CENTENNIAL HONORS COLLEGE
Western Illinois University
Undergraduate Research Day 2015
Poster Presentation
The 3D Morphology of the Enigmatic Carboniferous Arthropod, Schramixerxes gerem
(Montceau-les-Mines) via Micro Computed Tomography (microCT)
Andrew Turner and Justin Christensen
Faculty Mentor: Thomas Hegna
Geology
Schramixerxes gerem is a euthycarcinoid arthropod from the late Carboniferous (Gzhelian) Montceau-lesMines Lagerstätte in France. It is preserved three-dimensionally inside of siderite nodules.
Euthycarcinoids, like Schramixerexes have an uncertain systematic affinity. Euthycarcinoids have a
distinct head region made up of two segments and having one pair of antennae and one pair of mandibles,
a limb-bearing ‘preabdomen’, and a limbless ‘postabdomen’. They have variously been allied with the
early crustaceans and myriapods. To investigate their evolutionary significance, we have subjected
several fossil nodules containing Schramixerxes to microCT scanning. MicroCT scanning fossils is a way
to recovery the delicate morphology of an animal that is often hidden inside the rock, and reconstruct the
animal in 3D. Using freely available programs called SPEARSedit and SPIERSview, we were able to
separate the mold of the animal preserved in the nodule from the surrounding rock—including all of the
delicate appendages still hidden within the nodule. During this process, we were able to select the
different body parts of Schramixerxes gerem and label them. The two programs are also an effective way
to eliminate ‘noise’ in the microCT scan. Preliminary reconstructions of two specimens of Schramixerxes
are presented here.