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

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 Re ...

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 ...

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

from the late

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

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 Ba ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

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

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

and associated teeth. It was named by

Pascal Godefroit Pascal Godefroit is a Belgian paleontologist. He discovered dinosaurs like '' Olorotitan'' in 2003. Godefroit is the director of earth and life sciences at the Royal Belgian Institute of Natural Sciences The Museum of Natural Sciences (, ; , ...

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 flowering plants whose seeds contain only one Embryo#Plant embryos, embryonic leaf, or cotyledon. A monocot taxon has been in use for several decades, but ...

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

. 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 ''Rhabdodon'' (meaning "fluted tooth") is a genus of ornithopod dinosaur that lived in Europe approximately 70-66 million years ago in the Late Cretaceous. The genus contains a single species, ''R. priscus''. It is similar in build to a very rob ...

'' and ''

Zalmoxes ''Zalmoxes'' is a genus of rhabdodontid ornithopod dinosaur from the Maastrichtian age of the Late Cretaceous in what is now Romania. The genus is known from specimens first named as the species '' Mochlodon robustum'' in 1899 by Franz Nopcsa ...

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

. 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 Archosauriformes, archosauriforms, first appearing during the Triassic Period. Among Extant ...

, which is shorter than ''Rhabdodon''.

Teeth

Like ''Rhabdodon'', ''Zalmoxes'', and ''

Mochlodon ''Mochlodon'' is a genus of rhabdodontid dinosaurs from the Late Cretaceous of Austria and Hungary. It lived during the Late Cretaceous (85-80 Ma) and two species are known: ''M. suessi'' and ''M. vorosi''. Discovery and species In 1859 coal ...

'', 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, solid surfaces. Causes of wear can be mechanical (e.g., erosion) or Chemistry, chemical (e.g., corrosion). The study of wear and related processes is referred to as trib ...

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

hadrosaurid Hadrosaurids (), also hadrosaurs or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod fami ...

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

Edmontosaurus ''Edmontosaurus'' ( ) (meaning "lizard from Edmonton"), with the second species often colloquially and historically known as ''Anatosaurus'' or ''Anatotitan'' (meaning "duck lizard" and "giant duck"), is a genus of hadrosaurid (duck-billed) din ...

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

dentin Dentin ( ) (American English) or dentine ( or ) (British English) () is a calcified tissue (biology), tissue of the body and, along with tooth enamel, enamel, cementum, and pulp (tooth), pulp, is one of the four major components of teeth. It i ...

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 the t ...

. ''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 Replacement(s) or Replace may refer to: Music * The Replacements (band), an American alternative rock band Film and television * ''The Replacements'' (film), a 2000 American sports comedy * ''The Replacement'' (2021 film), a 2021 Spanish thr ...

, 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, or simply Aix, is a List of communes in France with over 20,000 inhabitants, city and Communes of France, commune in southern France, about north of Marseille. A former capital of Provence, it is the Subprefectures in France, s ...

basin,

Bouches-du-Rhône Bouches-du-Rhône ( ; , ; ; "the Mouths of the Rhône") is a Departments of France, department in southern France. It borders Vaucluse to the north, Gard to the west and Var (department), Var to the east. The Mediterranean Sea lies to the sout ...

. The

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s at this locality, which was discovered by Xavier Valentin in 1992, are part of the Begudian regional

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

(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. Campa ...

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

paleontology Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure ge ...

and

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

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 (; ) 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 is locate ...

, 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 wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

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 that covers the natural sciences, including physics, chemistry, earth sciences, medic ...

''. 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 is a geographical region and historical province of southeastern France, which stretches from the left bank of the lower Rhône to the west to the France–Italy border, Italian border to the east; it is bordered by the Mediterrane ...

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

Greek Greek may refer to: 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 of all kno ...

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 languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

for Provence. For the study, a

CT scan A computed tomography scan (CT scan), formerly called computed axial tomography scan (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 or ...

of the type maxilla was conducted at the

University of Liège The University of Liège (), or ULiège, is a major public university of the French Community of Belgium founded in 1817 and based in Liège, Wallonia, Belgium. Its official language is French (language), French. History The university was foun ...

, 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 ...

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 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 ...

. Rhabdodontids, which were more basal, 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 chemical formula, formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of glycosidic bond, β(1→4) linked glucose, D-glucose units. Cellulose is an important s ...

-rich and perhaps

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

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

plants, such as the palms ''

Sabalites ''Sabalites'' is an extinct genus of palm. Species belonging to the genus lived in the late Cretaceous to Miocene and have been found in South America, North America, Europe, and Asia. The genus is characterized by its costapalmate leaves, which ...

'' and '' Pandanites'', common in Europe at the time. Sclerenchyma fibres, abundant in monocot leaves but largely absent in

eudicots The eudicots or eudicotyledons are flowering plants that have two seed leaves (cotyledons) upon germination. The term derives from ''dicotyledon'' (etymologically, ''eu'' = true; ''di'' = two; ''cotyledon'' = seed leaf). Historically, authors h ...

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, from Ancient Greek δεκάς (''dekás''), meaning "ten", and πούς (''poús''), meaning "foot", is a large order (biology), order of crustaceans within the class Malacostraca, and includes crabs, lobsters, crayfis ...

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

, and

unionid The Unionidae are a Family (biology), family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids. The range of distribution for this family is world-wide. It is a ...

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

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 thr ...

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

'', in addition to teeth from

nodosaurid Nodosauridae is a family of ankylosaurian dinosaurs known from the Late Jurassic to the Late Cretaceous periods in what is now Asia, Europe, North America, and possibly South America. While traditionally regarded as a monophyletic clade as the s ...

ankylosaurs Ankylosauria is a group of herbivorous dinosaurs of the clade Ornithischia. It includes the great majority of dinosaurs with Armour (zoology), armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short ...

as well as neoceratosaurian and

dromaeosaurid Dromaeosauridae () is a family (biology), family of feathered coelurosaurian Theropoda, theropod dinosaurs. They were generally small to medium-sized feathered carnivores that flourished in the Cretaceous period (geology), Period. The name Drom ...

theropods Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

. Additional faunal elements include the

eusuchia Eusuchia is a clade of neosuchian Crocodylomorpha, crocodylomorphs that first appeared in the Early Cretaceous, which includes modern Crocodilia, crocodilians. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survi ...

n ''

Allodaposuchus ''Allodaposuchus'' is an extinct genus of crocodyliforms that lived in what is now southern Europe during the Campanian and Maastrichtian stages, and possibly the Santonian stage, of the Late Cretaceous. Although generally classified as a non-cro ...

'',

pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...

s, the turtles ''

Solemys ''Solemys'' is an extinct genus of helyochelydrid stem-turtle known from the Late Cretaceous (late Campanian-early Maastrichtian) of southern France and eastern Spain Spain, or the Kingdom of Spain, is a country in Southern Europe, Sout ...

'' 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 o ...

'', the

hybodont Hybodontiformes, commonly called hybodonts, are an extinct group of shark-like cartilaginous fish (chondrichthyans) which existed from the late Devonian to the Late Cretaceous. Hybodonts share a close common ancestry with modern sharks and rays ( ...

elasmobranch Elasmobranchii () is a subclass of Chondrichthyes or cartilaginous fish, including modern sharks ( division Selachii), and batomorphs (division Batomorphi, including rays, skates, and sawfish). Members of this subclass are characterised by h ...

'' Meristonoides'', and a

gar Gars are an ancient group of ray-finned fish in the family Lepisosteidae. They comprise seven living species of fish in two genera that inhabit fresh, brackish, and occasionally marine waters of eastern North America, Central America and Cuba ...

References