Science Literature

A few years ago, a new fossil cricket species was discovered and named. This year, after the discovery of a second fossil, the specimen was renamed and assigned to the extant genus Schizodactylus of the family Schizodactylidae. It should be noted that no other fossils of this modern family are known.

"Schizodactylidae, or splay-footed crickets, are an unusual group of large, fearsome-looking predatory insects related to the true crickets, katydids and grasshoppers, in the order Orthoptera," said University of Illinois entomologist and lead author Sam Heads, of the Illinois Natural History Survey. "They get their common name from the large, paddle-like projections on their feet, which help support their large bodies as they move around their sandy habitats, hunting down prey."

The new fossil (source here)

We should remind ourselves that the details of classifying genera and species is a matter of human judgment, but the tendency is to consider all differences as significant. There was enough in common to assign the fossil to an extant genus, but it was given a distinct species name.

"The Schizodactylus specimen had features that were different enough from other members of the genus to warrant its own species (Schizodactylus groeningae). For instance, its legs and the lobe-shaped structures on its feet had slightly different shapes than species living today. Even so, its general features differ very little, Heads said, revealing that the genus has been in a period of "evolutionary stasis" for at least the last 100 million years. "It's obviously doing something right," Heads said of the new species and its body plan."

It is of interest to note how living fossils are described. Sometimes, they are "some of evolution's greatest survivors", and the splay-footed cricket is "obviously doing something right". The Economist reporter says that the insect illustrates the "first rule of natural selection": "If it ain't broke, don't fix it." LiveScience took a different view, making the point that the animal has been "stuck in time for the past 100 million years or so". Evolutionary theory wins all ways: if the animals document stasis, then they are fit for their environment and the environment has not changed with time. If they document change, then natural selection is at work, acting on natural variations. Images of the modern cricket are here and here.

The problem with evolutionary theory today is that it finds nothing significant to learn from these examples of stasis. "If it ain't broke, don't fix it" seems to exhaust their mental powers. However, there are a host of issues waiting to be explored: What do these organisms tell us about limits to variation? What can be learned about biological innovation? Can microevolution be extrapolated to macroevolution? Is it realistic to expect environments to show the same stasis as these animals and plants? Living fossils are not just quirky - they are telling us something significant about the biological world. For more, go here.

On the placement of the Cretaceous orthopteran Brauckmannia groeningae from Brazil, with notes on the relationships of Schizodactylidae (Orthoptera, Ensifera)
Sam W. Heads, Lea Leuzinger
ZooKeys, 2011, 77, 17-30 | doi: 10.3897/zookeys.77.769

Abstract: The fossil orthopteran Brauckmannia groeningae Martins-Neto (Orthoptera, Ensifera) from the Early Cretaceous Crato Formation of Brazil, currently misplaced at both the genus and family level, is transferred to the family Schizodactylidae and assigned to the extant genus Schizodactylus Brulle; ergo, Brauckmannia enters synonymy under Schizodactylus and Brauckmanniidae enters synonymy under Schizodactylidae. Schizodactylus groeningae (Martins-Neto), comb. n. agrees in size and general habitus with extant members of the genus, but can be readily separated by the robust, subovoid form of the metatibiae and the distinctive morphology of the lateral metabasitarsal processes. This species represents the first fossil occurrence of Schizodactylidae and the only New World record of this ancient lineage. Phylogenetic relationships of the schizodactylids are reviewed and a sister-group relationship with Grylloidea advocated based on a reappraisal of morphological and molecular evidence.

See also:

Rare Insect Fossil Reveals 100 Million Years of Evolutionary Stasis, ScienceDaily (Feb. 4, 2011)