Science Literature

Leaf insects are a very small percentage of the order Phasmatodea, and are evidently very specialized in their mimicry behaviour and morphology. Rare fossils of leaf insects are found, but a recent report documents an example of a male specimen that is "exquisitely preserved and displays the same foliaceous appearance as extant male leaf insects." This fossil leaf insect "bears considerable resemblance to extant individuals in size and cryptic morphology, indicating minimal change in 47 million years. This absence of evolutionary change is an outstanding example of morphological and, probably, behavioral stasis."

Stasis is one of those characteristics found in the fossil record that gained prominence when punctuated equilibrium was proposed, but has not generally developed theoretically since 1972. The missing emphasis in the discussion is information. An ID perspective at least allows some aspects of stasis to be approached in an original and constructive way.

The first fossil leaf insect: 47 million years of specialized cryptic morphology and behavior
Sonja Wedmann, Sven Bradler, and Jes Rust.
Proceedings of the National Academy of Sciences, January 9, 2007, 104: 565-569. | 10.1073/pnas.0606937104

Abstract: Stick and leaf insects (insect order Phasmatodea) are represented primarily by twig-imitating slender forms. Only a small percentage ( 1%) of extant phasmids belong to the leaf insects (Phylliinae), which exhibit an extreme form of morphological and behavioral leaf mimicry. Fossils of phasmid insects are extremely rare worldwide. Here we report the first fossil leaf insect, Eophyllium messelensis gen. et sp. nov., from 47-million-year-old deposits at Messel in Germany. The new specimen, a male, is exquisitely preserved and displays the same foliaceous appearance as extant male leaf insects. Clearly, an advanced form of extant angiosperm leaf mimicry had already evolved early in the Eocene. We infer that this trait was combined with a special behavior, catalepsy or "adaptive stillness," enabling Eophyllium to deceive visually oriented predators. Potential predators reported from the Eocene are birds, early primates, and bats. The combination of primitive and derived characters revealed by Eophyllium allows the determination of its exact phylogenetic position and illuminates the evolution of leaf mimicry for this insect group. It provides direct evidence that Phylliinae originated at least 47 Mya. Eophyllium enlarges the known geographical range of Phylliinae, currently restricted to southeast Asia, which is apparently a relict distribution. This fossil leaf insect bears considerable resemblance to extant individuals in size and cryptic morphology, indicating minimal change in 47 million years. This absence of evolutionary change is an outstanding example of morphological and, probably, behavioral stasis.

See also:
Scientists discover first fossil of a leaf insect
physorg.com, 8 February 2007