Figure 10.22. Cladogram of Hadrosauridae. Derived characters include: at I three or more replacement teeth per tooth position, posterior extension of the dentary tooth row to behind the apex of the coronoid process, absence of the surangular foramen, absence or fusion of the supraorbital to the orbit rim, long coracoid process, dorsoventrally narrow proximal scapula, very deep, often tunnel-like intercondylar extensor groove; at 2 absence of the coronoid bone, reduction in surangular contribution to coronoid process, double-layered premaxillary oral margin, triangular occiput, eight or more sacral vertebrae, reduced carpus, fully open pubic obturator foramen, absence of distal tarsals II and III; at 3 maxilla lacking an anterior process but developing a sloping dorsal shelf, groove on the posterolateral process of the premaxilla, low maxillary apex, a parietal crest less than half the length of the supratemporal fenestrae; at 4 presence of a caudal margin on the circumnarial fossa.

Figure 10.22. Cladogram of Hadrosauridae. Derived characters include: at I three or more replacement teeth per tooth position, posterior extension of the dentary tooth row to behind the apex of the coronoid process, absence of the surangular foramen, absence or fusion of the supraorbital to the orbit rim, long coracoid process, dorsoventrally narrow proximal scapula, very deep, often tunnel-like intercondylar extensor groove; at 2 absence of the coronoid bone, reduction in surangular contribution to coronoid process, double-layered premaxillary oral margin, triangular occiput, eight or more sacral vertebrae, reduced carpus, fully open pubic obturator foramen, absence of distal tarsals II and III; at 3 maxilla lacking an anterior process but developing a sloping dorsal shelf, groove on the posterolateral process of the premaxilla, low maxillary apex, a parietal crest less than half the length of the supratemporal fenestrae; at 4 presence of a caudal margin on the circumnarial fossa.

collectively dubbed Euhadrosauria. Immediately outside Euhadrosauria but within Hadrosauridae are Telmatosaurus and probably Bactrosaurus, Claosaurus, and Tanius. Euhadrosaurian hadrosaurids are united by several changes in the skull (among them, absence of a coronoid bone, modification of the oral margin of the premaxilla, triangular form to the back of the skull), eight or more sacral vertebrae, and alteration of the hand, pelvis, and ankle.

Features uniting Lambeosaurinae, the clade of "hollow-crested" hadrosaurids, are all associated with modifications of the skull having to do with the evolution of the nasal cavity into a supracranial crest. Most basal among lambeosaurines is Tsintaosaurus, which had first been considered a hadrosaurine, but is now known to possess key lambeo-saurine features. Lambeosaurines above Tsintaosaurus - Parasaurolophus, Corythosaurus, Hypacrosaurus, and Lambeosaurus - are united by additional

Ornithopods meet history: a short account of their discovery changes in the supracranial crest and an increase in height of the neural spines of the back vertebrae. Among the four last-mentioned lambeo-saurines, relationships include Parasaurolophus as the basal taxon and Corythosaurus, Hypacrosaurus, and Lambeosaurus sharing closest, but still not yet fully resolved relationships.

The phylogenetic relationships of hadrosaurines are currently not well supported. The clade itself is united by a single feature of the expression of the external nares on the snout. The basal hadrosaurine appears to be Lophorhothon, with a succession of yet higher clades that includes one formed of Naashoibitosaurus, Saurolophus, and an Argentinean form referred to Kritosaurus, and the other consisting of successively more exclusive relationships among Prosaurolophus, Gryposaurus, Edmontosaurus, Brachylophosaurus, and Maiasaura.

In addition, there is a host of hadrosaurids that - for one reason or another, mostly having to do with their incomplete preservation - are yet unresolved at the highest reaches of the iguanodontian tree. These include Gilmoreosaurus, Tanius, Jaxartosaurus, Aralosaurus, Barsboldia, and Nipponosaurus from Asia, Secernosaurus from South America, and Hadrosaurus and Kritosaurus from North America. As always, further discoveries and careful research will most likely provide us with that important bit of information to place these wayward ornithopods in their phylogenetic context.

In 1822, Gideon and Mary Ann Mantell discovered peculiar-looking teeth from the Wealden beds of the Tilgate Forest in what is now West Sussex, England. These teeth, later given the name Iguanodon (iguana -lizard; don - teeth) by Gideon Mantell in 1825, provided humans with their first inkling of some of the behemoth denizens of the Mesozoic. From that time forward, Iguanodon fossils began to accumulate in Mantell's and other collections - teeth, jaws, limb bones, and vertebrae, and a number of English paleontologists, among them T. H. Huxley, R. Owen, and Mantell himself, set about the task of studying them. Out of their work came a picture of dinosaurs, ornithopods among them, as gigantic (estimated length in excess of 35 m), pachy-dermoid reptiles that walked on all fours in the most lumbering fashion. In keeping with this picture, a spike-like bone found with Iguanodon remains was fitted to its nose, which gave the dinosaur a profile like a modern rhinoceros.

Nearly a quarter century later and some 6000 km across the Atlantic Ocean, Joseph Leidy of the Academy of Natural Sciences of Philadelphia obtained some large bones from a quarry in Upper Cretaceous marls in nearby Haddonfield, New Jersey. These fossils, named Hadrosaurus (hadro -stout) by Leidy in 1858, created quite a stir in the mid-1800s, in part because they settled some important early issues about dinosaur biology. For example, Leidy used the disparity in length between the fore- and hindlimb to argue that Hadrosaurus (and by inference Iguanodon) walked predominantly on its hindlimbs. But even more important - and influential -Hadrosaurus was the first dinosaur to be mounted and exhibited to the public. It is said that attendance sky-rocketed at the museums where the 10 m long Hadrosaurus was displayed; dinosaurs have always been big draws.

Thereafter through the turn of the nineteenth century, there was to be a flurry of activity on both sides of the Atlantic. In 1869, Huxley and P. Matheron, respectively, were to name two relatively small (2-3 m long) ornithopods: Hypsilophodon (hypsi - high; loph - crest) from the same beds as Iguanodon, but from the Isle of Wight off the southern coast of England, and Rhabdodon (rhabdo - ribbon) from the Late Cretaceous of southern France.

However important these discoveries were to become, almost everything was eclipsed in 1878 by the recovery of complete and multitudinous (an unbelievable 31, to be exact) Iguanodon skeletons from a coal seam some 300 m beneath the small mining town of Bernissart in southern Belgium. Over the next seven years, Louis Dollo, curator of paleontology at the Institut Royal de Science Naturelle de Belgique in Brussels, described and interpreted this Bernissart bonanza (Figure 10.23). His studies focused on the new anatomical information provided by the material, on the taxonomic composition of the assemblage (two species of Iguanodon), on the size and posture of the body (7-10 m long; bipedal posture much like that of Hadrosaurus from New Jersey), and on the functional significance of particular skeletal elements (the spike went on the hand, not the nose.).

Turning back to North America, it was the opening of the Western Interior of the USA to paleontological exploration that prompted further discoveries during the last three decades of the 1800s. In short order, discovery in 1872 of new hadrosaurid material from Late Cretaceous age beds of Kansas (subsequently dubbed Claosaurus (klao - break) by O. C. Marsh in 1890) was followed by the 1885 announcement of Camptosaurus (kamptos - flexible), a new, medium-sized (5-7 m long) ornithopod dinosaur from the Upper Jurassic Morrison Formation of Wyoming. Nine years later, in 1894, Marsh again described a new ornithopod, this time a smaller contemporary of Camptosaurus, which he named Dryosaurus (dryos - oak).

The close of the nineteenth century marked a major turnover in dinosaur paleontologists; E. D. Cope died in 1896 and Marsh in 1899 (see Box 6.2). The new generation of dinosaur researchers of the first quarter of the twentieth century was to make an outstanding series of discoveries, particularly in newly explored regions of North America, but also in Asia, Africa, and South America. The first discoveries of the 1900s, however, were made not here, but in Transylvania, in the foothills of the Southern Carpathian Mountains. Here, dinosaur fossils found on the estate of the Nopcsa family were described by F. Nopcsa in 1900 as Limnosaurus (limnos - lake). Because this name had been used previously for a fossil crocodile, Limnosaurus was renamed Telmatosaurus (telmat -swamp) by Nopcsa in 1903.

Thereafter, the first quarter-century of the 1900s saw a mushrooming of ornithopod discoveries. Of the 11 new lands of ornithopod dinosaurs, all but three were collected from the small, but rich, badlands

Figure ! 0.23. Several death-posed Iguanodon, the great beast of Bernissart, Belgium.

of Upper Cretaceous rocks along the Red Deer River of Alberta, Canada, during the Great Canadian Dinosaur Rush. Floating on log rafts and dragging horse-drawn wagons, B. Brown excavated a host of now-classic hadrosaurids, including Saurolophus (lophus - crest) in 1912, Hypacrosaurus (hypakros - highest, referring to spines) in 1913, Corythosaurus (koryth -crown) in 1914, and Prosaurolophus (pro - before) in 1916. Close behind were two Canadian dinosaur paleontologists, L. M. Lambe and W. A. Parks. Lambe's discoveries include Gryposaurus (grypos - hooked), named in 1914, and Edmontosaurus (from Edmonton), named in 1920, while Parks christened Parasaurolophus (para - near) in 1922 and Lambeosaurus (after Lambe) in 1923. He also described a new ornithopod (as a new species of Thescelosaurus; see below), which in 1937 C. M. Sternberg renamed Parksosaurus (after Parks).

Elsewhere in the world, only three other ornithopods were described over this 20 year period. Prior to his exceptionally rewarding travels in Alberta, Brown spent time collecting ornithopod dinosaurs in the region of the San Juan Basin, New Mexico. From there, he described a new hadrosaurid, Kritosaurus (kritos - separate), in 1910. Thescelosaurus (theskelos - astonishing), a basal euornithopod, was discovered in Upper Cretaceous rocks of Wyoming by C. W. Gilmore in 1913, while Lycorhinus (lykos - wolf; rhinus - snout) - originally thought to be a synapsid but now known to be a heterodontosaurid ornithopod - was collected from Lower Jurassic rocks of South Africa and described by S. H. Haughton in 1924.

The second quarter-century produced a host of discoveries from elsewhere in the world, principally Asia and Australasia. Tanius (named for H.-C. Tan, the Chinese geologist who discovered its remains), a flat-headed hadrosaurid from China, was described by C. Wiman in 1929. F. von Huene, renowned dinosaur paleontologist from Tübingen, Germany, announced Fulgurotherium (fulgur - lightning; therion - beast, referring to

Lightning Ridge) from Lower Cretaceous rocks of New South Wales, Australia, in 1932; unfortunately it was regarded as a theropod dinosaur until the 1980s, when it was re-examined by R. E. Molnar. It is now properly regarded as a non-iguanodontian ornithopod.

With the 1930s came the first descriptions of ornithopod dinosaurs from the Central Asiatic Expeditions. Bactrosaurus (baktron - club, referring to vertebrae) and Mandschurosaurus (from Manchuria) - two hadrosaurids from the Late Cretaceous of the Inner Mongolian region of China - were described by Gilmore in 1933. The Inner Mongolian Mandschurosaurus was renamed Gilmoreosaurus in 1979 by M. K. Brett-Surman in honor of Gilmore's efforts to understand these first hadrosaurids from the Gobi Desert.

Although not so well known as the Gobi discoveries, there are dinosaurs from elsewhere in Asia. Nipponosaurus (Nippon is the Japanese name for their country), the first and most famous hadrosaurid from Japan, was named by T. Nagao in 1936, while Jaxartosaurus (from the Jaxartes River, Kazakhstan) was described by A. N. Riabinin in 1939. Upper Cretaceous beds of the Kazakhstan desert were to produce other ornithopod dinosaurs, as we will see.

To round out the first half of the twentieth century, R. S. Lull and N. E. Wright presented the first summary and revision of any of the ornithopod groups, this time for North American hadrosaurids, in 1942. Their work covered hadrosaurid anatomy, paleoecology, and taxonomy. Like similar earlier treatments of ceratopsians, stegosaurs, and thero-pods, this work was to become a landmark study for generations to come.

The years since 1950 have been marked by a healthy mixture of discovery, reflection, and revision on a worldwide scale. Beginning in Asia, studies published in the early 1950s by A. K. Rozhdestvensky introduced a new species of Saurolophus, this time from Mongolia, and a new iguanodontian from the Early Cretaceous, also from Mongolia. Originally named Iguanodon orientalis, this form is now known as Altirhinus, thanks to research by Norman published in 1998. Also from Asia came Tsintaosaurus (from Tsintao), described by C.-C. Young in 1958. This Late Cretaceous hadrosaurid from Shandong, China, is truly one of the most unusual, sporting a unicorn-type horn from the top of its skull.

Elsewhere, work continued on the dinosaurs collected at the beginning of the century in Tendaguru, Tanzania (see Box 11.1). In 1955, W. Janensch began publishing work on his new ornithopod Dysalotosaurus (dysalotos - uncatchable, later to be referred to Dryosaurus).3 And back in North America, a new hadrosaurid from the Late Cretaceous of Alberta was described as Brachylophosaurus (brachys - short) by Sternberg in 1953, while further south and to the east W. Langston Jr

3 There is a double entendre in this fossil's name.The name Dysalotosaurus - ("uncatchable lizard") is sometimes thought to be a reference to its gracile, sleek, morphology, but in fact the species name, lettowvorbecki, suggests the real intent behind the name. A World War I German general, Paul Emil von Lettow-Vorbeck stationed in Tanzania, proved uncatchable to pursuing British and South African armies. In 1919 (just after the end ofWord War I), the unrepentant German paleontologist, H. Virchow, in naming thisTanzanian dinosaur; celebrated this fact with its name.

christened Lophorhothon (rhothon - nose), a new hadrosaurid from the Late Cretaceous of Alabama.

In 1962, A. W. Crompton and A.J. Charig announced a new, and quite peculiar form, Heterodontosaurus (heteros - different; odont - tooth). This creature with tusks and molar-like teeth from the Early Jurassic of South Africa has been in and out of skirmishes over its affinities within Ornithischia, but now appears to be secure as an ornithopod. Most importantly for early ornithopods, Heterodontosaurus is now known from virtually complete skulls and an exquisite skeleton.

Later that decade, results of the Sino-Soviet Paleontological Expedition in China became available. The first ornithopod to come from these efforts, Probactrosaurus was described by Rozhdestvensky in 1966. Hailing from the Early Cretaceous of Inner Mongolia, China, Probactrosaurus has featured widely in discussions of the ancestry of Hadrosauridae and has recently been redescribed by Norman. Hadrosaurids also received a new member, in the form of Aralosaurus (from the Upper Cretaceous Aral region of Kazakhstan), described by Rozhdestvensky in 1968.

Finally, from the close of the 1960s throughout the early 80s, P. M. Galton began what can only be called a tour de force on ornithopod osteology, taxonomy, and phylogeny. A virtual one-man-show, Galton was eventually to take on: reconstructions of the limb musculature, locomotor mechanics, jaw mechanics, and feeding in several euornithopods; taxonomic revisions and redescriptions of Parksosaurus, Hypsilophodon, Thescelosaurus, and Dryosaurus; the naming of new taxa (Othnielia (for Othniel Charles Marsh), from the Late Jurassic of Colorado, Utah, and Wyoming, Valdosaurus (valdus - Weald, from the Wealden deposits) from the Early Cretaceous of England and Niger, and Bugenasaura (see below); and the paleobiogeographical and evolutionary patterns in the entire ornithopod group.

Although Galton's work on such a diverse array of ornithopods dominated from the end of the 1960s until the advent of cladistic approaches to phylogeny reconstruction (Chapter 3), a host of discoveries throughout this interval added important new information on ornithopod diversity. Indeed, the 1970s were to see more discoveries than even during the most prolific times of the Canadian Dinosaur Rush. J. H. Ostrom started the ball rolling in 1970 with Tenontosaurus (tenon -tendon), an Early Cretaceous ornithopod from Montana whose affinities have been of some contention, but which is now regard a basal iguano-dontian. Halfway around the world was discovered Shantungosaurus, a gigantic hadrosaurid described in 1973 by S. Hu from the Late Cretaceous of Shandong, China.

Two new heterodontosaurids were also announced in 1975. The first, by C. E. Gow, was named Lanasaurus (lana - wooly; named to honor Harvard University's A. W. Crompton, whose nickname is "Fuzz"). Like Heterodontosaurus, Lanasaurus also comes from the Early Jurassic of South Africa. The second heterodontosaurid, named Abrictosaurus (abriktos -awake) by Hopson in 1975, hails from similar Lower Jurassic rocks of both

South Africa and neighboring Lesotho. Unlike Heterodontosaurus, these two new forms are known from only fragmentary skull material.

Further to the north on the African continent, we shift from het-erodontosaurids to iguanodontians, for in 1976 P. Taquet announced the peculiar, high-spined Ouranosaurus (in Nigerian, ourane - brave). This ornithopod, from the Early Cretaceous of Niger, bears only a modest similarity to Iguanodon and has been pivotal to some of the more recent discussions of ornithopod phylogeny.

The new ornithopods of 1979 came shotgun-style from three of the four corners of the globe: from China, Argentina, and the USA. From the Middle Jurassic of Sichuan, China, the new basal euornithopod Yandusaurus (Chinese: yan - salt; du - capital), was described by X.-L. He. Secernosaurus (secerno - divide), the first hadrosaurid from the Southern Hemisphere, was announced by Brett-Surman from Upper Cretaceous beds of Rio Negro, Argentina. And Horner and R. Makela stunned the world with Maiasaura (maia - good mother), a hadrosaurid from the Late Cretaceous of Montana, whose remains included adult and hatchling specimens provided the first inkling of parental care in dinosaurs.

The unleashing of new ornithopods slowed down only slightly during the 1980s. In North America, Zephyrosaurus (Zephyros, Greek god of the west wind) was an Early Cretaceous basal euornithopod described by H.-D. Sues in 1980, while Orodromeus (oros - mountain; dromeus -runner), another basal euornithopod, was named by Horner and Weishampel in 1988. Both species come from Montana. In Asia, we were introduced to Barsboldia (named for Mongolian paleontologist R. Barsbold by T. Maryanslca and H. Osmolska in 1981), a hadrosaurid from the Late Cretaceous of Mongolia, and Gongbusaurus (Chinese, gong -worker; bu - board; referring to Board of Works), a Late Jurassic euornithopod from Sichuan and Xinjiang provinces, China described by Z.-M. Dong and colleagues in 1983. Australia had a boom decade for ornithopods during the 1980s, with Muttaburrasaurus (from Muttaburra, described by A. Bartholomai and R. E. Molnar in 1981), an iguanodontian from the Early Cretaceous of Queensland, and Atlascopcosaurus (for Atlas Copco Co., which supplied excavation equipment) and Leaellynasaura (for Leaellyn Rich, who helped in the discovery), two euornithopods from the Early Cretaceous of Australia that were described in 1989 by T. H. Rich and P. Vickers-Rich. Ten years later, Rich and Vickers-Rich were to announce the existence of another basal euornithopod from the Early Cretaceous of Australia - Qantassaurus (named for Qantas, the Australian airline) - in 1999.

As important as it is to find new taxa, other studies tackled important problems of ornithopod paleobiology and evolution. P. Dodson and Norman separately began to create inroads into these problems in 1980 by redescribing ornithopod anatomy and questioning aspects of ornithopod systematics (Dodson on Camptosaurus and Tenontosaurus, Norman on Iguanodon). Also in 1984, the time was right for full-blown cladistic interpretations of ornithopod phylogeny: Norman and Sereno published cladistic analyses that included ornithopod dinosaurs and both researchers followed up these earlier studies with more detailed work in 1986.

The 1990s continued the march to find new ornithopods and to understand their place in the Mesozoic world. By mid-decade, we had Agilisaurus (agili - agile), Drinker (named in honor of Edward Drinker Cope), and Bugenasaura ("large cheeked lizard"), all basal euornithopods, the first described by Q. Pang from the Middle Jurassic of Sichuan, China, the second by R. T. Bakker and co-workers from the Late Jurassic of Wyoming, and the last by Galton from the Late Cretaceous of the western USA. Three hadrosaurids were also christened over this same time. Two come from the Late Cretaceous of New Mexico - Anasazisaurus ("Anasazi lizard") and Naashoibitosaurus ("Naashoibito lizard"; both described by A.-P. Hunt and S. Lucas) and the third discovered from Upper Cretaceous rocks of Siberian Russia, named Amurosaurus (for the Amur River, which forms part of the boundary between Russia and China) by Y. Bolotsky and S. Kurzanov.

By the close of the century, another five ornithopods were to be named. Two were non-iguanodontian ornithopods from the Late Cretaceous of Argentina: Gasparinisaura (named for Zulma Gasparini, Argentinean specialist on extinct crocodilians; Gasparinisaura was originally thought to be a basal iguanodontian) named by R. A. Coria and L. Salgado, and Notohypsilophodon (noto - southern) described by Martinez. The rest, basal iguanodontians all, have had much to say about the phylogeny of this group, particularly as relates to hadrosaurid origins. These include: Eolambia ("dawn lambeosaur") from the Early Cretaceous of Utah, named by J. J. Kirkland; Protohadros ("first hadrosaur") from the early Late Cretaceous of Texas, named by Head; and Lurdosaurus ("heavy lizard"), a massive form that lived with Ouranosaurus in the Early Cretaceous of what is now Niger, described by P. Taquet and D. A. Russell.

This first decade of the new millennium has hardly started and ornithopod discoveries still abound. China is once again proving its richness: Charonosaurus (named for Charon, the boatman in Greek mythology who ferried the souls of the dead across the River Styx to Hades), a lambeosaurine described by P. Godefroit and colleagues from the Late Cretaceous of northern China; Nanyangosaurus (named for Nanyang in Henan Province, where this iguanodontian was discovered) and Jinzhousaurus (named for Jinzhou, the large area in western Liaoning Province), both from the Early Cretaceous of China and both close to hadrosaurid origins, the former named by X. Xu and colleagues and the latter by X. Wang and Xu. Another ornithopod, Jeholosaurus ("Jehol lizard") comes from the Lower Cretaceous rocks in China that have yielded the feathered dinosaurs (see Chapter 14); it was described by Xu and colleagues.

Two other ornithopods - from Europe - have been described so far in the first years of the 2000s. Draconyx ("dragon claw"), a basal iguanodontian described by 0. Mateus and M. An tunes, comes from the Late Jurassic of Portugal. And Zalmoxes (named for the Dacian deity Zalmoxes), known since the time of Nopcsa as Rhabdodon, is the sister-group to

Iguanodontia described by Weishampel and colleagues from the Late

Cretaceous of Romania.

The last of the so far known millennial ornithopods is Planicoxa

("flat hipbone"), an iguanodontian from the Early Cretaceous of Utah, described by T. DiCroce and K. Carpenter.

Important readings Dodson, P. 1975. Taxonomic implications of relative growth in lambeo-

saurine hadrosaurids. Systematic Zoology, 24,37-54.

Galton, P. M. 1974. The ornithischian dinosaur Hypsilophodon from the Wealden of the Isle of Wight. Bulletin of the British Museum (Natural History) Geology, 25,1-152.

Hopson, J. A. 1975. The evolution of cranial display structures in hadrosaurian dinosaurs. Paleobiology, 1, 21-43.

Horner, J. R. 1984. The nesting behavior of dinosaurs. Scientific American, 250,130-137.

Horner, J. R., Weishampel, D. B. and Forster, C. A. 2004. Hadrosauridae. In Weishampel, D. B., Dodson, P. and Osmolska, H. (eds.), The Dinosauria, 2nd edn. University of California Press, Berkeley, pp. 438-463.

Lull, R. S. and Wright, N. E. 1942. Hadrosaurian dinosaurs of North America. Geological Society of America Special Paper 40, pp. 1-242.

Norman, D. B. 1980. On the ornithischian dinosaur Iguanodon bernissartensis from the Lower Cretaceous of Bernissart (Belgium). Institut Royal de Science Naturelle de Belgique, Mémoire, 178,1-103.

Norman, D. B. 1986. On the anatomy of Iguanodon atherfieldensis (Ornithischia: Ornithopoda). Bulletin, Institut Royal de Science Naturelle de Belgique, Science de la Terre, 56, 281-372.

Norman, D. B. 2004. Basai Iguanodontia. In Weishampel, D. B., Dodson, P. and Osmôlslca, H. (eds.), The Dinosauria, 2nd edn. University of California Press, Berkeley, pp. 413-437.

Norman, D. B., Sues, H.-D., Coria, R. A. and Witmer, L. M. 2004. Basai Ornithopoda. In Weishampel, D. B., Dodson, P., and Osmôlslca, H. (eds.), The Dinosauria, 2nd edn. University of California Press, Berkeley, pp. 393-412.

Ostrom, J. H. 1961. Cranial morphology of the hadrosaurian dinosaurs of North America. Bulletin of the American Museum of Natural History, 122, 33-186.

Taquet, P. 1976. Géologie et paléontologie du gisement de Gadoufaoua (Aptien du Niger). Cahiers de Paléontologie, pp. 1-191.

Weishampel, D. B. 1984. The evolution of jaw mechanisms in ornithopod dinosaurs. Advances in Anatomy, Embryology and Cell Biology, 87,1-110.

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