Fallotaspidoidea
The ”Fallotaspidoidea” are a superfamily of trilobites, a group of extinct marine arthropods. It lived during the Lower Cambrian and species occurred on all paleocontinents except for the Gondwana heartland. A member of this group, Profallotaspis jakutensis, has long been the earliest known trilobite, but recently the redlichiid Lemdadella has been claimed as occurring even earlier.
Distribution
”Fallotaspidoidea” occur in the Lower Cambrian of North America, Europe, northwestern Africa and northern Asia.Dispersion of the “Fallotaspidoidea”
Lieberman suggests that fallotaspidoids, the first hard-shelled trilobites, originate in the paleocontinent Siberia. The group quickly spread to southern Europe and northwestern Africa, which were part of the margin of Gondwana, and northwestern Laurentia. The sutured Redlichiina developed from the fallotaspidoids somewhere in Siberia and the Gondwana-margin, and from there spread to all of Gondwana, including current China and Australia, where fallotaspidoids and other Olenellina were absent. In Laurentia the Fallotaspidoids were succeeded by Nevadioids, Judomioids and Olenelloids, the latter remaining the dominant group of trilobites until the extinction of all Olenellina at the very end of the Lower Cambrian, after which Redlichiina, Ptychopariida and Corynexochida took over.Taxonomy
The views of scholars on the relationships of the taxa now assigned to the ”Fallotaspidoidea” have changed regularly over the past half century or so. Initially, the Olenellidae, which also encompassed the subfamily Fallotaspidinae, was regarded the sistergroup of the Daguinaspididae, a view that made it into the Treatise of 1959. Later, the genera now in the ”Fallotaspidoidea” were considered part of the Holmiinae, the sistergroup of the Olenellinae and the Nevadiinae.[Image:Fallotaspoidea cladogram.jpeg|thumb|Schematic showing the relationships between the genera within the Fallotaspoidea and with other trilobites] Bergström recognized within the family Daguinaspididae five subfamilies: the Daguinaspidinae and the Fallotaspidinae, together comprising the current ”Fallotaspidoidea”, in addition to the Nevadiinae, the Neltneriinae and the Callaviniinae. This was followed by the view that the Archaeaspididae, the Fallotaspididae and the Daguinaspididae were all families of their own and sistergroups of the Olenellidae, Homiidae, and Nevadiidae. Ahlberg et al., moved the Archaeaspis-group as a subfamily to the Callaviidae, leaving the Fallotaspis-group and the Daguinaspis-group as subfamilies in the Daguinaspididae. Palmer and Repina erected two superfamilies, the Olenelloidea and the Fallotaspidoidea, the latter consisting of the Fallotaspididae, and the Archaeaspididae, next to the Nevadiidae, the Neltneriidae and the Judomiidae. This opinion was reflected in the Revised Treatise of 1997.[Image:Eofallotaspis.jpg|thumb|left|Drawing of Eofallotaspis tioutensis from Morocco]
More recent cladistic analysis suggests that the ”Fallotaspidoidea” are the sister group of all other Olenellina. The ”Fallotaspidoidea” remain paraphyletic, even after reorganizing it, because it gave rise to the trilobites with dorsal sutures. Applying a strictly cladistic approach would call for including the ”Fallotaspidoidea” in the Redlichiina, and possibly raising the status of the remaining Olenellina to become an order.