grasshopper-like insect and a leaf-spotted fungal spore that provide information about the microhabitat of the fossil grass. The spikelet has structural and developmental features that existed in grasses of the Early Cenozoic and establishes an important benchmark for future studies of the origin and division of genera in its subtribe.

Due to the spikelet’s excellent preservation, observations could be made under direct light with stereoscopic and compound microscopes, Poinar said.

“The spikelet has some characteristics of extant wetland members of the genus Molinia in tribe Molinieae, subtribe Moliniinae,” Poinar said. “Molinia species are concentrated around the Baltic Sea, but some of the characteristics of these species are different from what we see in this fossil.”

Informally known as moor grass, Molinia is a kind of wetland. In addition to the Baltic region, Molinia is found in sand in coastal to subalpine habitats, and in marshes and sphagnum bogs in forests. A fen is a wet area of ​​peat accumulation that is fed by mineral-rich surface or groundwater.

The spikelet specimen of Eograminis balticus originated from the Samland Peninsula in the Kalinin district of the Russian Federation, Poinar said.

The genus name derives from the Latin words for age (éon) and grass (graminis).