New and rediscovered primitive ants (Hymenoptera: Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships

All Cretaceous records of ants are reviewed, and evidence originally given for their placement is evaluated. Cretaceous Formicoidea preserved in rocks lack preservation of critical ant synapomorphies like the metapleural gland, which are preserved in specimens in amber. For this reason, the Armaniidae Dlussky, from the Cretaceous of Russia, are placed here as Formicoidea incertae sedis, not in the Formicidae proper. The oldest amber with ants is from New Jersey. Seven complete and partial specimens of Formicidae, recently discovered in Turonian (92 Ma) amber from central New Jersey, are described and discussed. The specimens consist of four males and three workers. One complete and well-preserved worker is Sphecomyrma freyi Wilson and Brown 1967, known previously from two workers in a piece of Turonian amber from Cliffwood Beach, New Jersey. Well preserved in the new worker are external and even some internal features of the metapleural gland-a definitive formicid synapomorphy-which are described in detail for the first time. This specimen is designated as a neotype to replace the disintegrated holotype of this species. One complete male specimen is tentatively assigned to Sphecomyrma, which would be the first known male of the genus. One complete and one partial male, both from the same piece of amber, are a new, plesiomorphic species of Baikuris Dlussky (Baikuris casei, n. sp.), the genus previously known only from upper Cretaceous (Santonian) amber of Taymyr, northern Siberia. Two workers represent a new genus and species of Cretaceous Formicidae, Brownimecia clavata n. gen., n. sp., based on distinctively clubbed antennae, proportions of the antennal articles, and thin mandibles that lack teeth and extensively cross, and a ponerine-like constriction * Paleontology of New Jersey amber, Part VI. ' Curator, Department of Entomology, American Museum of Natural History. 2 Research Scientist, Department of Entomology, American Museum of Natural History. Copyright C American Museum of Natural History 1997 ISSN 0003-0082 / Price $5.60 AMERICAN MUSEUM NOVITATES between abdominal segments M and IV (gaster segments I and II). Brownimecia is more closely related to extant Formicidae than are Sphecomyrminae, the genus being the earliest known member of the extant subfamily Ponerinae. The fourth male belongs to a third genus, undescribed. These are the oldest definitive ants. Composition, monophyly, and systematic position of the subfamily Sphecomyrminae are discussed. Modifications were made to the data of Baroni Urbani et al. (1992) and reanalyses were made of the basal relationships of the Formicidae including Sphecomyrma and Brownimecia. Discrepencies with the cladograms of Baroni Urbani et al. (1992) are discussed. Including the fossil taxon Formiciinae Lutz (compressed remains from the Eocene of Germany) in the cladistic analysis, as done by Baroni Urbani et al., imparts too many missing values for meaningful analysis. Sphecomyrma, not discussed by Baroni Urbani et al., retains its basal position in the Formicidae in the present analysis. Discovery of new and exclusively primitive ants in upper Cretaceous ambers indicates an origin of the ants probably in the lowermost Cretaceous, but no older, contrary to a recent molecular hypothesis.