A phylogenetic analysis of the ancient Asian scorpion family Pseudochactidae

 

As previously mentioned, the ancient, relictual Asian scorpion family Pseudochactidae Gromov, 1998 is probably one of the most interesting scorpion families in the world. It consist of both of extinct and extant taxa, and the latter is often labeled as "living fossils" due to their unique morphology. 

In a recent article, Lorenzo Prendini and co-workers present a new phylogenetic analysis of the genus with new information about the phylogeny and taxonomy of this fascinating family and its evolution. 

Abstract:
The ancient, relictual Asian scorpion family Pseudochactidae Gromov, 1998, has a disjunct distribution. Five genera and seven species of living pseudochactids are assigned to one epigean subfamily, Pseudochactinae Gromov, 1998, from Central Asia and southern China, and two hypogean subfamilies, Troglokhammouaninae Prendini et al., 2021, and Vietbocapinae Lourenço, 2012, from caves of the Khammouan-Phong Nha-Kẻ Bàng Karst in the northern Annamite (Trường Sơn) Mountains of Laos and Vietnam. The extinct subfamily Chaerilobuthinae Lourenço and Beigel, 2011, comprises one genus and 15 species, hypothesized to be endogean, from mid-Cretaceous Burmese amber. The discovery and uncertainty regarding the phylogenetic placement of Qianxie solegladi Tang, 2022, from South China, together with the discovery that the Cretaceous amber Chaerilobuthinae, from the Burma Terrane, is the sister group of the extant pseudochactid subfamily Vietbocapinae provided an opportunity to revisit the phylogeny and biogeography of Pseudochactidae, and their adaptation to subterranean habitats in Southeast Asia. In the present contribution, pseudochactid phylogeny is reanalyzed using three mitochondrial markers (12S rDNA, 16S rDNA, Cytochrome c Oxidase Subunit I), three nuclear markers (18S rDNA, 28S rDNA, Internal Transcribed Spacer) and 143 morphological characters, for all extant pseudochactid taxa and seven exemplar species of the extinct Chaerilobuthinae. Divergence time and ancestral range estimation are conducted and the evolution of troglomorphic characters investigated to reassess how this lineage of “living fossils” dispersed and diversified. Recent changes to the systematics of Pseudochactidae are confirmed. The four subfamilies, genera, and species were monophyletic with high support and the following scheme of relationships: (Pseudochactinae (Troglokhammouaninae (Chaerilobuthinae + Vietbocapinae))). Phylogenetic analyses, reinforced by a multivariate morphometric analysis and pairwise genetic distances, confirm the validity of the monotypic, epigean Chinese genus, Qianxie Tang, 2022, which formed a monophyletic group with the epigean Central Asian genus, Pseudochactas Gromov, 1998, rather than the hypogean Southeast Asian genus, Troglokhammouanus Lourenço, 2007. Qianxie solegladi is transferred to Pseudochactinae. A revised time tree of Pseudochactidae suggests that the Burmese Chaerilobuthinae diverged from the Indochinese subfamilies, Troglokhammouaninae and Vietbocapinae, in the Early Cretaceous (ca. 117 Ma), consistent with Early Devonian rifting of the Burma Terrane.

Reference:
Prendini L, Xuan Q, Du SE, Wang C-BE, Ehrenthal VL, Loria SF. Phylogeny and divergence time estimation of relictual Asian scorpion family suggests Early Cretaceous connections between Burma Terrane and Eurasia, and corrects placement of Chinese taxon. American Museum Novitates. 2026(4051):1–55. [Open Access]

Family Pseudochactidae 

A new genus and species in the enigmatic family Pseudochactidae from China

 

The family Pseudochactidae Gromov, 1998 consisted for many year of only one genus and one species. In recent years a few more genera and species have been described, many from isolated areas. Victoria Tang has now described a new genus and species from the Yunnan Province of China, greatly increasing the distribution of this family.

Qianxie Tang, 2022

Qianxie solegladi Tang, 2022

The new species seems to be found only above ground and it exhibits no troglomorphism, which is different from its presumed sister genus, Troglokhammouanus Lourenço, 2007.

Abstract:
A new monotypic genus belonging to the basal scorpion family Pseudochactidae Gromov, 1998, Qianxie solegladi gen et. sp. n., is described from Yunnan Province of China. The family is recorded from China for the first time, vastly extending its known geographic range. The new genus shares morphological characters with both Pseudochactas Gromov, 1998 and Troglokhammouanus Lourenço, 2007. It differs from Pseudochactas and is similar to Troglokhammouanus in the shapes of anterior and posterolateral carapace margins, form of the circumocular sutures, distance between median ocelli, development of dorsoventral projection of patella, length of tarsal spinules, recurvature of the lateral margins and concavity of the surface of the sternum. It is similar to Pseudochactas in the degree of carapace granulation, pedipalp manus carination, secondary accessory and retroventral carinae of the chela manus, numbers of lamellae and teeth on the pectines, development of the median lateral carinae of metasomal segments III–IV and ventromedian carina of metasomal segment V. The new genus is hypothesized to be more closely related to Troglokhammouanus than to Pseudochactas and is placed in the subfamily Troglokhammouaninae.

References:
Tang V. A new scorpion genus and species from China, Qianxie solegladi gen. et sp. n. (Scorpiones: Pseudochactidae). Euscorpius. 2022(351):1-19. [Open Access]

Family Pseudochactidae