Invictarx (meaning "unconquerable fortress") is a monospecific genus of nodosaurid dinosaur from New Mexico that lived during the Late Cretaceous (lower Campanian, 78.5 Ma) in what is now the upper Allison Member of the Menefee Formation.

Invictarx shares similarities with Glyptodontopelta from the Naashoibito member of the Ojo Alamo Formation, New Mexico.

[1] In May 2011, an incomplete postcranial skeleton of an ankylosaur was discovered from the upper Allison Member of the Menefee Formation, San Juan Basin by Daniel Williamson.

The specific name, zephyri, is derived from is the genitive form of the Greek noun Zephyrus, meaning (of the) western wind, referring to the "blustery conditions that prevail among the outcrops where the specimens were discovered".

[1] McDonald & Wolfe (2018) diagnosed Invictarx based on the cervical or pectoral, thoracic, and pelvic osteoderms exhibiting an overall smooth surface texture, with little to no projecting rugosity, with abundant pits distributed randomly over the entire external surface, and with no neurovascular grooves or a small number of bifurcating and non-bifurcating neurovascular grooves distributed randomly, a feature similar to Glyptodontopelta; thoracic osteoderms exhibit a low, rounded keel with a deep groove extending craniocaudally along the apex, similar to Anodontosaurus and Platypelta; and the presence of possible a co-ossified pelvic shield that consists of polygonal osteoderms of uniform size, similar to Nodosaurus, Stegopelta, Glyptodontopelta, Europelta and Aletopelta.

The vertebrae possess parapophyses that are distinct and are rugose swellings on the sides of the neural arch.

As in the nodosaurids Sauropelta, Europelta, Silvisaurus and Struthiosaurus austriacus, the neural canal is ellipse-shaped with its axis oriented towards the upper edge and sides.

The cervical or pectoral osteoderm preserves margins that are rugose and small projecting bumps with abundant neurovascular pits.

Two fragments referred to UMNH VP 28350 were identified as being partial components of the cervical or pectoral half-rings.

The first morphotype includes two partial osteoderms that are very thick with flat bases and sharp, prominent midline keels.

The third morphotype includes one osteoderm which exhibits a deep groove extending craniocaudally along the apex of the keel.

The fourth morphotype is represented by numerous flat, thin osteoderms that have highly rugose margins.

[1] Two fragments from the pelvic region assigned to UMNH VP 28350 have a flat external and basal surfaces with small pits.

[1] Invictarx is known from the upper Allison Member of the Menefee Formation which has been dated to the lower Campanian stage, 78.5 Ma.

[1] The Menefee Formation represents a widespread alluvial floodplain and consists of mudstone, siltstone, sandstone, and coal.

[2] The sandstones that comprises the Menefee Formation that are fixed within carbonaceous shales of coastal swamp or lagoon origin and are thought to have been created by flood tidal deltas that north and east across New Mexico and towards the retreating Western Interior Seaway.