beetles, umenocoleid roaches, and achiliid planthoppers. Burmese amber from the Hukawng Valley in northern Myanmar is the only commercially exploited Cretaceous amber. Uranium–lead dating of zircon crystals associated with the deposit have given an estimated depositional age of approximately 99 million years ago. Over 1,300 species have been described from the amber, with over 300 in 2019 alone. Baltic amber is found as irregular nodules in marine glauconitic sand, known as blue earth, occurring in Upper Eocene strata of Sambia in Prussia. It appears to have been partly derived from older Eocene deposits and it occurs also as a derivative phase in later formations, such as glacial drift. Relics of an abundant flora occur as inclusions trapped within the amber while the resin was yet fresh, suggesting relations with the flora of eastern Asia and the southern part of North America. Heinrich Göppert named the common amber-yielding pine of the Baltic forests Pinites succiniter, but as the wood does not seem to differ from that of the existing genus it has been also called Pinus succinifera. It is improbable that the production of amber was limited to a single species; and indeed a large number of conifers belonging to different genera are represented in the amber-flora. Paleontological significance Amber is a unique preservational mode, preserving otherwise unfossilizable parts of organisms; as such it is helpful in the reconstruction of ecosystems as well as organisms; the chemical composition of the resin, however, is of limited utility in reconstructing the phylogenetic affinity of the resin producer.Amber sometimes contains animals or plant matter that became caught in the resin as it was secreted. Insects, spiders and even their webs, annelids, frogs, crustaceans, bacteria and amoebae, marine microfossils, wood, flowers and fruit, hair, feathers and other small organisms have been recovered in Cretaceous ambers (deposited c. ). The preservation of prehistoric organisms in amber forms a key plot point in Michael Crichton's 1990 novel Jurassic Park and the 1993 movie adaptation by Steven Spielberg. In the story, scientists are able to extract the preserved blood of dinosaurs from prehistoric mosquitoes trapped in amber, from which they genetically clone living dinosaurs. Scientifically this is as yet impossible, since no amber with fossilized mosquitoes has ever yielded preserved blood. Amber is, however, conducive to preserving DNA, since it dehydrates and thus stabilizes organisms trapped inside. One projection in 1999 estimated that DNA trapped in amber could