New remarkable hell ants (Formicidae: Haidomyrmecinae stat. nov.) from mid-Cretaceous amber of northern Myanmar

Haidomyrmecines (hell ants) are a group of putatively predatory ants defined by mandibles that are dorsoventrally expanded, and highly modified heads with a variety of cranial appendages. These ants are known exclusively from three Cretaceous amber deposits in France, Myanmar, and Canada. Here we describe four new genera and five new species from specimens preserved in mid-Cretaceous (uppermost Albian–lowermost Cenomanian, ca. 99 Ma) amber from the Kachin State of northern Myanmar: Dhagnathos autokrator gen. et sp. nov., Chonidris insolita gen. et sp. nov., Aquilomyrmex huangi gen. et sp. nov., Protoceratomyrmex revelatus gen. et sp. nov., and Linguamyrmex brevicornis sp. nov. We propose a new subfamilial rank for hell ants, i.e., Haidomyrmecinae stat. nov., based on recent phylogenetic analyses. A diagnosis and a key to the genera and species of Haidomyrmecinae are provided. The mouthparts and cranial features of these remarkable taxa display a series of morphological syndromes that likely relate to specialized prey capture. The diversity of these and other described hell ants underscores the extensive radiation of adaptive forms that were present early in ant evolution.