Wednesday, 6 November 2013

3D images of a Cretaceous Mantis Shrimp.

Mantis Shrimps (Stomatopoda) are large burrowing Crustaceans found in shallow marine environments throughout the tropics and subtropics. They are common, often exceed 30 cm in length, and are frequently brightly coloured. However despite this they are poorly understood due to their burrowing lifestyle, typically only emerging above the surface to snatch prey before vanishing again. Mantis Shrimps can excavate burrows into limestone, and occasionally are introduced inadvertently to aquariums in pieces of Coral; a Mantis Shrimp in an aquarium can create a lot of problems, as they are hard to locate, eat fish, and sometimes grow large and strong enough to shatter aquarium glass. They have a fossil record going back to the Cretaceous, with possible specimens from as early as the Silurian.

The fossil species Ursquilla yehoachi was originally described as Eryon yehoachi, and described as a Decapod Crustacean by Jean Remy and Moshé Avnimélech in 1955, from a single specimen from the Ouadi Seiyal Valley in eastern Israel. It was redescribed and recognized as the tail end of a Mantis Shrimp by Martin Glaessner of the University of Adelaide in 1969. The species was redescribed again and given the name Ursquilla yehoachi (the genus Eryon being in use for a Decapod Crustacean) by Cees Hof of the University of Amsterdam in 1998 who was also able to describe three further specimens from Israel and Jordan; one collected by the Geological Survey of Israel in 1994, and two others on a single slab which had been presented to the Natural History Museum in London in 1906

Hof's work on Ursquilla yehoachi involved the creating of a series of peels; moulds of the fossils (in which the inner side of the dorsal exoskeleton is preserved) which enable the study of the animal's morphology in 3D. However the peel technique can be problematic, as it can potentially damage fossils.

In a paper published in the journal Palaeontologica Electronica on 30 July 2013, a team of scientists led by Carolin Haug of the Department of Cytology and Evolutionary Biology at the Zoological Institute and Museum of the University of Greifswald describe a fifth specimen of Ursquilla yehoachi, collected in the Negev Desert of Israel by Stan Natkaniec of Düsseldorf, and subsequently donated to the Staatliches Museum für Naturkunde Stuttgart, as well as redescriptions of the previously described specimens.

Like Hof, Haug et al. wished to construct 3D models of the specimens, but they were reluctant to further use the peel technique. Instead they used a flat-bed scanner to create paired images of the same specimens, which were then used to create a stereo-anaglyph image in Adobe Photoshop. This creates a  depth inversion of the stereo image which Haug et al. refer to as a 'virtual peel'.

3D stereoscopic 'virtual peel' of the Stuttgart specimen of Ursquilla yehoachi. Haug et al. (2013).

See also A fossil Isopod Crustacean from the Early Miocene of the Vienna BasinTwo new species of Amphipod Crustacean from the Gulf of ThailandA new species of Peppermint Shrimp from the CaribbeanFour new species of parasitic Copepods from Japan and A new Isopod Crustacean from a limestone cave in Brazil.

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