Short Communication

Eurypterids, or sea scorpions, are an important group of midPaleozoic chelicerate arthropods whose evolution and palaeoecological significance have attracted much attention in recent years. One of the most remarkable eurypterid families is Mixopteridae, whose members are quite large and superficially scorpion-like eurypterids bearing highly specialized anterior appendages. Their second, and especially the third, pair of prosomal limbs are enlarged and very spiny. These limbs were presumably used for prey-capture, and analogies can be drawn with the 'catching basket, formed by the spiny pedipalps of whip spiders (Amblypygi) among the arachnids.

Our knowledge of these bizarre animals is limited to only four species in two genera described 80 years ago: Mixopterus kiaeri from Norway, M. multispinosus from New York, M. simonsoni from Estonia, and Lanarkopterus dolichoschelus from Scotland; all are Silurian in age and come exclusively from the palaeocontinent of Laurussia, which constrains our knowledge of the morphological diversity, geographical distribution and evolutionary history of the group. Here, we describe a new mixopterid, Terropterus xiushanensis gen. et sp. nov., from the Lower Silurian (Llandovery) Xiushan Formation of Xiushan, characterized by a unique arrangement of spines on prosomal limb III; and two incomplete, but larger fossils (Terropterus sp.) from the Lower Silurian (Llandovery) Fentou Formation of Wuhan in Hubei Province. These discoveries represent the first mixopterids from Gondwana and the oldest known mixopterids, and thus add to our knowledge of mixopterid orphological diversity and geographical distribution.