Selected article on the Silurian world and its legacies
A life restoration of Orthoceras.
The molluscs or mollusks, compose the large phylum of invertebrate animals known as the phylum Mollusca. Around 85,000 extantspecies of molluscs are recognized. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. They are highly diverse, not only in size and in anatomical structure, but also in behaviour and in habitat. The phylum is typically divided into 9 or 10 taxonomicclasses, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish and octopus, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species. The gastropods (snails and slugs) are by far the most numerous molluscs in terms of classified species. The scientific study of molluscs is called malacology. The three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, and the structure of the nervous system.
Good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period 538.8 to 485.4 million years ago. However, the evolutionary history both of molluscs' emergence from the ancestral Lophotrochozoa and of their diversification into the well-known living and fossil forms are still subjects of vigorous debate among scientists. (see more...)
Selected article on the Silurian in human science, culture and economics
Geologic map of the US state of Georgia.
The geologic map of Georgia (a state within the United States) is a special-purpose map made to show geological features. Rock units or geologic strata are shown by colors or symbols to indicate where they are exposed at the surface. Structural features such as faults and shear zones are also shown. Since the first national geological map, in 1809, there have been numerous maps which included the geology of Georgia. The first Georgia specific geologic map was created in 1825. The most recent state-produced geologic map of Georgia, by the Georgia Department of Natural Resources is 1:500,000 scale, and was created in 1976 by the department's Georgia Geological Survey. It was generated from a base map produced by the United States Geological Survey. The state geologist and Director of the Geological Survey of Georgia was Sam M. Pickering, Jr. Since 1976, several geological maps of Georgia, featuring the state's five distinct geologic regions, have been produced by the federal government. (see more...)
...that fossil Thelodont fish (depiction pictured) surprised scientists by showing that stomachs evolved before jaws?
...that eighty years on, scientists are still debating whether the Palæozoicfossils known as Chitinozoans(SEM image pictured) represent plants, animals or eggs?
... that Kulindroplax is the first known mollusk showing an unambiguous combination of exterior shells and a worm-like body?
... that the extinctbivalve subfamily Praenuculinae can be told apart from its sister subfamily by looking at teeth?
