how are they classified?
As "incertae sedis"
History and classification
Archibald and colleagues originally classified "Ypresiomyrma" as "incertae sedis" (Latin for "of uncertain placement") within the ant subfamily Myrmeciinae,
what is ypresiomyrma? It is an extinct genus of ants in the subfamily Myrmeciinae.
Ypresiomyrma orbiculata, Ypresiomyrma bartletti, Ypresiomyrma rebekkae, Ypresiomyrma orientalis "Ypresiomyrma" is classified as "incertae sedis" within the ant subfamily Myrmeciinae, as the ants could not be identified to any tribe level. They were members of the subfamily Myrmeciinae .
Ypresiomyrma Ypresiomyrma Ypresiomyrma
History and classification History and classification Introduction
Along with the genus description, the paper contained descriptions of the type species "Ypresiomyrma orbiculata" and "Ypresiomyrma bartletti", both from the McAbee Fossil Beds in British Columbia, part of the Eocene Okanagan Highlands lake system. Archibald, Cover and Moreau also included a redescription of the Danish species "Pachycondyla rebekkae" under the new name combination "Ypresiomyrma rebekkae". A fourth species, "Ypresiomyrma orientalis" was described in 2015. "Ypresiomyrma" as "incertae sedis" (Latin for "of uncertain placement") within the ant subfamily Myrmeciinae, as the ants could not be identified to any tribe level. Ypresiomyrma is an extinct genus of ants in the subfamily Myrmeciinae that was described in 2006. 
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Ypresiomyrma [SEP] History and classification
Archibald, Cover and Moreau also included a redescription of the Danish species "Pachycondyla rebekkae" under the new name combination "Ypresiomyrma rebekkae". A fourth species, "Ypresiomyrma orientalis" was described in 2015. Archibald and colleagues originally classified "Ypresiomyrma" as "incertae sedis" (Latin for "of uncertain placement") within the ant subfamily Myrmeciinae, as the ants could not be identified to any tribe level. However, a 2008 paper by Cesare Baroni Urbani of the University of Basel, Switzerland, expressed doubt that members of "Ypresiomyrma" were even ants. He notes that the development of the malar area (an area between the compound eyes and the mandibles) was different and not reduced, as a reduced malar is synapomorphic (key diagnostic traits) in Myrmeciinae.