(CNN)When it comes to dinosaurs, many of us think of towering skeletons dominating the atriums of the world's great natural history museums.
But it's the tiniest fossils that have transformed paleontology over the past five years.
Some of the field's most extraordinary discoveries have come from amber: A dinosaur tail, parts of primitive birds, insects, lizards and flowers have all been found entombed in globs of 100 million-year-old tree resin.
They offer a tantalizing, three-dimensional look at dinosaur times. The vivid creatures and plants look like they just died yesterday with soft tissue in place and details like skin, coloring, feathers, teeth, leaves and petals exquisitely preserved -- details that are often lost in the crush of fossils formed in rock.
But this treasure comes with baggage.
Richest deposits are in a country marred by civil war
Amber is found in several places around the world, but amber deposits dating from the time before dinosaurs went extinct are rare. Some of the richest deposits have been found in Myanmar's Kachin State, in the northern part of the country, near the border of China. Government forces and ethnic minorities have fought in this region for years.
In 2017, Myanmar's military, which stand accused of genocide against the Rohingya ethnic group in the west of the country, began seizing control of the amber mines from the indigenous Kachins, adding to the strife.
"There is evidence of human rights abuses that are directly linked to the mining of amber, and I would say as paleontologists, but also as people, we have to think of the ethical implications of what we do," said Emily Rayfield, a paleobiology professor at the University of Bristol's School of Earth Sciences in the United Kingdom and president of the Society of Vertebrate Paleontology (SVP), an organization dedicated to the study of vertebrate fossils.
The society is calling on colleagues to refrain from working on amber sourced from Myanmar since June 2017, when the military took over the mines. It has also asked more than 300 scientific journals to stop publishing research based on amber fossils found since that date.
"We do not condone promoting our scientific endeavor at the expense of people facing humanitarian crisis," said Rayfield and other society leadership, in a strongly worded letter to journal publishers in April.
The society's members expressed concern that many prized Burmese amber specimens end up in private hands through commercial trading, rather than public institutions, making it difficult for scientists around the world to study them.