Matheronodon

Matheronodon (meaning "Matheron tooth") is a genus of rhabdodontid ornithopod dinosaur from the Late Cretaceous of France. The genus contains a single species, M. provincialis, which is known from a single maxilla 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 plants.[1]

Matheronodon
Temporal range: Late Campanian, 74–72 Ma
Matheronodon 1
Holotype maxilla
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Family: Rhabdodontidae
Genus: Matheronodon
Godefroit et al., 2017
Type species
Matheronodon provincialis
Godefroit et al., 2017

Description

Like other rhabodontids, Matheronodon would have been a bipedal herbivore. The length of the genus has been estimated at 5 metres (16 ft) by its lead describer Pascal Godefroit.[2]

The maxilla of Matheronodon is a short, robust bone. The front portion is particularly shortened and also angled upwards, differentiating Matheronodon from other rhabdodontids. It measures 22 cm (8.7 in) long, and 10 cm (3.9 in) 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. Also at the base of the dorsal process is a small triangular projection delimiting the back of the antorbital fenestra, which is shorter than Rhabdodon.[1]

Teeth

Matheronodon 2
Reconstruction of the teeth in the maxilla

Like Rhabdodon, Zalmoxes, and Mochlodon, the maxillary tooth crowns of Matheronodon are shaped like cleavers. They are unusually large, being up to 5 cm (2.0 in) 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 is oriented 60° below the horizontal, like Zalmoxes and Mochlodon. Enamel covers all sides of the teeth, unlike hadrosaurids, being thicker on the inner surface (particularly on the ridges, compared to Edmontosaurus). Also unlike hadrosaurids, the tubular structure of the dentine below the enamel does not appear to vary in orientation. The scratches on the dentine's surface are vertical like Zalmoxes and Mochlodon.[1]

Even though the maxilla is large, it bears only eight tooth sockets. 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.[1]

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.[1]

Discovery and naming

Matheronodon 3
Teeth from the maxilla (a-d) and lower jaw (e-g)

All specimens of Matheronodon have been found at the locality of Velaux-La Bastide Neuve, in the Aix-en-Provence basin, Bouches-du-Rhône, France. The sandstones at this locality, which was discovered by Xavier Valentin in 1992,[3] are part of the Begudian regional stage (which correlates to the late Campanian epoch, about 74 to 72 million years ago[4]). After their discovery, the fossils were stored in the paleontology and archaeology collections of the municipality of Velaux, and labelled as belonging to the Musée du Moulin Seigneurial/Velaux-La Bastide Neuve (MMS/VBN). The type specimen 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).[1]

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. 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, or the southeastern region of France) and the suffix -odon, a derivative of odous (Greek for "tooth"). They also named the type and only species M. provincialis, with provincialis being Latin for Provence. For the study, a CT scan of the type maxilla was conducted at the University of Liège, and a thin section of an isolated maxillary tooth was examined under a microscope.[1]

Palaeobiology

Matheronodon 4
Microstructure of a thin slice from an isolated tooth

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 ornithopods, 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. 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.[1]

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-rich and perhaps conifer-based diets of hadrosaurs. Mantheronodon and its relatives may have fed on monocot 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 and conifers, result in tougher plant tissue, and would have necessitated the more powerful bites of rhabdodontids to be consumed.[1]

Palaeoecology

Velaux-La Bastide Neuve represents a continental deposit.[4] However, it was probably close to the shoreline, judging by the presence of claws from decapods,[3] gastropods, and unionid mussels at the site. Fossils from the locality are well-preserved and were likely slowly transported.[4] Other dinosaurs discovered at the site include the titanosaur Atsinganosaurus, in addition to teeth from nodosaurid ankylosaurs[3] as well as neoceratosaurian and dromaeosaurid theropods. Additional faunal elements include the eusuchian Allodaposuchus, pterosaurs, the turtles Solemys and Polysternon, the hybodont elasmobranch Meristonoides, and a gar.[4]

See also

References

  1. ^ a b c d e f g h i Godefroit, P.; Garcia, G.; Gomez, B.; Stein, K.; Cincotta, A.; Lefèvre, U.; Valentin, X. (2017). "Extreme tooth enlargement in a new Late Cretaceous rhabdodontid dinosaur from Southern France". Scientific Reports. 7 (1): 13098. doi:10.1038/s41598-017-13160-2. PMC 5658417. PMID 29074952.
  2. ^ Beall, A. (2017). "This 'ugly' dinosaur had giant scissor-like teeth". Alphr. Dennis Publishing. It was around five metres long, I guess.
  3. ^ a b c Garcia, G.; Amico, S.; Fournier, F.; Thouand, E.; Valentin, X. (2010). "A new Titanosaur genus (Dinosauria, Sauropoda) from the Late Cretaceous of southern France and its paleobiogeographic implications". Bulletin de la Société Géologique de France. 181 (3): 269–277. doi:10.2113/gssgfbull.181.3.269.
  4. ^ a b c d Martin, J. E.; Delfino, M.; Garcia, G.; Godefroit, P.; Berton, S.; Valentin, X. (2016). "New specimens of Allodaposuchus precedens from France: intraspecific variability and the diversity of European Late Cretaceous eusuchians". Zoological Journal of the Linnean Society. 176 (3): 607–631. doi:10.1111/zoj.12331.
Aquilarhinus

Aquilarhinus (meaning "eagle snout" after the unusual beak morphology) is a genus of hadrosaurid ornithopod dinosaur from the Aguja Formation from Texas in the United States. The type and only species is Aquilarhinus palimentus. Due to its unusual dentary, it has been inferred to have had shovel-like beak morphology, different from the beaks of other hadrosaurs. It was originally classified as a Kritosaurus sp. before being reclassified as a new genus in 2019.

Aralosaurini

Aralosaurini is a tribe of basal lambeosaurine hadrosaurs endemic to Eurasia. It currently contains Aralosaurus (from the Aral sea of Kazakhstan) and Canardia (from Toulouse, Southern France).

Canardia

Canardia is an extinct genus of aralosaurin lambeosaurine dinosaur known from the Late Cretaceous Marnes d’Auzas Formation (late Maastrichtian stage) of Toulouse, Haute-Garonne Department, southern France. The type species Canardia garonnensis was first described and named by Albert Prieto-Márquez, Fabio M. Dalla Vecchia, Rodrigo Gaete and Àngel Galobart in 2013.

Choyrodon

Choyrodon is a genus of hadrosauroid dinosaur from the Early Cretaceous Albian-age Khuren Dukh Formation of Mongolia. The type and only species is Choyrodon barsboldi. The generic name is derived from the city of Choyr, and -odon, from Greek for tooth; the specific name barsboldi honours paleontologist Rinchen Barsbold. The material consists of a holotype partial skull and cervical ribs, with two other partial skulls both with associated postcranial material. It was found to be the sister taxon of Eolambia.

Elasmaria

Elasmaria is a clade of iguanodont ornithopods known from Cretaceous deposits in South America, Antarctica, and Australia.

Huxleysaurus

Huxleysaurus (meaning "Huxley's lizard") is a genus of herbivorous styracosternan ornithopod dinosaur.

Iguanodontia

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-billed dinosaurs". Iguanodontians were one of the first groups of dinosaurs to be found. They are among the best known of the dinosaurs, and were among the most diverse and widespread herbivorous dinosaur groups of the Cretaceous period.

Jaxartosaurus

Jaxartosaurus is a genus of hadrosaurid dinosaur similar to Corythosaurus which lived during the Late Cretaceous. Its fossils were found in Kazakhstan.

Jeyawati

Jeyawati is a genus of hadrosauroid dinosaur which lived during the Turonian stage of the Late Cretaceous. The type species, J. rugoculus, was described in 2010, based on fossils recovered in the U.S. state of New Mexico.The holotype, MSM P4166, was discovered in the Moreno Hill Formation. A cladistic analysis indicates that Jeyawati was more plesiomorphic (ancestral) than Shuangmiaosaurus, Telmatosaurus, and Bactrosaurus, but more derived (less like the common ancestor) than Eolambia, Probactrosaurus, and Protohadros.

Koshisaurus

Koshisaurus is a monospecific genus of basal hadrosauroid from the Kitadani Formation in Japan. The discovery of the genus suggests that hadrosauroids had higher diversity along the eastern margin of Asia in the Early Cretaceous. "Koshi" means an old Japanese regional name including Fukui prefecture where fossils of the genus were discovered.

Laiyangosaurus

Laiyangosaurus ("Laiyang lizard") is a genus of saurolophine hadrosaurid from the Late Cretaceous of China. It is known from one species, L.youngi, found in the Laiyang Basin within the province of Shandong.

Lapampasaurus

Lapampasaurus is an extinct genus of hadrosaurid known from the Late Cretaceous Allen Formation (late Campanian or early Maastrichtian stage) of La Pampa Province, Argentina. It contains a single species, Lapampasaurus cholinoi.The generic name refers to the Argentine province of La Pampa. The specific name honours the late collector José Cholino. The material includes cervical, dorsal, sacral and caudal vertebrae, the forelimb girdle, and the partial hindlimb.

Osmakasaurus

Osmakasaurus is a genus of herbivorous iguanodontian dinosaur. It is a basal iguanodontian which lived during the lower Cretaceous period (Valanginian age) in what is now Buffalo Gap of South Dakota, United States. It is known from the Chilson Member of the Lakota Formation. This genus was named by Andrew T. McDonald in 2011 and the type species is Osmakasaurus depressus. O. depressus was previously referred to as Camptosaurus depressus, and was first described in 1909 by Charles W. Gilmore.

Pareisactus

Pareisactus (from the Greek "pareisaktos", meaning "intruder", referring to being represented as a single element among hundreds of hadrosaurid bones) is a genus of rhabdodontid ornithopod dinosaur from the Late Cretaceous Conquès Member of the Tremp Formation in the Southern Pyrenees of Spain. The type and only species is P. evrostos, known only from a single scapula.

Plesiohadros

Plesiohadros is an extinct genus of hadrosauroid dinosaur. It is known from a partial skeleton including the skull collected at Alag Teg locality, from the Campanian Djadochta Formation of southern Mongolia. The type species is Plesiohadros djadokhtaensis.

Rhabdodontidae

Rhabdodontidae is a family of herbivorous ornithopod dinosaurs that first appeared during the late Barremian of Spain, 129.4–125.0 million years ago, in the middle of the Lower Cretaceous. With their deep skulls and jaws, Rhabdodontids were similar to large, robust iguanodonts. The family was first proposed by David B. Weishampel and colleagues in 2003. Rhabdodontid fossils have been mainly found in Europe in formations dating to the Late Cretaceous.

The defining characteristics of the clade Rhabdodontidae include the spade-shape of the teeth, the presence of three or more premaxillary teeth, the distinct difference between the two maxillary and dentary teeth ridge patterns, and the uniquely shaped femur, humerus, and ulna. Members of Rhabdodontidae have an adult body length of 1.6 to 6.0 meters.

Sahaliyania

Sahaliyania (from "black" in Manchu, a reference to the Amur/Heilongjiang River) is a genus of lambeosaurine hadrosaurid dinosaur (crested duckbilled dinosaur) from the Late Cretaceous of Heilongjiang, China.

Tsintaosaurini

Tsintaosaurini is a tribe of basal lambeosaurine hadrosaurs native to Eurasia. It currently contains only Tsintaosaurus (from China) and Pararhabdodon (from Spain ).Koutalisaurus, also known from late Cretaceous Spain and formerly referred to Pararhabdodon

, may also be a tsintaosaurin because of its association with the latter genus; some recent work also suggests it may indeed be referrable to Pararhabdodon.

Xuwulong

Xuwulong is a genus of hadrosauroid dinosaur from the Early Cretaceous period. It lived during the early Cretaceous period (Aptian-Albian age) in what is now Yujingzi Basin in the Jiuquan area, Gansu Province of northwestern China. It is known from the holotype – GSGM F00001, an articulated specimen including a complete cranium, almost complete axial skeleton, and complete left pelvic girdle from Xinminpu Group. Xuwulong was named by You Hailu, Li Daqing and Liu Weichang in 2011 and the type species is Xuwulong yueluni.

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