Thalassina anomala lobster 172mm with articulated claws and body, commonly known as the Mangrove lobster. The fossil mangrove lobsters are seen in the fossil records from the Palaeocene 66mya (million years ago), through to the Holocene epoch. This particular fossil lobster is dated between the Pleistocene period, approximately between 1,600,000 years to the Holocene epoch 11,700 years ago and originates from Gunn Point, Darwin, Northern Territory of Australia.
Encased in phosphatic nodules of fossilised mud, these lobsters are usually left in there original matrix, a hard limestone to keep them intact. However occasionally it is possible using specialist equipment for a experienced preparitor to prepare them further, revealing more of their exoskeleton. The fossil shell, similar to other ancient fossil arthropods is made of chitin, calcium carbonate. The chitin exoskeleton was a tough resilient and rigid shell which was shed through the lobsters growth cycle. Where the arthropod was jointed the shell was thinner to allow better movement. All to often during deposition and petrification the fossil lobsters break up around the joints and the parts of the exoskeleton become separated. This fossil is exceedingly interesting as that is not the case. This particular lobster is almost complete, it is rare to find complete specimens or partial exoskeletons preserved in such good condition. The shell having a very appealing pallor with a range of soft greys enhancing the overall appearance, including the matrix itself.
In the matrix you can be observed seven segments of the tail, part of the carapace and leg segments although some are missing, the claws have two out of four missing tips.The arthropod would have shed its exoskeleton in its lifetime as it grew like other arthropods. It is possible these fossilised exoskeletons could be the result of such a process of growth. Many palaeontologist theorise that the lobsters of Gunn Point were trapped within their burrows by natural disasters and covered over during storms, or anaerobic events. This reasoning is a result of occasionally finding fossil lobsters as this nearly complete, not disassembled, a result of being confined within a burrow or trapped until its eventual demise.
Classification: Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, Order Decapoda, Suborder Gebiidea, Family Thalassinidae, Thalassia anomala.