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The hard tick Compluriscutula vetulumPoinar and Buckley, 2008 (Ixodida: Ixodidae) from the mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar was first described in a new, extinct genus based on a larva. Here, several more larvae are documented providing additional morphological data based on optical studies using a Keyence VHX-6000 Digital Microscope supplemented by computed microtomography (µ-CT). We confirm the presence of 14 festoons (not 13) on the posterior margin of the body, a character unique for the genus. We further describe an unusual pattern of hypostome dentition in the mouthparts, with an unequal and uneven 2/2 arrangement. Moreover, on the internal side of the palps, to the second and third segments five tooth-like elements are present, similar to the hypostome dentition. Fossil ticks are generally very rare, thus the discovery of numerous new specimens of C. vetulumsuggests that it may have been relatively common in the Burmese amber forest. Larval instars predominate in the fossil record and we might speculate that they preferred arboricolous hosts.

Three examples of metastriate hard ticks (Ixodida: Ixodidae) with apparent affinities to modern Australasian genera are described from the mid-Cretaceous (ca. 100 Ma) Burmese amber of Myanmar. Two nymphs of Bothriocroton muelleri sp. nov. represent the oldest (and only) fossil record of this genus, living members of which are restricted to Australia and predominantly feed on monitor lizards, snakes and echidnas. A female of Archaeocroton kaufmani sp. nov. shares its basis capitulum shape with the tuatara tick Archaeocroton sphenodonti (Dumbleton, 1943), the only extant member of this genus and an endemic species for New Zealand. The presence of 2 Australasian genera in Burmese amber is consistent with a previous record of an Ixodes Latreille, 1795 tick from this deposit which resembles Australian members of this genus. They further support an emerging hypothesis that fauna of the amber forest, which may have been on an island at the time of deposition, was at least partly Gondwanan in origin. A revised evolutionary tree for Ixodida is presented compiling data from several new Burmese amber ticks described in the last few years. [ABSTRACT FROM AUTHOR]