Mark Wilson May 15th, 2011 In advance of my next field trip to
Israel (watch this space!), our highlighted fossil this week is
the scleractinian coral Microsolena, a genus named by the French
naturalist Jean Vincent Félix Lamouroux in 1821. The specimen
above was collected from the Matmor Formation in Hamakhtesh
Hagadol in the Negev Desert. It is Callovian in age,
specifically the athleta Zone. (I know a lot of details about
this area!) This coral is thus roughly 160-165 million years
old. Scleractinian corals appeared first in the Triassic and are
the primary coral in today’s oceans. Unlike their extinct
Paleozoic cousins, scleractinians have skeletons made of
aragonite rather than calcite. Aragonite is relatively unstable
and easily dissolves over geological time. Our specimen above
has been replaced with the more stable calcite. This means that
the exterior is preserved well enough to identify to the genus
level, but details in the interior necessary for species
determination have been recrystallized beyon