Everyone has heard of the demise of the dinosaurs around 65 million years ago, and has probably seen a trilobite. Moths are not so common in the geological record. Jes Rust of the University of Göttingen is one lucky palaeontologist. In the lowermost sediments of the Tertiary Period in Denmark, about 55 million years old, he found a huge swarm of lepidopterans with representatives of at least seven species. (Rust, J., 2000. Fossil record of mass moth migration. Nature, 405, p. 530-531.
Rust reckons that the 1700 specimens bedded in marine sediments represent mass migrations over the precursor of the modern North Sea. They are not just in a single layer, but several horizons. The find probably records annual, summer migrations much like those occurring today when winds are calm and land temperatures high. Rust’s analysis suggests no major climatic or environmental shifts took place during deposition the 30 metres of sediment of the evocatively named Fur Formation. To add to the oddity of the local geology, he has also found that slightly older sediments in the area contain giant ants, damsel flies and crickets, that by any stretch of the imagination could not have flown far. They represent near-shore sedimentation, whereas the moth beds, devoid of such feeble fliers, formed in deeper water. Stratigraphers should note that this is the first case where insects have traced a marine transgression.
Our feathered friends
Notwithstanding Sir Fred Hoyle’s contention that the famous Archaeopterix fossils from the 145 million-year old Solenhofen Limestone are forgeries, feathers are found as fossils. But a recent find throws a lizard among the pigeons (precisely a small, squat reptile from the Triassic of central Asia) as regards the not unpleasant view that birds are the surviving descendants of the last dinosaurs. (Jones, T.D. et al., 2000. Nonavian feathers in a late-Triassic archosaur. Science, 288, p. 2202-2205; Stokstad, E., 2000. Feathers, or flight of fancy. Science, 288, p.2124-2125).
Fossils of Longisquama insignis have appendages that are remarkably like feathers, though less well-preserved examples were first regarded as long scales, hence the beast’s name. If they are feathers, Longisquama is far too old to be a dinosaur, but may have begun a line of feathered reptilians from which the birds eventually evolved. The authors of the new interpretation argue that feathers are unlikely to have evolved more than once. Most vertebrate palaeontologists cite the very close skeletal similarities between theropod dinosaurs and birds as evidence for a close evolutionary relationship, sometime in the Cretaceous Period. Feather specialists are dubious, suggesting the similarity is superficial and that Longisquama‘s ‘plumage’ are more like ribbed membranes.