Extant taxon

Phylogenetic tree

Key (lock)

Evolutionary biology

Biology

Zoology

Gene

Cretaceous

Monophyly

Genus

Paleontology

Larva

Ecology

Isopoda

Clade

Biochemistry

Crustacean

PalZ

Within Isopoda (woodlice and relatives), there are lineages characterised by a parasitic lifestyle that all belong to Cymothoida and likely form a monophyletic group. Representatives of Epicaridea (ingroup of Cymothoida) are parasitic on crustaceans and usually go through three distinct larval stages. The fossil record of Epicaridea is sparse and thus little is known about the palaeoecology and the origin of the complex life cycle of modern epicarideans. We present an assemblage of over 100 epicarideans preserved in a single piece of Late Cretaceous Myanmar amber. All individuals are morphologically similar to cryptoniscium stage larvae. The cryptoniscium stage usually constitutes the third and last larval stage. In modern representatives of Epicaridea, the cryptoniscium larvae are planktic and search for suitable host animals or adult females. These fossil specimens, though similar to some extant species, differ from other fossil epicaridean larvae in many aspects. Thus, a new species (and a new genus), Cryptolacruma nidis , is erected. Several factors can favour the preservation of multiple conspecific animals in a single piece of amber. However, the enormous density of epicarideans in the herein presented amber piece can only be explained by circumstances that result in high local densities of individuals, close to the resin-producing tree.

Mass occurrence of small isopodan crustaceans in 100-million-year-old amber: an extraordinary view on behaviour of extinct organisms