THE OSTEOLOGY OF THE HOLOTYPE OF THE BRITISH IGUANODONTIAN DINOSAUR MANTELLISAURUS ATHERFIELDENSIS

ABSTRACT

Iguanodontian dinosaurs are known from Middle Jurassic to Late Cretaceous deposits worldwide and are historically important because they include the first fossils to be identified as giant extinct reptiles that later became known as dinosaurs. Due to historical taxonomic practices and the fragmentary nature of many specimens, discoveries from the 19th century were referred to Iguanodon with little appraisal, resulting in the genus becoming something of a ‘wastebasket taxon’. Reinterpretations of holotype specimens are an important step in attempting to understand the evolutionary history of iguanodontian dinosaurs. Here, we redescribe the holotype of Mantellisaurus atherfieldensis, one of the most complete British dinosaur specimens, from the Barremian/Aptian of the Isle of Wight, UK, and assess its phylogenetic position. We find that Mantellisaurus atherfieldensis is a valid taxon distinct from the genus Iguanodon based on three autapomorphies of the premaxilla, maxilla, and scapula, and resolves as an early diverging hadrosauroid styracosternan, representing an important step in the evolutionary history of the ornithopods.

RÉSUMÉ

Les dinosaures iguanodontiens sont connus dans le monde entier du Jurassique moyen à la fin du Crétacé. Ils sont historiquement importants car ils comprennent les premiers fossiles identifiés comme des reptiles géants éteints qui ont ensuite été connus sous le nom de dinosaures. En raison des pratiques taxonomiques historiques et de la nature fragmentaire de nombreux spécimens, les découvertes du XIXe siècle ont été référées à Iguanodon avec peu de précision, ce qui a fait que le genre est devenu une sorte de « taxon fourre-tout ». Les réinterprétations de spécimens d’holotypes sont une étape importante pour tenter de comprendre l’histoire évolutive des dinosaures iguanodontiens. Ici, nous redécrivons l’holotype de Mantellisaurus atherfieldensis, l’un des spécimens de dinosaures britanniques les plus complets, datant du Barrémien/Aptien de l’île de Wight (Royaume-Uni), et nous ré-évaluons sa position phylogénétique. Nous trouvons que Mantellisaurus atherfieldensis est un taxon valide distinct du genre Iguanodon et ceci basé sur trois autapomorphies du prémaxillaire, du maxillaire et de l’omoplate. Nos analyses phylogénétiques le place comme un hadrosaure styracosternan ayant divergée tôt dans l’histoire des ornithopodes, ce qui en fait un représentant important dans la compréhension de l’histoire évolutive de ce groupe. [Translation by Anne-Claire Fabre.]

ZUSAMMENFASSUNG

Iguanodontische Dinosaurier, bekannt durch weltweite mitteljurassische bis spätkreidezeitliche Ablagerungen, sind von historischer Bedeutung, da sie die ersten Fossilien enthalten, die als riesige, ausgestorbene Reptilien, später Dinosaurier, identifiziert wurden. Aufgrund historischer taxonomischer Praktiken und der fragmentarischer Eigenschaft vieler Exemplare wurden Entdeckungen aus dem 19. Jahrhundert ohne große Begutachtung als Iguanodon referenziert, was dazu führte, dass die Gattung eine Art „Papierkorb Taxon “wurde. Neuinterpretationen von Holotyp-Exemplaren sind ein wichtiger Schritt bei dem Versuch, die Evolutionsgeschichte der iguanodontischen Dinosaurier zu verstehen. Hier beschreiben wir den Holotyp von Mantellisaurus atherfieldensis neu; eines der vollständigen, britischen Dinosaurier Exemplaren aus dem Barremium/Aptium von der Isle of Wight, UK, und beurteilen seine phylogenetische stellung. Wir stellen fest, dass Mantellisaurus atherfieldensis ein gültiges Taxon ist, das sich von der Gattung Iguanodon unterscheidet, basierend auf drei autapomorphien der Praemaxillare, Maxilla und Scapula, und stellt ein früh divergierendes Hadrosauridae Styracosternan dar, welches einen wichtigen Schritt in der evolutionären Geschichte der Ornithopoden repräsentiert. [Translation by Julia Clark.]

АБСТРАКТ

Динозавры-игуанодонты известны по всему миру благодаря залежам датированным промежутком между средне-юрским и поздне-меловым периодами и имеют историческое значение, так как в их составе обнаружены окаменелости, впервые идентифицированы как гигантские вымершие рептилии, которые в последствии стали известны как динозавры. В связи с исторической таксономической практикой и фрагментарной природе многих образцов, открытия 19 века можно отнести к Iguanodon лишь частично, что привело к тому что этот род стал чем-то вроде потерянного таксона в классификации. Переосмысление образцов голотипа является важным шагом на пути понятия истории эволюции динозавров-игуанодонтов. Следовательно, здесь мы заново пересматриваем голотип Mantellisaurus atherfieldensis, который является одним из наиболее полных образцов Британских динозавров, найденых в период обозначенный как баррема/апта на острове Уайт в Великобритании, и оцениваем его филогенетическую принадлежность. Мы обнаруживаем, что Mantellisaurus atherfieldensis является отдельным таксоном, отличающимся от рода Iguanodon, на основе трех аутапоморфий предчелюстной кости, верхней челюсти и лопатки, и иденфицируется как гадрозавроидный стиракостернан. Эти выводы являются важной вехой в истории эволюции орнитоподов. [Translated by Anastasia Doronina.]

SYSTEMATIC INDEX

Numbers in bold type indicate a page on which a description or diagnosis is given or commences; numbers in italics indicate pages where a text-figure occurs. Plates with figure numbers are included.

• Altirhinus kurzanovi, 8, 10–12, 14, 16, 18, 19, 33–35, 37, 42–44

• altus, Dryosaurus, 6, 14, 20, 35

• Amurosaurus riabinini, 17

• annectens, Edmontosaurus, 16, 34, 35, 51

• aphanoecetes, Uteodon, 7, 20, 21, 23, 25, 29, 33, 34, 37, 38, 39, 44, 45, 46, 47

• arenatus, Lurdusaurus, 35, 44

• atherfieldensis, Mantellisaurus, 2, 4–7, 5, 5, 6, 8, 9–12, 9, 11–13, 14, 15, 16–18, 17, 18, 19–27, 20, 21, 23, 29, 30–36, 33, 34, 37–39, 38, 40, 44, 45, 44, 45, 47–49, 49, 50, 51, 53; pl. 1

• atopus, Lophorhothon, 14

• Bactrosaurus johnsoni, 6, 8, 9, 14–16, 18, 34, 35, 37, 42, 43, 45

• Barilium dawsoni, 27, 28, 30, 42, 43, 45

• barsboldi, Choyrodon, 7, 10, 12, 14, 17, 43, 44

• Batyrosaurus rozhdestvenskyi, 17, 35, 36

• Bayannurosaurus perfectus, 7, 8, 14, 18, 44, 46

• beltrani, Morelladon, 43

• bernissartensis, Iguanodon, 1, 2, 6–8, 10–12, 14–16, 18–21, 23–25, 27–29, 31, 33–37, 39, 40, 42–44, 46, 49, 50

• Bolong yixianensis, 16, 18, 45

• Brachylophosaurus canadensis, 11, 14, 16, 29, 34, 35, 37, 39

• Brighstoneus simmondsi, 16

• byrdi, Protohadros, 9, 14–16

• canadensis, Brachylophosaurus, 11, 14, 16, 29, 34, 35, 37, 39

• canaliculatus, Valdosaurus, 45, 46, 49

• caroljonesa, Eolambia, 6, 8–12, 17–19, 34, 35, 37, 38, 42–45

• Cedrorestes crichtoni, 42

• Choyrodon barsboldi, 7, 10, 12, 14, 17, 43, 44

• crichtoni, Cedrorestes, 42

• Cumnoria prestwichii, 7, 10, 19–21, 23–25, 27, 29, 33, 38, 39, 42, 46, 47, 49, 50

• cyrtocristatus, Parasaurolophus, 12

• Dakotadon lakotaensis, 18

• dawsoni, Barilium, 27, 28, 30, 42, 43, 45

• diagnosticus, Lesothosaurus, 37, 51

• dossi, Tenontosaurus, 8, 43

• Dryosaurus altus, 6, 14, 20, 35

• Dysalotosaurus lettowvorbecki, 14, 17, 23, 33–35, 37, 38, 43, 46, 47

• Edmontosaurus regalis, 14, 15, 17, 18, 37, 39, 45, 46

• Edmontosaurus annectens, 16, 34, 35, 51

• Eolambia caroljonesa, 6, 8–12, 17–19, 34, 35, 37, 38, 42–45

• Equijubus normani, 6–8, 11, 14, 16, 19, 21, 23, 25, 27, 36, 42, 43, 46

• fittoni, Hypselospinus, 1, 10, 17, 42

• foxii, Hypsilophodon, 14, 16, 37, 38, 43

• Fukuisaurus tetoriensis, 18

• gilmorei, Shuangmiaosaurus, 18

• Gilmoreosaurus mongoliensis, 7, 10, 14, 20, 23, 24, 30, 34, 35, 37, 39, 42, 43, 45–47

• gobiensis, Probactrosaurus, 7, 9–12, 14, 18, 19, 29, 33–35, 42–44, 46

• Gobihadros mongoliensis, 8, 10, 11, 16, 37, 47

• Gryposaurus latidens, 8, 11, 18, 35

• Hippodraco scutodens, 15, 16, 33–35, 37

• hoggii, Owenodon, 20

• Hypselospinus fittoni, 1, 10, 17, 42

• Hypsilophodon foxii, 14, 16, 37, 38, 43

• Iguanodon bernissartensis, 1, 2, 6–8, 10–12, 14–16, 18–21, 23–25, 27–29, 31, 33–37, 39, 40, 42–44, 46, 49, 50

• insularis, Tethyshadros, 31, 46

• Jeyawati rugoculus, 14

• Jinzhousaurus yangi, 8, 10, 12, 15, 16, 21, 23, 25, 36, 40, 43

• johnsoni, Bactrosaurus, 6, 8, 9, 14–16, 18, 34, 35, 37, 42, 43, 45

• katsuyama, Koshisaurus, 10

• kerri, Theiophytalia, 7, 8, 10

• khoratensis, Sirindhorna, 7, 18

• kohlerorum, Koutalisaurus, 17, 18

• Koshisaurus katsuyama, 10

• Koutalisaurus kohlerorum, 17, 18

• Kukufeldia tilgatensis, 10, 17, 19

• kurzanovi, Altirhinus, 8, 10–12, 14, 16, 18, 19, 33–35, 37, 42–44

• lakotaensis, Dakotadon, 18

• langdoni, Muttaburrasaurus, 16

• Lanzhousaurus magnidens, 18, 36, 44

• laticaudus, Magnapaulia, 8, 37, 42

• latidens, Gryposaurus, 8, 11, 18, 35

• Lesothosaurus diagnosticus, 37, 51

• lettowvorbecki, Dysalotosaurus, 14, 17, 23, 33–35, 37, 38, 43, 46, 47

• Lophorhothon atopus, 14

• Lurdusaurus arenatus, 35, 44

• Magnapaulia laticaudus, 8, 37, 42

• magnidens, Lanzhousaurus, 18, 36, 44

• Maiasaura peeblesorum, 16

• Mantellisaurus atherfieldensis, 2, 4–7, 5, 5, 6, 8, 9–12, 9, 11–13, 14, 15, 16–18, 17, 18, 19–27, 20, 21, 23, 29, 30–36, 33, 34, 37–39, 38, 40, 44, 45, 44, 45, 47–49, 49, 50, 51, 53; pl. 1

• Mochlodon vorosi, 14, 17

• mongoliensis, Gilmoreosaurus, 7, 10, 14, 20, 23, 24, 30, 34, 35, 37, 39, 42, 43, 45–47

• mongoliensis, Gobihadros, 8, 10, 11, 16, 37, 47

• Morelladon beltrani, 43

• Muttaburrasaurus langdoni, 16

• nigeriensis, Ouranosaurus, 7, 8, 10, 11, 14, 16–18, 21, 23, 25, 28, 29, 33–35, 37–39, 42–46, 49

• normani, Equijubus, 6–8, 11, 14, 16, 19, 21, 23, 25, 27, 36, 42, 43, 46

• Ouranosaurus nigeriensis, 7, 8, 10, 11, 14, 16–18, 21, 23, 25, 28, 29, 33–35, 37–39, 42–46, 49

• Owenodon hoggii, 20

• paraceramosa, Pseudofrenolopsis, 4

• Parasaurolophus tubicen, 12

• Parasaurolophus cyrtocristatus, 12

• peeblesorum, Maiasaura, 16

• perfectus, Bayannurosaurus, 7, 8, 14, 18, 44, 46

• prestwichii, Cumnoria, 7, 10, 19–21, 23–25, 27, 29, 33, 38, 39, 42, 46, 47, 49, 50

• Proa valdearinnoensis, 8, 10, 14, 17, 18, 42–44

• Probactrosaurus gobiensis, 7, 9–12, 14, 18, 19, 29, 33–35, 42–44, 46

• Protohadros byrdi, 9, 14–16

• Pseudofrenolopsis paraceramosa, 4

• regalis, Edmontosaurus, 14, 15, 17, 18, 37, 39, 45, 46

• riabinini, Amurosaurus, 17

• robustus, Zalmoxes, 12, 14, 17, 23, 28, 29, 34, 37, 42, 45

• rozhdestvenskyi, Batyrosaurus, 17, 35, 36

• rugoculus, Jeyawati, 14

• scutodens, Hippodraco, 15, 16, 33–35, 37

• shqiperorum, Zalmoxes, 8, 14, 23, 37, 39, 43, 50

• Shuangmiaosaurus gilmorei, 18

• simmondsi, Brighstoneus, 16

• sinensis, Tanius, 37, 43

• Sirindhorna khoratensis, 7, 18

• Tanius sinensis, 37, 43

• Telmatosaurus transsylvanicus, 8, 10, 14, 34, 37, 46

• Tenontosaurus tilletti, 7, 8, 14, 15, 17, 21, 23–25, 27–29, 31, 35, 37–39, 44, 45, 47, 49

• Tenontosaurus dossi, 8, 43

• Tethyshadros insularis, 31, 46

• tetoriensis, Fukuisaurus, 18

• Theiophytalia kerri, 7, 8, 10

• tilgatensis, Kukufeldia, 10, 17, 19

• tilletti, Tenontosaurus, 7, 8, 14, 15, 17, 21, 23–25, 27–29, 31, 35, 37–39, 44, 45, 47, 49

• transsylvanicus, Telmatosaurus, 8, 10, 14, 34, 37, 46

• tubicen, Parasaurolophus, 12

• Uteodon aphanoecetes, 7, 20, 21, 23, 25, 29, 33, 34, 37, 38, 39, 44, 45, 46, 47

• valdearinnoensis, Proa, 8, 10, 14, 17, 18, 42–44

• Valdosaurus canaliculatus, 45, 46, 49

• vorosi, Mochlodon, 14, 17

• Xuwulong yueluni, 10, 11

• yangchengensis, Zhanghenglong, 18

• yangi, Jinzhousaurus, 8, 10, 12, 15, 16, 21, 23, 25, 36, 40, 43

• yixianensis, Bolong, 16, 18, 45

• yueluni, Xuwulong, 10, 11

• Zalmoxes robustus, 12, 14, 17, 23, 28, 29, 34, 37, 42, 45

• Zalmoxes shqiperorum, 8, 14, 23, 37, 39, 43, 50

• Zhanghenglong yangchengensis, 18