Mymoorapelta is an ankylosaur from the Late Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 (Kimmeridgian

Kimmeridgian

In the geologic timescale, the Kimmeridgian is an age or stage in the Late or Upper Jurassic epoch or series. It spans the time between 155.7 ± 4 Ma and 150.8 ± 4 Ma . The Kimmeridgian follows the Oxfordian and precedes the Tithonian....

-Tithonian

Tithonian

In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...

) Morrison Formation

Morrison Formation

The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...

 (Brushy Basin Member) of western Colorado

Colorado

Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...

. The taxon is known from portions of a disarticulated skull, parts of three different skeletons and other postcranial remains. Present in stratigraphic zones 4 and 5 of the Morrison Formation.

There is presently some controversy as to this ankylosaur's position within the Ankylosauria

Ankylosauria

Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are first known to have appeared in the early Jurassic Period of...

. Vickaryous et al. (2004) considered it Ankylosauria incertae sedis

Incertae sedis

, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...

, while Kirkland et Carpenter (1994) placed it within the Family Polacanthidae. A new cladistic analysis performed by Thompson et al., 2011 suggests that Mymoorapelta is a basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 nodosaurid. To date, only a single species has been named for this taxon, M. maysi. Along with Gargoyleosaurus

Gargoyleosaurus

Gargoyleosaurus is one of the earliest ankylosaurs known from reasonably complete fossil remains. Its skull measures in length, and its total body length is an estimated . It may have weighed as much as...

 parkpinorum, Mymoorapelta is one of the earliest known ankylosaurs, providing a look at the early evolution

Evolution

Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 and diversification of this group of dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s.