Mimetaster is an extinct genus of marrellomorph arthropod. The type species, Mimetaster hexagonalis is known from the Lower Devonian (Pragian-Emsian) Hunsrück Slate, and amongst the most common arthropods from the locality, with over 120 specimens including three juveniles.
Mimetaster is an extinct genus of marrellomorph arthropod. The type species, Mimetaster hexagonalis is known from the Lower Devonian (Pragian-Emsian) Hunsrück Slate, and amongst the most common arthropods from the locality, with over 120 specimens including three juveniles.
==Description== left|thumb|Diagram of M. hexagonalis in dorsal view The head shield of M. hexagonalis had an average length of , was oval shaped and raised on its upper surface, with three pairs of elongate straight projections radiating outwards, which have pairs of spines. On the upper surface was attached pair of probable eyes on segmented stalks. Attached on the underside was a pair of forward-projecting elongate segmented antennae, the first 10 segments of which were elongate, while the subsequent 14 were short and flagella-like, as well as two pairs of large uniramous (single-branched) leg-like appendages. The first of the two pairs was substantially larger than the second. Also present on the underside of the head was a hypostome, as well as a "ventral organ" of unclear function. The trunk consisted of up to 32 segments, each approximately long and each of which except the last bore a pair of biramous (two-branched) appendages, which gradually decreased in size posteriorly. The endopods (lower, leg-like branches) of the biramous appendages had 7 segments/podomeres, each with endites (structures present on the underside) at the end of each segment except the last. The exopods (upper branches of the limbs) had up to 40 segments, each of which had an individual seta (hair-like structures) projecting downwards.
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).