A remarkable assemblage of ticks from mid-Cretaceous Burmese amber

Abstract

Four fossil ticks (Arachnida: Parasitiformes: Ixodida) are described from mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar. Ixodes antiquorum sp. nov. (Ixodidae) is the first Mesozoic record of Ixodes and the oldest representative of the most species-rich extant tick genus. Its affinities appear to lie with modern Australian forms, consistent with the hypothesis that Burmese amber hosted Gondwanan faunal elements. Even more remarkable is Khimaira fossus gen. et sp. nov. which combines a body resembling that of a soft tick (Argasidae) with a basis capitulum more like that of a hard tick (Ixodidae). We refer it to Khimairidae fam. nov. as a possible transitional form between the two main families of ticks alive today. Another member of the extinct Deinocrotonidae is described as Deinocroton copia sp. nov., while the first described adult female for Cornupalpatum burmanicum is associated with a dinosaur feather barb.

Graphical abstract

Fig. 1.

Ixodes antiquorum sp. nov. (Ixodidae) from Burmese amber designated as the holotype for this species. Indicated are dorsal (left) and ventral (right) images. The absence of festoons and the anterior anal groove can be clearly discerned. Arrows indicate the presence of notch-like processes on the joints. Line drawings at the bottom indicate important aspects described in the text. Scale bars indicated are 0.1 mm for the photos and 1 mm for line drawings.

Fig. 2.

A fossil of a female Cornupalpatum burmanicum (Ixodidae). Indicated are dorsal (up) and ventral (down images). The genital aperture, anus and the posterior V anal groove can be clearly discerned. A dinosaurian feather can be seen on the dorsal side. A line drawing at the bottom indicates important features. The scale bar in all figures is 1 mm.

Fig. 3.

Deinocroton copia sp. nov. (Deinocrotonidae) in Burmese amber designated as the holotype for this species. Indicated are dorsal and ventral views. Line drawings indicate pertinent features. The scale bars for the photos are 0.1 mm and for the line drawing 1 mm.

Fig. 4.

Khimaira fossus gen. et sp. nov. (Khimairidae) in Burmese amber designated as the holotype for this species and the family Khimairida. The terminal gnathostoma, scutum and mammillated alloscutum can be clearly discerned. The line drawing indicates pertinent features. The scale bars for the photos are 0.1 mm and for the line drawing 1 mm.

Fig. 5.

A representation of the possible systematic relationships among living and extinct tick families adapted from Peñalver et al. (2017) and Mans et al. (2019). Extinct lineages are depicted by red branches, while the potential divergence points for the Khimairidae are indicated as sister lineage to the Ixodidae/Argasidae (preferred placement), or the Ixodidae, or the Argasidae.