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

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.

Selachochthonius naledi sp. nov. (Pseudoscorpiones, Pseudotyrannochthoniidae), a new troglobitic species from South Africa

“…The new species bears tripinnate spines, which resembles Pseudotyrannochthonius and Centrochthonius, individually inserted on a single row on the ledge of first pedal coxa (Fig. 3A-C) (Morikawa 1956;Harms and Harvey 2013;Schwarze et al 2021). The new species herein described is attributed to Selachochthonius due to reduced size of the intercoxal tubercle, the smooth aspect of coxal spines and the presence of 18 carapacal setae.…”

“…This family is diagnosed by the presence of ib and isb trichobothria located at the base of the fixed finger and coxal spines present only in coxae I (Harms and Harvey 2013). While the Northern Hemisphere members of the family present a more variable carapacal chaetotaxy, the Southern Hemisphere species share the presence of 18 carapace setae (Schwarze et al 2021). In South Africa, pseudotyrannochthoniid pseudoscorpions are represented by two genera, namely Afrochthonius and Selachochthonius, from which the latter can be identified mainly by the presence of an intercoxal tubercle (Ellingsen 1912;Beier 1930).…”

Caeculus fedrae sp. nov., a new fossil species of rake-legged mite (Acari: Caeculidae) from Baltic amber.

“…However, the ecology of the extant taxa corresponding to fossil taxa described from this amber in recent years agrees with the new conception of this paleoenvironment as a mosaic of diverse environments with warm temperature (Sadowski et al 2017). In addition to taxa associated with moist habitats as labidostommatids mites (Sidorchuk and Bertrand 2013), pseudotyrannochthonid pseudoscorpions (Schwarze et al 2022) and harvestmen (Dunlop 2007; Dunlop and Mitov 2015; Dunlop et al 2018, other taxa currently restricted to arid habitats have been described from this amber, including teneriffid and opilioacarid mites and solifuges (Sayre 199; Dunlop et al 2004).…”

Four new species of cave-adapted pseudoscorpions (Pseudoscorpiones, Pseudotyrannochthoniidae) from Guizhou, China

“…Up to now, the genus Allochthonius contains a total of 30 species (nine species from China), and of these 30 species, only nine species have no eyes. Of these nine blind species, only A. brevitus Hu & Zhang, 2012 comes from China and it is an epigean species, while the other eight species were found in caves in Japan (Morikawa 1956;Zhang 2011, 2012;Zhang and Zhang 2014;Gao et al 2016;Schwarze et al 2021;Viana and Ferreira 2021;WPC 2022).…”

“…Of these nine blind species, only A. brevitus Hu & Zhang, 2012 comes from China and it is an epigean species, while the other eight species were found in caves in Japan ( Morikawa 1956 ; Hu and Zhang 2011 , 2012 ; Zhang and Zhang 2014 ; Gao et al 2016 ; Schwarze et al 2021 ; Viana and Ferreira 2021 ; WPC 2022 ).…”