Mymoorapelta (Meaning "Shield from the Mygatt-Moore Quarry" after a combination of the names of the discoverers of the Mygatt-Moore Quarry that fossils were originally collected from, and the Greek word πέλτα, meaning "shield") is a nodosaurid ankylosaur from the Late Jurassic (Kimmeridgian-Tithonian, around 155 to 150 million years ago) Morrison Formation (Brushy Basin Member) of western Colorado and central Utah, USA.

Five different armor types have been observed in Mymoorapelta, ranging from elongated, sharp spines on the side of the body to a giant sacral shield composed of tiny osteoderms, called ossicles, that covered the top of the pelvis.

The Mygatt-Moore Quarry was first discovered in March of 1981 by hikers Vanetta Moore and Pete and Marilyn Mygatt in Mesa County, west-central Colorado.

[1] The specific name is after Chris Mays, the president of the Dinamation International Corporation and Society, who funded the initial excavation of the Mygatt-Moore Quarry.

[5][7][3] All of the fossils found at Mygatt-Moore Quarry and Cactus Park are currently deposited in the Dinosaur Journey Museum of Western Colorado in Fruita.

The wear facets on Ankylosaur teeth vary greatly, but in nodosaurids they are usually more extensive and steeply inclined than in ankylosaurids, demonstrating underlying patterns of shape-constrained function.

The mandibular adductor chamber and the coronoid process are generally taller in nodosaurids than in ankylosaurs, suggesting differences in the size and attachment of muscles.

The transverse processes of the dorsal vertebrae do not ascend steeply and are instead gradually heightened, similar to the condition in basal ankylosaurs, and differing from that of nodosaurids.

This trait is only present in nodosaurids and basal anklosaurs, but in taxa like Liaoningosaurus and more derived ankylosaurids they overlap by at least 50% of its length, making them more fused together.

[1][5] The scapular spine forms a vertical ridge opposite the glenoid in Mymoorapelta, as in other ankylosaurids and in an indeterminate ankylosaur scapula found in the nearby Dry Mesa Quarry.

These have not been found in articulation, so their exact placement on the body is unknown, though their position can be surmised based on the well preserved skeletons of other nodosaurids and ankylosaurs.

[16][1] It was theorized by Kirkland and Carpenter that the largest of these plates were attached to the proximal part of the tail, and protruded laterally along the sides of the body.

[4] Mymoorapelta was a low-browsing herbivore like its relatives, likely feeding on the ferns, cycads, and conifers that dominated the flora of its time due to the lack of complex grasses in the Jurassic.

[27][12] In ankylosaurs, the Jurassic and mid-Cretaceous forms with narrow and pointed muzzles were apparently the most selective feeders, akin to extant mammalian browsers.

The preservation of complete a hyoid in taxa like the ankylosaurid Pinacosaurus and the nodosaurid Edmontonia demonstrate that ankylosaurs had fleshy, muscular tongues that could have assisted with feeding on plants that grew low to the ground.

The earliest evidence of nodosaurid dental occlusion is in Sauropelta, which demonstrated a basic motion, in that the power strokes moved vertically.

In contrast to later nodosaurids, tooth-to-tooth contact was incidental or local when present and a biphasial jaw mechanism was lacking in both Mymoorapelta and Gargoyleosaurus.

The Hanksville-Burpee specimen's taphonomy (how and where it decomposed to end up as a fossil) suggests that the individual had died inland, contrary to the coastal distribution previously inferred for nodosaurids.

[38] Mymoorapelta is one of the basalmost known genera of Nodosauridae, an extinct family of medium to large, heavily built, quadrupedal, herbivorous dinosaurs which possess small, leaf-shaped teeth.

155 mya), with Mymoorapelta and the similarly sized Gargoyleosaurus being early members of the evolutionary radiation which would continue into the Cretaceous in accordance with Cope's Rule.

[20][43][44] Euankylosauria encompasses all members of Ankylosauria except for the clade Parankylosauria, which is a smaller group known exclusively from a few taxa that lived in the Cretaceous of Gondwana, rather than the euankylosaurs, who were endemic to Laurasia.

[45]When Mymoorapelta was originally named, Kirkland and Carpenter placed the taxon as a potential nodosaurid, though at that time there were only a few taxa to compare the material to.

[20] A 2010 phylogenetic analysis utilizing undescribed material resulted with Mymoorapelta as the sister taxon to Gargoyleosaurus in their own group outside of Polacanthidae, Nodosauridae, and Ankylosauridae.

[6] The Morrison Basin where dinosaurs lived stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the Front Range of the Rocky Mountains started pushing up to the west.

The Mygatt-Moore Quarry where Mymoorapelta was first found has been dated between 151.89 and 152.47 million years old, firmly placing it within the Brushy Basin Member of the Morrison Formation.

[3] As for vertebrates, three different kinds of fish have been described from the quarry based on fossils of astonishing quality, including Hulettia hawesi and Morrolepis schaefferi.

[3] Fossils of several other dinosaurs are known from the quarry, including the theropod Ceratosaurus, the sauropods Camarasaurus and Diplodocus, and potentially the small ornithischian Nanosaurus.

Remains of other vertebrate groups like crocodyliforms and turtles are rare in the quarry, indicating the lack of continuous standing water in the form of lakes or ponds.

[51] Fossils of Mymoorapelta and the theropod Allosaurus that preserve bite marks have been described from the Mygatt-Moore Quarry by Stephanie Drumheller et al. (2020), alongside other bones found with feeding traces.

Based on the position and nutrient value associated with the various skeletal elements with bite marks, it is predicted that Mymoorapelta was either predated upon or scavenged shortly after death.