Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects radiodont morphology and ecology remained unclear because the typically fragmentary nature fossil material. Here, we describe new hurdiid based on abundant exceptionally well-preserved fossils from Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov . is characterized by an extra-large horseshoe-shaped...

Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among largest and most diversified lower palaeozoic predators. These animals widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders apex Here, we describe hurdiid radiodont known so far, Titanokorys gainesi , gen. et sp. nov., Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated reach half metre in length, this...

Abstract Radiodonts (stem Euarthropoda) were ecologically diverse, but species generally displayed limited functional specialization of appendages along the body axis compared with crown group euarthropods. This is puzzling, because such considered to have been an important driver euarthropod ecological diversification. One way circumvent this constraint could different parts frontal appendages, known in radiodonts. hypothesis has yet be tested explicitly. Here we redescribe poorly...

Agnostids (agnostinids and eodiscinids) are a widespread biostratigraphically important group of Cambro-Ordovician euarthropods whose evolutionary affinities have been highly controversial. Their dumbbell-shaped calcified tergum was traditionally suggested to unite them with trilobites, but agnostinids alternatively interpreted as stem-crustaceans, based on Orsten larval material from the Cambrian Sweden. We describe exceptionally preserved soft tissues mature individuals Peronopsis...

Cnidarians are regarded as one of the earliest-diverging animal phyla. One hallmarks cnidarian body plan is evolution a free-swimming medusa in some medusozoan classes, but origin this innovation remains poorly constrained by fossil record and molecular data. Previously described macrofossils, putatively representing stages crown-group medusozoans from Cambrian Utah South China, here reinterpreted ctenophore-grade organisms. Other putative Ediacaran to fossils consist mainly microfossils...

Abstract Radiodonta is a clade of stem euarthropods central importance to our understanding the evolution this phylum. Radiodonts include some largest early Paleozoic animals; however, little known about their ontogeny. We present an analysis molting patterns and ontogeny in radiodont Stanleycaris based on 265 exceptionally preserved specimens from mid-Cambrian (Wuliuan) Burgess Shale. Ranging size 10 83 mm, they constitute most extensive ontogenetic series known. Using novel morphospace...

Abstract Ordovician open marine Lagerstätten are relatively rare and widely dispersed, producing a patchy picture of the diversity biogeography nonmineralized organisms challenging our understanding fate Cambrian groups. Here, for first time, we report soft-bodied fossils, including well-preserved marrellomorph arthropod, fragmentary carapaces, macroalgae, from Late (Katian) Upper Member Kirkfield Formation near Brechin, Ontario. The unmineralized elements associated exceptionally preserved...

Including additional photos of specimens, full list modifications and results analysis, specimen data a characters considered relevant to the Agnostid Problem.

Including supplementary figures and tables, parsimony maximum likelihood methods, list of characters taxa in phylogenetic analyses