graptolites

Let me introduce you to graptolites. These odd little prehistoric creatures were colonies of tiny marine animals which formed protective cup-like structures around their bodies and filter-fed on microscopic plankton. They’re classified as hemichordates, and their closest living relatives are a similar member of that group called pterobranchs.

They appeared in the fossil record between about 490 and 320 million years ago, and came in a wide range of shapes and sizes. There were single rows, double rows, branches, spirals, forks, and even net-like forms. The earliest types lived attached to the sea floor, but later ones floated around freely near the surface of the ocean and could reach lengths of up to 1.5m (~5ft). Some may have attached themselves to seaweed and floating debris, others are thought to have dangled from their own little bubble-like flotation rafts.

Their remains are so numerous and widespread that they’re very useful as “index fossils”, allowing paleontologists to precisely date the age of the rocks they’re found in.

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GRAPTOLITES are an extinct group of small colonial animals that lived in cup-like tubes; they are a kind of proto-chordate, and are distantly related to vertebrates like us. Their tubes were arranged along the outer edges of long canals or “arms” up to a metre long. The arms were likely to have been joined to a buoyant central float in later species; earlier, less advanced species either grew on the sea bottom or attached themselves to floating plants. The fossils are almost always found preserved as flattened impressions on rock surfaces, which is where their name comes from (Greek for “written rock”, due to looking like writing on rocks). Graptolites were most successful in the Ordovician and went extinct in the late Carboniferous. (via)

Sometimes doing a palaeontology degree can be really difficult and tedious. For example today I spent hour upon hour looking at rocks like this finding and identifying graptolites (such as this Monograptus convolutus pictured). This was the most interesting species included in the 200 plus graptolites I identified today for my biostratigraphy coursework. All evening I have spent writing up my results for cladistics tomorrow, atleast that was about identifying features of dinosaurs! I need sleep >.<