Cretaceous crown male ant reveals the rise of modern lineages

Most of the described Mesozoic ants belong to stem groups that existed only during the Cretaceous. The earliest crown ants have hitherto been known from the Turonian (Late Cretaceous, ca. 94–90Ma) deposits of the USA, Kazakhstan, and Botswana. However, the discovery of an alate male in Kachin amber from the earliest Cenomanian (ca. 99Ma), representing a new genus and species, <i>Antiquiformica alata</i>, revises the narrative on ant diversification. <i>Antiquiformica</i> is clearly differentiated from all known males of stem ants in the distinctly geniculate antenna with an elongate scape, extending far beyond the occipital margin of the head and half the length of the funiculus, and in the partly reduced forewing venation. Furthermore, the combination of a one-segmented waist with a well-developed node, an elongate scape extending beyond the occipital margin, and reduced forewing venation, in particular, the completely reduced crossveins m-cu and rs-m and absence of closed cells rm and mcu, demonstrates that the fossil belongs to the extant subfamily Formicinae. The result of Fourier Transform Infrared Spectroscopy (FTIR) indicates that the piece of amber containing <i>A. alata</i> originated from the mines of Kachin, Myanmar. The new fossil significantly revises our understanding of the early evolution of Formicinae. The discovery of <i>Antiquiformica</i> in Cenomanian amber indicates that the subfamily Formicinae arose at least by the start of the Late Cretaceous, while crown ants certainly arose earlier, in the earliest Cretaceous or even in the Late Jurassic, although paleontological evidence is lacking to support the latter hypothesis.