The origin and initial rise of pelagic cephalopods in the Ordovician.

Background: During the Ordovician the global diversity increased dramatically at family, genus and species levels. Partially the diversification is explained by an increased nutrient, and phytoplankton availability in the open water. Cephalopods are among the top predators of today's open oceans.

Molecular systematics and global phylogeography of angel sharks (genus Squatina).

Angel sharks of the genus Squatina represent a group comprising 22 extant benthic species inhabiting continental shelves and upper slopes. In the present study, a comprehensive phylogenetic reconstruction of 17 Squatina species based on two mitochondrial markers (COI and 16S rRNA) is provided. The phylogenetic reconstructions are used to test biogeographic patterns.

Calibrating the chelicerate clock: a paleontological reply to Jeyaprakash and Hoy.

Divergence times inferred for major lineages of Chelicerata (scorpions, spiders, mites, pycnogonids and xiphosurans) in a recent paper on mitochondrial phylogeny by Jeyaprakash and Hoy are compared to the known stratigraphical occurrences of these groups. Erroneous statements concerning fossil date estimates in the original study are corrected. We emphasize that the fossil record of chelicerates is more complete than is sometimes assumed, and that paleontology plays a key role in dating cladogenesis by setting minimum divergence times, which can and do falsify molecular clock estimates where the inferred divergence is substantially younger than the known fossil record.