Pronunciation: in-VIK-tarks
Meaning: Unconquerable fortress
Author/s: McDonald and Wolfe (2018)
Synonyms: Non known
First Discovery: San Juan, New Mexico
Acta Ordinal: #997
Invictarx zephyri
Invictarx zephyri is a member of Nodosauridae—the lightly armoured branch of ankylosaurs, and counterpart to the tank-like ankylosaurids—from the Menefee Formation of New Mexico. Its fossils are sparse: limb fragments, the odd rib, vertebral scraps, and a scattering of osteoderms or bony shields that are unusually smooth in texture, with little to nothing in the way of bumpy rugosities typical of most ankylosaurs, yet densely pitted across their entire surface. But in a group where armour texture tends to be consistent within lineages, that combination was distinctive enough for palaeontologists to recognise Invictarx as something distinct, even though the rest of the skeleton remains almost entirely unknown.
Invictarx lived alongside an indeterminate crocodilian and an ankylosaur, the alligatoroids Brachychampsa and the enormous Deinosuchus, and a grab-bag of turtles—a baenid, a trionychid, and one mystery model—each of them armoured in their own way. But the Menefee ecosystem wasn’t merely a parade of osteoderms. It was a sub-tropical coastal plain with rivers and streams, deltas, shallow swamps and lagoons, where at least three of the major non-armoured dinosaur branches were also present: the hadrosaur Ornatops moving in small herds along the floodplain margins, the ceratopsid Menefeeceratops browsing in denser patches of vegetation, a small Saurornitholestes-like dromaeosaurid darting through the undergrowth, and the tyrannosauroid Dynamoterror stalking the river corridors as the dominant terrestrial predator.
Invictarx lived alongside an indeterminate crocodilian and an ankylosaur, the alligatoroids Brachychampsa and the enormous Deinosuchus, and a grab-bag of turtles—a baenid, a trionychid, and one mystery model—each of them armoured in their own way. But the Menefee ecosystem wasn’t merely a parade of osteoderms. It was a sub-tropical coastal plain with rivers and streams, deltas, shallow swamps and lagoons, where at least three of the major non-armoured dinosaur branches were also present: the hadrosaur Ornatops moving in small herds along the floodplain margins, the ceratopsid Menefeeceratops browsing in denser patches of vegetation, a small Saurornitholestes-like dromaeosaurid darting through the undergrowth, and the tyrannosauroid Dynamoterror stalking the river corridors as the dominant terrestrial predator.
(Unconquerable fortress of the western wind)Etymology
Invictarx is derived from the Latin "invictus" (invincible or unconquerable) and "arx" (fortress), referring to the well-armored nature of ankylosaurian dinosaurs.
The species epithet, zephyri, is derived from "zephyrus" (west wind), in reference to the blustery conditions that prevail among the outcrops where the specimens were discovered.
ZooBank registry:
urn:lsid:zoobank.org:act:223160EC-F6B7-4637-9C2F-796EAF4A2816.
Discovery
The remains of Invictarx were discovered at "Juans Lake Beds" in the upper part of the Allison Member of the Menefee Formation, San Juan County, New Mexico, between 2011 and 2015, during a project led by Andrew McDonald and Douglas Wolfe, supported by the University of Pennsylvania and volunteers from the Southwest Paleontological Society, and later by the Western Science Center (WSC) and Zuni Dinosaur Institute for Geosciences.The holotype (WSC 16505) consists of rib fragments, six complete or partial identifiable osteoderms (WSC 16505.1–WSC 16505.6), and fragments of additional osteoderms, found in October 2015 by Keith Brockmann and Judy Evans. Osteoderms, from the Greek "osteo" (bone) and "derm" (skin), are bony elements embedded within the skin, forming everything from simple scales to huge armour plates. Referred specimens include UMNH VP 28350 (three back vertebrae, rib fragments, a partial left arm [pieces of the humerus, ulna, and radius], a piece of the right radius, one incomplete hand bone, and numerous incomplete osteoderms), found in May 2011 by Dan Williamson, and UMNH VP 28351 (fragments of several back vertebrae and ribs, numerous incomplete but identifiable osteoderms, and fragments of additional osteoderms), found in October 2011 by Andrew T. McDonald.
