Marginocephalia

Marginocephalia (/mär′jə-nō-sə-făl′ē-ən/ Latin: margin-head) is a clade of ornithischian dinosaurs that is characterized by a bony shelf or margin at the back of the skull. These fringes were likely used for display. There are two clades included in Marginocephalia: the thick-skulled Pachycephalosauria and the horned Ceratopsia. All members of Marginocephalia were primarily herbivores. They basally used gastroliths to aid in digestion of tough plant matter until they convergently evolved tooth batteries in Neoceratopsia (or "new Ceratopsia") and Pachycephalosauria. Marginocephalia first evolved in the Jurassic Period and became more common in the Cretaceous.[1] They are basally small facultative quadrupeds while derived members of the group are large obligate quadrupeds.[2] Primitive marginocephalians are found in Asia, but the group migrated upwards into North America.[3]

Pachycephalosaurs, or "thick-headed reptiles", have primitive features that include basally small sized bodies, obligate bipedalism, and simple teeth with one row in operation at a time that are replaced as they are worn down. As they evolved, pachycephalosaurs evolved much thicker and advanced skull roofs including dome forms with horn-like ornamentation. Some research suggests these domes were used like helmets for protection while head-butting members in intraspecific combat.[4] Some research suggests their necks were not strong enough to support such an impact.[1] Flat-headed pachycephalosaur speciments have been found in Asia, and there is great controversy on the meaning of these flat heads. Recent research suggests the flat heads could be a juvenile state before developing the dome shape in the adult stage. It could also be evidence of sexual dimorphism with the female being more flat-headed.[5][6]

Ceratopsians, or "horned-faces", differ from pachycephalosaurs in the presence of a rostral bone, or beak. They are also known for having a jugal horn and a thin parietal-squamosal shelf that extends back and up into a frill.[7] This frill could have been used for anchoring jaw muscles, as well as for display.[1] The horns were likely used for establishing dominance, or defending territories.[8] It is also possible they were a factor in sexual display and species recognition. One of the basalmost members of this group is Psittacosaurus, which is one of the most species-rich dinosaur genera from Asia. Ceratopsians later evolved into very large quadrupeds with elaborate facial horns such as Triceratops, Styracosaurus, and Centrosaurus. There was no change in richness of species throughout the Cretaceous before the Cretaceous-Paleogene extinction.[9]

Marginocephalians
Temporal range: Late JurassicLate Cretaceous, 161–66 Ma
Triceratops side view
Skull of Triceratops horridus
Berlin Naturkundemuseum Dino Schaedel
Skull of Stygimoloch spinifer
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Cerapoda
Clade: Marginocephalia
Sereno, 1986
Subgroups

Feeding

Marginocephalians have simple, peg-like teeth surrounded by rhamphoteca, a horny sheath of keratin. The teeth are arranged in batteries for easy replacement and have serrations which may have been useful for cutting up vegetation.[1] Marginocephalia evolved several methods for breaking down vegetation. Pachycephalosaurs had especially large abdomens with broad girths and elongate sacral ribs suggesting the presence of a large stomach. This is presumed to have been useful for breaking down tough vegetation through bacterial fermentation.[10] Another adaptation for advanced vegetation digestion is seen in Ceratopsians, which evolved features to improve their chewing apparatus. Derived ceratopsians have vertical grinding surfaces on their teeth to maximize break-down of tough vegetation.[11] There is also evidence of advanced adductor musculature that extends from a large coronoid process on the mandible up to the ceratopsian frill, which would increase chewing force.[12] Pachycephalosaurs had gastroliths to help in digestion of food, but only primitive ceratopsians, such as Psittacosaurus, have been found to have gastroliths.[13]

Margins and social behavior

Marginocephalian remains reveal significant evidence of being social creatures, much of which is related to the many possible functions of the bony skull margins. Some possible functions of the variably shaped and sized margins are to ward off predators, display, ritualized combat, defense of territory, or establishing social ordering.[14] Both pachycephalosaurs and ceratopsians show evidence of interspecific communication, and there may be evidence of intraspecific communication.[15][16]

Pachycephalosaurs, with their dome-shaped heads, are commonly thought to have used their thick skulls for butting into each other. Their brains and vertebrae are positioned in ways to protect from the impact of head-butting. Also, the columnar structure found in bone remains is consistent with models used to recreate the practice of head-butting.[17] However, some pachycephalosaurs such at Stygimoloch have vascularization in the skull cap that would not have supported head-butting behavior.[18] Thus, the heads could have been used as ornamentation or to butt into the softer flank of other pachycephalosaurs for intraspecific communication or as a form of agonistic behavior.[19]

The frills of ceratopsians are incredibly diverse. They may have been used for protective purposes as the frill sometimes splays over the neck. However, some say that the frill would have provided little protection from other large dinosaurs such as Tyrannosaurus.[20] Other possible functions include intraspecific communication for mating purposes[21] or as a visual display of territorial protection, as seen in many common day organisms such as red-breasted robins.[22] The frills also could have been used for species recognition purposes, as they seem to develop fairly early in life.[15] There has also been evidence that ceratopsians care for their young, as bone-beds have been found of adult individuals with a nest of juveniles,[23] although some refute this as viable evidence of care for young.[24] There have also been bone-beds found with hundreds of adult ceratopsians, indicating herd activity.[25] A few specimens have been found with puncture wounds, supporting the use of horns as protective or combative weapons.[26] Other research examining juvenile ceratopsians reveals a change in horn morphology over time, suggesting frills and horns could have been used for intraspecific communication of age.[27] Horns also could have been used for thermoregulation as indicated by isotope analysis,[28] as aid in knocking down vegetation,[29] or for horn-locking agonistic behavior.[30]

Sexual dimorphism

The study of sexual dimorphism in dinosaurs is incredibly difficult. The varying size and intricacy of margins in Marginocephalia have shown many signs of sexual dimorphism.[14] Although the intricate frills of marginocephalians sometimes seem to present with dimorphic features, many doubt the validity of these claims.[14] Stegoceras validum, a pachycephalosaur, can be segregated into two groups based on the size and shape of their skulls. These two group classifications separated the species population in half, which is highly indicative of sexual dimorphism.[31] However, some report that the two groups may actually represent two separate species.[32] Protoceratops, a type of ceratopsian, also shows signs of sexual dimorphism. However, their frills don't seem to develop until later in life, and may be coordinated with sexual maturity.[33]

Locomotion

In general, primitive marginocephalians were bipedal or facultative quadrupedal, and derived individuals were obligate quadrupedal.[2] This is especially prominent in Ceratopsia, where only the primitive Psittacosaurus is bipedal. All the derived forms were strong quadrupeds, although their stance is controversial. Some think they were fairly columnar, with front limbs erect under the body, which would have been more efficient for speed.[34] Others think the legs were more sprawling, as evidenced by the shape of the forelimb bones.[35] Although not as fast, this posture would have been efficient for grazing vegetation on the ground.[36] Less is known about bipedal pachycephalosaur locomotion, although they must have had a fairly broad girth in order to make room for their enlarged gut.

Classification

The cladogram below follows a 2009 analysis by Zheng and colleagues.[37]

Marginocephalia
Pachycephalosauria

Stenopelix

Wannanosaurus

Goyocephale

Homalocephale

Pachycephalosauridae

Ceratopsia

Micropachycephalosaurus

Chaoyangsaurus

Psittacosauridae

Neoceratopsia

Liaoceratops

Archaeoceratops

Leptoceratopsidae

Coronosauria

Cladogram after Butler et al., 2011.[38]

Marginocephalia
Pachycephalosauria

Wannanosaurus

Goyocephale

Homalocephale

Pachycephalosauridae

Ceratopsia

Micropachycephalosaurus

Chaoyangsaurus

Stenopelix

Yinlong

Psittacosauridae

Neoceratopsia

Liaoceratops

Archaeoceratops

Leptoceratopsidae

Coronosauria

References

  1. ^ a b c d Fastovsky, David E., Weishampel, David B. (2009). Dinosaurs: A Concise Natural History. New York: Cambridge University Press. pp. 110–132. ISBN 978-0-521-88996-4.CS1 maint: Multiple names: authors list (link)
  2. ^ a b Maidment, Susannah C. R.; Linton, Deborah H.; Upchurch, Paul; Barrett, Paul M. (2012-05-22). "Limb-Bone Scaling Indicates Diverse Stance and Gait in Quadrupedal Ornithischian Dinosaurs". PLOS ONE. 7 (5): e36904. Bibcode:2012PLoSO...736904M. doi:10.1371/journal.pone.0036904. ISSN 1932-6203. PMC 3358279. PMID 22666333.open access
  3. ^ Godefroid, Pascal; Lambert, Olivier (2007). "A re-appraisal of Craspedodon llonzeensis DOLLO, 1883 from the Upper Cretaceous of Belgium: the first record of a neoceratopsian dinosaur in Europe?". Sciences de la Terre. 77: 83–93. Retrieved 2016-05-29.
  4. ^ Snively, Eric; Cox, Andres (2008). "Structural Mechanics of Pachycephalosaur Crania Permitted Head-Butting Behavior". Palaeontologia Electronica. 11 (1).
  5. ^ Schott, Ryan K.; Evans, David C.; Goodwin, Mark B.; Horner, John R.; Brown, Caleb Marshall; Longrich, Nicholas R. (2011-06-29). "Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation". PLoS ONE. 6 (6): e21092. Bibcode:2011PLoSO...621092S. doi:10.1371/journal.pone.0021092. ISSN 1932-6203. PMC 3126802. PMID 21738608.
  6. ^ Horner, John R.; Goodwin, Mark B. (2009-10-27). "Extreme Cranial Ontogeny in the Upper Cretaceous Dinosaur Pachycephalosaurus". PLOS ONE. 4 (10): e7626. Bibcode:2009PLoSO...4.7626H. doi:10.1371/journal.pone.0007626. ISSN 1932-6203. PMC 2762616. PMID 19859556.
  7. ^ Dodson, P. (1996). The horned dinosaurs: A natural history. Princeton, NJ: Princeton University Press.
  8. ^ Farlow, James O.; Dodson, Peter (1975-01-01). "The Behavioral Significance of Frill and Horn Morphology in Ceratopsian Dinosaurs". Evolution. 29 (2): 353–361. doi:10.2307/2407222. JSTOR 2407222. PMID 28555861.
  9. ^ Farke, Andrew A. (2011-01-20). "Anatomy and Taxonomic Status of the Chasmosaurine Ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A". PLOS ONE. 6 (1): e16196. Bibcode:2011PLoSO...616196F. doi:10.1371/journal.pone.0016196. ISSN 1932-6203. PMC 3024410. PMID 21283763.
  10. ^ Farlow, James O. (1987-01-01). "Speculations About the Diet and Digestive Physiology of Herbivorous Dinosaurs". Paleobiology. 13 (1): 60–72. JSTOR 2400838.
  11. ^ Varriale, Frank Joseph (2011-01-01). "Dental microwear and the evolution of mastication in ceratopsian dinosaurs". THE JOHNS HOPKINS UNIVERSITY.
  12. ^ Lull, R. S. (1908-05-01). "The cranial musculature and the origin of the frill in the ceratopsian dinosaurs". American Journal of Science. s4-25 (149): 387–399. doi:10.2475/ajs.s4-25.149.387. ISSN 0002-9599.
  13. ^ Weishampel, David B.; Jianu, Coralia-Maria (2011). Transylvanian Dinosaurs. Baltimore: The Johns Hopkins University Press. pp. 123–140. ISBN 9781421400273.
  14. ^ a b c Padian, K.; Horner, J. R. (2011-01-01). "The evolution of 'bizarre structures' in dinosaurs: biomechanics, sexual selection, social selection or species recognition?". Journal of Zoology. 283 (1): 3–17. doi:10.1111/j.1469-7998.2010.00719.x. ISSN 1469-7998.
  15. ^ a b Goodwin, Mark B.; Clemens, William A.; Horner, John R.; Padian, Kevin (2006-03-30). "The smallest known triceratops skull: new observations on ceratopsid cranial anatomy and ontogeny". Journal of Vertebrate Paleontology. 26 (1): 103–112. doi:10.1671/0272-4634(2006)26[103:TSKTSN]2.0.CO;2. ISSN 0272-4634.
  16. ^ Mallon, Jordan C.; Holmes, Robert; Eberth, David A.; Ryan, Michael J.; Anderson, Jason S. (2011-09-01). "Variation in the skull of Anchiceratops (Dinosauria, Ceratopsidae) from the Horseshoe Canyon Formation (Upper Cretaceous) of Alberta". Journal of Vertebrate Paleontology. 31 (5): 1047–1071. doi:10.1080/02724634.2011.601484. ISSN 0272-4634.
  17. ^ Galton, Peter M.; Sues, Hans-Dieter (2011-02-08). "New data on pachycephalosaurid dinosaurs (Reptilia: Ornithischia) from North America". Canadian Journal of Earth Sciences. 20 (3): 462–472. Bibcode:1983CaJES..20..462G. doi:10.1139/e83-043. ISSN 1480-3313.
  18. ^ Goodwin, Mark (2004). "Cranial histology of pachycephalosaurs (Ornithischia: Marginocephalia) reveals transitory structures inconsistent with head-butting behavior". Paleobiology. 30 (2): 253–267. doi:10.1666/0094-8373(2004)030<0253:chopom>2.0.co;2.
  19. ^ Carpenter, Kenneth (1997-12-01). "Agonistic behavior in pachycephalosaurs (Ornithischia, Dinosauria); a new look at head-butting behavior". Rocky Mountain Geology. 32 (1): 19–25. ISSN 1555-7332.
  20. ^ Hone, David W. E.; Wood, Dylan; Knell, Robert J. (2016-01-13). "Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling". Palaeontologia Electronica. 19 (1): 1–13. ISSN 1094-8074.
  21. ^ Hone, David W.e.; Naish, Darren; Cuthill, Innes C. (2012-04-01). "Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs?". Lethaia. 45 (2): 139–156. doi:10.1111/j.1502-3931.2011.00300.x. ISSN 1502-3931.
  22. ^ Dunn, Michael; Copelston, Michael; Workman, Lance (2004-01-01). "Trade-offs and seasonal variation in territorial defence and predator evasion in the European Robin Erithacus rubecula". Ibis. 146 (1): 77–84. doi:10.1111/j.1474-919X.2004.00221.x. ISSN 1474-919X.
  23. ^ Meng, Qingjin; Liu, Jinyuan; Varricchio, David J.; Huang, Timothy; Gao, Chunling (2004-09-09). "Palaeontology: Parental care in an ornithischian dinosaur". Nature. 431 (7005): 145–146. Bibcode:2004Natur.431..145M. doi:10.1038/431145a. ISSN 0028-0836. PMID 15356619.
  24. ^ Isles, Timothy E. (2009-09-01). "The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour" (PDF). Historical Biology. 21 (3–4): 139–214. doi:10.1080/08912960903450505. ISSN 0891-2963.
  25. ^ Qi, Zhao; Barrett, Paul M.; Eberth, David A. (2007-09-01). "Social Behaviour and Mass Mortality in the Basal Ceratopsian Dinosaur Psittacosaurus (early Cretaceous, People's Republic of China)". Palaeontology. 50 (5): 1023–1029. doi:10.1111/j.1475-4983.2007.00709.x. ISSN 1475-4983.
  26. ^ Farke, Andrew A.; Wolff, Ewan D. S.; Tanke, Darren H. (2009-01-28). "Evidence of Combat in Triceratops". PLOS ONE. 4 (1): e4252. Bibcode:2009PLoSO...4.4252F. doi:10.1371/journal.pone.0004252. ISSN 1932-6203. PMC 2617760. PMID 19172995.
  27. ^ Horner, John R (2001-01-01). "Dinosaur Behaviour". eLS. John Wiley & Sons, Ltd. doi:10.1002/9780470015902.a0003318.pub3. ISBN 9780470015902.
  28. ^ Barrick, Reese E.; Stoskopf, Michael K.; Marcot, Jonathan D.; Russell, Dale A.; Showers, William J. (1998-12-28). "The thermoregulatory functions of the Triceratops frill and horns: heat flow measured with oxygen isotopes". Journal of Vertebrate Paleontology. 18 (4): 746–750. doi:10.1080/02724634.1998.10011103. ISSN 0272-4634.
  29. ^ Tait, John; Brown, Barnum (1928-01-01). How the Ceratopsia carried and used their head. Montreal. OCLC 18023726.
  30. ^ Farke, Andrew, A. (2004). "Horn Use in Triceratops (Dinosauria: Ceratopsidae): Testing Behavioral Hypotheses Using Scale Models". Palaeontologia Electronica. 7 (1): 10.
  31. ^ Chapman, Ralph E.; Galton, Peter M.; Sepkoski, J. John; Wall, William P. (1981-01-01). "A Morphometric Study of the Cranium of the Pachycephalosaurid Dinosaur Stegoceras". Journal of Paleontology. 55 (3): 608–618. JSTOR 1304275.
  32. ^ Schott, Ryan K.; Evans, David C.; Goodwin, Mark B.; Horner, John R.; Brown, Caleb Marshall; Longrich, Nicholas R. (2011-06-29). "Cranial Ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): A Quantitative Model of Pachycephalosaur Dome Growth and Variation". PLOS ONE. 6 (6): e21092. Bibcode:2011PLoSO...621092S. doi:10.1371/journal.pone.0021092. ISSN 1932-6203. PMC 3126802. PMID 21738608.
  33. ^ Dodson, Peter (1976-01-01). "Quantitative Aspects of Relative Growth and Sexual Dimorphism in Protoceratops". Journal of Paleontology. 50 (5): 929–940. JSTOR 1303590.
  34. ^ Paul, Gregory S.; Christiansen, Per (2000-06-01). "Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion". Paleobiology. 26 (3): 450–465. doi:10.1666/0094-8373(2000)0262.0.CO;2 (inactive 2019-01-22). ISSN 1938-5331.
  35. ^ Thompson, Stefan; Holmes, Robert (2007). "Forelimb Stance and Step Cycle in Chasmosaurus Irvinenesis (Dinosauria: Neoceratopsia)". Palaeontologia Electronica. 10 (1): 17.
  36. ^ Paul, Gregory S.; Christiansen, Per (2000-06-20). "Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion". Paleobiology. 26 (3): 450–465. doi:10.1666/0094-8373(2000)026<0450:FPINDI>2.0.CO;2. ISSN 0094-8373.
  37. ^ Zheng, Xiao-Ting; You, Hai-Lu; Xu, Xing; Dong, Zhi-Ming (19 March 2009). "An Early Cretaceous heterodontosaurid dinosaur with filamentous integumentary structures". Nature. 458 (7236): 333–336. Bibcode:2009Natur.458..333Z. doi:10.1038/nature07856. PMID 19295609.
  38. ^ Richard J. Butler, Jin Liyong, Chen Jun, Pascal Godefroit (2011). "The postcranial osteology and phylogenetic position of the small ornithischian dinosaur Changchunsaurus parvus from the Quantou Formation (Cretaceous: Aptian–Cenomanian) of Jilin Province, north-eastern China". Palaeontology. 54 (3): 667–683. doi:10.1111/j.1475-4983.2011.01046.x.CS1 maint: Multiple names: authors list (link)
Agilisaurus

Agilisaurus (; 'agile lizard') is a genus of ornithischian dinosaur from the Middle Jurassic Period of what is now eastern Asia. The name is derived from the Latin "agilis" meaning 'agile' and the Greek "sauros" meaning 'lizard', and refers to the agility suggested by its lightweight skeleton and long legs. Its tibia (lower leg bone) 207.0 mm in length, was longer than its femur (upper leg bone) 199.0 mm in length, which indicates that it was an extremely fast bipedal runner, using its long tail for balance, although it may have walked on all fours when browsing for food. It was a small herbivore, about 2 meters (6.5 feet) in length, and like all ornithischians, it had a beak-like structure on the ends of both upper and lower jaws to help it crop plant material.

Averostra

Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.

Avetheropoda

Avetheropoda, or "bird theropods", is a clade that includes carnosaurians and coelurosaurs to the exclusion of other dinosaurs.

Cerapoda

Cerapoda ("ceratopsians and ornithopods") is a clade of the dinosaur order Ornithischia.

Changchunsaurus

Changchunsaurus (meaning "Changchun lizard") is an extinct genus of small herbivorous parksosaurid dinosaur from Early Cretaceous deposits of Gongzhuling, Jilin, China. It is the first named dinosaur genus from Jilin.

Dinosauriformes

Dinosauriformes is a clade of archosaurian reptiles that include the dinosaurs and their most immediate relatives. All dinosauriformes are distinguished by several features, such as shortened forelimbs and a partially to fully perforated acetabulum, the hole in the hip socket traditionally used to define dinosaurs. The oldest known member is Asilisaurus, dating to about 245 million years ago in the Anisian age of the middle Triassic period.

Evolution of dinosaurs

This article gives an outline and examples of dinosaur evolution. For a detailed list of interrelationships see Dinosaur classification.

Dinosaurs evolved within a single lineage of archosaurs 243-233 Ma (million years ago) from the Anisian to the Carnian ages, the latter part of the middle Triassic. Dinosauria is a well-supported clade, present in 98% of bootstraps. It is diagnosed by many features including loss of the postfrontal on the skull and an elongate deltopectoral crest on the humerus.In March 2017, scientists reported a new way of classifying the dinosaur family tree, based on newer and more evidence than available earlier. According to the new classification, the original dinosaurs, arising 200 million years ago, were small, two-footed omnivorous animals with large grasping hands. Descendants (for the non-avian dinosaurs) lasted until 66 million years ago.

Genasauria

Genasauria is a clade of extinct beaked, primarily herbivorous dinosaurs. Paleontologist Paul Sereno first named Genasauria in 1986. The name Genasauria is derived from the Latin word gena meaning ‘cheek’ and the Greek word saúra (σαύρα) meaning ‘lizard.’ Genasauria is the most inclusive clade within the order Ornithischia. According to Sereno (1986), Genasauria represents all ornithischians except for the most primitive ornithischian, Lesothosaurus. Sereno’s formal definition is, “Ankylosaurus, Triceratops, their most recent common ancestor and all descendants.” It is hypothesized that Genasauria had diverged from Lesothosaurus by the Early Jurassic. Cranial features that characterize Genasauria include a medial offset of the maxillary dentition, a sprout-shaped mandibular symphysis, moderately sized coronoid process, and an edentulous (without teeth) anterior portion of the premaxilla. A distinguishing postcranial feature of Genasauria is a pubic peduncle of the ilium that is less robust than the ischial peduncle.

Genasauria is commonly divided into Neornithischia and Thyreophora. Neornithischia is characterized by asymmetrical distributions of enamel covering the crowns of the cheek teeth, an open acetabulum, and a laterally protruding ischial peduncle of the ilium. Neornithischia includes ornithopods, pachycephalosaurs, and ceratopsians. Thyreophora is characterized by body armor and includes stegosaurs, ankylosaurs, Scelidosaurus, and Scutellosaurus.

Haya griva

Haya is an extinct genus of basal neornithischian dinosaur known from Mongolia.

Jeholosauridae

Jeholosaurids were herbivorous neornithischian dinosaurs from the Cretaceous Period (Aptian - Santonian, with a possible Campanian record) of Asia. The family was first proposed by Han et al. in 2012. The jeholosaurids were defined as those ornithischians more closely related to Jeholosaurus shangyuanensis than to Hypsilophodon foxii, Iguanodon bernissartensis, Protoceratops andrewsi, Pachycephalosaurus wyomingensis, or Thescelosaurus neglectus. The Jeholosauridae includes the type genus Jeholosaurus and Yueosaurus.

Jeholosaurus

Jeholosaurus is a genus of ornithischian dinosaur from the Early Cretaceous Period. It is thought to have been a herbivorous small ornithopod.

Jingshanosaurus

Jingshanosaurus (meaning "Jingshan lizard") is a genus of sauropodomorph dinosaurs from the early Jurassic period.

Neornithischia

Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. They are 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. Neornithischians include a variety of basal forms historically known as "hypsilophodonts", including the Parksosauridae; in addition, there are derived forms classified in the groups Marginocephalia and Ornithopoda. The former includes clades Pachycephalosauria and Ceratopsia, while the latter typically includes Hypsilophodon and the more derived Iguanodontia.

Neotheropoda

Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.

Orionides

Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.

Ornithischia

Ornithischia () is an extinct clade of mainly herbivorous dinosaurs characterized by a pelvic structure similar to that of birds. The name Ornithischia, or "bird-hipped", reflects this similarity and is derived from the Greek stem ornith- (ὀρνιθ-), meaning "of a bird", and ischion (ἴσχιον), plural ischia, meaning "hip joint". However, birds are only distantly related to this group as birds are theropod dinosaurs.Ornithischians with well known anatomical adaptations include the ceratopsians or "horn-faced" dinosaurs (e.g. Triceratops), armored dinosaurs (Thyreophora) such as stegosaurs and ankylosaurs, pachycephalosaurids and the ornithopods. There is strong evidence that certain groups of ornithischians lived in herds, often segregated by age group, with juveniles forming their own flocks separate from adults. Some were at least partially covered in filamentous (hair- or feather- like) pelts, and there is much debate over whether these filaments found in specimens of Tianyulong, Psittacosaurus, and Kulindadromeus may have been primitive feathers.

Unaysauridae

Unaysauridae is a family of basal sauropodomorphs from the Late Triassic of India and Brazil.

Yinlong

Yinlong (隱龍, meaning "hidden dragon") is a genus of basal ceratopsian dinosaur from the Late Jurassic Period of central Asia. It was a small, primarily bipedal herbivore. Yinlong is the oldest and most primitive ceratopsian known.

Yueosaurus

Yueosaurus is an extinct genus of basal ornithopod dinosaur known from Zhejiang Province, China.

Marginocephalia (Pachycephalosauria and Ceratopsia)

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