Hypsilophodontidae

Last updated

Hypsilophodontidae
Temporal range: Early Cretaceous, 130–125  Ma
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
↓
Hypsilophodon Melb Museum email.jpg
Hypsilophodon skeleton
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade:† Ornithischia
Clade:† Neornithischia
Clade:† Clypeodonta
Family:† Hypsilophodontidae
Dollo, 1882 [1]
Subgroups [2]
Synonyms
  • HypsilophodontinaeNopcsa, 1928
  • HypsilophodontiaCooper, 1985

Hypsilophodontidae (or Hypsilophodontia) is a traditionally used family of ornithopod dinosaurs, generally considered invalid today. It historically included many small bodied bipedal neornithischian taxa from around the world, and spanning from the Middle Jurassic until the Late Cretaceous. This inclusive status was supported by some phylogenetic analyses from the 1990s and mid 2000s, [3] [4] although there have also been many finding that the family is an unnatural grouping which should only include the type genus, Hypsilophodon , with the other genera being within clades like Thescelosauridae and Elasmaria. [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] A 2014 analysis by Norman recovered a grouping of Hypsilophodon, Rhabdodontidae and Tenontosaurus , which he referred to as Hypsilophodontia. [2] That clade is formally defined in the PhyloCode as "the smallest clade within Ornithopoda containing Hypsilophodon foxii and Tenontosaurus tilletti provided it does not include Iguanodon bernissartensis ". [16] All other analyses from around the same time have instead found these latter taxa to be within Iguanodontia. [12] [17] The family Hypsilophodontidae is formally defined in the PhyloCode by Daniel Madzia and colleagues in 2021 as "the largest clade containing Hypsilophodon foxii , but not Iguanodon bernissartensis and Rhabdodon priscus ". [16]

Contents

Linnaean usage

Skeleton of Laosaurus consors as drawn by Othniel Marsh (since named Othnielosaurus and later Nanosaurus) Marsh laosaurus.jpg
Skeleton of Laosaurus consors as drawn by Othniel Marsh (since named Othnielosaurus and later Nanosaurus )

Hypsilophodontidae was named originally in 1882 by Louis Dollo, as a family to include Hypsilophodon and other small ornithopods with a single row of teeth, four pedal digits, and a rhomboid sternum. For several decades after its naming the family only included Hypsilophodon. [4] In 1911 Karl von Zittel published a textbook on vertebrate classifications, in which he included multiple genera in "Hypsilophodontidae" (sic for Hypsilophodontidae [18] ), including Hypsilophodon, Nanosaurus , Laosaurus and Dryosaurus . Zittel considered the family to unite all taxa that lacked premaxilla teeth, had a single row of maxilla teeth, neck vertebrae which have flat articulations or a flat front and round back, fused sacral vertebrae, a femur shorter than the tibia, 5 fingered manus' and 4 toed peds. [19] Thescelosaurus was named in 1913 by Charles Gilmore, and its skeleton was described in detail by the same author in 1915. Gilmore had originally classified Thescelosaurus within Camptosauridae, but in the 1915 description he determined that it shared far more features with Hypsilophodontidae. He reclassified Laosaurus, Nanosaurus and Dryosaurus in the family Laosauridae, leaving only Thescelosaurus and Hypsilophodon in Hypsilophodontidae. The characteristics of the family were also re-analysed, and Gilmore showed that the premaxilla actually had teeth, a characteristic of the family; the 3rd manus digit had 4 phalanges; the femur was either shorter or longer than the tibia; and dorsal ribs had only a single articulation point. [18]

Skeleton of Thescelosaurus edmontonensis in display as preserved Thescelosaurus neglectus, CMN.jpg
Skeleton of Thescelosaurus edmontonensis in display as preserved

The first expansive analysis on the relationships of Hypsilophodontidae was that of Swinton in 1936, during a redescription of Hypsilophodon from new specimens. The possible hypsilophodonts Geranosaurus and Stenopelix were removed from the clade (then the subfamily Hypsilophodontinae), and considered to be intermediate basal ornithopods, as there were no features linking them to Hypsilophodon. Thescelosaurus was considered within the family, because of the large number of shared features, as well as Dysalotosaurus , from the Kimmeridgian of Tanzania. Laosaurus and Dryosaurus were not considered hypsilophodonts because of their lack of distinguishable features, as Swinton concluded that they were probably in the family Laosauridae, intermediate between Hypsilophodontidae and Iguanodontidae, and were probably synonyms of each other as well. [20] Charles M. Sternberg (1940) considered there to be multiple genera within the family, all sharing fully enamelled teeth, divided into two subfamilies, Hypsilophodontinae and Thescelosaurinae. Within Hypsilophodontinae–grouped by a longer scapula, thinner forelimb and femora shorter than tibiae–Sternberg included Hypsilophodon, Dysalotosaurus, and Parksosaurus (renaming of Thescelosaurus warreni). Only Thescelosaurus was included in Thescelosaurinae, as it had a tibia shorter than the femur. [21]

Peter M. Galton in 1972 re-studied the relationships of taxa within Ornithischia. Thescelosaurus was removed from Hypsilophodontidae because of its short limbs, meaning it was probably not cursorial, unlike all other hypsilophodonts. The presence of premaxilla teeth, once used to diagnose the group, was found to be present in unrelated taxa like Heterodontosaurus , Protoceratops and Silvisaurus . Galton made Hypsilophodontidae paraphyletic, as he considered Thescelosaurus to be a hypsilophodont, but excluded it from the family Hypsilophodontidae. The phylogenetic hypothesis of Galton is shown below. Taxa considered hypsilophodontids are enclosed by green. [22]

Ornithischia

Cladistic usage

Question of monophyly

In 1992 David Weishampel and Ronald Heinrich reviewed the systematics and phylogenetics of Hypsilophodontidae. Hypsilophodontidae was supported as a monophyletic clade that encompassed "thescelosaurids", Hypsilophodon and Yandusaurus . The family was diagnosed by the absence of ridges that end as denticles in teeth (reversed in Hypsilophodon); presence of a single central ridge on dentary teeth; ossified sternal plates on torso ribs; and a straight and unexpanded shape of the prepubis. Their resulting cladogram is reproduced below: [4]

The following cladogram of hypsilophodont relationships depicts the paraphyletic hypotheses; the "natural Hypsilophodontidae" hypothesis has been falling out of favor since the mid-late 1990s. It is after Brown et al. (2013), the most recent analysis of hypsilophodonts. [17] Ornithischia, Ornithopoda, and Iguanodontia were not designated in their result, and so are left out here. Additional ornithopods beyond Tenontosaurus are omitted. Dinosaurs traditionally described as hypsilophodonts are found from Agilisaurus or Hexinlusaurus to Hypsilophodon or Gasparinisaura.

Skeleton of Convolosaurus (the Proctor Lake hypsilophodont) Proctor Lake hypsilophodont.jpg
Skeleton of Convolosaurus (the Proctor Lake hypsilophodont)

Norman's Hypsilophodontia

A more recent alternate phylogeny, by Norman in 2014, resolved a monophyletic Hypsilophodontia (the family Hypsilophodontidae was not used because of its history). Hypsilophodon grouped with Rhabdodontidae and Tenontosaurus . [2]

Other research

In one analysis in her 2022 review of iguanodontian phylogenetic relationships, Karen E. Poole recovered a large Hypsilophodontidae as the sister taxon of Iguanodontia, which consisted of several "traditional" hypsilophodontids, as well as Thescelosauridae. The Bayesian topology of her phylogenetic analyses is shown in the cladogram below: [23]

The size of Hypsilophodon and the type specimen of Vectidromeus compared to a human Vectidromeus silhouette by Nick Longrich.jpg
The size of Hypsilophodon and the type specimen of Vectidromeus compared to a human

In 2023, Longrich et al. described Vectidromeus as a new genus of hypsilophodontid. Although they did not perform a phylogenetic analysis, they suggested that, since other taxa previously assigned to Hypsilophodontidae had subsequently been moved to other groups, Vectidromeus and Hypsilophodon remained as the only members of the clade. [24]

Related Research Articles

<span class="mw-page-title-main">Ornithischia</span> Extinct clade of dinosaurs

Ornithischia is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure superficially similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith- (ὀρνιθ-), meaning "bird", and ischion (ἴσχιον), meaning "hip". However, birds are only distantly related to this group, as birds are theropod dinosaurs.

<i>Hypsilophodon</i> Extinct genus of dinosaurs

Hypsilophodon is a neornithischian dinosaur genus from the Early Cretaceous period of England. It has traditionally been considered an early member of the group Ornithopoda, but recent research has put this into question.

<span class="mw-page-title-main">Ornithopoda</span> Extinct suborder of dinosaurs

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 small-sized, while advanced members of the subgroup Iguanodontia became quadrupedal and developed large body size. Their major evolutionary advantage was the progressive development of a chewing apparatus that became the most sophisticated ever developed by a non-avian dinosaur, rivaling that of modern mammals such as the domestic cow. They reached their apex of diversity and ecological dominance in the hadrosaurids, before they were wiped out by the Cretaceous–Paleogene extinction event along with all other non-avian dinosaurs. Members are known worldwide.

<i>Valdosaurus</i> Extinct genus of dinosaurs

Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England, Spain and possibly also Romania. It lived during the Early Cretaceous.

Thescelosaurus is an extinct genus of neornithischian dinosaur that lived during the Late Cretaceous period in North America. It was among the last of the non-avian dinosaurs to appear before the entire group went extinct during the Cretaceous–Paleogene extinction event around 66 million years ago. The genus Thescelosaurus is the type genus and also the largest member of the eponymous Thescelosauridae. Adult Thescelosaurus would have measured roughly 3–4 metres (10–13 ft) long and probably weighed several hundred kilograms. It moved on two legs, and its body was counter-balanced by its long tail, which made up half of the body length and was stiffened by rod-like ossified tendons. The animal had a long, low snout that ended in a beak. It had more teeth than related genera, and the teeth were of different types. The hand bore five fingers, and the foot four toes. Thin plates attached to its ribs, the function of which is unknown. It is also unknown to what extent the body was feathered, but at least parts of the legs appear to have been covered in scales.

<i>Notohypsilophodon</i> Extinct genus of dinosaurs

Notohypsilophodon is a genus of ornithopod dinosaur from the Late Cretaceous of Argentina. It was described as the only "hypsilophodont" known from South America, although this assessment is not universally supported, and Gasparinisaura is now believed to have been a basal euornithopod as well.

<i>Parksosaurus</i> Extinct genus of dinosaurs

Parksosaurus is a genus of neornithischian dinosaur from the early Maastrichtian-age Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. It is based on most of a partially articulated skeleton and partial skull, showing it to have been a small, bipedal, herbivorous dinosaur. It is one of the few described non-hadrosaurid ornithopods from the end of the Cretaceous in North America, existing around 70 million years ago.

<i>Alocodon</i> Extinct genus of dinosaurs

Alocodon is a genus of ornithischian dinosaur known from multiple teeth from the Middle or Late Jurassic Cabaços Formation of Portugal, and also the Forest Marble and Chipping Norton Formations of England. A single species is known, A. kuehnei.

<i>Zephyrosaurus</i> Extinct genus of dinosaurs

Zephyrosaurus is a genus of orodromine ornithischian dinosaur. It is based on a partial skull and postcranial fragments discovered in the Aptian-Albian-age Lower Cretaceous Cloverly Formation of Carbon County, Montana, USA. New remains are under description, and tracks from Maryland and Virginia, also in the US, have been attributed to animals similar to Zephyrosaurus. It lived approximately 113 mya.

Trimucrodon is a genus of ornithischian dinosaur from the Late Jurassic Lourinhã Formation of Portugal. The type, and currently only, species is T. cuneatus.

<span class="mw-page-title-main">Neornithischia</span> Extinct clade of dinosaurs

Neornithischia is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the inside of their lower teeth. The teeth wore unevenly with chewing and developed sharp ridges that allowed neornithischians to break down tougher plant food than other dinosaurs.

<i>Kangnasaurus</i> Extinct genus of dinosaurs

Kangnasaurus is a genus of iguanodontian ornithopod dinosaur found in supposedly Early Cretaceous rocks of South Africa. It is known from a tooth and possibly some postcranial remains found in the early-Aptian Kalahari Deposits Formation. It was probably similar to Dryosaurus.

<i>Laosaurus</i> Extinct genus of dinosaurs

Laosaurus is a genus of neornithischian dinosaur. The type species, Laosaurus celer, was first described by O.C. Marsh in 1878 from remains from the Oxfordian-Tithonian-age Upper Jurassic Morrison Formation of Wyoming. The validity of this genus is doubtful because it is based on fragmentary fossils. A second species from the Morrison Formation, L. gracilis, and a species from the late Cretaceous Allison Formation of Alberta, Canada, Laosaurus minimus, are also considered dubious.

<i>Nanosaurus</i> Extinct genus of dinosaurs

Nanosaurus is an extinct genus of neornithischian dinosaur that lived about 155 to 148 million years ago, during the Late Jurassic in North America. Its fossils are known from the Morrison Formation of the south-western United States. The type and only species, Nanosaurus agilis, was described and named by Othniel Charles Marsh in 1877. The taxon has a complicated taxonomic history, largely the work of Marsh and Peter M. Galton, involving the genera Laosaurus, Hallopus, Drinker, Othnielia, and Othnielosaurus, the latter three now being considered to be synonyms of Nanosaurus. It had historically been classified as a hypsilophodont or fabrosaur, types of generalized small bipedal herbivore, but more recent research has abandoned these groupings as paraphyletic and Nanosaurus is today considered a basal member of Neornithischia.

<i>Phyllodon</i> Extinct genus of dinosaurs

Phyllodon was a genus of small ornithischian dinosaur from the Kimmeridgian-aged Upper Jurassic Camadas de Guimarota Formation of Leiria, Portugal and possibly also the Bathonian-aged Chipping Norton Limestone of England. It may have been closely related to contemporaneous dinosaurs in North America.

<span class="mw-page-title-main">Dryosauridae</span> Extinct family of dinosaurs

Dryosauridae was a family of primitive iguanodonts, first proposed by Milner & Norman in 1984. They are known from Middle Jurassic to Early Cretaceous rocks of Africa, Europe, and North America.

<span class="mw-page-title-main">Thescelosauridae</span> Extinct family of dinosaurs

Thescelosauridae is a clade of neornithischians from the Cretaceous of East Asia and North America. The group was originally used as a name by Charles M. Sternberg in 1937, but was not formally defined until 2013, where it was used by Brown and colleagues as the group uniting Thescelosaurus and Orodromeus, based on their phylogenetic results. During a phylogenetic revision of neornithischians by Clint Boyd in 2015, the authorship of Thescelosauridae was given to Brown and colleagues, which meant that the similar name Parksosauridae, informally defined in 2002 by Buchholz, would have had priority over Thescelosauridae. The two clades had slightly different definitions, with Parksosauridae referring to all animals closer to Parksosaurus than Hypsilophodon, but they contained the same taxa so Boyd used Parksosauridae under the assumption it had priority. However, in formalizing the clade following the regulations of the PhyloCode, Madzia, Boyd, and colleagues identified in 2021 that Sternberg was the proper authority for Thescelosauridae, giving it priority over Parksosauridae. As well, they gave Thescelosauridae the definition of the largest clade containing Thescelosaurus neglectus but not Iguanodon bernissartensis, as long as Hypsilophodon foxii was not in the group, modifying previous definitions for Thescelosauridae in order to maintain its modern use, so that the clade was not applied if Thescelosaurus fell within Hypsilophodontidae, a family that has not been recently used but may be revived if the systematic position of Hypsilophodon was solidified at some point in the future. Madzia et al. identified the analysis of Madzia et al. in 2018 as the reference analysis for the name Thescelosauridae, an analysis based on a revised version of the 2015 Boyd analysis.

<i>Owenodon</i> Extinct genus of dinosaurs

Owenodon is a genus of iguanodontian dinosaur known from a partial lower jaw discovered in Early Cretaceous-age rocks of Dorset, United Kingdom, and possibly also Romania and Spain. The first and only definitive specimen was found in the Lulworth Formation of the Purbeck Limestone Group, dating to the middle Berriasian stage. It was first described by Richard Owen as a species Iguanodon, I. hoggii, honouring naturalist A.J. Hogg who had originally collected the fossil. Owen described the mandible as it was, partially embedded in a limestone block, but it was given to the Natural History Museum, London where it was accessioned as NHMUK PV R 2998 and further prepared. Some damage occurred to a tooth crown and part of the bone while stored in the collections. Redescription of I. hoggii by David Norman and Paul Barrett subsequently transferred the species to Camptosaurus in 2002, as well as tentatively referring other camptosaur-like material from the Purbeck beds to the species. The identity of the species was questioned, with Kenneth Carpenter and Yvonne Wilson, and Greg Paul, separating "C." hoggi from Camptosaurus as an intermediate ornithopod, until Peter Galton named the new genus Owenodon for it in 2009. Galton removed the material assigned by Norman and Barrett from Owenodon, but referred isolated teeth from the Bauxite of Cornet, Romania, and the El Castellar Formation of Spain to O. hoggii. The taxon, believed by Galton to be intermediate between Camptosaurus and Iguanodon, is of uncertain relationships, with the limited material preventing clear understanding of its position within ornithopod evolution. Phylogenetic studies have found Owenodon to be more primitive, equivalent to, or more derived than Camptosaurus, but it is often excluded to improve results.

<span class="mw-page-title-main">Elasmaria</span> Extinct clade of dinosaurs

Elasmaria is a clade of ornithopods known from Cretaceous deposits in South America, Antarctica, and Australia that contains many bipedal ornithopods that were previously considered "hypsilophodonts".

<span class="mw-page-title-main">Hadrosauromorpha</span> Extinct clade of dinosaurs

Hadrosauromorpha is a clade 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 formally defined in the PhyloCode as "the largest clade containing Hadrosaurus foulkii, but not Probactrosaurus gobiensis". This results in different taxon inclusion depending on the analysis.

References

  1. ↑ Dollo, L. (1882). "Première note sur les dinosauriens de Bernissart". Bulletin du Musée d'Histoire Naturelle de Belgique. 1: 161–180.
  2. 1 2 3 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. 173: 92–189. doi: 10.1111/zoj.12193 .
  3. ↑ Sues, Hans-Dieter; Norman, David B. (1990). "Hypsilophodontidae, Tenontosaurus, Dryosauridae". In Weishampel, David B.; Dodson, Peter; Osmólska Halszka (eds.). The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 498–509. ISBN   978-0-520-06727-1.
  4. 1 2 3 Weishampel, David B.; Heinrich, Ronald E. (1992). "Systematics of Hypsilophodontidae and Basal Iguanodontia (Dinosauria: Ornithopoda)" (PDF). Historical Biology. 6 (3): 159–184. doi:10.1080/10292389209380426.
  5. ↑ Scheetz, Rodney D. (1998). "Phylogeny of basal ornithopod dinosaurs and the dissolution of the Hypsilophodontidae". Journal of Vertebrate Paleontology. 18 (3, Suppl): 1–94. doi:10.1080/02724634.1998.10011116.
  6. ↑ Winkler, Dale A.; Murry, Phillip A.; Jacobs, Louis L. (1998). "The new ornithopod dinosaur from Proctor Lake, Texas, and the deconstruction of the family Hypsilophodontidae". Journal of Vertebrate Paleontology. 18 (3, Suppl): 87A. doi:10.1080/02724634.1998.10011116.
  7. ↑ Buchholz, Peter W. (2002). "Phylogeny and biogeography of basal Ornithischia". The Mesozoic in Wyoming, Tate 2002. Casper, Wyoming: The Geological Museum, Casper College. pp. 18–34.
  8. ↑ Weishampel, David B.; Jianu, Coralia-Maria; Csiki, Z.; Norman, David B. (2003). "Osteology and phylogeny of Zalmoxes (n.g.), an unusual euornithopod dinosaur from the latest Cretaceous of Romania". Journal of Systematic Palaeontology. 1 (2): 1–56. doi:10.1017/S1477201903001032. S2CID   86339025.
  9. ↑ Norman, David B.; Sues, Hans-Dieter; Witmer, Larry M.; Coria, Rodolfo A. (2004). "Basal Ornithopoda". In Weishampel, David B.; Dodson, Peter; Osmólska Halszka (eds.). The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 393–412. ISBN   978-0-520-24209-8.
  10. ↑ Varricchio, David J.; Martin, Anthony J.; Katsura, Yoshihiro (2007). "First trace and body fossil evidence of a burrowing, denning dinosaur". Proceedings of the Royal Society B: Biological Sciences. 274 (1616): 1361–1368. doi:10.1098/rspb.2006.0443. PMC   2176205 . PMID   17374596.
  11. ↑ Boyd, Clint A.; Brown, Caleb M.; Scheetz, Rodney D.; Clarke, Julia A. (2009). "Taxonomic revision of the basal neornithischian taxa Thescelosaurus and Bugenasaura". Journal of Vertebrate Paleontology. 29 (3): 758–770. doi:10.1671/039.029.0328. S2CID   84273584.
  12. 1 2 Boyd, Clint A. (2015). "The systematic relationships and biogeographic history of ornithischian dinosaurs". PeerJ. 3 (e1523): e1523. doi: 10.7717/peerj.1523 . PMC   4690359 . PMID   26713260.
  13. ↑ Gasulla, José Miguel; Escaso, Fernando; Narváez, Iván; Ortega, Francisco; Sanz, José Luis (2015). "A New Sail-Backed Styracosternan (Dinosauria: Ornithopoda) from the Early Cretaceous of Morella, Spain". PLOS ONE. 10 (12): e0144167. Bibcode:2015PLoSO..1044167G. doi: 10.1371/journal.pone.0144167 . PMC   4691198 . PMID   26673161.
  14. ↑ Butler, Richard J.; Smith, Roger M.H.; Norman, David B. (2007). "A primitive ornithischian dinosaur from the Late Triassic of South Africa, and the early evolution and diversification of Ornithischia". Proceedings of the Royal Society B: Biological Sciences. 274 (1621): 2041–6. doi:10.1098/rspb.2007.0367. PMC   2275175 . PMID   17567562.
  15. ↑ Butler, Richard J.; Upchurch, Paul; Norman, David B. (2008). "The phylogeny of the ornithischian dinosaurs". Journal of Systematic Palaeontology. 6 (1): 1–40. doi:10.1017/S1477201907002271. S2CID   86728076.
  16. 1 2 Madzia, D.; Arbour, V.M.; Boyd, C.A.; Farke, A.A.; Cruzado-Caballero, P.; Evans, D.C. (2021). "The phylogenetic nomenclature of ornithischian dinosaurs". PeerJ. 9: e12362. doi: 10.7717/peerj.12362 . PMC   8667728 . PMID   34966571.
  17. 1 2 Brown, C. M.; Evans, D. C.; Ryan, M. J.; Russell, A. P. (2013). "New data on the diversity and abundance of small-bodied ornithopods (Dinosauria, Ornithischia) from the Belly River Group (Campanian) of Alberta". Journal of Vertebrate Paleontology. 33 (3): 495–520. doi:10.1080/02724634.2013.746229. S2CID   129160518.
  18. 1 2 Gilmore, C.W. (1915). "Osteology of Thescelosaurus, an orthopodous dinosaur from the Lance Formation of Wyoming". Proceedings of the United States National Museum. 49 (2127): 591–616. doi:10.5479/si.00963801.49-2127.591.
  19. ↑ Zittel, K.A. von (1911). Grundzüge der Paläontologie (Paläzoologie) II. Abtielung Vertebrata (in German) (2 ed.). Berlin and München: Druck und verlad von R. Oldenbourg. p. 289.
  20. ↑ Swinton, W.E. (1936). "Notes on the Osteology of Hypsilophodon, and on the Family Hypsilophodontidae". Journal of Zoology. 106 (2): 555–578. doi:10.1111/j.1469-7998.1936.tb08518.x.
  21. ↑ Sternberg, C.M. (1940). "Thescelosaurus edmontonensis, n. sp., and classification of the Hypsilophodontidae". Journal of Paleontology. 14 (5): 481–494. JSTOR   1298552.
  22. ↑ Galton, P.M. (1972). "Classification and Evolution of Ornithopod Dinosaurs". Nature. 239 (5373): 464–466. Bibcode:1972Natur.239..464G. doi:10.1038/239464a0. S2CID   4196759.
  23. ↑ Poole KE (2022). "Phylogeny of iguanodontian dinosaurs and the evolution of quadrupedality". Palaeontologia Electronica. 25 (3). 25.3.a30. doi: 10.26879/702 .
  24. ↑ Longrich, Nicholas R.; Martill, David M.; Munt, Martin; Green, Mick; Penn, Mark; Smith, Shaun (2023-09-13). "Vectidromeus insularis, a new hypsilophodontid dinosaur from the Lower Cretaceous Wessex Formation of the Isle of Wight, England". Cretaceous Research. 154: 105707. doi:10.1016/j.cretres.2023.105707. S2CID   261933503.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.