The anatomy of Garzapelta's armour displays a mix of features otherwise seen in Rioarribasuchus chamaensis, a member of the Paratypothoracini, and taxa of the subfamily Desmatosuchinae.

Reyes, Martz and Small suggest that Garzapelta was likely a paratypothoracin that simply evolved lateral osteoderms similar to those of desmatosuchins, reasoning that its armour does not articulate in the way seen in members of the latter group.

The remains of Garzaspelta were discovered in 1989 in the UU Sand Creek locality (MOTT 3882) in the middle units of the Cooper Canyon Formation by paleontologist Bill Mueller and fossil collector Emmett Shedd.

The age of the locality is not entirely clear, but based on its stratigraphy relative to the Miller Ranch Sandstone it may date to the latest Adamanian or earliest Revueltian, a period of faunal turnover for aetosaurs.

The specimen, TTU-P 10449, received some attention by Jeffrey W. Martz and his colleagues in 2003 in a study that argued that, given its unique anatomy, it was likely to represent a distinct taxon.

[1] The first part of the name Garzapelta reflects the geographic origin of the animal, as the type locality lies in Garza County, Texas.

The species name meanwhile honours Bill D. Mueller not only for his participation in discovering the original material but also for his overall contribution to aetosaur research and Triassic paleontology in Texas.

The dorsal eminence of the paramedian osteoderms, a prominent ridge on their surface, is offset from the midline and located further towards the back, yet does not touch the edge of the element.

[1] Stagonolepidoidea Stenomyti Aetosaurus Coahomasuchus Apachesuchus Typothorax Redondasuchus Garzapelta muelleri Rioarribasuchus Kocurypelta Venkatasuchus Tecovasuchus Paratypothorax Neoaetosauroides Calyptosuchus Scutarx Adamanasuchus Stagonolepis robertsoni Stagonolepis olenkae Garzapelta muelleri Gorgetosuchus Longosuchus Lucasuchus Sierritasuchus Desmatosuchus Aetosaurinae The results recovered for lateral and paramedian osteoderms together agrees with the results yielded by just looking at the lateral osteoderms, again placing it as a stagonolepidoid just outside of Desmatosuchini.

The results of the overall phylogeny would support the former interpretation, which in turn would suggest that the paratypothoracine paramedian osteoderms are the ancestral condition, which was simply lost by all other aetosaurs and reversed in Garzapelta.