Preservation permitting patterns of developmental evolution can be reconstructed within long extinct clades, and the rich fossil record of trilobite ontogeny and phylogeny provides an unparalleled opportunity for doing so. Furthermore, knowledge of Hox gene expression patterns among living arthropods permit inferences about possible Hox gene deployment in trilobites. The trilobite anteroposteri...

The Ordovician radiation of marine life was among the most substantial pulses of diversification in Earth history and coincided in time with a major increase in the global level of orogenic activity. To investigate a possible causal link between these two patterns, the geographic distributions of 6576 individual appearances of Ordovician vician genera around the world were evaluated with respec...

Parablackwelderia is the oldest known stalk-eyed trilobite and thrived during the middle–late Cambrian (Guzhangian Age) in eastern Gondwanaland. The elongated palpebral lobe extends outward and forward from the anterior corner of the cranidium and shows positive allometry, becoming markedly longer and relatively thinner in large specimens. The animal occurred in muddy environments and may have ...

Fossilised arthropod compound eyes have frequently been described. Among the oldest known are those from the lower Cambrian of the Chengjiang Lagerstätte (China, c 525 Ma). All these compound eyes, though often excellently preserved, however, represent just the outer shells, because soft tissues, or even individual cells, usually do not fossilise. Using modern techniques, including μct-scanning...

The Cheiruridae are a diverse group of trilobites and several subfamilies within the clade have been the focus of recent phylogenetic studies. This paper focuses on the relationships of one of those subfamilies, the Ordovician Eccoptochilinae. We analyze sixteen species from six genera within the traditionally defined group, using the pilekiid Anacheirurus frederici as an outgroup. To assess th...