Cretaceous crown male ant reveals the rise of modern lineages.

Most described Mesozoic ants belong to stem groups that existed only during the Cretaceous period. Previously, the earliest known crown ants were dated to the Turonian (Late Cretaceous, ca. 94-90 million years ago (Ma)) deposits found in the USA, Kazakhstan, and Botswana. However, the recent discovery of an alate male ant in Kachin amber from the earliest Cenomanian (ca. 99 Ma), representing a new genus and species, Antiquiformica alata, revises the narrative on ant diversification. Antiquiformica can be distinctly differentiated from all known male stem ants by its geniculate antennae with elongated scape, extending far beyond the occipital margin of the head and half the length of the funiculus, as well as its partly reduced forewing venation. Furthermore, the combination of a one-segmented waist with a well-developed node, elongated scape extending beyond the occipital margin, and reduced forewing venation, particularly the completely reduced m-cu and rs-m crossveins and absence of rm and mcu closed cells, firmly places the fossil within the extant subfamily Formicinae. Fourier transform infrared spectroscopy (FTIR) confirmed that the amber containing Antiquiformica alata originated from the Kachin mines in Myanmar. This discovery significantly revises our understanding of the early evolution of Formicinae. The presence of Antiquiformica in Cenomanian amber indicates that the subfamily Formicinae emerged at least by the start of the Late Cretaceous, with crown ants likely originating earlier during the earliest Cretaceous or possibly the Late Jurassic, although paleontological evidence is lacking to support the latter hypothesis.

A wide hybrid zone mediated by precipitation contributed to confused geographical structure of Scutiger boulengeri.

Confused geographical structure of a population and mitonuclear discordance are shaped by a combination of rapid changes in population demographics and shifts in ecology. In this study, we generated a time-calibrated phylogeny of Scutiger boulengeri, an endemic Xizang alpine toad occurring in mountain streams on the Qinghai-Xizang (Tibet) Plateau (QTP). Based on three mitochondrial DNA (mtDNA) genes, eight clades were assigned to three deeply divergent lineages. Analysis of nuclear DNA (nuDNA) genes revealed three distinct clusters without geographic structure, indicating significantly high rates of gene flow. Coalescent theory framework analysis (approximate Bayesian computation model DIYABC and Migrate-N) suggested that divergence of the main intraspecific clusters was the result of hybridization after secondary contact in the Holocene around 0.59 million years ago (Ma). The ratio of mtDNA F ST (fixation index) to nuDNA F ST was 2.3, thus failing to show male-biased dispersal. Geographic cline analysis showed that a wide hybrid zone was initially established in southwestern China, without significant reproductive isolation but with strong introgression in S. boulengeri, suggesting high hybrid fitness. Furthermore, mtDNA genes exhibited isolation by distance (IBD) while nuDNA genes exhibited significant isolation by environment (IBE). Results suggested that mitonuclear discordance may have initially been caused by geographic isolation, followed by precipitation-mediated hybridization, producing a wide hybrid zone and geographic structure confusion of nuDNA genes in S. boulengeri. This study indicated that complicated historical processes may have led to specific genetic patterns, with a specific climate factor facilitating gene flow in the system.

Fossils from the Middle Jurassic of China shed light on morphology of Choristopsychidae (Insecta, Mecoptera).

Choristopsychidae, established by Martynov in 1937 with a single isolated forewing, is a little known extinct family in Mecoptera. Since then, no new members of this enigmatic family have been described. Based on 23 well-preserved specimens with complete body and wings from the Middle Jurassic of northeastern China, we report one new genus and three new species of Choristopsychidae, two new species of the genus Choristopsyche Martynov, 1937: Choristopsyche perfecta sp. n. and Choristopsyche asticta sp. n.; one new species of Paristopsyche gen. n.: Paristopsyche angelineae sp. n.; and re-describe Choristopsyche tenuinervis Martynov, 1937. In addition, we emend the diagnoses of Choristopsychidae and Choristopsyche. Analyzing the forewing length/width ratios of representative species in Mecoptera, we confirm that choristopsychids have the lowest ratio of forewing length/width, meaning broadest forewings. These findings, the first fossil choristopsychids with well-preserved body structure and the first record of Choristopsychidae in China, shed light on the morphology of these taxa and broaden their distribution from Tajikistan to China, while increasing the diversity of Mesozoic Mecoptera in China.

Mid-Mesozoic flea-like ectoparasites of feathered or haired vertebrates.

Parasite-host associations among insects and mammals or birds are well attended by neontological studies [1]. An Eocene bird louse compression fossil [2, 3] and several flea specimens from Eocene and Oligocene ambers [4-8], reported to date, are exceptionally similar to living louse and flea taxa. But the origin, morphology, and early evolution of parasites and their associations with hosts are poorly known [9, 10] due to sparse records of putative ectoparasites with uncertain classification in the Mesozoic, most lacking mouthpart information and other critical details of the head morphology [11-15]. Here we present two primitive flea-like species assigned to the Pseudopulicidae Gao, Shih et Ren familia nova (fam. nov.), Pseudopulex jurassicus Gao, Shih et Ren genus novum et species nova (gen. et sp. nov) from the Middle Jurassic [16] and P. magnus Gao, Shih et Ren sp. nov. from the Early Cretaceous in China [17]. They exhibit many features of ectoparasitic insects. Large body size and long serrated stylets for piercing tough and thick skin or hides of hosts suggest that these primitive ectoparasites might have lived on and sucked the blood of relatively large hosts, such as contemporaneous feathered dinosaurs and/or pterosaurs or medium-sized mammals (found in the Early Cretaceous, but not the Middle Jurassic).