Variations of isoleucine epimerization ratios in Glycymeris sp. shells in time-averaged raised marine deposits in the Mediterranean

Abstract

This chapter presents insects as a fossil record. The small size and external cuticle of insects are largely responsible for the many modes of fossilization, which are much more varied than for vertebrates and plants. Insect fossils are most commonly encountered as impressions or compressions in sediments generally as disarticulated cuticle and particularly as wings because these are especially resistant to decay. Because wing venation has many systematically significant features, isolated wings often can be identified at least to family level. Remains in sediments are highly compressed, but can still reveal microscopic structures such as flagellomeres, tarsomeres, microtrichia, wing scales, and even color patterns. The earliest remains of terrestrial animals are arthropods from the Silurian, including primitive scorpions, millipedes, and Trigonotarbida. Two major hypotheses on the origins of the hexapods are that they are most closely related to either the myriapods or the Crustacea. Crustacea may actually have the oldest fossil record of all animals because some Precambrian fossils have recently been reinterpreted as crustaceans. If hexapods are closely related to crustaceans, it is most likely to be a group within Crustacea, and the earliest evidence of this stem group will probably be found in the Silurian.