Mymoorapelta
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''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 Nodosauridae is a family of ankylosaurian dinosaurs known from the Late Jurassic to the Late Cretaceous periods in what is now Asia, Europe, North America, and possibly South America. While traditionally regarded as a monophyletic clade as the s ...
ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful l ...
from the Late
Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
(
Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 154.8 ±0.8 Ma and 149.2 ±0.7 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
-
Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
, around 155 to 150 million years ago)
Morrison Formation The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock 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, siltston ...
(Brushy Basin Member) of western
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
and central
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
,
USA The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 states and a federal capital district, Washington, D.C. The 48 contiguous ...
. The animal is known from a single species, ''Mymoorapelta maysi'', and few specimens are known. The most complete specimen is the
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
individual from the Mygatt-Moore Quarry, which includes , a partial , , and other bones. It was initially described by James Kirkland and
Kenneth Carpenter Kenneth Carpenter (born 21 September 1949) is an American paleontologist. He is the former director of the USU Eastern Prehistoric Museum and author or co-author of books on dinosaurs and Mesozoic life. His main research interests are armore ...
in 1994. Along with ''
Gargoyleosaurus ''Gargoyleosaurus'' (meaning "gargoyle lizard") is one of the earliest ankylosaurs known from reasonably complete fossil remains. The holotype was discovered in 1995 at the Bone Cabin Quarry West locality, in Albany County, Wyoming in exposures ...
'', it is one of the earliest known nodosaurids. ''Mymoorapelta'' is one of the smaller known nodosaurids, with the estimated length of the largest specimen only reaching . It had a narrow snout and almost triangular skull in dorsal view, with two large horns pointing backwards from the brow and two horns below these that pointed backwards and down on the . Five different armor types have been observed in ''Mymoorapelta'', ranging from elongated, sharp spines on the side of the body to a giant shield composed of tiny osteoderms, called ''ossicles'', that covered the top of the pelvis. In contrast to the club-tailed ankylosaurids, the tail bore spikes that ''Mymoorapelta'' likely used for defense. ''Mymoorapelta'' was a low browser in the Morrison ecosystem, feeding on
cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
s and
conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s, in contrast to the high-browsing ''
Apatosaurus ''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, a ...
'' known from the same quarries. Other dinosaur groups were also present, including the large
theropods Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
''
Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
'' and ''
Ceratosaurus ''Ceratosaurus'' (from Greek 'horn' and 'lizard') is a genus of carnivorous theropod dinosaur that lived in the Late Jurassic period (Kimmeridgian to Tithonian ages). The genus was first described in 1884 by American paleontologist Othni ...
'' and possibly the
ornithischia Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name ''Ornithischia'', or "bird-hipped", reflects this similarity and is derived from the Greek ...
n ''
Nanosaurus ''Nanosaurus'' ("small or dwarf lizard") is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-we ...
''. Both of the theropods have also been found in association with the animal, and we have evidence that the former preyed on ''Mymoorapelta.''


Discovery and naming


Original discovery

The Mygatt-Moore Quarry was first discovered in March 1981 by hikers Vanetta Moore and Pete and Marilyn Mygatt in Mesa County, west-central
Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...
. The quarry's strata come from the Brushy Basin Member of the
Morrison Formation The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock 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, siltston ...
, which dates to the
Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...
.Kirkland, J. I., & Carpenter, K. (1994)
North America's first pre-cretaceous ankylosaur (Dinosauria) from the Upper Jurassic Morrison Formation of western Colorado.
''Brigham Young University Geology Studies'', ''40'', 25-42.
Fossils of ''Mymoorapelta'' were first discovered in the quarry in 1990, and since then over 160 elements have been found scattered over of the quarry.Foster, J., Hunt-Foster, R., Gorman, M., Trujillo, K., Suarez, C., McHugh, J., ... & Schoenstein, H. (2018). Paleontology, taphonomy, and sedimentology of the Mygatt-Moore Quarry, a large dinosaur bonebed in the Morrison formation, western Colorado—implications for Upper Jurassic dinosaur preservation modes. ''Geology of the Intermountain West'', ''5'', 23-93. A few of these elements are part of a single adult individual and were described by American paleontologists James Kirkland and
Kenneth Carpenter Kenneth Carpenter (born 21 September 1949) is an American paleontologist. He is the former director of the USU Eastern Prehistoric Museum and author or co-author of books on dinosaurs and Mesozoic life. His main research interests are armore ...
in 1994. This specimen (MWC 1815) would be designated the holotype of the species and includes a left (hip bone) with preserved bitemarks. Kirkland and Carpenter named the species ''Mymoorapelta maysi'', the generic name deriving from the names of Marilyn Mygatt and the Moores, who had discovered the quarry, and the Greek root ''pelta'', meaning "shield", due to the preserved armor. 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. ''Mymoorapelta'' was the first Jurassic
ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful l ...
named from North America, with the closely related ''
Gargoyleosaurus ''Gargoyleosaurus'' (meaning "gargoyle lizard") is one of the earliest ankylosaurs known from reasonably complete fossil remains. The holotype was discovered in 1995 at the Bone Cabin Quarry West locality, in Albany County, Wyoming in exposures ...
'' being named four years later in 1998.Carpenter, K., Miles, C. and Cloward, K. (1998). "Skull of a Jurassic ankylosaur (Dinosauria)." ''Nature'' 393: 782–783. Other parts of the type specimen that were excavated from the quarry include several (back) and (tail) vertebrae, , isolated limb bones, and many osteoderms, including the signature triangular cervical spine of basal ankylosaurs.Hunt, A. P., & Scheetz, R. D. (1998)
Ankylosaur (Dinosauria) specimens from the Upper Jurassic Morrison Formation
''The Upper Jurassic Morrison Formation: An Interdisciplinary Study: Denver Museum of Natural History, Denver, USA: May 26–28, 1994'', ''22'', 145-177.
Some osteoderms which have been found in the quarry and referred to ''Mymoorapelta'' come from a higher stratigraphic layer, suggesting that a second individual is preserved.


Later finds

In 1998, a partial skeleton referred to ''Mymoorapelta'' was described by Kirkland ''et al'' from Cactus Park, Colorado, though at the time the fossil was still undergoing
fossil preparation Fossil preparation is a complex of tasks that can include excavating, revealing, conserving, and replicating the ancient remains and traces of organisms. It is an integral part of the science of paleontology, of museum exhibition, and the preser ...
. The skeleton preserved natural molds and body fossils of the sacrum, caudal vertebrae, (bones attached to the underside of the tail vertebrae in
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s), (foot), and many pieces of the dermal armor, including parts of the sacral shield, which was a type of armor that would cover the top of the pelvis. Though skull material was mentioned to be preserved it is still in preparation and undescribed.Foster, J. (2007). Jurassic West: The Dinosaurs of the Morrison Formation and Their World. Indiana University Press. pp. 327–329. Some of the material, namely from the pes and sacral shield, was preserved in articulation making it the only known articulated specimen of the taxon. In a 2010 abstract, Kirkland and colleagues mentioned the discovery of many more elements of ''Mymoorapelta'' at Mygatt-Moore Quarry including a nearly complete skull and every postcranial element except the pubis and femur.Kirkland, J. I., Hunt-Foster, R. K., Foster, J. R., & Loewen, M. (2010). Newly recovered skeletal elements of the Late Jurassic dinosaur Mymoorapelta from its type locality in the Morrison Formation permits re-evaluation of ankylosaur phylogeny. ''Journal of Vertebrate Paleontology'', ''30'', 116A. 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. 2015 saw the presentation of an abstract by Katie Tremaine ''et al'' that mentions a new ''Mymoorapelta'' specimen unearthed at Hanksville-Burpee Quarry near Hanksville, Utah.Tremaine, K., D’Emic, M., Williams, S., Hunt-Foster, R.K., Foster, J., and Mathews, J., (2015), Paleoecological implications of a new specimen of the ankylosaur Mymoorapelta maysi from the Hanksville-Burpee Quarry, latest Jurassic (Tithonian) Morrison Formation (Brushy Basin Member) bs. Journal of Vertebrate Paleontology Program and Abstracts, p. 226. The specimen includes one individual preserving: 24 osteoderms, three ribs, one vertebra, and a femur, though more material has yet to be excavated. The discovery of a single, dorsal osteoderm that had been collected from the Peterson Quarry outside of
Albuquerque Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...
,
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
was described in 2016.Burns, M. E., & Lucas, S. G. (2016)
Biostratigraphy of Ankylosaur (Dinosauria: Ornithischia) Osteoderms from New Mexico.
''Fossil Record 4: Bulletin 67'', ''67'', 9.
The osteoderm is morphologically (based on external anatomy) similar to ''Mymoorapelta'', however it is stratigraphically (based on rock layers) closer to ''Gargoyleosaurus.''


Description

''Mymoorapelta'' is one of the smallest ankylosaurs known and the smallest known
quadrupedal Quadrupedalism is a form of Animal locomotion, locomotion in which animals have four legs that are used to weight-bearing, bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four l ...
dinosaur from the Morrison Formation. However, few individuals have been found and only a portion of the known material has been described in detail. The Cactus Park specimen is the largest described individual, with its length being estimated at around long in 1998. Body mass estimates based on the type specimen give a weight of around .


Skull and dentition

The specifically has not been described in detail, but the preserved
morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...
(external anatomy) is very similar to that of ''Gargoyleosaurus'', which also hails from the Morrison Formation. It had a narrow snout and almost triangular shaped skull in dorsal (top) view, with two large horns pointing backward from the back of the brow, and two horns below these that pointed backward and down from the (cheek bone). A preserved jugal described in 1998 has a wedge-shaped, armored morphology and projects ventrolaterally (down and outwards) like in ankylosaurids. The (bones at the tip of the snout) probably possessed a narrow, toothed, and trapezoidal muzzle like in ''Gargoyleosaurus''. In the back of the skull, the -articular area (place of contact between the skull and lower jaw) faces slightly medially (towards the midline of the body), and is subtly lengthened anteroposteriorly (front to back). The distal surface of the quadrate, especially on the medial condyle, is robust and elongated anteroposteriorly. In all ankylosaurs, the jaw joint (joint connecting the skull to the jaw bone) is placed ventrally to the occlusal plane (contact surface between teeth). The (bony projection on the lower jaw) is very well developed in nodosaurids, and the jaw joint is well depressed in turn, which corresponds to a higher relative
bite force Bite force quotient (BFQ) is a numerical value commonly used to represent the bite force of an animal adjusted for its body mass, while also taking factors like the allometry effects. The BFQ is calculated as the regression of the quotient of an ...
. Most ankylosaurs have
heterodont In anatomy, a heterodont (from Greek, meaning 'different teeth') is an animal which possesses more than a single tooth morphology. Human dentition is heterodont and diphyodont as an example. In vertebrates, heterodont pertains to animals wher ...
dentition (variation in tooth morphology), but not in ''Gargoyleosaurus,'' which shows only subtle morphological differences in the premaxillary, maxillary, and dentary teeth. Ankylosaur teeth are compressed labiolingually and are phylliform (leaf-shaped), with an apical cusp and secondary cusps along the mesial and distal edges. Nodosaurid teeth are blade-like, larger, and usually more complex than the basic cusps of ankylosaurids, having a larger crown, a rough enamel surface, confluent fluting with grooves of the marginal cusps, and a crenelated (shelf-like bulge surrounding the base of a
tooth crown In dentistry, the crown is the visible part of the tooth above the gingival margin and is an essential component of dental anatomy. Covered by Tooth enamel, enamel, the crown plays a crucial role in cutting, tearing, and grinding food. Its shap ...
). 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. In early nodosaurids like ''Gargoyleosaurus'' and '' Gastonia'', the (a
dermal The dermis or corium is a layer of skin between the epidermis (with which it makes up the cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from stress and strain. It is divided i ...
, paired bone of the
palate The palate () is the roof of the mouth in humans and other mammals. It separates the oral cavity from the nasal cavity. A similar structure is found in crocodilians, but in most other tetrapods, the oral and nasal cavities are not truly sep ...
) is not yet well developed anteroposteriorly and mediolaterally, but in later species they are much wider, with more robust lateral wings, and they are more expanded anteroposteriorly than in basal forms, reaching the level of the distal quadrate condyles. This suggests more developed pterygoid muscles in later nodosaurids than in ankylosaurids, reflecting a more efficient jaw adductor system in nodosaurids. 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.


Postcranial skeleton

A large part of the postcranial (behind the skull) skeleton of ''Mymoorapelta'' is known. For instance, many (vertebrae of the neck) are known, though many of them have not been fully researched or excavated. In the cervicals, the faces (ends) of the are wider than they are tall and display a heart-shaped morphology. The centra overall are anteroposteriorly short with lengths that are around equal to their width. The are short and thick,and possess round, circular neural canals. A deep, tear-shaped fossa (small opening in bone) is present between the (backwards projections of the vertebral arch). Several dorsal (back, sometimes referred to as thoracic) vertebrae are known from ''Mymoorapelta,'' and they are unique when compared to those of Cretaceous nodosaurids. The centra are cylindrical, longer posteriorly, and less laterally compressed than those of other, later nodosaurids like ''
Sauropelta ''Sauropelta'' ( ; meaning 'lizard shield') is a genus of nodosaurid dinosaur that existed in the Early Cretaceous Period of North America. One species (''S. edwardsorum'') has been named. Anatomically, ''Sauropelta'' is one of the most well-und ...
'' and '' Dracopelta''. The anterior dorsals are unique in that they bear a triangular pit between the (forwards projections of the vertebral arch), which are also much more elongate at the anterior end of the vertebra. Meanwhile, the postzygapophyses are truncated at the posterior end, with the left and right postzygapophyses divided by a large groove. The mid dorsal vertebrae differ in that they are rounded ventrally and have a weak keel at the bottom. 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. ''Mymoorapelta'' has 13 ribs, all of which have triangular cross-sections and a weak T-shape, in contrast to other ankylosaurs. ''Mymoorapelta'' is also one of the few ankylosaurs with 4 sacral ribs, a trait it shares with only 3 other taxa.Raven, T. J. (2021). ''The Taxonomic, Phylogenetic, Biogeographic and Macroevolutionary History of the Armoured Dinosaurs (Ornithischia: Thyreophora)''(Doctoral dissertation, University of Brighton). The caudal (tail) vertebrae of ''Mymoorapelta'' and other nodosaurids are longer than they are wide, and dorsoventrally (top-bottom) flattened with a reduction of the neural spines when compared to the anterior caudals. The haemal spine takes on a rounded, hatchet-shaped appearance. The prezygapophyses are short and extend past the anterior edge of the centra by only 25% or less. 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. ''Mymoorapelta'' lacks tail club handles or tail club knobs, as in other nodosaurids, giving them less ankylosis. The transition from anterior to posterior caudal vertebrae is less abrupt compared to ankylosaurids, which have an abrupt transition at the midcaudals, the lack of this abrupt transition would give the tail more flexibility, which is unique to nodosaurids when compared to the strongly fused tails of ankylosaurids.Arbour, V. M., & Currie, P. J. (2015)
Ankylosaurid dinosaur tail clubs evolved through stepwise acquisition of key features.
''Journal of anatomy'', ''227''(4), 514-523.
The vertebral centra and neural spines are much shorter when compared to ''Gargoyleosaurus.'' ''Mymoorapelta,'' like other dinosaurs, preserves chevrons along the undersides of the caudal vertebrae, and just like in many other ankylosaurs, the chevrons are strongly fused to the lower posterior part of the centra, and the haemal arches extend parallel to the elongate vertebral centra. The extension of these arches is greater anteriorly than posteriorly, forming a continuous bony structure underneath the haemal canal. One of the preserved chevrons measures and is strongly recurved posteriorly. 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. In the pelvic region, ''Mymoorapelta'' displays an intermediate between some features of basal and more derived ankylosaurs. The ischium is bent as in other nodosaurids and polacanthines, indicating that a straight ischium is a derived feature in ankylosaurids. In the forelimbs, the ulna has a broad, massive olecranon process that preserves rugosities. The coronoid process develops about 1/3rd of the way down the ulna's shaft, compared to 1/4th of the way down in taxa like ''
Stegopelta ''Stegopelta'' (meaning "roofed shield") is a genus of struthiosaurin nodosaurid dinosaur. It is based on a partial skeleton from the latest Albian- earliest Cenomanian-age Lower and Upper Cretaceous Belle Fourche Member of the Frontier Forma ...
'' and ''
Polacanthus ''Polacanthus'', deriving its name from the Ancient Greek polys-/πολύς- "many" and akantha/ἄκανθα "thorn" or "prickle", is an early armoured, spiked, plant-eating ankylosaurian dinosaur from the early Cretaceous period of England. In ...
.'' In the pes (foot), the genus preserves short, wide metapodials with long phalanges, with the distal phalanges looking triangular and pointed in side view, contrary to other nodosaurids like ''
Edmontonia ''Edmontonia'' is a genus of panoplosaurin nodosaurid dinosaur from the Late Cretaceous Period. It is part of the Nodosauridae, a family within Ankylosauria. It is named after the Edmonton Formation (now the Horseshoe Canyon Formation in Canada ...
''.


Armor

A prominent feature of ''Mymoorapelta'' was its armor, which mostly consisted of large spiked osteoderms (bony armor) protruding from the lateral and dorsal sides of the body. 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. In ''Mymoorapelta'', there are five different preserved armor types: elongated spines with a large, hollow base; thin triangular plates with a narrow, asymmetrical base; small bladelike spines with a rounded, solid base; isolated, flat, keeled scutes; and scutes fused into a single plate of armor. The large spine is assumed to have extended from the base of the neck outward laterally, with the point curving posteriorly. Evidence from '' Borealopelta'' also supports the extension of the spike by a large keratin sheath. The aforementioned thin triangular plates, of which eight are known, are preserved similarly to those in ''Polacanthus'' further down the body. 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. A specimen of ''Mymoorapelta'' preserves one of these at in length. A single, small triangular plate was reported in 1994 and it preserves a thin, bladelike morphology, though its position is unknown. Twelve of the previously mentioned keeled, flat scutes were recovered from a specimen of ''Mymoorapelta'' in 1994, they preserve a keeled oval shape and an external surface that bears uniform, weak pitting, and a privation of neurovascular grooves (the system that controls blood flow and
homeostasis In biology, homeostasis (British English, British also homoeostasis; ) is the state of steady internal physics, physical and chemistry, chemical conditions maintained by organism, living systems. This is the condition of optimal functioning fo ...
) and (small openings within bones). In the internal structure of the scutes, half of the space is made up of
trabecular bone A trabecula (: trabeculae, from Latin for 'small beam') is a small, often microscopic, tissue element in the form of a small beam, strut or rod that supports or anchors a framework of parts within a body or organ. A trabecula generally has a ...
, while the rest is made up of thick external and basal cortices. Lastly, a small fragment of dermal armor preserves a rosette (a large osteoderm surrounded by smaller osteoderms, forming a flower-like arrangement) formed by a large central scute surrounded on all sides by smaller ossicles. This piece of armor comes from the sacral shield, which is a large plate of small, connected armor across the sacrum and pelvis for protection. A more complete sacral shield was preserved in the Cactus Park specimen, with estimates placing the complete sacral shield at in width for a pelvis that is wide. The sacral shield also preserves two middle rows of larger scutes, with each row preserving seven. ''Mymoorapelta'' preserves a category 2 sacral shield, which is characterized by bosses (keeled osteoderms) that border tubercles (elevated knobs) as well as rosettes of co-ossified osteoderms. This category of sacral shield is mostly found in the "polacanthids", but the status of this group is generally unstable, and the trait is also known in some ankylosaurids like ''
Shamosaurus ''Shamosaurus'' is an extinct genus of herbivorous basal ankylosaurid ankylosaur from Early Cretaceous (Aptian to Albian stage) deposits of Höövör, Mongolia. Discovery and naming In 1977, a Soviet-Mongolian expedition discovered the skelet ...
''. The category 2 shield is most similar to that of category 3, though the latter preserves polygonal osteoderms that lack rosettes. However,
Victoria Arbour Victoria Megan Arbour is a Canadian evolutionary biologist and vertebrate palaeontologist at Royal BC Museum, where she is Curator of Palaeontology. An "expert on the armoured dinosaurs known as ankylosaurs", Arbour analyzes fossils and create ...
''et al.'' (2011) suggested that category 1 shields could simply be an ontogenetic (growth) stage of category 2, as they have very similar morphology but are not co-ossified, which is an ontogenetic trait present in extant armored animals like armadillos and alligators. The current categorisation of sacral shields into distinct categories finds its origins in a 2011 paper by Arbour, Michael E. Burns and Philip J. Currie, and gives three distinct characteristics, one for each of the three categories. Category 1 shields are characterized by non-coosified osteoderms, category 2 shields by coossified rosettes, and category 3 by uniformly sized coossified polygons. On the upper surface of the back and tail, the skin was covered in small osteoderms, which are sometimes referred to as ossicles, in-between larger plates of armor as inferred by ''Sauropelta'', though ossicles themselves are not known confidently outside of the sacral shield in ''Mymoorapelta''. The armor of ''Mymoorapelta'' differs from that of ''Gargoyleosaurus'' in that the former has solid conical armor compared to the thin-walled armor of the latter.


Paleobiology


Diet and feeding

''Mymoorapelta'' was a low-browsing herbivore like its relatives, likely feeding on the
fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
s,
cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk (botany), trunk with a crown (botany), crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants o ...
s, and
conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...
s that dominated the
flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...
of its time due to the lack of complex
grasses Poaceae ( ), also called Gramineae ( ), is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos, the grasses of natural grassland and species cultivated in ...
in the Jurassic. Nodosaurids like ''Mymoorapelta'' had narrow snouts, an adaptation seen today in animals that are selective browsers as opposed to the wide muzzles of grazers. In ankylosaurs, the Jurassic and mid-Cretaceous forms with narrow and pointed muzzles were apparently the most selective feeders, akin to extant mammalian browsers. This is in stark contrast to the later ankylosaurs that were adapted to bulk feeding on food with lower nutritional value. The preservation of complete a in taxa like the ankylosaurid ''
Pinacosaurus ''Pinacosaurus'' (meaning "Plank lizard") is a genus of ankylosaurid thyreophoran dinosaur that lived in Asia during the Late Cretaceous (Campanian, roughly 75 to 71 million years ago), mainly in Mongolia and China. The first remains of the genu ...
'' 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. Tongue protrusion and prehension is not confidently known, but lingual food manipulation could have been used in later ankylosaurids to crop food, like in giraffes. The preservation of cheek plates in ''Edmontonia'' and ''Panoplosaurus'' provide evidence for fleshy cheeks and chewing, with the cheek covering the tooth rows both for defense and to prevent food loss when eating. Tooth occlusion is not directly preserved in ''Mymoorapelta'' or its close relative ''Gargoyleosaurus'', but it has been found in other nodosaurids from the Cretaceous. 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''. Ankylosaurs generally demonstrate more variable wear patterns than the contemporary ceratopsids and
hadrosaurids Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...
of the Cretaceous. Even though ankylosaurs may not have fed on
fibrous Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ...
and
woody plant A woody plant is a plant that produces wood as its structural tissue and thus has a hard stem. In cold climates, woody plants further survive winter or dry season above ground, as opposed to Herbaceous plant, herbaceous plants that die back to t ...
s, they may have had a varied diet which included tough leaves and pulpy fruits.


Habitat preference

Due to competition with
diplodocid Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including '' Diplodocus'' and '' Supersaurus'', some of which may ha ...
sauropods, ''Mymoorapelta'' seems more adapted for open environments. ''Mymoorapelta'' has a very limited known distribution, having only been found at two sites in Western Colorado, in addition to the Hanksville-Burpee and potential Albuquerque specimens. This could be due to ''Mymoorapelta'' preferring to feed on a specific variety of plant, constricting its possible distribution. The Hanksville-Burpee specimen's
taphonomy Taphonomy is the study of how organisms decay and become fossilized or preserved in the paleontological record. The term ''taphonomy'' (from Greek language, Greek , 'burial' and , 'law') was introduced to paleontology in 1940 by Soviet scientis ...
(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.


Limb movements

Reconstructions of ankylosaur forelimb musculature made by Coombs in 1978 suggest that the forelimbs bore the majority of the animal's weight and that they were adapted for high force delivery on the front feet, possibly for food gathering. In addition, Coombs suggested that ankylosaurs may have been capable diggers, though the hoof-like structure of the would have limited fossorial capibilities. Ankylosaurs were likely to have been slow-moving and sluggish animals, though they may have been capable of quick movements when necessary. ''Mymoorapelta'' preserves very short limbs with even shorter distal limb elements, which is in contrast to the longer distal limb elements known in other nodosaurids but similar to the condition found in ankylosaurids and ''Polacanthus''.


Armor and tail

The scientific literature mostly considers the armor of ankylosauroids to have been used for defensive purposes, mainly to fend off any attacking carnivores. The tails of these animals have a complex evolutionary history, with basal taxa like ''Mymoorapelta'' possessing a flexible tail with pointed osteoderms on either side and on top. The aforementioned flexibility of the tail would allow for a greater range of motion than the stiff tails of later ankylosaurids and nodosaurids. It is thought that the tail could also have been used in defense against predators, though more recent findings by Arbour ''et al''. in 2022 also consider the possibility that the tails of ankylosaurids were used for intraspecific combat and might have primarily evolved to fill a function here, which might indicate a similar use in more basal taxa like ''Mymoorapelta'' and ''Gargoyleosaurus''.


Classification

''Mymoorapelta'' is one of the basalmost known genera of
Nodosauridae Nodosauridae is a family of ankylosaurian dinosaurs known from the Late Jurassic to the Late Cretaceous periods in what is now Asia, Europe, North America, and possibly South America. While traditionally regarded as a monophyletic clade as the ...
, an extinct family of medium to large, heavily built, quadrupedal,
herbivorous A herbivore is an animal anatomically and physiologically evolved to feed on plants, especially upon vascular tissues such as foliage, fruits or seeds, as the main component of its diet. These more broadly also encompass animals that eat n ...
dinosaurs which possess small, leaf-shaped teeth. The clade was named in 1890 by Othniel Charles Marsh, who designated the Cretaceous genus '' Nodosaurus'' as the type genus based on the heavy dermal armor, solid bones, large forelimbs, and ungulate feet it preserves. Nodosaurids first evolved in the
Late Jurassic The Late Jurassic is the third Epoch (geology), epoch of the Jurassic Period, and it spans the geologic time scale, geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic stratum, strata.Owen ...
(ca. 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. The nodosaurids went extinct in the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
(ca. 66 mya) during the
Cretaceous–Paleogene extinction event The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the extinction event, mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event cau ...
along with the other non-avian dinosaurs. Nodosaurids are situated within the group Euankylosauria, together with the closely related family
Ankylosauridae Ankylosauridae () is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Pal ...
. Nodosaurids differ from ankylosaurids in the fact that ankylosaurids evolved more recently, during the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
, and in several distinct anatomical characteristics; most notably the lack of mace-like tail clubs, with nodosaurs having osteoderm-lined, flexible tails instead, and the possession of sacral shields. Many nodosaurids also had spikes projecting outwards from their shoulders, and two armored half-rings on their neck, among other traits. A third proposed family, Polacanthidae, was erected for several genera that were similar to nodosaurids but had more fragile armor and a different distribution. However, it has seen little support from phylogenetic analyses in recent years and is in a state of flux. Euankylosauria encompasses all members of Ankylosauria except for the clade
Parankylosauria Parankylosauria is a group of Basal (phylogenetics), basal ankylosaurian dinosaurs known from the Cretaceous of South America, Antarctica, and Australia. It is thought the group split from other ankylosaurs during the mid-Jurassic period, despite ...
, which is a smaller group known exclusively from a few taxa that lived in the Cretaceous of
Gondwana Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
, rather than the euankylosaurs, who were endemic to
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
.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. The phylogenetic placement was changed in 1998 when it was considered closer to the European polacanthids, though this affiliation has been doubted. Matthew Vickaryous et al. (2004) considered the genus Ankylosauria ''
incertae sedis or is a term used for a taxonomy (biology), taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty ...
,'' while a
cladistic analysis Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
performed by Thompson ''et al.'' (2011) suggests that ''Mymoorapelta'' is a basal nodosaurid as originally theorized by Kirkland and Carpenter. 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. In a
2018 Events January * January 1 – Bulgaria takes over the Presidency of the Council of the European Union, after the Estonian presidency. * January 4 – SPLM-IO rebels loyal to Chan Garang Lual start a raid against Juba, capital of ...
phylogenetic analysis by Rivera-Sylva and colleagues which has been reproduced below, ''Mymoorapelta'' is recovered as a basal nodosaurid in a clade with ''
Sauroplites ''Sauroplites'' (meaning "saurian hoplite") is a genus of herbivorous ankylosaurian dinosaur from the Early Cretaceous of China. Discovery and naming In 1930, the Swedish paleontologist Anders Birger Bohlin during the Swedish-Chinese expeditions ...
'' and '' Dongyangopelta'' that represents the most basal group within Nodosauridae, while ''Gargoyleosaurus'' is recovered as more derived, further proving their distinction. Alternatively, ''Mymoorapelta'' may also be an ankylosaur outside both Nodosauridae and Ankylosauridae. The phylogenetic analyses of Rivera-Sylva and colleagues (left) and Thomas Raven and colleagues (right) found ''Mymoorapelta'' as a basal member of either Nodosauridae or Ankylosauridae.


Paleoecology

The Morrison Formation is a sequence of shallow marine and alluvial sediments which, according to
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...
, ranges between 156.3 million years old ( Ma) at its base, to ~150 ma at the top, placing it in the late Oxfordian,
Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 154.8 ±0.8 Ma and 149.2 ±0.7 Ma (million years ago). The Kimmeridgian follows the Oxfordian ...
, and early
Tithonian In the geological timescale, the Tithonian is the latest age (geology), age of the Late Jurassic Epoch and the uppermost stage (stratigraphy), stage of the Upper Jurassic Series. It spans the time between 149.2 ±0.7 annum, Ma and 143.1 ±0.6 (mi ...
stages of the Upper Jurassic period. The paleoenvironment of the Morrison Formation is interpreted as a
semiarid A semi-arid climate, semi-desert climate, or steppe climate is a dry climate sub-type. It is located on regions that receive precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of sem ...
environment with distinct wet and
dry season The dry season is a yearly period of low rainfall, especially in the tropics. The weather in the tropics is dominated by the tropical rain belt, which moves from the northern to the southern tropics and back over the course of the year. The t ...
s, and flat
floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
s. Vegetation varied from river-lining forests of conifers,
tree fern Tree ferns are arborescent (tree-like) ferns that grow with a trunk (botany), trunk elevating the fronds above ground level, making them trees. Many extant tree ferns are members of the order Cyatheales, to which belong the families Cyatheaceae ( ...
s, and ferns (gallery forests), to fern savannas with occasional trees such as the
Araucaria ''Araucaria'' (; original pronunciation: .ɾawˈka. ɾja is a genus of evergreen coniferous trees in the family Araucariaceae. While today they are largely confined to the Southern Hemisphere, during the Jurassic and Cretaceous they were glo ...
-like conifer ''
Brachyphyllum ''Brachyphyllum'' (meaning "short leaf") is a form genus of fossil coniferous plant foliage. Plants of the genus have been variously assigned to several different conifer groups including Araucariaceae and Cheirolepidiaceae. They are known from ...
''. The Morrison Basin where dinosaurs lived stretched from New Mexico to Alberta and Saskatchewan, and was formed when the precursors to the
Front Range The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming. It is the first mountain range encounter ...
of the Rocky Mountains started pushing up to the west. The deposits from their east-facing
drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
s were carried by streams and
river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
s and deposited in
swamp A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
y lowlands, lakes, river channels and floodplains. 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. The broader paleoenvironment of the area has been interpreted as a riparian (riverine) ecosystem with abundant flora and a high water table, with the quarry itself having been interpreted as an attritional accumulation of dinosaur fossils at a seasonal waterhole. This has allowed it to become one of the most fossil abundant sites in the United States, with the site notably preserving plants, pollen, coprolites, and even skin impressions preserved alongside dinosaur fossils. The quarry's abundant plant fossils include
horsetails ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which f ...
, cycads, Gingkoales,
Czekanowskiales Czekanowskiales, also known as Leptostrobales, are an extinct group of seed plants. Members of the family are distinguished by persistent leaves borne on deciduous short shoots, subtended by scale-like leaves. The leaves are highly dissected (d ...
, and many different Coniferales represented by leaf, wood, and pollen fossils. Invertebrates represented in the quarry include
gastropods Gastropods (), commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and from the land. Ther ...
and, most notably, fossils of fossil
crayfish Crayfish are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some spe ...
. 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''. The most common fossils from the quarry are dinosaurian in nature. ''
Allosaurus ''Allosaurus'' ( ) is an extinct genus of theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic period ( Kimmeridgian to late Tithonian ages). The first fossil remains that could definitively be ascribed to th ...
,'' a large carnivorous theropod, and ''
Apatosaurus ''Apatosaurus'' (; meaning "deceptive lizard") is a genus of herbivorous sauropod dinosaur that lived in North America during the Late Jurassic period. Othniel Charles Marsh described and named the first-known species, ''A. ajax'', in 1877, a ...
'', a large
diplodocid Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including '' Diplodocus'' and '' Supersaurus'', some of which may ha ...
sauropod, are the two most common dinosaurs in the quarry, with ''Mymoorapelta'' being the third most common at the site. Fossils of several other dinosaurs are known from the quarry, including the theropod ''
Ceratosaurus ''Ceratosaurus'' (from Greek 'horn' and 'lizard') is a genus of carnivorous theropod dinosaur that lived in the Late Jurassic period (Kimmeridgian to Tithonian ages). The genus was first described in 1884 by American paleontologist Othni ...
'', the sauropods ''
Camarasaurus ''Camarasaurus'' ( ) is a genus of sauropod dinosaur that lived in North America during the Late Jurassic period. Its fossil remains have been found in the Morrison Formation, dating to the Kimmeridgian and Tithonian ages of the Jurassic, betwe ...
'' and ''
Diplodocus ''Diplodocus'' (, , or ) is an extinct genus of diplodocid sauropod dinosaurs known from the Late Jurassic of North America. The first fossils of ''Diplodocus'' were discovered in 1877 by S. W. Williston. The generic name, coined by Othnie ...
'', and potentially the small ornithischian ''
Nanosaurus ''Nanosaurus'' ("small or dwarf lizard") is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-we ...
''. Remains of other vertebrate groups like crocodyliforms and
turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...
s are rare in the quarry, indicating the lack of continuous standing water in the form of
lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...
s or
pond A pond is a small, still, land-based body of water formed by pooling inside a depression (geology), depression, either naturally or artificiality, artificially. A pond is smaller than a lake and there are no official criteria distinguishing ...
s. 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. Unlike the others, the fossils of ''Mymoorapelta'' and ''Allosaurus'' preserve striations that, when measured to determine denticle (serration) width, produced tooth and body size extrapolations greater than any known specimen of ''Allosaurus'' or ''Ceratosaurus,'' the two large predators of the quarry that are known from osteological remains. The extrapolations are instead coherent either with an unusually large specimen of ''Allosaurus'', or a separate large taxon like ''
Torvosaurus ''Torvosaurus'' () is a genus of large Megalosaurinae, megalosaurine Theropoda, theropod dinosaur that lived approximately 165 to 148 million years ago during the Callovian to Tithonian ages of the late Middle Jurassic, Middle and Late Jurassi ...
'' or ''
Saurophaganax ''Saurophaganax'' ("lord of lizard-eaters") is a dubious, chimeric genus of large saurischian dinosaur, possibly a sauropod, from the Late Jurassic ( Kimmeridgian) Morrison Formation of Oklahoma, United States. This taxon was historically co ...
,'' neither of which preserves fossil material within the quarry''.'' The result either increases the known diversity of the site based on ichnological evidence alone, or represents powerful evidence of cannibalism in ''Allosaurus''. 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.


See also

* ''
Gargoyleosaurus ''Gargoyleosaurus'' (meaning "gargoyle lizard") is one of the earliest ankylosaurs known from reasonably complete fossil remains. The holotype was discovered in 1995 at the Bone Cabin Quarry West locality, in Albany County, Wyoming in exposures ...
'' * '' Gastonia'' * ''
Polacanthus ''Polacanthus'', deriving its name from the Ancient Greek polys-/πολύς- "many" and akantha/ἄκανθα "thorn" or "prickle", is an early armoured, spiked, plant-eating ankylosaurian dinosaur from the early Cretaceous period of England. In ...
'' *
Timeline of ankylosaur research This timeline of ankylosaur research is a chronological listing of events in the History of paleontology, history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spik ...


References

{{Taxonbar, from=Q134139 Nodosauridae Dinosaur genera Kimmeridgian dinosaurs Morrison Formation Fossil taxa described in 1994 Taxa named by James I. Kirkland Taxa named by Kenneth Carpenter Dinosaurs of the United States