The oldest fossil annelids come from the Early Cambrian Sirius Passet and Guanshan biotas and Middle Cambrian Burgess Shale. While these are among the best preserved polychaete fossils, their relationship to living taxa is contentious, having been interpreted either as members of extant clades or as a grade outside the crown group. New morphological observations from five Cambrian species inclu...

The vast differences between vertebrate and arthropod eyes suggest that the recently discovered homologous master control genes for eye development had another function before eyes evolved in the early Cambrian.

Understanding the identity of segments and the evolution of their appendages is a prime concern of arthropod evolution studies. This has been challenging for long extinct stem-groups. Now, Cambrian fossils offer insights that will help further evolutionary considerations.

New geochronological and geochemical data document a new widely distributed succession of igneous sedimentary rocks within the Sibumasu that extend from SW Yunnan through SE Asia as far Sumatra. Our revealed presence an Ordovician-Silurian (mainly ?490–430 Ma) zone. The early Paleozoic granites in zone display similar elemental Sr–Nd–Pb–Hf isotopic compositions. They were derived common mixed s...

We report the discovery of sipunculan worms from the Lower Cambrian Maotianshan Shale, near Kunming (southwest China). Their sipunculan identity is evidenced by the general morphology of the animals (sausage-shaped body with a slender retractable introvert and a wider trunk) and by other features, both external (e.g. perioral crown of tentacles, and hooks, papillae and wrinkle rings on the body...

Development of the animal body plan is controlled by large gene regulatory networks (GRNs), and hence evolution of body plans must depend upon change in the architecture of developmental GRNs. However, these networks are composed of diverse components that evolve at different rates and in different ways. Because of the hierarchical organization of developmental GRNs, some kinds of change affect...

An important survival strategy for animal species is the so-called niche differentiation between larva and adult. Different developmental stages of the same animal occupy different ecological niches to avoid competing for food or other essential resources. Here, we describe an exceptionally preserved larval stage of the short great appendage (SGA) arthropod (megacheiran) Leanchoilia illecebrosa...

Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a 'weird wonder' (Wonderful life, 1989) Opabinia, together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the natu...

Cambrian lobopodians are important for understanding the evolution of arthropods, but despite their soft-bodied preservation, the organization of the cephalic region remains obscure. Here we describe new material of the early Cambrian lobopodian Onychodictyon ferox from southern China, which reveals hitherto unknown head structures. These include a proboscis with a terminal mouth, an anterior a...

The distinctive, branched thrombolite, Favosamaceria cooperi new group and form, is found widely in the Great Basin, USA, where it is restricted to the Late Cambrian Saukia trilobite Zone. This thrombolite is distinguished by a hedgerow, mazelike organization of ridges similar to garden walls (maceriae) in plan view, branching of ridges into daughter ridges and columns, the polymorphic nature o...