A Carboniferous Non-Onychophoran Lobopodian Reveals Long-Term Survival of a Cambrian Morphotype

SummaryLobopodians, a nonmonophyletic assemblage of worm-shaped soft-bodied animals most closely related to arthropods, show two major morphotypes: long-legged and short-legged forms. The morphotype with stubby, conical legs has a long evolutionary history, from the early Cambrian [1] through the Carboniferous [2, 3], including the living onychophorans and tardigrades [4–6]. Species with tubular lobopods exceeding the body diameter have been reported exclusively from the Cambrian [7–12]; the three-dimensionally preserved Orstenotubulus evamuellerae from the uppermost middle Cambrian “Orsten” (Sweden) is the youngest long-legged lobopodian reported thus far [8]. Here we describe a new long-legged lobopodian, Carbotubulus waloszeki gen. et sp. nov., from Mazon Creek, Illinois, USA (∼296 million years ago) [13]. This first post-Cambrian long-legged lobopodian extends the range of this morphotype by about 200 million years. The three-dimensionally preserved specimen differs significantly from the associated short-legged form Ilyodes inopinata [2], of which we also present new head details. The discovery of a Carboniferous long-legged lobopodian provides a more striking example of the long-term survival of Cambrian morphotypes than, for example, the occurrence of a Burgess Shale-type biota in the Ordovician of Morocco [14] and dampens the effect of any major extinction of taxa at the end of the middle Cambrian [15, 16]