Tatuidris tatusia is the only species in Tatuidris, a monotypic genus and one of only two extant genera in the subfamily Agroecomyrmecinae.
A new species, T. kapasi, was described by Lacau & Groc in 2012, but has now been relegated to a junior synonym under T. tatusia based on the extent of the morphological variability encountered throughout this broad geographic range.
Analysis of DNA barcodes indicated a pattern of genetic isolation by distance, suggesting the presence of a single species undergoing allopatric differentiation.

It was first described by Brown & Kempf in 1968 based on two workers collected in a Berlese sample of humus in El Salvador.
Due to morphological similarities, they considered it a very primitive ant and placed it in what was then a myrmicine tribe, the Agroecomyrmecini, together with ants known from Early Eocene Baltic amber (Agroecomyrmex) and late Eocene Florissant shale (Eulithomyrmex).

It bears superficial resemblance to some extant genera (Strumigenys, Ishakidris, Pilotrochus, and Phalacromyrmex) but these similarities are considered to be due to convergent evolution.
Due to similarities in the habitus, Brown & Kempf (1968) linked Tatuidris to the Dacetini genus Glamyromyrmex (currently a junior synonym of Strumigenys) and Phalacromyrmex.
However they concluded: "analysis of these similarities indicates [...] that they are mostly convergent and not based on close phylogenetic relationship".
Further work explored the similarities of Tatuidris with Ishakidris (Bolton 1984) and Pilotrochus (Brown 1977).
While these taxa share some characteristics, including an expanded head vertex, deep antennal scrobes and a compact mesosoma, the similarities were again deemed convergent.

Since the original description, the systematic status of the tribe has been the focus of debate.
Bolton (2003) was the first to suggest the taxonomic instability of Tatuidris within Myrmicinae and raised the genus to the level of a new subfamily, the Agroecomyrmecinae, suggesting that Agroecomyrmecinae might be the sister taxon to Myrmicinae.
The subfamily rank was re-assessed by Baroni Urbani & de Andrade in 2007, this was the first attempt to include Tatuidris as a terminal taxon in a morphological cladistic analysis.
In their study, Baroni Urbani & de Andrade identified morphological synapomorphies shared between Tatuidris and the dacetines, justifying the inclusion of the genus within Myrmicinae.
In addition, two autapomorphies (a differently shaped petiolar tergum and sternum, and the eyes at or close to the apex of the antennal scrobe) separated Tatuidris from all other extant ant genera included in their study.

Unlike phylogenetic studies based on morphological traits, molecular analyses of the internal phylogeny of the ants have given strong evidence that the armadillo ants are neither closely related to nor nested within the Myrmicinae.
Brady et al. (
2006), Moreau et al. (
2006) and Rabeling et al. (
2008) reconstructed phylogenetic trees with the agroecomyrmecines inside the 'poneroid' group of subfamilies, close to the Paraponerinae, and gave support for the exclusion of the genus from the Myrmicinae, a subfamily located inside the 'formicoid' clade.
Given the early appearance of the Agroecomyrmecinae in the geologic record, the similarities of armadillo ants to Myrmicinae were hypothesized to represent convergence and/or retention of plesiomorphic forms.

The name Tatuidris means "armadillo ant", which is also the common name for this species; tatu comes from the Tupi and Portuguese word for "armadillo"; the specific epithet for the single described species, tatusia, is an old generic name for armadillo.
Tatuidris tatusia is the only species in Tatuidris, a monotypic genus and one of only two extant genera in the subfamily Agroecomyrmecinae. A new species, T. kapasi, was described by Lacau & Groc in 2012, but has now been relegated to a junior synonym under T. tatusia based on the extent of the morphological variability encountered throughout this broad geographic range. Analysis of DNA barcodes indicated a pattern of genetic isolation by distance, suggesting the presence of a single species undergoing allopatric differentiation.
It was first described by Brown & Kempf in 1968 based on two workers collected in a Berlese sample of humus in El Salvador. Due to morphological similarities, they considered it a very primitive ant and placed it in what was then a myrmicine tribe, the Agroecomyrmecini, together with ants known from Early Eocene Baltic amber (Agroecomyrmex) and late Eocene Florissant shale (Eulithomyrmex).
It bears superficial resemblance to some extant genera (Strumigenys, Ishakidris, Pilotrochus, and Phalacromyrmex) but these similarities are considered to be due to convergent evolution. Due to similarities in the habitus, Brown & Kempf (1968) linked Tatuidris to the Dacetini genus Glamyromyrmex (currently a junior synonym of Strumigenys) and Phalacromyrmex. However they concluded: "analysis of these similarities indicates [...] that they are mostly convergent and not based on close phylogenetic relationship". Further work explored the similarities of Tatuidris with Ishakidris (Bolton 1984) and Pilotrochus (Brown 1977). While these taxa share some characteristics, including an expanded head vertex, deep antennal scrobes and a compact mesosoma, the similarities were again deemed convergent.
Since the original description, the systematic status of the tribe has been the focus of debate. Bolton (2003) was the first to suggest the taxonomic instability of Tatuidris within Myrmicinae and raised the genus to the level of a new subfamily, the Agroecomyrmecinae, suggesting that Agroecomyrmecinae might be the sister taxon to Myrmicinae. The subfamily rank was re-assessed by Baroni Urbani & de Andrade in 2007, this was the first attempt to include Tatuidris as a terminal taxon in a morphological cladistic analysis. In their study, Baroni Urbani & de Andrade identified morphological synapomorphies shared between Tatuidris and the dacetines, justifying the inclusion of the genus within Myrmicinae. In addition, two autapomorphies (a differently shaped petiolar tergum and sternum, and the eyes at or close to the apex of the antennal scrobe) separated Tatuidris from all other extant ant genera included in their study.
Unlike phylogenetic studies based on morphological traits, molecular analyses of the internal phylogeny of the ants have given strong evidence that the armadillo ants are neither closely related to nor nested within the Myrmicinae. Brady et al. (2006), Moreau et al. (2006) and Rabeling et al. (2008) reconstructed phylogenetic trees with the agroecomyrmecines inside the 'poneroid' group of subfamilies, close to the Paraponerinae, and gave support for the exclusion of the genus from the Myrmicinae, a subfamily located inside the 'formicoid' clade. Given the early appearance of the Agroecomyrmecinae in the geologic record, the similarities of armadillo ants to Myrmicinae were hypothesized to represent convergence and/or retention of plesiomorphic forms.
The name Tatuidris means "armadillo ant", which is also the common name for this species; tatu comes from the Tupi and Portuguese word for "armadillo"; the specific epithet for the single described species, tatusia, is an old generic name for armadillo.
Tatuidris