Amber from western Amazonia reveals Neotropical diversity during the middle Miocene

Abstract

Tertiary insects and arachnids have been virtually unknown from the vast western Amazonian basin. We report here the discovery of amber from this region containing a diverse fossil arthropod fauna (13 hexapod families and 3 arachnid species) and abundant microfossil inclusions (pollen, spores, algae, and cyanophyceae). This unique fossil assemblage, recovered from middle Miocene deposits of northeastern Peru, greatly increases the known diversity of Cenozoic tropical-equatorial arthropods and microorganisms and provides insights into the biogeography and evolutionary history of modern Neotropical biota. It also strengthens evidence for the presence of more modern, high-diversity tropical rainforest ecosystems during the middle Miocene in western Amazonia.

Fig. 1.

Map of the Iquitos area (northeastern Peru) showing the geographic location of the middle Miocene amber-bearing locality of Tamshiyacu (IQ 26), denoted by an open circle. Map was redrawn from ref. .

Fig. 2.

Amber-bearing Tamshiyacu section (IQ 26, Iquitos area, northeastern Peru). (A) Middle Miocene amber-bearing level is indicated by black arrow. (B) Large amber clast from the level in A (length ≈ 70 mm) at natural size.

Fig. 3.

Photographs of Euarthropoda in amber from the Miocene of Iquitos (northeastern Peru). (A) Coleoptera: Cucujoidea: Sphindidae. (Scale bar, 0.6 mm.) (B) Psocoptera, family undetermined. (Scale bar, 4 mm.) (C) Diptera: Ceratopogonidae (female). (Scale bar, 0.7 mm.) (D) Diptera: Chironomidae (male). (Scale bar, 1 mm.) (E) Hemiptera: Aleyrodidae (male). (Scale bar, 0.8 mm.) (F) Arachnida: Acarina (mite). (Scale bar, 0.2 mm.)

Fig. 4.

Microfossils in Miocene amber from western Amazonia (Iquitos, northeastern Peru) in photographs taken under a light microscope. (A) Eubacteria. (B) Nostocaceae (Cyanobacteria). (C) Quilonia sp., pluricellate spores, specimens close to the modern Alternaria. (D) Polycellulaesporonites sp., also found in modern Alternaria species. (E) Pluricellulaesporites sp. (F) Scenedesmus sp. (G) Frasnacritetrus sp., four-branched spore (only two are visible here in the microscope focus). (H) Phragmothyrites sp., small subcircular ascostroma. (I) Hypoxylonites sp., fungal or algal spores. (J) Triporopollenites sp., pollen grain of a Proteaceae (Eudicotyledons: Magnoliophyta).