The first fossils of the most basal pseudoscorpion family (Arachnida: Pseudoscorpiones: Pseudotyrannochthoniidae): evidence for major biogeographical shifts in the European paleofauna

Daniel Schwarze,Ulrich Kotthoff,Jörg U Hammel,Danilo Harms

doi:10.1007/s12542-021-00565-8

Daniel Schwarze, Ulrich Kotthoff + Show 2 more

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https://doi.org/10.1007/s12542-021-00565-8

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Abstract

Pseudoscorpions belong to the oldest terrestrial lineages with origins in the Devonian (ca. 385 Ma) but their fossil record is extremely sparse and little is known about their diversification over time. Here, we describe the first fossil species of the pseudoscorpion family Pseudotyrannochthoniidae that resemble the Devonian fossils in major details, such as the chaetotaxy of the pedipalps. We describe two new species, Allochthonius balticus sp. nov. from Baltic amber and Centrochthonius bitterfeldicus sp. nov. from Bitterfeld amber in northern Europe. Both species can unequivocally be assigned to extant genera and provide further evidence for dramatic range shifts in European invertebrate biota since the Paleogene. Allochthonius Chamberlin, 1929 is a diverse genus in eastern Asia (China, Korea, and Japan) today but does not occur anywhere in central Asia, Europe or North America. Centrochthonius Beier, 1931 is a poorly known genus but seems to be restricted to high altitude habitats in central Asia (China, Kyrgyzstan, and Nepal). With range retractions to regions more than 4600 km away from the European amber deposits, the fossils highlight total lineage extinction in Europe and survival in refugia that are climatically and botanically most similar to the Baltic amber forest of the Eocene. Overall, our results support the concept of morphological but potentially also ecological stasis in major pseudoscorpion lineages over long periods of time and agree with previous studies that suggested a warm temperate rather than subtropical or tropical climate for the time of amber deposition.

Highlights

Pseudoscorpions (Arachnida: Pseudoscorpiones de Geer 1778) are a diverse order of arachnids with ca. 3700 extant species from all continents except Antarctica (Benavides et al 2019)
According to a recent transcriptomic study, this family may have roots in the Upper Devonian (Benavides et al 2019; Fig. 1) and present-day distributions suggest continental drift as a major driver of diversification (Harms and Harvey 2013; Harms et al 2019). Fossil data support this scenario because the Palaeozoic pseudoscorpion Dracochela deprehendor Schawaller, Shear and Bonamo, 1991 from Gilboa shows a highly similar arrangement of the pedipalp trichobothria that is not shared by any other family, extinct or alive (Judson 2012)
No pseudotyrannochthoniid fossils were known until Ahrens et al (2019) recently illustrated a specimen from Bitterfeld amber

Summary

Introduction

Pseudoscorpions (Arachnida: Pseudoscorpiones de Geer 1778) are a diverse order of arachnids with ca. 3700 extant species from all continents except Antarctica (Benavides et al 2019). Pseudotyrannochthonius is known from the Northern Hemisphere with 3 species from the western U.S.A and 4 species from caves in Japan and South Korea (Harvey 2013); the latter classified originally as a separate genus Spelaeochthonius Morikawa, 1954 that is currently placed in the synonymy of Pseudotyrannochthonius These cave species and the American counterparts share with Centrochthonius the presence of 16 setae on the carapace and differ substantially from the type species of Pseudotyrannochthonius from Chile which has 18 setae on the carapace and a completely different arrangement of the coxal spines (Beier 1930). They are replaced on the surface by species of Allochthonius

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Discussion