Pronunciation: mie-MOHR-uh-PEL-tuh
Meaning: Shield of Mygatt-Moore
Author/s: Kirkland and Carpenter (1994)
Synonyms: None known
First Discovery: Colorado, USA
Discovery Chart Position: #390
Mymoorapelta maysi
Mymoorapelta was the first Jurassic-aged ankylosaur named from North America and, at three meters in length yet fully grown, is the smallest adult quadrupedal dinosaur known from the Morrison Formation. But despite being of modest size, it's been a bit of a trouble maker, whipping up no end of controversy regarding its position within Ankylosauria: the armour-plated branch of "shield-bearing" dinosaurs known collectively as thyreophorans.
When Kirkland and Carpenter named Mymoorapelta in 1994, they were convinced it was a shoo-in polacanthid because of hollow-based triangular armour plates, a fused hip-shield and grooved spines on its vertebrae similar to those found on the name-bearer, Polacanthus. In 2004, Vickaryous et al. disagreed, believing it to be way more primitive than any other ankylosaur and, as such, couldn't be classified as anything more specific than Ankylosauria incertae sedis (of uncertain placement). They came to that very conclusion with Dracopelta at the same time. To add a little more sauce, Mymoorapelta shares some features with primitive stegosaurs such as Huayangosaurus and Kentrosaurus, particularly in the proportions of its massive ulna (a lower arm bone) and curved ilium (a hip bone), which, if nothing else, suggests it may have held a stegosaurian-type stance, with short but powerful forelimbs and narrow hips set high.
Several experts have noted similarities between the ulna of Mymoorapelta and a corresponding bone from the Bearreraig Sandstone Formation of Bearreraig Bay on the Isle of Skye. All has been quiet on the possibility of Bonny Scotland and western Colorado sharing a similar Jurassic fauna since 2000, so maybe the Scottish bone doesn't belong to an ankylosaur after all.
When Kirkland and Carpenter named Mymoorapelta in 1994, they were convinced it was a shoo-in polacanthid because of hollow-based triangular armour plates, a fused hip-shield and grooved spines on its vertebrae similar to those found on the name-bearer, Polacanthus. In 2004, Vickaryous et al. disagreed, believing it to be way more primitive than any other ankylosaur and, as such, couldn't be classified as anything more specific than Ankylosauria incertae sedis (of uncertain placement). They came to that very conclusion with Dracopelta at the same time. To add a little more sauce, Mymoorapelta shares some features with primitive stegosaurs such as Huayangosaurus and Kentrosaurus, particularly in the proportions of its massive ulna (a lower arm bone) and curved ilium (a hip bone), which, if nothing else, suggests it may have held a stegosaurian-type stance, with short but powerful forelimbs and narrow hips set high.
Several experts have noted similarities between the ulna of Mymoorapelta and a corresponding bone from the Bearreraig Sandstone Formation of Bearreraig Bay on the Isle of Skye. All has been quiet on the possibility of Bonny Scotland and western Colorado sharing a similar Jurassic fauna since 2000, so maybe the Scottish bone doesn't belong to an ankylosaur after all.
[May's Mygatt-Moore (Quarry) Shield]Etymology
Mymoorapelta honors Peter and Marilyn Mygatt, and John and Vanetta Moore, who stumbled upon the Mygatt-Moore Quarry in march 1981. "Pelta", which is a common suffix for armoured dinosaurs, means "shield" in Greek.
The species epithet, maysi, honors Chris Mays: president of the Dinamation Corporation and founder of the not-for-profit Dinamation International Society.
Discovery
Mymoorapelta was discovered at Mygatt-Moore Quarry (MWC Loc. 1.05.86)—which is thought to have been a watering hole—in the Brushy Basin Member of the Morrison Formation, Mesa County, western Colorado, USA, by Peter and Marilyn Mygatt and John and Vanetta Moore in March of 1981. The holotype (MWC 1815) consists of a left Ilium (the uppermost bone of the hip). Other material from the site, apparently pertaining to a single individual due to a lack of overlapping parts, includes four back vertebrae (MWC 1800-1803), seven tail vertebrae (MWC 1804-1808 and MCW1839 a-b), ribs (MWC 1809-1813 and MCW 1840), a right ulna (MCW 1814), hand bones (MCW 1816-1817 and MCW 939), and numerous armour plates and spines (MCW 1818-1838). All fossils look like they have been gnawed on, but it's impossible to tell whether its killer was responsible or if it was scavenged after death.
