''Magnuviator'' is a genus of extinct iguanomorph lizard from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', the ...

Montana Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columbi ...

, US. It contains one species, ''M. ovimonsensis'', described in 2017 by DeMar ''et al.'' from two specimens that were discovered in the

Egg Mountain The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...

nesting site. ''Magnuviator'' is closest related to the Asian ''

Saichangurvel ''Saichangurvel'' (meaning "beautiful lizard" in Mongolian) is an extinct genus of iguanian lizards from the Late Cretaceous of Mongolia. It is a member of a clade called Gobiguania, an exclusively Late Cretaceous group of iguanian lizards that ...

'' and ''

Temujinia Gobiguania is an extinct clade of iguanian lizards from the Late Cretaceous. All known gobiguanians are endemic to the Gobi Desert of Mongolia. Gobiguania was given a phylogenetic definition by Jack Conrad and Mark Norell in 2007 as all taxa mor ...

'', which form the group Temujiniidae. Unlike other members of the Iguanomorpha, however, ''Magnuviator'' bears a distinct articulating notch on its

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

for the ankle bones (

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...

and

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. St ...

), which has traditionally been considered a characteristic of non-iguanomorph lizards. The morphology of its teeth suggests that its diet would have mainly consisted of

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...

s, like the modern phyrnosomatid

iguania Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed t ...

ns ''

Callisaurus The zebra-tailed lizard (''Callisaurus draconoides'') is a species of lizard in the family Phrynosomatidae. The species is native to the Southwestern United States and adjacent northwestern Mexico. There are nine recognized subspecies. Habitat ...

'' and ''

Urosaurus ''Urosaurus'' is a genus of lizards, commonly known as tree lizards or brush lizards, belonging to the New World family Phrynosomatidae. Description Species in the genus ''Urosaurus'' can be distinguished from members of the genus '' Sceloporu ...

'', although it also shows some adaptations to

herbivory A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

Description

For an iguanomorph, ''Magnuviator'' was large, measuring long without the tail. Both of the known specimens were adults, judging by the extensive fusion of the

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 ...

( ilium,

ischium The ischium () form ...

, and pubis) at the

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...

Skull

On the skull, the

frontal bone The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, par ...

is fused completely into a single element, or azygous, with no visible sutures. Viewed from the top, it is hourglass-shaped, with the narrowest point being above the eye socket, and the surface is somewhat roughened. It contacts the

prefrontal bone The prefrontal bone is a bone separating the lacrimal and frontal bones in many tetrapod skulls. It first evolved in the sarcopterygian clade Rhipidistia, which includes lungfish and the Tetrapodomorpha. The prefrontal is found in most modern and ...

at its front end; the contact is curved, such that the prefrontal wraps around the front of the frontal. The prefrontal itself bears a protrusion of bone. At the back, the frontal contacts the

parietal bone The parietal bones () are two bones in the Human skull, skull which, when joined at a fibrous joint, form the sides and roof of the Human skull, cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, an ...

; here, there is a very visible and wide suture that is slightly concave relative to the front of the skull, and the opening of the

parietal eye A parietal eye, also known as a third eye or pineal eye, is a part of the epithalamus present in some vertebrates. The eye is located at the top of the head, is photoreceptive and is associated with the pineal gland, regulating circadian rhythm ...

is located in the middle of this suture. The back halves of the sides of the frontal bear rounded ridges. The

postorbital bone The ''postorbital'' is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some ve ...

has three branches, with the front and interior edges of the bone being concave when viewed from the top, while the outer edge was mostly straight. On the postorbital, the interior edge bears a projection around its midpoint, and forms the front 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 ...

. At the bottom, the postorbital tapers to a rounded point, and articulates with the backward-projecting and overlapping postorbital process of the

jugal bone The jugal is a skull bone found in most reptiles, amphibians and birds. In mammals, the jugal is often called the malar or zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species. Anatomy ...

; at the back, it also tapers, and has a narrow groove that would have articulated with the

squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

. The distance between these two articulations is rather short, suggesting that most of the bottom of the postorbital would have been hidden in life. The

itself bears a branch that stretches towards the top of the skull. Although it is poorly preserved, the half-moon-shaped

postfrontal bone 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 ...

would have extended from a process from the postorbital up to the level of the suture between the frontal and parietal, overlapping the postorbital when viewed from the top. The end that contacted the postorbital appears to be split into two. On the underside of the jaw, the

palatine bone In anatomy, the palatine bones () are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxillae, they comprise the hard palate. (''Palate'' is derived from the Latin ''pa ...

uniquely bears an opening near the front end that extends forward into the skull to connect to the

infraorbital canal The infraorbital canal is a canal found at the base of the orbit that opens on to the maxilla. It is continuous with the infraorbital groove and opens onto the maxilla at the infraorbital foramen. The infraorbital nerve and infraorbital artery t ...

Mandible and postcrania

The jaw of ''Magnuviator'' is long and slender, and the Meckelian canal is open. On the jaw, there are 22 to 24 closely spaced columnar teeth. They are

pleurodont Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl. The labial (cheek) side of pleurodont teeth are fused (ankylosed) to the inner surface of the jaw bones which host them. T ...

, meaning that they extend out from the interior side of the jawbone, they are roughly equal in height, and they do not have V-shaped wear facets. At the front of the jaw, the teeth have a single cusp (monocuspid); further back, the teeth gain an additional cusp at the back (bicuspid), then an additional one at the front (tricuspid). The splenial bone uniquely reaches forward to about 2/3 the length of the tooth row. On the splenial, the anterior inferior alveolar foramen is also located partially on the

dentary In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, and is uniquely located behind and above the anterior mylohyoid foramen. Meanwhile, the

angular bone The angular is a large bone in the lower jaw (mandible) of amphibians and reptiles (birds included), which is connected to all other lower jaw bones: the dentary (which is the entire lower jaw in mammals), the splenial, the suprangular, and the art ...

bears a process in front of the jaw joint. On the vertebrae, the zygosphere processes are separate, and located on a distinct foot, or

pedicle Pedicle or pedicel may refer to: Human anatomy *Pedicle of vertebral arch, the segment between the transverse process and the vertebral body, and is often used as a radiographic marker and entry point in vertebroplasty and kyphoplasty procedures ...

, of the vertebral arch. 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 ...

, the

clavicle The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the rig ...

is expanded and bears a notch on its interior edge, while the

interclavicle An interclavicle is a bone which, in most tetrapods, is located between the clavicles. Therian mammals ( marsupials and placentals) are the only tetrapods which never have an interclavicle, although some members of other groups also lack one. In th ...

bears an expansion on its front end. The

scapulocoracoid The scapulocoracoid is the unit of the pectoral girdle that contains the coracoid and scapula. The coracoid itself is a beak-shaped bone that is commonly found in most vertebrates with a few exceptions. The scapula is commonly known as the ''shoulde ...

bears a primary

coracoid A coracoid (from Greek κόραξ, ''koraks'', raven) is a paired bone which is part of the shoulder assembly in all vertebrates except therian mammals (marsupials and placentals). In therian mammals (including humans), a coracoid process is prese ...

fenestra, but apparently not a secondary coracoid fenestra. Whether or not it has a

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

r fenestra is unclear. On the pubis, the

symphysis A symphysis (, pl. symphyses) is a fibrocartilaginous fusion between two bones. It is a type of cartilaginous joint, specifically a secondary cartilaginous joint. # A symphysis is an amphiarthrosis, a slightly movable joint. # A growing together ...

was rather thin. Unlike all other iguanomorphs, the

bears a special notch for articulation with the astragalum-

Discovery and naming

Both known specimens of ''Magnuviator'' are known from the

locality of the

Two Medicine Formation The Two Medicine Formation is a geological formation, or rock body, in northwestern Montana and southern Alberta that was deposited between and (million years ago), during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky M ...

, which represents a nesting site. This locality is located in

Teton County, Montana Teton County is a county in the U.S. state of Montana. As of the 2020 census, the population was 6,226. Its county seat is Choteau. The county was founded in 1893. Geography According to the United States Census Bureau, the county has a total ...

, and would have been at 48° N in the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campanian s ...

age of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

period; more specifically, it has been dated to 75.5 ± 0.4 million years ago. The two specimens are MOR 6627, the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, and MOR 7042, both nearly complete skeletons stored at the

Museum of the Rockies Museum of the Rockies is a museum in Bozeman, Montana. Originally affiliated with Montana State University in Bozeman, and now also, the Smithsonian Institution, the museum is largely known for its paleontological collections. The Museum houses ...

. They were collected by Dr. David Varricchio, who coauthored a study that described the genus which was published in 2017. The genus name ''Magnuviator'' combines the Latin words ''magnus'' ("mighty") and ''viator'' ("traveller"), in reference to its large size and close affinities to the Asian Temujiniidae. Meanwhile, the specific name ''ovimonsensis'', from Latin ''ovi'' ("egg"), ''mons'' ("mountain"), and ''ensis'' ("from"), refers directly to the Egg Mountain locality.

Classification

In 2017, ''Magnuviator'' was found to be an iguanomorph, most closely related to the Asian Temujiniidae (which contains ''

'' and ''

''). Three characteristics allow ''Magnuviator'' to be recognized as a member of the Iguanomorpha: the

being located at the

frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...

- parietal suture; the boss on the prefrontal; and the angular process in front of the jaw joint. Like the Temujiniidae, the

splenial The splenial is a small bone in the lower jaw of reptiles, amphibians and birds, usually located on the lingual side (closest to the tongue) between the angular and surangular The suprangular or surangular is a jaw bone found in most land verteb ...

anterior inferior alveolar foramen is shared between the splenial and the

in ''Magnuviator'', and it also has a thin

pubic symphysis The pubic symphysis is a secondary cartilaginous joint between the left and right superior rami of the pubis of the hip bones. It is in front of and below the urinary bladder. In males, the suspensory ligament of the penis attaches to the pubic ...

. However, unlike the Temujiniidae but like most other iguanomorphs, ''Magnuviator'' also has an upwards-directed process of the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal The quadratojugal is a skull bone present in many vertebrates, including ...

. It also differs from the

Pleurodonta Pleurodonta (from Greek '' lateral teeth'', in reference to the position of the teeth on the jaw) is one of the two subdivisions of Iguania, the other being Acrodonta ('' teeth on the top f the jaw'). Pleurodonta includes all families previously ...

in that the Meckelian canal is open; and from the

Chamaeleontiformes Chamaeleontiformes is a hypothesized clade (evolutionary grouping) of iguanian lizards defined as all taxa sharing a more recent common ancestor with ''Chamaeleo chamaeleon'' (the common chamaeleon) than with '' Hoplocercus spinosus'' (the Brazi ...

, containing the Acrodonta, in its lack of enlarged, fang-like teeth, the lack of V-shaped wear facets on the teeth, and its possession of more teeth in general. Its presence of an astralago-

calcaneal In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. St ...

notch is only otherwise seen in non-iguanians. The following phylogenetic tree illustrates the position of ''Magnuviator'' among iguanomorphs. As the oldest known North American iguanomorph, ''Magnuviator'' helps to complete the picture of the emergence of the

, a clade only definitely known from the Eocene forward due to scarcity of fossil remains in the southern parts of North America. Molecular phylogenies have predicted that Pleurodonta originated in the Late Cretaceous. The location, temporal context, and phylogenetic placement of ''Magnuviator'' indicates at both ''Magnuviator'' itself, as well as the Pleurodonta, are part of a low-latitude evolutionary radiation of iguanomorphs across the continent of

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 Pan ...

in response to warm, tropical climates. This radiation may have occurred even earlier, possibly within the Early Cretaceous.

Paleobiology

Diet

Both

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

and

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

ns have teeth with multiple cusps, but herbivorous iguanians tend to have wider, flatter, blade-like teeth. ''Magnuviator'' has a mixture of different tooth morphologies, from the herbivory-adapted teeth described above to the blunt, peg-like teeth like the insectivorous ''

Phrynosoma Horned lizards (''Phrynosoma''), also known as horny toads or horntoads, are a genus of North American lizards and the type genus of the family Phrynosomatidae. The common names refer directly to their horns or to their flattened, rounded bodies, ...

'' (horned lizard). Overall, the slender, cylindrical teeth of ''Magnuviator'' best recall the phyrnosomatids ''

'' (zebra-tailed lizard) and ''

'' (tree lizard), some species of which feed mostly on

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

s and

s. Given that

hymenoptera Hymenoptera is a large order (biology), order of insects, comprising the sawfly, sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are Par ...

pupa A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...

l cases, probably attributable to wasps, are known from the Egg Mountain locality, it is plausible that ''Magnuviator'' would have fed on these wasps. It would, however, have also been energetically capable of digesting plants, given its large size.

Paleoecology

The Egg Mountain locality, which ''Magnuviator'' inhabited, represented a seasonally

semi-arid 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 semi-ar ...

upland

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

. Fossils known from the locality exclusively represent terrestrial animals; dinosaurs found at Egg Mountain include the

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 ...

Orodromeus makelai ''Orodromeus'' (meaning "Mountain Runner") is a genus of herbivorous orodromine thescelosaurid dinosaur from the Late Cretaceous of North America. Only one species is known, the type species ''Orodromeus makelai''. Discovery and naming The rem ...

'' and small specimens of the

paravian Paraves are a widespread group of theropod dinosaurs that originated in the Middle Jurassic period. In addition to the extinct dromaeosaurids, troodontids, anchiornithids, and possibly the scansoriopterygids, the group also contains the aviala ...

'' Troodon sp.'', and the mammals '' Alphadon halleyi'' and '' Cimexomys judithae'' are also known from the locality. Also from Egg Mountain are unnamed

varanoid Varanoidea is a superfamily of lizards, including the well-known family Varanidae (the monitors and goannas). Also included in the Varanoidea are the Lanthanotidae (earless monitor lizards), and the extinct Palaeovaranidae. Throughout their l ...

lizards, as well as various non-body fossils, including

l cases, nests, and dinosaurian

coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...

s. Overall, the environment of the Egg Mountain locality more closely parallels that of the

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

Djadochta Formation The Djadochta Formation (sometimes transcribed and also known as Djadokhta, Djadokata, or Dzhadokhtskaya) is a highly fossiliferous geological formation situated in Central Asia, Gobi Desert, dating from the Late Cretaceous period, about 75 milli ...

(from where temujiniids and other basal iguanomorphs are known), than that of its contemporary non-iguanomorph

squamates Squamata (, Latin ''squamatus'', 'scaly, having scales') is the largest order of reptiles, comprising lizards, snakes, and amphisbaenians (worm lizards), which are collectively known as squamates or scaled reptiles. With over 10,900 species, i ...

in North America (largely preserved in lowland systems of freshwater rivers).

References

{{Taxonbar, from=Q28823531 Cretaceous lizards Fossil taxa described in 2017 Campanian life Paleontology in Montana Late Cretaceous lepidosaurs of North America