The copepod family Centropagidae is widely distributed and occurs in marine, estuarine, freshwater, and inland saline settings. Molecular phylogenies based upon the 16S and 28S genes demonstrate a complex biogeographic history, involving at least five independent invasions of continental waters from the sea. The first colonization was ancient, likely into part of Gondwanaland, and resulted in a...

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 ...

Oceans, or other wide expanses of inhospitable environment, interrupt present day distributions of many plant groups. Using molecular dating techniques, generally incorporating fossil evidence, we can estimate when such distributions originated. Numerous dating analyses have recently precipitated a paradigm shift in the general explanations for the phenomenon, away from older geological causes,...

I present a general model for true polar wander (TPW), in the context of supercontinents and simple modes of mantle convection. Old, mantle-stationary supercontinents shield their underlying mesosphere from the cooling effects of subduction, and an axis of mantle upwelling is established that is complementary to the downwelling girdle of subduction zones encircling the old supercontinent. The u...

[1] Mantle density heterogeneities, imaged using seismic tomography, contain information about timedependent mantle flow and mantle structures that existed in the past. We model the history of mantle flow using a tomographic image of the mantle beneath southern Africa as an initial condition while reversing the direction of flow and analytically incorporating cooling plates as a boundary condit...