Hadrosauromorpha

Hadrosauromorpha is a cohort of iguanodontian ornithopods, defined in 2014 by David B. Norman to divide Hadrosauroidea into the basal taxa with compressed manual bones and a pollex, and the derived taxa that lack them. The clade is defined as all the taxa closer to Edmontosaurus regalis than Probactrosaurus gobiensis. This results in different taxon inclusion depending on the analysis.

Hadrosauromorphs
Temporal range: Late Cretaceous, 96.7–66 Ma
Bactrosaurus johnsoni 1
Skeleton of Bactrosaurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ornithopoda
Clade: Hadrosauriformes
Superfamily: Hadrosauroidea
Clade: Hadrosauromorpha
Norman, 2015 vide Norman, 2014
Subgroups[1][2][3]

Classification

Hadrosauromorpha was first used in literature by David B. Norman in 2014 in a discussion of phylogenetics of Hypselospinus. In his 2014 paper Norman references another of his publications as the authority for Hadrosauromorpha, a chapter in the book Hadrosaurs.[1] However, the book was in fact published later, in 2015.[4] Following Article 19.4 of the PhyloCode, the authorship of the clade is thus Norman (2015), while the authorship of the definition is Norman (2014).[5]

Definition

Hadrosauromorpha was defined by Norman (2014 and 2015) as hadrosauroid taxa closer to Edmontosaurus regalis than Probactrosaurus gobiensis.[1][4] This definition was contested by Mickey Mortimer, who stated that to follow the PhyloCode the taxon Hadrosaurus must be included in the definition, as it is the type genus of Hadrosauromorpha.[6] By this definition, Norman (2015) considered Hadrosauromorpha to include Hadrosauridae, as well as the taxa Tethyshadros and Bactrosaurus.[4] Norman in 2014 had included more taxa in Hadrosauromorpha, those of Norman (2015) as well as Levnesovia, Gilmoreosaurus and Telmatosaurus, the last of which was considered inside Hadrosauridae by Norman in 2015.[1] Another phylogenetic analysis by Xing et al. in 2014 also found that Eolambia and Protohadros, both found outside Hadrosauromorpha by Norman, fell within his definition, as well as a large number of other taxa.[2]

Phylogeny

Many different versions of phylogenies have been conducted on the group of hadrosauromorphs.[2] Norman (2014) created his own analysis, which includes 105 different morphological characters and 27 select ornithopod taxa. His phylogeny is shown below, using his specific clade definitions:[1]

Hadrosauriformes (Altirhinus + Edmontosaurus)

Altirhinus

Eolambia

Equijubus

Probactrosaurus

Hadrosauromorpha

Tethyshadros

Levnesovia

Bactrosaurus

Gilmoreosaurus

Telmatosaurus

Euhadrosauria

Norman's definitions have been heavily criticized by Mickey Mortimer as being unnecessary changes which cause more confusion to classification.[6] Other phylogenetic analyses, like Xing et al.'s shown below, use traditional clade definitions (Hadrosauromorpha has been added as defined[1]) and have recovered different results.[2] Huehuecanauhtlus has also been found as one of the most derived hadrosauromorphans, between Gilmoreosaurus and Hadrosauridae.[3]

Eolambia
Skull and restoration of Eolambia, possibly one of the most basal hadrosauromorphans
Hadrosauroidea

Equijubus

Xuwulong

Probactrosaurus

Hadrosauromorpha

Jintasaurus

Eolambia

Protohadros

Levnesovia

Tanius

Bactrosaurus

Gilmoreosaurus

Shuangmiaosaurus

Nanningosaurus

Telmatosaurus

Tethyshadros

Claosaurus

Zhanghenglong

Nanyangosaurus

Hadrosauridae

Description

Dinosaurium, Probactrosaurus gobiensis 2
Skeleton of Probactrosaurus, the taxon just outside Hadrosauromorpha

Probactrosaurus was selected as the outgroup to Hadrosauromorpha because of numerous differences that Norman (2014) thought to be significant. The tooth crowns in the dentary are asymmetrical and have multiple vertical ridges; there is a foramen in the surangular; and the quadrate bone has a more prominent depression for the articulation of the jugal. None of these features are found in the skulls of the more derived hadrosauromorphans. The premaxilla contacts the prefrontal, and the jugal contact with the ectopterygoid bone of the palate is reduced.[1]

In the appendicular regions, hadrosauromorphans the scapulae are not J shaped, instead having an overhanging projection. The lower forelimb bones are more slender in both hadrosauromorphans and Probactosaurus, unlike their more robust ancestors. Probactosaurus, however, possesses the basal condition of having a small, conical pollex, like in earlier ornithopods such as Iguanodon or Hypselospinus. This absence of a pollex is also linked to a reduction of the carpal bones, and a less mobile manus. The ilium bones of Probactrosaurus are more angular than in hadrosauromorphs, which lack a brevis shelf. It was also identified that the femoral shaft is straight in hadrosauromorphans and the pedal bones are truncated[1]

References

  1. ^ a b c d e f g h Norman, D.B. (2014). "On the history, osteology, and systematic position of the Wealden (Hastings group) dinosaur Hypselospinus fittoni (Iguanodontia: Styracosterna)". Zoological Journal of the Linnean Society. 2014: 1–98. doi:10.1111/zoj.12193.
  2. ^ a b c d Xing, H.; Wang, D.; Han, F.; Sullivan, C.; Ma, Q.; He, Y.; Hone, D.W.E.; Yan, R.; Du, F.; Xu, X. (2014). "A New Basal Hadrosauroid Dinosaur (Dinosauria: Ornithopoda) with Transitional Features from the Late Cretaceous of Henan Province, China". PLoS One. 9 (6): e98821. doi:10.1371/journal.pone.0098821. PMC 4047018.
  3. ^ a b Ramírez-Velasco, A.A.; Benammi, M.; Prieto-Márquez, A.; Ortega, J.A.; Hernández-Rivera, R. (2012). "Huehuecanauhtlus tiquichensis, a new hadrosauroid dinosaur (Ornithischia: Ornithopoda) from the Santonian (Late Cretaceous) of Michoacán, Mexico". Canadian Journal of Earth Sciences. 49 (2): 379–395. doi:10.1139/e11-062.
  4. ^ a b c Norman, D.B. (2015). "Iguanodonts from the Wealden of England: do they contribute to the discussion concerning hadrosaur origins?". In Evans, D.C.; Eberth, D.A. (eds.). Hadrosaurs. Indiana University Press. pp. 10–43. ISBN 978-0-253-01385-9.
  5. ^ "Chapter VIII. Authorship of Names and Definitions. Article 19". The PhyloCode. Retrieved 1 September 2017.
  6. ^ a b Mortimer, M. (2014). "Norman's nomenclature's notoriously negative". The Theropod Database Blog. Retrieved 1 September 2017.
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).

Bactrosaurus

Bactrosaurus (; meaning "Club lizard," "baktron" = club + sauros = lizard) is a genus of herbivorous dinosaur that lived in east China during the late Cretaceous, about 70 mya, though some Bactrosaurus fossils have been dated back to 90 mya. The position Bactrosaurus occupies in the Cretaceous makes it one of the earliest known hadrosauroids, and although it is not known from a full skeleton, Bactrosaurus is one of the best known of these forms of hadrosaurs predecessors.

Claosaurus

Claosaurus ( KLAY-o-SAWR-əs; Greek κλάω, klao meaning 'broken' and σαῦρος, sauros meaning 'lizard'; "broken lizard", referring to the odd position of the fossils when discovered) is a genus of primitive hadrosaurian (early duck-billed dinosaur) that lived during the Late Cretaceous Period (Campanian).

Traditionally classified as an early member of the family Hadrosauridae, a 2008 analysis found Claosaurus agilis to be outside of the clade containing Hadrosaurus and other hadrosaurids, making it the closest not-hadrosaurid relative of true hadrosaurids within the clade Hadrosauria.

Elasmaria

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

Gilmoreosaurus

Gilmoreosaurus is the name given to a genus of dinosaur from the Cretaceous of Asia. The type species is Gilmoreosaurus mongoliensis. It is believed to be a hadrosaur or iguanodont from the Iren Dabasu Formation of Mongolia, dating to 70 Ma ago. Additional specimens have been described as distinct species, including G. atavus from the Khodzhakul Formation of Uzbekistan (120 Ma ago) and G. arkhangelskyi from the Bissekty Formation (89 Ma ago). However, these are based on very fragmentary remains, and their classification is dubious. An additional species, G. kysylkumensis (also from the Bissekty Formation) is sometimes included, though it has also been referred to the related genus Bactrosaurus.

The first Gilmoreosaurus fossil remains were collected by George Olsen in 1923 and consisted of disarticulated bones from several individuals at different localities. They were originally assigned to the genus Mandschurosaurus but later given the separate genus Gilmoreosaurus, which was characterized by its combination of basal iguanodontian and hadrosaurid traits. Although a consensus on the exact taxonomic placement of this genus remains unreached, a 2010 study by Prieto-Márquez and Norell places the animal in a closely related outgroup to Hadrosauridae, based on a reassessment of its taxonomic status using a large-sample phylogenic analysis.In 2003, evidence of tumors, including hemangiomas, desmoplastic fibroma, metastatic cancer, and osteoblastoma was discovered in fossilized Gilmoreosaurus skeletons. Rothschild et al. tested dinosaur vertebrae for tumors using computerized tomography and fluoroscope screening. Several other hadrosaurids, including Brachylophosaurus, Edmontosaurus, and Bactrosaurus, also tested positive. Although more than 10,000 fossils were examined in this manner, the tumors were limited to Gilmoreosaurus and closely related genera. The tumors may have been caused by environmental factors or genetic propensity.

Gobihadros

Gobihadros is a genus of basal hadrosauroid dinosaur from the Late Cretaceous of Mongolia. It contains one species, Gobihadros mongoliensis. The holotype specimen was recovered from the Bayan Shireh Formation (Cenomanian-Santonian). Its length was estimated at just under 3 meters (10 feet) long.

Hadrosauroidea

Hadrosauroidea is a clade or superfamily of ornithischian dinosaurs that includes the "duck-billed" dinosaurs, or hadrosaurids, and all dinosaurs more closely related to them than to Iguanodon.They are from Asia, Europe and Africa. Many primitive hadrosauroids, such as the Asian Probactrosaurus and Altirhinus, have traditionally been included in a paraphyletic (unnatural grouping) "Iguanodontidae". With cladistic analysis, the traditional Iguanodontidae has been largely disbanded, and probably includes only Iguanodon and perhaps its closest relatives.

Huehuecanauhtlus

Huehuecanauhtlus is an extinct genus of hadrosauroid dinosaur known from the Late Cretaceous (Santonian stage) of Michoacán, western Mexico. It contains a single species, Huehuecanauhtlus tiquichensis.

Jintasaurus

Jintasaurus (Chinese: 金塔龙; pinyin: Jīntǎ lóng) is a genus of hadrosauriform dinosaur described by Hai-Lu You (尤海鲁, Yóu Hǎilǔ) and Da-Qing Li (李大庆, Lǐ Dàqìng) in 2009. The type species is J. meniscus. Jintasaurus lived during the Early Cretaceous of what is now Gansu, northwestern China. The fossils were discovered in Jinta County, Jiuquan, Gansu, China. The discovery supports the theory that hadrosaurs originated in Asia. The holotype and only known specimen includes the postorbital skull, lacking the jugal and quadratojugal.

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.

Levnesovia

Levnesovia is a genus of hadrosauroid dinosaur from the Late Cretaceous Bissekty Formation of Uzbekistan. It was related to Bactrosaurus. The type species is L. transoxiana. The genus name honours the late Russian paleontologist Lev Nesov, and the specific name refers to the ancient region Transoxiana. It is known from the minority of the skull and would have reached around two meters in length.

Lophorhothon

Lophorhothon (Langston, 1960) is a genus of hadrosauroid dinosaur from the Late Cretaceous, the first genus of dinosaur discovered in Alabama, in the United States.

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.

Probactrosaurus

Probactrosaurus (meaning "before Bactrosaurus") is an early herbivorous hadrosauroid iguanodont dinosaur. It lived in Mongolia and China during the Late Cretaceous period.

Tanius

Tanius (meaning "of Tan") is a genus of hadrosauroid dinosaur. It lived in the Late Cretaceous of China. The type species, named and described in 1929 by Carl Wiman, is Tanius sinensis. The generic name honours the Chinese paleontologist Tan Xichou ("H.C. Tan"). The specific epithet refers to China. In 2010 Gregory S. Paul estimated the length of Tanius at seven metres and the weight at two tonnes.

Telmatosaurus

Telmatosaurus (meaning "marsh lizard") is a genus of basal hadrosaurid dinosaur from the Late Cretaceous. It was a relatively small hadrosaur, approximately five meters (16 ft) long, found in what is now Romania.

Tethyshadros

Tethyshadros ("Tethyan hadrosauroid") is a genus of dwarf hadrosauroid dinosaur from Trieste, Italy. The type and only species is T. insularis.

Yunganglong

Yunganglong is an extinct genus of basal hadrosauroid dinosaur known from the early Late Cretaceous lower Zhumapu Formation of Zuoyun County, Shanxi Province of northeastern China. It contains a single species, Yunganglong datongensis.

Zhanghenglong

Zhanghenglong is an extinct genus of herbivorous hadrosauroid iguanodont dinosaur known from the Late Cretaceous (middle Santonian stage) Majiacun Formation in Xixia County of Henan Province, China. It contains a single species, Zhanghenglong yangchengensis, represented by a disarticulated and partial cranium and postcranial skeleton.

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