1. A molecular signature of chitin in Paleozoic arthropods
Structural, molecular and isotopic composition of organic fossils and their relationship to modern counterparts
Derek E.G. Briggs, Department of Geology and Geophysics, Yale University, P.O. Box , New Haven, CT 06520
A molecular signature of chitin in Paleozoic arthropods
A synchrotron based Scanning Transmission X-ray Microscope/ microspectrometer (STXM) was used to generate functional group ‘maps’ of modern and fossil (Pennsylvanian, ~310 My) scorpion cuticle. The modern scorpion cuticle is ~25 m thick. The fossil scorpion cuticle is much thinner (~2m) and is only a remnant of the original.
The modern cuticle shows variation in the distribution of nitrogen bearing functionality (A). Regions rich in N appear brighter. The outer cuticle (top left) is relatively depleted in N. The N content is higher within the thicker inner cuticle particularly in irregular layers. The modern cuticle
also shows variation in the
distribution of aliphatic
carbon (B). The outer region
appears brighter and is
enriched. The layers of the
inner cuticle enriched in
aliphatic carbon are the
same as those enriched in
nitrogen, revealing a higher
protein content.
Nitrogen
Carbon
Outer
Modern
Inner
Fossil
Even though it is much thinner and only represents part of the original, the fossil scorpion cuticle retains compositional lamination in both nitrogen and aliphatic carbon content (C, D).
X-ray Absorption Near Edge Structure (XANES) spectra revealed a molecular signature of chitin in the fossil scorpion cuticle and also in a Silurian (~417 My) eurypterid (E). E