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

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

, 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 82.4 Ma and 74.4 Ma, during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky Mountai ...

nesting site. ''Magnuviator'' is closest related to the Asian '' Saichangurvel'' and '' Temujinia'', which form the group Temujiniidae. Unlike other members of the Iguanomorpha, however, ''Magnuviator'' bears a distinct articulating notch on its

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

for the ankle bones (

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

and

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...

), 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 ...

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 ...

ns '' Callisaurus'' and ''

Urosaurus ''Urosaurus'' is a genus of lizards, commonly known as tree lizards or brush lizards, belonging to the New World family Phrynosomatidae. They are native to North America, specifically the arid and semiarid regions of the western United States and ...

'', although it also shows some adaptations to

herbivory 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 ...

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 (: pelves or pelvises) is the lower part of an Anatomy, anatomical Trunk (anatomy), trunk, between the human abdomen, abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also c ...

( ilium,

ischium The ischium (; : is ...

, and pubis) at the

acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

Skull

On the skull, the

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

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 skull which, when joined at a fibrous joint known as a cranial suture, form the sides and roof of the neurocranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four bord ...

; 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 (third eye, pineal eye) is a part of the epithalamus in some vertebrates. The eye is at the top of the head; is photoreceptive; and is associated with the pineal gland, which regulates circadian rhythmicity and hormone production ...

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 ...

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 Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

. 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 bone, zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by spe ...

; 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 ...

. 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 postfrontal is a paired cranial bone found in many tetrapods. It occupies an area of the skull roof between and behind the orbits (eye sockets), lateral to the frontal and parietal bones, and anterior to the postorbital bone. The postfrontal ...

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 (; derived from the Latin ''palatum'') are two irregular bones of the facial skeleton in many animal species, located above the uvula in the throat. Together with the maxilla, they comprise the hard palate. Stru ...

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 The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the mandible (lower jaw) which exposes the Meckelian cartilage.pleurodont Pleurodont is a form of tooth implantation common in reptiles of the order Squamata, as well as in at least one temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 've ...

, 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 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 surangular or suprangular is a jaw bone found in most land ver ...

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 jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

, 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 ...

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 o ...

, the

clavicle The clavicle, collarbone, or keybone is a slender, S-shaped long bone approximately long that serves as a strut between the scapula, shoulder blade and the sternum (breastbone). There are two clavicles, one on each side of the body. The clavic ...

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 ...

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 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 present as part of the scapula, but this is n ...

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

scapula The scapula (: 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 either side ...

r fenestra is unclear. On the pubis, the

symphysis A symphysis (, : 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 o ...

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 82.4 Ma and 74.4 Ma, during Campanian (Late Cretaceous) time. It crops out to the east of the Rocky Mountai ...

, 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 tota ...

, 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. Campa ...

age of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

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 (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 ...

, 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 - Bozeman, Montana State University in Bozeman, and now also, the Smithsonian Institution. The museum is largely known for its Paleontology, ...

. 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 ''viātor'' ("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 ''-ēnsis'' ("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 '' Saichangurvel'' and '' Temujinia''). Three characteristics allow ''Magnuviator'' to be recognized as a member of the Iguanomorpha: the

being located at the frontal- parietal suture; the boss on the

prefrontal Prefrontal may refer to: *Prefrontal bone, a skull bone in some tetrapods *Prefrontal cortex, a region of the brain of a mammal *Prefrontal scales The prefrontal scales on snakes and other reptiles are the scales adjacent and anterior to the fr ...

; 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 reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology ...

anterior inferior alveolar foramen is shared between the splenial and the

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

pubic symphysis The pubic symphysis (: symphyses) 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 attache ...

. 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 bones form the cheek series of the skull. The bone forms an ancestra ...

. It also differs from the

Pleurodonta Pleurodonta (from Greek '' lateral teeth'', is an clade of lizards 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 al ...

in that the

Meckelian canal The Meckelian groove (or Meckel's groove, Meckelian fossa, or Meckelian foramen, or Meckelian canal) is an opening in the medial (inner) surface of the mandible (lower jaw) which exposes the Meckelian cartilage. and from the Chamaeleontiformes, 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; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is th ...

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 Pa ...

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 which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...

and

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 ...

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 ''Phrynosoma'', whose members are known as the horned lizards, horny toads, or horntoads, is a genus of North American lizards and the type genus of the family Phrynosomatidae. Their common names refer directly to their horns or to their flattene ...

'' (horned lizard). Overall, the slender, cylindrical teeth of ''Magnuviator'' best recall the phyrnosomatids '' Callisaurus'' (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 monophyletic lineage within the superfamil ...

s and

s. Given that

hymenoptera Hymenoptera is a large order of insects, comprising the 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 parasitic. Females typi ...

pupa A pupa (; : 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 life cycle, the stages th ...

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 aridity, dry climate sub-type. It is located on regions that receive precipitation below Evapotranspiration#Potential evapotranspiration, potential evapotranspiration, but not as l ...

upland

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 ...

. 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 (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...

'' Orodromeus makelai'' 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 av ...

'' Troodon sp.'', and the mammals '' Alphadon halleyi'' and ''

Cimexomys judithae ''Cimexomys'' is an extinct North American mammal that lived from the Upper Cretaceous to the Paleocene. For a while, it shared the world with dinosaurs, but outlived them. It was a member of the extinct order Multituberculata and lies within the ...

'' 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 long ...

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 ...

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

Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...

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

(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; most members of which are commonly known as lizards, with the group also including snakes. With over 11,991 species, it is also the second-largest order ...

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