Exceptionally preserved priapulid and other “worms” from the Upper Ordovician (Hirnantian) of Latvia

Three casts of possible priapulids, two casts of possible sea anemones, and unidentified worm casts are described from the Hirnantian of Latvia. The specimens occur as three-dimensional casts within fine-grained siltstone, lying parallel to the bedding plane. Rapid burial likely prevented the organisms from scavenging and decay, facilitating their preservation. Although the soft tissues themselves did not mineralize, the surrounding sediment appears to have consolidated quickly. The preservational pathway closely parallels that of recently described priapulid body and trace fossils from the lower Cambrian of Sweden. The studied sample also contains a graphoglyptid trace fossil, Protopaleodictyon, which is typical of relatively deeper-water settings. Hence, the trace-maker likely inhabited a relatively deep-water environment in the central part of the Baltic Basin. The assemblage of body and trace fossils and associated physical sedimentary structures indicates a deep-water, dynamic environment conducive to rapid burial and preservation.