Declining morphological diversity in snakefly larvae during last 100 million years.

Raphidioptera, the group of snakeflies, is a rather species-poor in-group of Holometabola. Yet, fossils of snakeflies indicate that the group was more diverse in the past. Here we compare the morphological diversity of snakefly larvae over time. Snakefly larvae are well represented in Cretaceous and Eocene ambers facilitating such a comparison. We used measurements of discrete dimensions as a basis for comparison. This reveals a larger diversity of snakefly larvae in the Cretaceous, especially in relation to head shapes and morphology of the antennae, which were much more variable. In particular, some Cretaceous larvae possessed greatly elongated head capsules and uniquely long and prominent antennae, unparalleled among modern forms. Already by the Eocene, snakefly larvae were less variable than those of the Cretaceous, although some still possessed longer antennae than modern-day larvae. The loss of morphological diversity supports the already well-established loss of taxonomic diversity in the group across time. Quite likely, this also indicates a loss of ecological diversity. These results are comparable to losses in different lineages of the closely related group Neuroptera. [ABSTRACT FROM AUTHOR]