''Matheronodon'' (meaning "Matheron tooth") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

rhabdodontid Rhabdodontidae is a family of herbivorous iguanodontian ornithopod dinosaurs whose earliest stem members appeared in the middle of the Lower Cretaceous. The oldest dated fossils of these stem members were found in the Barremian Castrillo de la R ...

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 worl ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the late

Cretaceous Period 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 ...

of the

Grès à Reptiles Formation Grès was a French haute couture fashion house founded by Madame Grès in 1942. Parfums Grès is the associated perfume house, which still exists, and is now based in Switzerland. History Germaine Émilie Krebs (1903–1993), known as Alix Bar ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan ar ...

. The genus contains a single species, ''M. provincialis'', which is known from a single

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The ...

and associated teeth. It was named by Pascal Godefroit and colleagues in 2017. The teeth of ''Matheronodon'' are large but few in number. The teeth are also in an unusual arrangement, emerging alternatingly from one of a pair of fused tooth sockets in its mouth. In life, the teeth would have functioned like a pair of scissors, allowing ''Matheronodon'' to feed on the tough leaves of

monocot Monocotyledons (), commonly referred to as monocots, ( Lilianae '' sensu'' Chase & Reveal) are grass and grass-like flowering plants (angiosperms), the seeds of which typically contain only one embryonic leaf, or cotyledon. They constitute on ...

plants.

Description

Like other rhabdodontids, ''Matheronodon'' would have been a bipedal herbivore. The length of the genus has been estimated at by its lead describer Pascal Godefroit. The

of ''Matheronodon'' is a short, robust bone. The front portion is particularly shortened and also angled upwards, differentiating ''Matheronodon'' from other rhabdodontids. It measures long, and high. When viewed from the top, the front portion is triangular, and forms a broad rostrodorsal shelf. Both '' Rhabdodon'' and '' Zalmoxes'' lack the shelf. There is a bar-like structure on the interior surface, the dorsal bar, which is also present in ''Rhabdodon''. Immediately below this bar, there is a horizontal groove, or transverse sulcus. Further behind, the upward-projecting dorsal process is wider and angled further backwards than ''Rhabdodon'', and larger than ''Zalmoxes''. From the base of this process, a "wing" extends backwards to articulate with 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. Anat ...

. Also at the base of the dorsal process is a small triangular projection delimiting the back of the

antorbital fenestra An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds ...

, which is shorter than ''Rhabdodon''.

Teeth

Like ''Rhabdodon'', ''Zalmoxes'', and '' Mochlodon'', the maxillary tooth crowns of ''Matheronodon'' are shaped like cleavers. They are unusually large, being up to long. More than these other rhabdodontids, there are at least 25 ridges on the inner surface of each tooth. The ridges are all roughly the same size, and there is no "primary" ridge, identifying ''Matheronodon'' as a rhabdodontid. A single

wear facet Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology. Wear ...

is oriented 60° below the horizontal, like ''Zalmoxes'' and ''Mochlodon''. Enamel covers all sides of the teeth, unlike

hadrosaurid Hadrosaurids (), 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 family, which incl ...

s, being thicker on the inner surface (particularly on the ridges, compared to ''

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton") is a genus of hadrosaurid (duck-billed) dinosaur. It contains two known species: '' Edmontosaurus regalis'' and '' Edmontosaurus annectens''. Fossils of ''E. regalis'' have been found in ro ...

''). Also unlike hadrosaurids, the tubular structure of the

dentin Dentin () (American English) or dentine ( or ) (British English) ( la, substantia eburnea) is a calcified tissue of the body and, along with enamel, cementum, and pulp, is one of the four major components of teeth. It is usually covered by e ...

e below the enamel does not appear to vary in orientation. The scratches on the dentine's surface are vertical like ''Zalmoxes'' and ''Mochlodon''. Even though the maxilla is large, it bears only eight

tooth sockets Dental alveoli (singular ''alveolus'') are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament. The lay term for dental alveoli is tooth sockets. A joint that connects the roots of th ...

. ''Zalmoxes'' has up to 10, and ''Rhabdodon'' has 11. The walls separating adjacent sockets appear to have been resorbed such that the sockets have fused into four pairs, which is not known in either ''Rhabdodon'' or ''Zalmoxes''. Only one functional tooth would have been present in each pair at any time. From the preserved replacement teeth, it appears that tooth replacement progressed from the back to the front of the jaw, with teeth alternatingly emerging from the front and rear sockets in each pair. The tooth of each front socket would have overlapped those from the rear socket, due to the size of the crowns. Unlike the teeth of the maxilla, the teeth of the lower jaw are leaf-shaped, and bear a primary ridge displaced backwards from the center of the crown. However, they are also large. The subsidiary ridges flanking the primary ridge are also more numerous than ''Rhabdodon'' or ''Mochlodon'', with there being at least 12 on each side. These ridges stretch to the bottom edge of the crown, instead of stopping short as in ''Mochlodon''.

Discovery and naming

All specimens of ''Matheronodon'' have been found at the locality of Velaux-La Bastide Neuve, in the

Aix-en-Provence Aix-en-Provence (, , ; oc, label=Provençal, Ais de Provença in classical norm, or in Mistralian norm, ; la, Aquae Sextiae), or simply Aix ( medieval Occitan: ''Aics''), is a city and commune in southern France, about north of Marseille. ...

basin,

Bouches-du-Rhône Bouches-du-Rhône ( , , ; oc, Bocas de Ròse ; "Mouths of the Rhône") is a department in Southern France. It borders Vaucluse to the north, Gard to the west and Var to the east. The Mediterranean Sea lies to the south. Its prefecture and l ...

. The

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s at this locality, which was discovered by Xavier Valentin in 1992, are part of the Begudian regional stage (which correlates to the late

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. Campani ...

epoch, about 74 to 72 million years ago). After their discovery, the fossils were stored in the

paleontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fos ...

and

archaeology Archaeology or archeology is the scientific study of human activity through the recovery and analysis of material culture. The archaeological record consists of Artifact (archaeology), artifacts, architecture, biofact (archaeology), biofacts ...

collections of the

municipality A municipality is usually a single administrative division having municipal corporation, corporate status and powers of self-government or jurisdiction as granted by national and regional laws to which it is subordinate. The term ''municipality ...

Velaux Velaux (; oc, Velaurs) is a commune in the Bouches-du-Rhône department in southern France. It is near Coudoux and Ventabren. Velaux is an old Provençal village set on a hill overlooking the high plains of the inland west side of Aix. It ...

, and labelled as belonging to the Musée du Moulin Seigneurial/Velaux-La Bastide Neuve (MMS/VBN). The

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes the ...

is MMS/VBN-02-102, a right maxilla; associated with it are maxillary teeth (-93-34, -09-149a, -09-150, and -12-22) and dentary teeth: (-02-11, -09-43c, and -12-A002). In 2017, the fossil material was described by Godefroit along with Géraldine Garcia, Bernard Gomez, Koen Stein, Aude Cincotta, Ulysse Lefèvre, and Valentin in a research paper published by the journal ''

Nature Communications ''Nature Communications'' is a peer-reviewed, open access, scientific journal published by Nature Portfolio since 2010. It is a multidisciplinary journal and it covers the natural sciences, including physics, chemistry, earth sciences, medicine, ...

''. They assigned this material to the genus ''Matheronodon'', with the name being formed from Philippe Matheron (who described the first dinosaur fossils found in

Provence Provence (, , , , ; oc, Provença or ''Prouvènço'' , ) is a geographical region and historical province of southeastern France, which extends from the left bank of the lower Rhône to the west to the France–Italy border, Italian border ...

, or the southeastern region of France) and the suffix ''-odon'', a derivative of ' (

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

for "tooth"). They also named the type and only species ''M. provincialis'', with ''provincialis'' being

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

for Provence. For the study, a

CT scan A computed tomography scan (CT scan; formerly called computed axial tomography scan or CAT scan) is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers ...

of the type maxilla was conducted at the

University of Liège The University of Liège (french: Université de Liège), or ULiège, is a major public university of the French Community of Belgium based in Liège, Wallonia, Belgium. Its official language is French. As of 2020, ULiège is ranked in the 301� ...

, and a

thin section In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron m ...

of an isolated maxillary tooth was examined under a microscope.

Palaeobiology

Inferences regarding the method of feeding in ''Matheronodon'' can be made from the unique morphology of its teeth. The hadrosaurs, a contemporary successful group of

s, had a large number of wide, high crowned teeth in tightly-packed rows. These were used in a complex method of chewing, a culmination of continued specialization throughout the evolution of

iguanodonts Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', ''Dryosaurus'', ''Iguanodon'', ''Tenontosaurus'', and the hadrosaurids or "duck-bill ...

. Rhabdodontids, which were more

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 ...

, had a far simpler arrangement, with teeth more similar to those of less specialized ornithopods. Fewer teeth were present in the jaw, but they were taller, thinner, and individually larger. In life, they would have functioned like a pair of scissors in powerful but simple slicing bites. The microstructure of the teeth in ''Mantheronodon'' was also adapted for this action. These differences would have led to different diets in the two groups of ornithopods. Where they co-occurred, they were likely ecologically partitioned. Rhabdodontids would have had more limited diets, compared to the diverse and likely

cellulose Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell wall ...

-rich and perhaps

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ex ...

-based diets of hadrosaurs. ''Mantheronodon'' and its relatives may have fed on

plants, such as the palms '' Sabalites'' and '' Pandanites'', common in Europe at the time. Sclerenchyma fibres, abundant in monocot leaves but largely absent in

eudicots The eudicots, Eudicotidae, or eudicotyledons are a clade of flowering plants mainly characterized by having two seed leaves upon germination. The term derives from Dicotyledons. Traditionally they were called tricolpates or non- magnoliid dic ...

and conifers, result in tougher plant tissue, and would have necessitated the more powerful bites of rhabdodontids to be consumed.

Palaeoecology

Velaux-La Bastide Neuve represents a continental deposit. However, it was probably close to the shoreline, judging by the presence of claws from

decapods The Decapoda or decapods (literally "ten-footed") are an order of crustaceans within the class Malacostraca, including many familiar groups, such as crabs, lobsters, crayfish, shrimp and prawns. Most decapods are scavengers. The order is es ...

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. ...

, and unionid

mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, whic ...

s at the site. Fossils from the locality are well-preserved and were likely slowly transported. Other dinosaurs discovered at the site include the

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

Atsinganosaurus ''Atsinganosaurus'' is a genus of titanosaurian sauropod dinosaur which existed in what is now France during the late Cretaceous period. Well-preserved remains (and the only known) of ''Atsinganosaurus'' were collected from the Grès à Reptile ...

'', in addition to teeth from

nodosaurid Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period in what is now North America, South America, Europe, and Asia. Description Nodosaurids, like their close relatives the ankylosaurids, w ...

ankylosaurs as well as neoceratosaurian and

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 ...

theropods Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

. Additional faunal elements include the eusuchian '' Allodaposuchus'',

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

s, the turtles '' Solemys'' and ''

Polysternon ''Polysternon'' is a genus of turtles in the extinct family Bothremydidae. It was described by Portis in 1882, and contains the species ''P. provinciale'' (originally placed in the genus ''Pleurosternon''), which existed during the Cretaceous of ...

'', the hybodont

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including sharks (superorder Selachii), rays, skates, and sawfish (superorder Batoidea). Members of this subclass are characterised by having five to seven pairs of g ...

'' Meristonoides'', and a

gar Gars are members of the family Lepisosteidae, which are the only surviving members of the Ginglymodi, an ancient holosteian group of ray-finned fish, which first appeared during the Triassic, over 240 million years ago. Gars comprise seven livin ...

References