Mid-Cretaceous coastal amber forest palaeoenvironment revealed by exceptionally preserved ostracods from an extant lineage

Abstract

As a famous fossil Lagerstätte, the mid-Cretaceous (ca. 100 Ma) amber from Kachin, northern Myanmar, harbors one of the most diverse Mesozoic palaeobiotas yet discovered. Over the past few years, reports of organisms trapped in Kachin amber have increased exponentially. Ostracods, as fully aquatic animals, are so far represented in Kachin amber by two records of specimens without soft parts (1 valve and two carapaces) as well as an exceptional assemblage with well-preserved soft parts comprising 39 specimens of three species assigned to the families Candonidae and Loxoconchidae. Since the last-mentioned focused on the exceptional preservation of giant sperm and reproductive organs in only one species, we here present in-depth morphological descriptions of all three species including a new genus: Myanmarcypris hui Wang et al., 2020, Electrocypria burmiteigen. et sp. nov., and Sanyuania sp. We further describe taphonomic traits indicating that the studied ostracods were quickly surrounded by resin and instantly immobilized. The palaeoenvironment is considered to be a vegetated brackish (mesohaline-oligohaline) lagoon.