I won’t discuss this new observation in detail, since the detail is mostly of interest to specialists, but it’s still a cool observation. A new paper in Proc. Nat. Acad. Sci. USA by Alexander Schmidt et al. (reference at bottom) describes specimens of two groups of arthropods—flies and mites—from Italian amber (fossilized resin) that is 230 million years old.
That pushes the amber-preserved individuals of these groups back a full 100 million years, and makes these the earliest fossils of the mite superfamily Eriophyoidea, a highly specialized group of plant parasites. Most eriophyoid species feed on angiosperms (flowering plants), producing galls, while about 5% of the species feed on gymnosperms (conifers, cycads, etc.); the latter mites are considered to be ancestral because the most primitive group of these mites still live on gymnosperms, and gymnosperms precede angiosperms in the fossil record (the latter originated from gymnosperm-like ancestors only about 130 myr ago).
And here’s the beast who makes them; note how bizarre and specialized it is:
The amber came from gymnosperms in a family of extinct conifers (Cheirolepidaceae); here’s one of their fossils (all captions in photos and drawings are from the original paper):
Cheirolepidiaceous shoots associated with amber. Museo delle Regole, Cortina d’Ampezzo, Italy, MRCA 7170.
The authors examined 70,000 (!) ancient amber droplets for arthopod inclusions, and found only three. I’ll show them all. The first is a midge, which is a fly (Diptera); it is disarticulated and small (1.5-2 mm). The specimen, though not whole, is very detailed.
(G and H) Disarticulated nematoceran fly, showing details of antenna and apical tarsomere. Museum of Geology and Paleontology, University of Padova, Italy, MGP 31345. Scale bars: B, 2 cm; C–F, 1 mm; G and H, 200 μm.
And here are the two mite specimens, preserved whole. Note that the scale bar is 10 microns, or 0.01 mm. These things are small!
Eriophyoidmite in the Italian Triassic amber: Triasacarus fedelei gen. et sp. nov., Holotype, MGP 31343. (A and C) Habitus in ventral view [reconstruction and photomicrograph, respectively; photo is a stacked image using differential interference contrast (DIC) illumination]. (B) Dorsal structures of anterior region, as viewed ventrally. (D) Gnathosoma, arrow pointing to infracapitular ledge [bright field (BF) illumination; f.p (focal plane) 2,347]. (E) Detail of F; arrows pointing to empodial featherclaws (BF, f.p. 2,324). (F) First and second leg pairs, with tip of proboscis in focus (arrow) and empodial featherclaw of first left leg indicated with arrow (BF, f.p. 2,324). (G) First and second leg pairs, with some solenidia denoted, tibial one by phi, tarsal ones by omega (DIC, f.p. 2,160). Scale bars: 10 μm.
Eriophyoid mite in the Italian Triassic amber: Ampezzoa triassica gen. et sp. nov., Holotype, MGP 31344. (A and B) Habitus, dorsal view. (A) Digitally stacked photomicrographic composite. (B) Rendering of complete specimen, as preserved. (C) Anterior portion of body, including gnathosoma. White arrows indicate infracapitular guides; black arrow points to second left leg (f.p. 2,904). (D) Portion of prodorsal and coxisternal region; arrows point to shadowy images of right legs I and II below prodorsal shield (f.p. 2,692). (E) Posterior apex of body; arrows point to caudal setae h2 (f.p. 2,932). All photos in DIC illumination. Scale bars: 10 μm.
What’s the significance? Well, it supports the phylogenetic (“family tree”) evidence that eriophyoid mites did indeed evolve feeding on gymnosperms, for these samples date 100 million years before angiosperms even existed. So it’s a nice confirmation of what we suspected from other data. It also supports the age of the mite group, since there was some doubt about when it originated. Other findings are of interest mainly to arthropod systematists, but the quality of these ancient specimens is so nice that I thought I’d present them.
Schmidt, A. R, S. Jancke, E. E. Lindquist, E. Ragazzi, G. Roghi, P. C. Nascimbene, K. Schmidt, T. Wappler, and D. A. Grimaldi. 2012. Arthropods in amber from the Triassic Period. Proc. Nat. Acad. Sci. USA 109: 14796-14801.