''Mierasaurus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

dinosaur from the

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

of Utah, United States. The taxon was first described and named in

2017 File:2017 Events Collage V2.png, From top left, clockwise: The War Against ISIS at the Battle of Mosul (2016-2017); aftermath of the Manchester Arena bombing; The Solar eclipse of August 21, 2017 ("Great American Eclipse"); North Korea tests a ser ...

Rafael Royo-Torres Dr. Rafael Royo-Torres is a Spanish Paleontologist. He works in Fundación Conjunto Paleontológico de Teruel-Dinópolis, in Teruel, Spain. He is one of the discoverers of ''Turiasaurus riodevensis'', together with Luis Alcalá Luis Alcalá Mart ...

and colleagues, from a mostly complete skeleton including a disarticulated partial skull and mandible, teeth, multiple vertebrae from along the length of the body, both scapulae, radius and ulna bones, a left manus, a complete

pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...

, both femora and the entire left hindlimb. Additionally, they referred a lower jaw and femur from juvenile individuals, which were found nearby, to the genus. Collectively, ''Mierasaurus'' is among the most completely known

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

n sauropods. The genus name honours Bernardo de Miera y Pacheco, the first European scientist to enter what is now Utah. The type species for ''Mierasaurus'' is ''Mierasaurus bobyoungi'', named after Robert Glen Young, a paleontologist who researched the Early Cretaceous of Utah. Along with its closest relative ''Moabosaurus'', also from the Early Cretaceous of Utah, ''Mierasaurus'' is among the last-surviving members of the Turiasauria, an otherwise Jurassic and European group which can be distinguished by heart-shaped teeth, slender humeri, and the presence of an extra depression on the surface of the ulnae, among other characteristics. ''Mierasaurus'' differs from ''Moabosaurus'' in characteristics such as lacking vertical ridges on its teeth, having relatively smooth bottom surfaces on its

cervical vertebrae In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...

, having

cervical rib A cervical rib in humans is an extra rib which arises from the seventh cervical vertebra. Their presence is a congenital abnormality located above the normal first rib. A cervical rib is estimated to occur in 0.2% to 0.5% (1 in 200 to 500) of the ...

s that do not prominently split into two at their tips, and lacking a bulge on the side of the femur. It is probable that the ancestors of ''Mierasaurus'' and ''Moabosaurus'' migrated, shortly before the emergence of the former, to western North America from surviving populations of turiasaurs in either Europe or eastern North America.

Discovery and naming

Since 2005, the Utah Geological Survey has conducted annual excavations for several weeks at a time at a site known as Doelling's Bowl, located on lands managed by the US

Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands. Headquartered in Washington DC, and with oversight over , it governs one eighth of the country's la ...

in east-central Utah, United States. The site is catalogued as UMNH VP.LOC.1208 at the Natural History Museum of Utah (UMNH), and as Utah Loc. 42Gr0300v at the Utah Geological Survey. Its exact location is not publicly available. Doelling's Bowl is known for a large bonebed, covering some and measuring approximately thick. The rocks appear to be locally flat, but form broad swales over the whole site. Out of this area, has been excavated, producing 1500 vertebrate bones. Rocks in the Doelling's Bowl bonebed mainly consist of green-grey

sandy Sandy may refer to: People and fictional characters *Sandy (given name), including a list of people and fictional characters * Sandy (surname), a list of people *Sandy (singer), Brazilian singer and actress Sandy Leah Lima (born 1983) * (Sandy) ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

, but also contain silcrete, casts of silificied plant roots, and chert pebbles. It belongs to the Cretaceous-aged

Yellow Cat Member The Cedar Mountain Formation is the name given to a distinctive sedimentary geologic formation in eastern Utah, spanning most of the early and mid-Cretaceous. The formation was named for Cedar Mountain in northern Emery County, Utah, where Willia ...

of the Cedar Mountain Formation. Dominguez and Escalante

In 2010, a skeleton of a subadult

dinosaur was discovered in an

arroyo Arroyo often refers to: * Arroyo (creek), an intermittently dry creek Arroyo may also refer to: People * Arroyo (surname) Places United States ;California * Arroyo Burro Beach, a public beach park in Santa Barbara County, California * Arroyo ...

within Gary's Island, a region at the western end of the bonebed named after its discoverer Gary Hunt. Only part of the specimen - a partial left forelimb ( scapula,

sternal plates The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Shap ...

, ulna, radius, and hand), a complete left hindlimb, and ten caudal (tail) vertebrae - was articulated. The feet of these limbs are buried in the sediment at a level deeper than the other remains, which suggests that the specimen died after being mired in soft mud. Other remains are scattered over an area of , including a partial skull and lower jaw; three teeth; the atlas and eight other

, along with eleven

s; eleven dorsal vertebrae, six dorsal

rib In vertebrate anatomy, ribs ( la, costae) are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the ches ...

s, and six sacral ribs; five other caudal vertebrae with two haemal arches; a right femur; and pelvic girdle elements, including an

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

ischium The ischium () form ...

, and two pubes. Although the remaining elements have been displaced and eroded by the arroyo, the specimen is still the most complete Cretaceous sauropod from North America. The specimen is catalogued as UMNH.VP.26004, but individual bones are catalogued with the prefix DBGI (Doelling's Bowl site). Additional specimens - a lower jaw from a juvenile specimen, UMNH.VP.26010, and a juvenile femur, UMNH.VP.26011 - were also referred to the same taxon. In 2017, all of these specimens were described by

, Paul Upchurch, James Kirkland, Donald DeBlieux, John Foster,

Alberto Cobos Alberto Cobos Periañez is a Spanish paleontologist. He works in Fundación Conjunto Paleontológico de Teruel-Dinópolis, in Teruel, Spain. He is one of the discoverers of ''Turiasaurus riodevensis'', together with Rafael Royo-Torres and Luis ...

, and

Luis Alcalá Luis Alcalá Martínez is a Spanish paleontologist. Biography Dr. Luis Alcalá is a Spanish Paleontologist. He is the director of Fundación Conjunto Paleontológico de Teruel-Dinópolis, in Teruel, Spain. He is one of the discoverers of ''Turi ...

as part of a research paper published in ''

Scientific Reports ''Scientific Reports'' is a peer-reviewed open-access scientific mega journal published by Nature Portfolio, covering all areas of the natural sciences. The journal was established in 2011. The journal states that their aim is to assess solely th ...

''. They named a new genus for the specimens, ''Mierasaurus''; the name honors Bernardo de Miera y Pacheco, a Spanish

cartographer Cartography (; from grc, χάρτης , "papyrus, sheet of paper, map"; and , "write") is the study and practice of making and using maps. Combining science, aesthetics and technique, cartography builds on the premise that reality (or an im ...

who was "the first European scientist to enter what is now Utah" in the

Domínguez–Escalante expedition The Domínguez–Escalante Expedition was a Spanish Empire, Spanish journey of Spanish colonization of the Americas, exploration conducted in 1776 by two Franciscan priests, Atanasio Domínguez and Silvestre Vélez de Escalante, to find an overl ...

of 1776. They also named the type and only species ''M. bobyoungi'' after Robert ("Bob") Young, in order to acknowledge "the importance of isunderappreciated research" the geology of the Early Cretaceous of Utah.

Description

Skull

The skull of ''Mierasaurus'' is overall similar to those of other turiasaurs, which have rounded snouts with retracted nostril openings. The lower jaw of ''Mierasaurus'' becomes increasingly taller towards the front, which is like ''

Camarasaurus ''Camarasaurus'' ( ) was a genus of quadrupedal, herbivorous dinosaurs and is the most common North American sauropod fossil. Its fossil remains have been found in the Morrison Formation, dating to the Late Jurassic epoch (Kimmeridgian to Titho ...

'' but unlike the

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

sauropod ''

Jobaria ''Jobaria'' is a genus of sauropod dinosaur that lived in what is now Niger during the middle Jurassic Period, between 164 and 161 million years ago. ''Jobaria'' is currently the only known valid sauropod from the Tiouraren, where it was discov ...

''. A sharp ridge extends across the bottom edge of the front of the lower jaw, seen in both dicraeosaurids and

diplodocids 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 ...

, and to some extent ''Camarasaurus''. The lower jaw bears thirteen teeth; the ones at the front are spatula-shaped while the ones at the rear are heart-shaped, which is a distinguishing characteristic of turiasaurs. Compared to ''Camarasaurus'', the teeth at the front of the jaw are more pointed and have taller crowns. There are no well-developed vertical ridges on the outer surface of the teeth, in contrast to its closest relative '' Moabosaurus''. In ''Mierasaurus'', the

skull roof The skull roof, or the roofing bones of the skull, are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In comparati ...

is overall flattened, lacking any convexities. Unlike more

derived Derive may refer to: * Derive (computer algebra system), a commercial system made by Texas Instruments * ''Dérive'' (magazine), an Austrian science magazine on urbanism *Dérive, a psychogeographical concept See also * *Derivation (disambiguatio ...

sauropods but also seen in ''Turiasaurus'', the frontal bone of ''Mierasaurus'' participates in the margin of the

supratemporal fenestra The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. Unique characteristics that differentiate ''Mierasaurus'' from other turiasaurs can be found in its

braincase In human anatomy, the neurocranium, also known as the braincase, brainpan, or brain-pan is the upper and back part of the skull, which forms a protective case around the brain. In the human skull, the neurocranium includes the calvaria or skul ...

: a ridge known as the otosphenoidal ridge extends from the front of the paroccipital process—a bony spur to which neck muscles attach—and runs along its inner edge; and the occipital condyle, which articulates with the atlas, has a pair of rounded ridges on the sides of its articular surfaces (which ''Moabosaurus'' lacks). Like ''Turiasaurus'', ''Mierasaurus'' has a pair of foramina at the top end of the transverse nuchal crest on the

supraoccipital bone The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

. Like in ''Moabosaurus'', the downward projections known as the basal tubera on the

basioccipital bone The basilar part of the occipital bone (also basioccipital) extends forward and upward from the foramen magnum, and presents in front an area more or less quadrilateral in outline. In the young skull this area is rough and uneven, and is joined ...

are L-shaped when viewed from the bottom.

Vertebrae

''Mierasaurus'' can be excluded from the Titanosauriformes due to the solid internal structure of its vertebrae and ribs, which indicates they lack air-filled cavities. Uniquely, on the bottom of the internal cavity of the atlantal intercentrum (term used for the unfused lower half of vertebral centrum of the atlas) in ''Mierasaurus'', there is a pair of depressions that articulates with the odontoid process of the axis (second cervical). ''Moabosaurus'' lacks these depressions, and the cervical rib articulation (parapophysis) is more robust. As seen in ''

Kaatedocus ''Kaatedocus'' is a genus of diplodocine flagellicaudatan sauropod known from the middle Late Jurassic (Kimmeridgian stage) of northern Wyoming, United States. It is known from well-preserved skull and cervical vertebrae which were collected in ...

'', the laminae extending from the

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

to the

prezygapophysis The articular processes or zygapophyses (Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process") of a vertebra are projections of the vertebra that serve the purpose of fitting with an adjacent vertebr ...

of the cervical vertebrae are well-developed and cap depressions underneath. The cervical neural spines are not strongly split (bifurcated) in ''Mierasaurus'', less so than those of ''Turiasaurus''. Also unlike ''Moabosaurus'', there are no keels or hollows on the bottom of the cervical centra. None of the

s are visibly bifurcated either, unlike both ''Turiasaurus'' and ''Moabosaurus'', although there are small upward projections at the tips of the first few cervical ribs which may represent incipient or rudimentary bifurcation. There is a ridge on the side of the tubercle of each rib, which is a unique diagnostic feature of ''Mierasaurus''. The rear dorsal vertebrae in ''Mierasaurus'' are concave on both ends ( amphicoelous), whereas the opposite ( opisthicoelous) is true for ''Mierasaurus'', ''Camarasaurus'', and titanosauriforms. ''Mierasaurus'' does not have the prespinal laminae (ridges on the front of the spine) present in the rear dorsal vertebrae of ''Moabosaurus'', and the articular process known as the

hyposphene The hyposphene-hypantrum articulation is an accessory joint found in the vertebrae of several fossil reptiles of the group Archosauromorpha. It consists of a process on the backside of the vertebrae, the hyposphene, that fits in a depression in the ...

is triangular in ''Mierasaurus'' while it is rectangular in ''Moabosaurus''. However, ''Mierasaurus'' shares with ''Moabosaurus'' dorsal neural spines with spinodiapophyseal laminae that bifurcate towards the top of each spine, with one branch extending forwards and one backwards. The caudal (tail) vertebrae are concave in front and convex behind ( procoelous), as in ''Turiasaurus'', ''Moabosaurus'', '' Losillasaurus'', and the Titanosauria. Also like titanosauriforms, the neural arches are located on the front halves of each centrum, and the haemal canals are long compared to the haemal arches that form them, at 41% of the bones' length. There are characteristic depressions at the lower outer sides of the haemal arches.

Limbs

The forelimbs of ''Mierasaurus'' exhibit many shared (

synapomorphic In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have ...

) turiasaurian traits. In the

shoulder girdle The shoulder girdle or pectoral girdle is the set of bones in the appendicular skeleton which connects to the arm on each side. In humans it consists of the clavicle and scapula; in those species with three bones in the shoulder, it consists of t ...

of ''Mierasaurus'', the articulation with the scapula on the coracoid is about half the bone's length. The

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

is slender, with an HRI (humerus robustness index) of only 0.27; the maximum width of the bottom end, similarly, measures only 40% of the bone's total length. A T-shaped/Y-shaped profile is present at the top end of the ulna due to the strong development of the rear-projecting process. Besides the depression for articulating with the radius, there is a second deep depression like ''Moabosaurus'', ''Turiasaurus'', ''Losillasaurus'', ''

Zby ''Zby'' is an extinct genus of turiasaurian sauropod dinosaur known from the Late Jurassic (late Kimmeridgian stage) of the Lourinhã Formation, central west Portugal. It contains a single species, ''Zby atlanticus''. It is named after Georges Zb ...

'', and ''

Dystrophaeus ''Dystrophaeus'' is the name given to an extinct genus of eusauropod dinosaur from the early Kimmeridgian stage of the Late Jurassic that existed around 154.8 Ma.Turner, C.E. and Peterson, F., (1999). "Biostratigraphy of dinosaurs in the Upper Ju ...

''. The top end of the radius is large, being at least half the length, of the bottom end. Unlike the rounded margins seen titanosauriforms, the front margin of the ilium is triangular in ''Mierasaurus''. Uniquely, ''Moabosaurus'' also has a very short ischium compared to its pubis; the former measures only 75% of the length of the latter, otherwise seen only among titanosaurs. However, the bulge on the side of the femur is missing, which differentiates ''Mierasaurus'' from both titanosauriforms and ''Moabosaurus'' (which has a slight bulge). The fourth trochanter of the femur is only located 40% of the way down from the top of the bone, compared to halfway for most other sauropods, and the

condyles A condyle (;Entry "condyle"
in
cnemial crest of the tibia points forwards. The inner surface of the astragalus in the ankle narrows to form a triangular process, like ''Turiasaurus''. On the five-digited foot, the number of

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

is 2, 3, 3, 2, and possibly 0. Unlike most other sauropods, with the exception of '' Vulcanodon'' and ''

Sanpasaurus ''Sanpasaurus'' ("Sanpa lizard") is a poorly known sauropod dinosaur from the Early to Late Jurassic of Sichuan, China. The type species, ''S. yaoi'', was described by Chung Chien Young, in 1944. The type remains, IVPP V.156, consists of 20 ve ...

'', the claws on the second and third digits are compressed vertically, not horizontally.

Classification

Based on inserting ''Mierasaurus'' into two prior analyses, one by José Carbadillo and Martin Sander in 2013 and another by Philip Mannion and colleagues in 2017, Royo-Torres and colleagues identified a number of synapomorphic traits that allow ''Mierasaurus'' to be placed among the Turiasauria. Asides from limb characteristics noted above, other synapomorphies include the slightly concave profile of the rear surface of the basal tubera; the heart-shaped teeth; the height of the dorsal neural arches below the level of the

articular processes The articular processes or zygapophyses (Greek ζυγον = "yoke" (because it links two vertebrae) + απο = "away" + φυσις = "process") of a vertebra are projections of the vertebra that serve the purpose of fitting with an adjacent vertebr ...

known as postzygapophyses being at least equal to that of their corresponding centra; the opisthocoelous condition of the rear dorsals; the slightly procoelous front caudals; the presence of depressions known as pleurocoels in the front caudals; the neural spines of the front caudals being less than 1.2 times the height of their corresponding centra; and the centra of the middle caudals being at least as wide as they are long. Although not an explicit synapomorphy, the secondary depression on the ulna also unites ''Mierasaurus'' with other turiasaurs. Turiasaurus skeleton

Within the Turiasauria, Royo-Torres and colleagues considered the likewise-Cretaceous ''Moabosaurus'' to be the closest relative of ''Mierasaurus''. They share the L-shaped profile of the basal tubera, and the bifurcating spinodiapophyseal laminae of the dorsal neural spines. However, they differ from each other by twelve characteristics. ''Moabosaurus'' lacks rounded ridges on its occipital condyle; has vertical ridges on its teeth; has a robust parapophysis; lacks depressions on its atlas intercentrum; has hollows and keels on the bottom of its cervical centra; has convex as opposed to straight centroprezygapophyseal laminae in its front cervicals; has bifurcating cervical ribs; lacks ridges or bulges accompanying the tubercles of its cervical ribs; has prespinal laminae in its middle and rear dorsals; has rectangular as opposed to triangular hyposphenes in its rear dorsals; has uniformly opisthocoelous dorsals; and has a bulge on its femur. The lack of prominent bifurcation in the cervical ribs also differentiates ''Mierasaurus'' from ''Turiasaurus'' and potentially other turiasaurs. The

phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

s recovered by Royo-Torres and colleagues from the two different analyses agreed upon the position of turiasaurs, placing them as a unified group containing ''Mierasaurus'', ''Moabosaurus'', ''Turiasaurus'', ''Losillasasurus'', and ''Zby'' outside of the

Neosauropoda Neosauropoda is a clade within Dinosauria, coined in 1986 by Argentine paleontologist José Bonaparte and currently described as ''Saltasaurus loricatus'', ''Diplodocus longus'', and all animals directly descended from their most recent common ...

(thus excluding them from both the

Diplodocoidea Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like ''Supersaurus'', ''Diplodocus'', ''Apatosaurus'', and ''Amphicoelias''. Most had very long necks and long, ...

and the Macronaria). Below, the tree based on the analysis of Mannion and colleagues is reproduced; it yielded well-resolved relationships within the Turiasauria, as opposed to the tree based on the analysis of Carbadillo and Sander. The continent-level geographic ranges of various taxa are included in the tree.

Paleoecology

Locality and contemporaries

The Doelling's Bowl locality is part of the lower segment of the

of the Cedar Mountain Formation, as indicated by the presence of a marker horizon of

calcrete Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, ...

. Traditionally, based on biostratigraphic correlation with ostracods and

charophytes Charophyta () is a group of freshwater green algae, called charophytes (), sometimes treated as a phylum, division, yet also as a superdivision or an unranked clade. The terrestrial plants, the Embryophyta emerged within Charophyta, possibly fro ...

, the lower Yellow Cat Member has been considered to belong to the

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

epoch of the Cretaceous period, at 124.2 ± 2.6 Ma (million years) old. However, based on uranium-lead dating of detrital zircon, this age has been more recently revised to less than ~139.7 ± 2.2 Ma, which is part of the Valanginian epoch. Detrital zircon dating provides only a maximum age, since the time between crystallization and deposition is unknown. The same dating measures produced two maximum age estimates of ~136.4 ± 1.1 Ma and ~132 Ma for the age of the upper segment. An older age of up to 142 Ma remains possible, as does a younger age around 124 Ma, which would be congruent with the ostracod and charophyte data. Doelling's Bowl is the origin of the type specimen of the

dromaeosaurid Dromaeosauridae () is a family of feathered theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous Period. The name Dromaeosauridae means 'running lizards', from Greek ('), meaning ...

theropod ''

Yurgovuchia ''Yurgovuchia'' (meaning "coyote") is a genus of dromaeosaurid theropod dinosaurs that lived in North America during the Early Cretaceous period in what is now the Cedar Mountain Formation. It contains a single species, ''Yurgovuchia doellingi''. ...

''. Additionally, in a layer about below the preserved feet of the type specimen of ''Mierasaurus'', a large specimen of the iguanodontian

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world ...

Iguanacolossus ''Iguanacolossus'' (meaning "Iguana Colossus" or "Colossal Iguana") is a genus of iguanodontian ornithopod dinosaur that lived in North America during the Early Cretaceous period. It is known from UMNH VP 20205, the associated holotype with a lar ...

'' was uncovered along with some smaller individuals. Indeterminate bones from small ornithopods, as well as part of the tail of a large ornithopod, were mixed in with the remains of ''Mierasaurus'' as well. A large allosauroid theropod is represented by teeth, and a new species of polacanthine ankylosaurian has also been found. Non-dinosaurs are represented by skull fragments and teeth from possibly goniopholididae crocodyliforms, as well as shell fragments of a turtle similar to ''

Naomichelys ''Naomichelys'' is an extinct genus of helochelydrid stem turtle known from the Cretaceous (Aptian-Campanian) of North America. It is the only member of the family known to be native to North America. Distribution ''Naomichelys'' is known nume ...

''. The area was a waterlogged

bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...

-like environment, judging by the plastic deformation of the bones, the presence of horizontal root systems, and the better-preserved condition of the top surfaces of the bones (which suggests that invertebrates grazed on the bottom surfaces). Cedar Mountain Formation Yellow Cat Fauna

Cedar Mountain Formation Yellow Cat Fauna

Paleobiogeography

Asides from ''Mierasaurus'' and ''Moabosaurus'', turiasaurs are exclusively Jurassic in age; turiasaurs had previously been considered to have gone extinct at the Jurassic-Cretaceous boundary. However, turiasaurs are not known from the Jurassic-aged (more specifically, dating to the

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

epoch) deposits of the

Morrison Formation The Morrison Formation is a distinctive sequence of Late Jurassic, 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, sandsto ...

, or from any other equivalent deposits in western ( Laramidian) North America. This means that they may have reached North America at some point after the Tithonian, although the possibility that they were present but have not been found cannot be excluded. It is also possible that they were present in eastern (

Appalachia Appalachia () is a cultural region in the Eastern United States that stretches from the Southern Tier of New York State to northern Alabama and Georgia. While the Appalachian Mountains stretch from Belle Isle in Newfoundland and Labrador, Ca ...

n) North America in the Late Jurassic, and spread to Laramidian North America subsequently. However, the presence of ''Mierasaurus'' in Valanginian deposits correlates with a substantial drop in sea level that occurred during the epoch, which may have formed a land bridge and allowed turiasaurs - and potentially other groups, such as

haramiyida Haramiyida ("thief" from Arabic الحرامية (al ḥarāmiyah), "thief, bandit") is a possibly polyphyletic order of mammaliaform cynodonts or mammals of controversial taxonomic affinites. Their teeth, which are by far the most common remains ...

n mammals - to spread from Europe to North America.

References

{{Taxonbar, from=Q42427954 Turiasauria Early Cretaceous dinosaurs of North America Valanginian life Paleontology in Utah