Fossil Jumping Plant Louse From Miocene Germany Reveals Ancient Insect Puzzle

A tiny insect preserved in 16-million-year-old lake sediments in southern Germany is rewriting what scientists know about an often-overlooked group of plant-feeding bugs. Researchers have described Caillardia sueva, a new species of jumping plant louse, from the Randeck Maar in Baden-Württemberg. The fossil, identified from the imprints of a single male specimen, represents the first Miocene record of the subfamily Aphalarinae in Europe and the first member of the family Aphalaridae ever found in southern Germany. The discovery, published in the journal Evolutionary Systematics, shines a rare spotlight on a group of insects whose fossil record is so sparse that every new specimen carries real evolutionary weight.

Jumping plant lice, or psyllids, are small sap-sucking insects related to aphids and scale insects. Measuring between one and ten millimeters, and mostly just two to four millimeters long, they are easy to miss both in life and in stone. Around 4,200 species are known today, distributed across seven families, and they show remarkable host specificity. Most psyllid species feed on a single plant genus, sometimes on just one species, which makes them valuable subjects for studying coevolution between insects and plants. Their greatest diversity lies in tropical and south temperate regions, where they have radiated into thousands of forms.

The fossil record of psyllids, however, is exceptionally thin. Their minute size makes them easily overlooked during fossil preparation, and even when specimens are recognized, identification is difficult without clear views of diagnostic anatomical structures. Complicating matters further, psyllids show frequent homoplasy in their morphological characters, meaning that features such as the presence or absence of genal processes or the pattern of forewing markings can evolve independently in unrelated lineages. This convergence makes taxonomic placement of both living and extinct species a technical challenge, and it is one reason the new fossil from Randeck Maar required careful comparative analysis before its formal description.

The Randeck Maar itself is a remarkable window into the Miocene world. Located on the escarpment of the Swabian Alb at an altitude of 750 meters, the site was formed when volcanic dykes penetrated Mesozoic rocks during the Miocene. Rising nepheline-melilithitic magma contacted groundwater, triggering phreatomagmatic eruptions that carved out a crater roughly 1.2 kilometers in diameter. The maar probably sat further south during the Miocene, at a paleolatitude around 45 degrees, before tectonic drift carried it to its present position. Overlying sediments of Early and Middle Miocene age, roughly 16 to 18 million years old, comprise bituminous laminites and laminated, varve-like limestones that preserve exceptionally well-preserved fossils, particularly insects.

The new species, formally named Caillardia sueva, was described by Burckhardt, Serbina and Kotthoff based on a male holotype deposited in the State Museum of Natural History Stuttgart. The species name derives from the Latin adjective suevus, meaning Swabian, in reference to the region where the fossil was found. Preservation is relatively good considering the specimen’s tiny size, with the right forewing slightly deformed while the left forewing appears intact. The insect shows a dark brown general coloration, a subrectangular vertex about twice as wide as long, and a broad forewing about twice as long as wide with an irregularly oval shape and broadly rounded apex. The forewing membrane is densely covered with dark brown dots, more spaced in the basal half and denser and partly confluent toward the tip, with a light area adjacent to one of the wing veins.

Assigning the fossil to its correct genus required detailed comparison of wing venation and structural features. The researchers placed Caillardia sueva within the extant genus Caillardia based on the absence of genal processes, the transversely rectangular pronotum in dorsal view, the shape and venation of the forewings, and the comparatively large male subgenital plate. Within the genus, the new species most closely resembles the males of C. maroccana and C. springatei in the oval, apically broadly rounded forewing densely covered with dark dots. It shares with C. springatei a relatively straight vein Rs, but differs from both species in having a weakly curved rather than straight vein C+Sc, a vein M about as long as vein M1+2 rather than distinctly longer, and a longer and lower cell cu1.

The biogeographical implications of this find are striking. Today, the twelve known species of Caillardia are distributed across arid and semi-arid regions of the Palaearctic, including North Africa, the Middle East, Iran, Central Asia, the Caucasus, parts of Siberia and northeastern China. No species of Caillardia inhabits Europe. Ten of the twelve described species develop on Haloxylon and Anabasis, shrubs and small trees of the Amaranthaceae family widely distributed across sandy habitats and deserts. The genus was originally erected in 1931 for the Tunisian species Caillardia haloxyli, which induces galls on Haloxylon schmittianum, and most species groups within the genus are defined by differences in paramere shape.

Paleoclimatic reconstructions for the Early and Middle Miocene of Central Europe indicate warm-temperate to subtropical, fully humid conditions with no evidence of arid habitats. The palaeohabitat of the Randeck Maar was probably diverse, comprising open water, a narrow reed belt and forested slopes around the lake, with vegetation indicating subhumid conditions and some seasonal dryness. This raises an intriguing puzzle: the fossil Caillardia sueva may have inhabited more humid environments during the Miocene than its extant relatives, which are confined to arid and semi-arid zones today. Given the humid subtropical climate reconstructed for Central Europe at that time, it seems unlikely that the fossil species also developed on Haloxylon or Anabasis, though in the absence of associated plant evidence a broader host range cannot be excluded.

The discovery provides additional evidence that while the Miocene fauna contained many insect lineages still present today, their geographic distributions differed substantially from current ones. Fossils like this are essential for tracing the evolution of morphological characters through geological time, providing a direct means of calibrating character change, documenting lineage diversification and establishing temporal constraints for molecular dating analyses. In divergence-time studies, fossils act as essential calibration points, and without them inferred divergence times can be completely wrong. Each well-preserved psyllid fossil therefore carries disproportionate scientific value for understanding how these host-specific insects evolved and spread across the globe.

The oldest known modern psyllid, Eogyropsylla paveloctogenarius, comes from the Middle Eocene and belongs to an extinct tribe within Aphalaridae, represented by seven genera and more than twenty species, mostly from Baltic amber and compression fossils from the Kishenehn Formation in the United States. By contrast, the Miocene psyllid fossil record reveals a more diverse fauna with many extant genera and species. The best-preserved Miocene fossils come from Dominican amber, containing sixteen genera and nineteen species, while only a single species has been described from Mexican amber. Known European Miocene psyllids were previously limited to compression fossils from Stavropol in Russia, where early descriptions lacked diagnostic detail and many identifications remain doubtful. The researchers hope that Caillardia sueva will draw attention to this neglected insect group and that more fossils may yet be discovered in European Miocene deposits, filling gaps in a record that has remained frustratingly incomplete for decades.

Subject of Research: The first fossil member of Aphalaridae ( Hemiptera , Sternorrhyncha , Psylloidea ) from the Miocene of Southern Germany (Randeck Maar)

Article Title: The first fossil member of Aphalaridae ( Hemiptera , Sternorrhyncha , Psylloidea ) from the Miocene of Southern Germany (Randeck Maar)

Article References: Serbina, L. Š., Kotthoff, U., & Burckhardt, D. (2026). The first fossil member of Aphalaridae (Hemiptera, Sternorrhyncha, Psylloidea) from the Miocene of Southern Germany (Randeck Maar). Evolutionary Systematics, 10(1), 113-118. https://doi.org/10.3897/evolsyst.10.190431

Image Credits: AI Generated

DOI: 10.3897/evolsyst.10.190431

Keywords: first, fossil, member, Aphalaridae, Hemiptera, Sternorrhyncha, Psylloidea, Miocene, Southern, Germany, Randeck, Maar