''Achistrum'' is an extinct genus of

sea cucumber Sea cucumbers are echinoderms from the class (biology), class Holothuroidea ( ). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number be ...

which existed in Poland during the

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

period, and the United States during the

Carboniferous The Carboniferous ( ) is a Geologic time scale, geologic period and System (stratigraphy), system of the Paleozoic era (geology), era that spans 60 million years, from the end of the Devonian Period Ma (million years ago) to the beginning of the ...

period.Triassic Holothurian Sclerites from Tatra Mountains
Krystyna Zawidzka. It contains the species ''Achistrum nicholsoni'' and ''Achistrum ludwigi''.

References

Apodida Carboniferous echinoderms Triassic echinoderms Fossils of Poland Fossil taxa described in 1881 {{paleo-holothuroidea-stub