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(Redirected from Hadrosaur)
'Hadrosaurids' or 'duck-billed' dinosaurs are members of the family 'Hadrosauridae', and include ornithopods such as ''Edmontosaurus'' and ''Parasaurolophus''. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had similar body layout. They were ornithischians.
Hadrosaurids are divided into two subfamilies. The lambeosaurines (Lambeosaurinae) have large cranial crests or tubes, and are less bulky. The hadrosaurines (Hadrosaurinae) lack the cranial crests or tubes and are larger.
The hadrosaurs are known as the duck-billed dinosaurs due to the similarity of their head to that of modern ducks. In some species, most notably ''Anatotitan'', the whole front of the skull was flat and broadened out to form a beak, ideal for clipping leaves and twigs from the forests of Asia, Europe and North America. However, the back of the mouth contained literally thousands of teeth suitable for grinding food before it was swallowed. Hadrosaurs, like their iguanodontian cousins, had a rudimentary dental specialisation analogous to incisors and molars. This has been hypothesized to have been a crucial factor in the success of this group in the Cretaceous, compared to the sauropods which were still largely dependent on gastroliths for grinding their food.
Fossilized skeletion (partial) of a young hadrosaur excavated and displayed at the Escalante-Grand Staircase National Mounument in Southern Utah. Click image for display placard text.
Hadrosaurids were the first dinosaur family to be identified in North America, the first traces being found in 1855-1856 with the discovery of fossil teeth. Joseph Leidy examined the teeth, and erected the genera ''Trachodon'' and ''Thespesius'' (others included ''Troodon'', ''Deinodon'' and ''Palaeoscincus''). One species was named ''Trachodon mirabilis''. Now it seems that the teeth genus ''Trachodon'' is a mixture of all sorts of cerapod dinosaurs, including ceratopsids. In 1858 the teeth were associated with Leidy's eponymous ''Hadrosaurus foulkii'', named after the fossil hobbyist William Parker Foulke. More and more teeth were found, resulting in even more (now obsolete) genera.
A second duck-bill skeleton was unearthed, and was named ''Diclonius mirabilis'' in 1883 by Edward Drinker Cope, which he incorrectly used in favor of ''Trachodon mirabilis''. But ''Trachodon'', together with other poorly typed genera, was used more widely and, when Cope's famous "''Diclonius mirabilis''" skeleton was mounted at the American Museum of Natural History, it was labeled as "Trachodont dinosaur". The duck-billed dinosaur family was then named Trachodontidae.
A very well-preserved complete hadrosaurid specimen (''Edmontosaurus annectens'') was recovered in 1908 by the fossil collector Charles Hazelius Sternberg and his three sons, in Converse County, Wyoming. It was known as the "''Trachodon'' mummy". This specimen's skin was almost completely preserved, together with some muscles and was analysed by Henry Osborn in 1912. Sternberg was in Cope's camp during his famous competition to name new species with Othniel Charles Marsh. This discovery was a victory for Cope in the Bone Wars.
Lawrence Lambe erected the genus ''Edmontosaurus'' ("lizard from Edmonton") in 1917 from a find in the lower Edmonton Formation (now Horseshoe Canyon Formation), Alberta. Hadrosaurid systematics were a mess until 1942, when Richard Swann Lull and Nelda Wright proposed the genus ''Anatosaurus''. Cope's famous mount at the AMNH became ''Anatosaurus copei''. In 1975, ''Anatosaurus'' was moved to ''Edmontosaurus'', because the species were just too similar to the ''Edmontosaurus'' type species, ''E. regalis'' and because ''Edmontosaurus'' was older, it had precedence. The original sample was probably a young ''Edmontosaurus''. One former ''Anatosaurus'' species was distinct enough from ''Edmontosaurus'' to be placed in a separate genus, named ''Anatotitan'', so in 1990 the AMNH mount was re-labelled ''Anatotitan copei''.
Some paleontologists found a hadrosaurid leg bone in Paleocene rocks, but it was probably reworked from a Cretaceous source.[1]
The family Hadrosauridae was first used by Edward Drinker Cope in 1869. Since its creation, a major division has been recognized in the group, between the (generally crested) subfamily Lambeosaurinae and (generally crestless) subfamily Hadrosaurinae. Phylogenetic analysis has increased the resolution of hadrosaurid relationships considerably (see Phylogeny below), leading to the widespread usage of tribes (a taxonomic unit below subfamily) to describe the finer relationships within each group of hadrosaurids. However, hadrosaurid tribes commonly recognized in online sources have not yet been formally defined or seen wide use in the literature. Several were briefly mentioned but not named as such in the first edition of ''The Dinosauria'', under informal names. In this 1990 reference, "gryposaurs" included ''Aralosaurus'', ''Gryposaurus'', ''Hadrosaurus'', and ''Kritosaurus''; "brachylophosaurs" included ''Brachylophosaurus'' and ''Maiasaura''; "saurolophs" included ''Lophorhothon'', ''Prosaurolophus'', and ''Saurolophus''; and "edmontosaurs" included ''Anatotitan'', ''Edmontosaurus'', and ''Shantungosaurus''. The Dinosauria, , David B., Weishampel, University of California Press, 1990, Lambeosaurines have also informally been split into "Parasaurolophini" (''Parasaurolophus'') and "Corythosaurini" (''Corythosaurus'', ''Hypacrosaurus'', and ''Lambeosaurus''). Dinosaurs: The Encyclopedia, , Donald F., Glut, McFarland & Co, 1997,
The following taxonomy includes dinosaurs currently referred to the Hadrosauridae and its subfamilies. Hadrosaurids that were accepted as valid but were not placed in a cladogram at the time of the 2004 review in ''The Dinosauria'', The Dinosauria, , John R., Horner, University of California Press, 2004, or, in the case of lambeosaurines, the 2007 redescription of ''Lambeosaurus magnicristatus'', Anatomy and relationships of ''Lambeosaurus magnicristatus'', a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta, , David C., Evans, Journal of Vertebrate Paleontology, 2007 are included at the highest level to which they were placed (either then, or in their description if they postdate the papers used here).
★ 'Family Hadrosauridae'
★
★ ''Telmatosaurus''
★
★ 'Subfamily Hadrosaurinae'
★
★
★ ''Brachylophosaurus''
★
★
★ ''Edmontosaurus'' (including ''Anatotitan'' in)
★
★
★ ''Gryposaurus''
★
★
★ "Kritosaurus" ''australis''
★
★
★ ''Lophorhothon''
★
★
★ ''Maiasaura''
★
★
★ ''Naashoibitosaurus''
★
★
★ ''Prosaurolophus''
★
★
★ ''Saurolophus''
★
★
★ Unclassified hadrosaurines
★
★
★
★ ''Anasazisaurus''
★
★
★
★ ''Hadrosaurus''
★
★
★
★ ''Kerberosaurus''
★
★
★
★ ''Kritosaurus''
★
★
★
★ ''Shantungosaurus''
★
★ 'Subfamily Lambeosaurinae'
★
★
★ ''Amurosaurus''
★
★
★ ''Aralosaurus''
★
★
★ ''Charonosaurus''
★
★
★ ''Corythosaurus''
★
★
★ ''Hypacrosaurus''
★
★
★ ''Jaxartosaurus''
★
★
★ ''Lambeosaurus''
★
★
★ ''Nipponosaurus''
★
★
★ ''Olorotitan''
★
★
★ ''Parasaurolophus''
★
★
★ ''Tsintaosaurus''
★
★
★ Unclassified lambeosaurines
★
★
★
★ ''Barsboldia''
★
★
★
★ ''Nanningosaurus''
★
★ Hadrosaurids of uncertain placement (''incertae sedis'')
★
★
★ ''Bactrosaurus''
★
★
★ ''Claosaurus''
★
★
★ ''Gilmoreosaurus''
★
★
★ ''Koutalisaurus''
★
★
★ ''Pararhabdodon''
★
★
★ ''Secernosaurus''
★
★
★ ''Tanius''
★
★
★ ''Zhuchengosaurus''
★
★ 'Dubious hadrosaurids'
★
★
★ ''Arstanosaurus''
★
★
★ ''Cionodon''
★
★
★ ''Diclonius''
★
★
★ ''Dysganus''
★
★
★ ''Hypsibema''
★
★
★ ''Mandschurosaurus''
★
★
★ ''Microhadrosaurus''
★
★
★ ''Orthomerus''
★
★
★ ''Pteropelyx''
★
★
★ ''Thespesius''
★
★
★ ''Trachodon''
Hadrosauridae was first defined as a clade, by Forster in a 1997 abstract, as simply "Labeosaurinae plus Hadrosaurinae and their most recent common ancestor." In 1998, Paul Sereno defined the clade Hadrosauridae as the most inclusive possible group containing ''Saurolophus'' (a well-known hadrosaurine) and ''Parasaurolophus'' (a well-known lambeosaurine), later emending the definition to include ''Hadrosaurus'', the type geus of the family, which ICZN rules state must be included, despite its status as a ''nomen dubium''. According to some studies, Sereno's definition would place a few other well-known hadrosaurs (such as ''Telmatosaurus'' and ''Bactrosaurus'') outside the family, which led Horner ''et al.'' (2004) to define the family to include ''Telmatosaurus'' by default.
The following cladogram is after the 2004 review by Jack Horner, David B. Weishampel, and Catherine Forster, in the second edition of ''The Dinosauria''.
The following cladogram is after the 2007 redescription of ''Lambeosaurus magnicristatus'' (Evans and Reisz, 2007):
1. Fassett, J, Zielinski, R.A., and Budahn, J.R. (2002). Dinosaurs that did not die; evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico. In: Koeberl, C., and MacLeod, K. (eds.). ''Catastrophic events and mass extinctions: impacts and beyond.'' ''Special Paper - Geological Society of America'' '356':307-336.
★ UCMP Tree of Life
★ Trachodon
'Hadrosaurids' or 'duck-billed' dinosaurs are members of the family 'Hadrosauridae', and include ornithopods such as ''Edmontosaurus'' and ''Parasaurolophus''. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper Jurassic/Lower Cretaceous iguanodontian dinosaurs and had similar body layout. They were ornithischians.
Hadrosaurids are divided into two subfamilies. The lambeosaurines (Lambeosaurinae) have large cranial crests or tubes, and are less bulky. The hadrosaurines (Hadrosaurinae) lack the cranial crests or tubes and are larger.
| Contents |
| Characteristics |
| Discoveries |
| Systematics |
| Taxonomy |
| Phylogeny |
| Lambeosaurinae cladogram |
| References |
| External links |
Characteristics
Skull of ''Edmontosaurus'', showing duck-bill and dentition Oxford University Museum of Natural History.
The hadrosaurs are known as the duck-billed dinosaurs due to the similarity of their head to that of modern ducks. In some species, most notably ''Anatotitan'', the whole front of the skull was flat and broadened out to form a beak, ideal for clipping leaves and twigs from the forests of Asia, Europe and North America. However, the back of the mouth contained literally thousands of teeth suitable for grinding food before it was swallowed. Hadrosaurs, like their iguanodontian cousins, had a rudimentary dental specialisation analogous to incisors and molars. This has been hypothesized to have been a crucial factor in the success of this group in the Cretaceous, compared to the sauropods which were still largely dependent on gastroliths for grinding their food.
Discoveries
An old drawing of the defunct hadrosaur genus "Trachodon"
Hadrosaurids were the first dinosaur family to be identified in North America, the first traces being found in 1855-1856 with the discovery of fossil teeth. Joseph Leidy examined the teeth, and erected the genera ''Trachodon'' and ''Thespesius'' (others included ''Troodon'', ''Deinodon'' and ''Palaeoscincus''). One species was named ''Trachodon mirabilis''. Now it seems that the teeth genus ''Trachodon'' is a mixture of all sorts of cerapod dinosaurs, including ceratopsids. In 1858 the teeth were associated with Leidy's eponymous ''Hadrosaurus foulkii'', named after the fossil hobbyist William Parker Foulke. More and more teeth were found, resulting in even more (now obsolete) genera.
Skin impressions of ''Edmontosaurus''.
A second duck-bill skeleton was unearthed, and was named ''Diclonius mirabilis'' in 1883 by Edward Drinker Cope, which he incorrectly used in favor of ''Trachodon mirabilis''. But ''Trachodon'', together with other poorly typed genera, was used more widely and, when Cope's famous "''Diclonius mirabilis''" skeleton was mounted at the American Museum of Natural History, it was labeled as "Trachodont dinosaur". The duck-billed dinosaur family was then named Trachodontidae.
A very well-preserved complete hadrosaurid specimen (''Edmontosaurus annectens'') was recovered in 1908 by the fossil collector Charles Hazelius Sternberg and his three sons, in Converse County, Wyoming. It was known as the "''Trachodon'' mummy". This specimen's skin was almost completely preserved, together with some muscles and was analysed by Henry Osborn in 1912. Sternberg was in Cope's camp during his famous competition to name new species with Othniel Charles Marsh. This discovery was a victory for Cope in the Bone Wars.
A well preserved specimen of ''Edmontosaurus''.
Lawrence Lambe erected the genus ''Edmontosaurus'' ("lizard from Edmonton") in 1917 from a find in the lower Edmonton Formation (now Horseshoe Canyon Formation), Alberta. Hadrosaurid systematics were a mess until 1942, when Richard Swann Lull and Nelda Wright proposed the genus ''Anatosaurus''. Cope's famous mount at the AMNH became ''Anatosaurus copei''. In 1975, ''Anatosaurus'' was moved to ''Edmontosaurus'', because the species were just too similar to the ''Edmontosaurus'' type species, ''E. regalis'' and because ''Edmontosaurus'' was older, it had precedence. The original sample was probably a young ''Edmontosaurus''. One former ''Anatosaurus'' species was distinct enough from ''Edmontosaurus'' to be placed in a separate genus, named ''Anatotitan'', so in 1990 the AMNH mount was re-labelled ''Anatotitan copei''.
Some paleontologists found a hadrosaurid leg bone in Paleocene rocks, but it was probably reworked from a Cretaceous source.[1]
Systematics
Taxonomy
The family Hadrosauridae was first used by Edward Drinker Cope in 1869. Since its creation, a major division has been recognized in the group, between the (generally crested) subfamily Lambeosaurinae and (generally crestless) subfamily Hadrosaurinae. Phylogenetic analysis has increased the resolution of hadrosaurid relationships considerably (see Phylogeny below), leading to the widespread usage of tribes (a taxonomic unit below subfamily) to describe the finer relationships within each group of hadrosaurids. However, hadrosaurid tribes commonly recognized in online sources have not yet been formally defined or seen wide use in the literature. Several were briefly mentioned but not named as such in the first edition of ''The Dinosauria'', under informal names. In this 1990 reference, "gryposaurs" included ''Aralosaurus'', ''Gryposaurus'', ''Hadrosaurus'', and ''Kritosaurus''; "brachylophosaurs" included ''Brachylophosaurus'' and ''Maiasaura''; "saurolophs" included ''Lophorhothon'', ''Prosaurolophus'', and ''Saurolophus''; and "edmontosaurs" included ''Anatotitan'', ''Edmontosaurus'', and ''Shantungosaurus''. The Dinosauria, , David B., Weishampel, University of California Press, 1990, Lambeosaurines have also informally been split into "Parasaurolophini" (''Parasaurolophus'') and "Corythosaurini" (''Corythosaurus'', ''Hypacrosaurus'', and ''Lambeosaurus''). Dinosaurs: The Encyclopedia, , Donald F., Glut, McFarland & Co, 1997,
The following taxonomy includes dinosaurs currently referred to the Hadrosauridae and its subfamilies. Hadrosaurids that were accepted as valid but were not placed in a cladogram at the time of the 2004 review in ''The Dinosauria'', The Dinosauria, , John R., Horner, University of California Press, 2004, or, in the case of lambeosaurines, the 2007 redescription of ''Lambeosaurus magnicristatus'', Anatomy and relationships of ''Lambeosaurus magnicristatus'', a crested hadrosaurid dinosaur (Ornithischia) from the Dinosaur Park Formation, Alberta, , David C., Evans, Journal of Vertebrate Paleontology, 2007 are included at the highest level to which they were placed (either then, or in their description if they postdate the papers used here).
★ 'Family Hadrosauridae'
★
★ ''Telmatosaurus''
★
★ 'Subfamily Hadrosaurinae'
★
★
★ ''Brachylophosaurus''
★
★
★ ''Edmontosaurus'' (including ''Anatotitan'' in)
★
★
★ ''Gryposaurus''
★
★
★ "Kritosaurus" ''australis''
★
★
★ ''Lophorhothon''
★
★
★ ''Maiasaura''
★
★
★ ''Naashoibitosaurus''
★
★
★ ''Prosaurolophus''
★
★
★ ''Saurolophus''
★
★
★ Unclassified hadrosaurines
★
★
★
★ ''Anasazisaurus''
★
★
★
★ ''Hadrosaurus''
★
★
★
★ ''Kerberosaurus''
★
★
★
★ ''Kritosaurus''
★
★
★
★ ''Shantungosaurus''
★
★ 'Subfamily Lambeosaurinae'
★
★
★ ''Amurosaurus''
★
★
★ ''Aralosaurus''
★
★
★ ''Charonosaurus''
★
★
★ ''Corythosaurus''
★
★
★ ''Hypacrosaurus''
★
★
★ ''Jaxartosaurus''
★
★
★ ''Lambeosaurus''
★
★
★ ''Nipponosaurus''
★
★
★ ''Olorotitan''
★
★
★ ''Parasaurolophus''
★
★
★ ''Tsintaosaurus''
★
★
★ Unclassified lambeosaurines
★
★
★
★ ''Barsboldia''
★
★
★
★ ''Nanningosaurus''
★
★ Hadrosaurids of uncertain placement (''incertae sedis'')
★
★
★ ''Bactrosaurus''
★
★
★ ''Claosaurus''
★
★
★ ''Gilmoreosaurus''
★
★
★ ''Koutalisaurus''
★
★
★ ''Pararhabdodon''
★
★
★ ''Secernosaurus''
★
★
★ ''Tanius''
★
★
★ ''Zhuchengosaurus''
★
★ 'Dubious hadrosaurids'
★
★
★ ''Arstanosaurus''
★
★
★ ''Cionodon''
★
★
★ ''Diclonius''
★
★
★ ''Dysganus''
★
★
★ ''Hypsibema''
★
★
★ ''Mandschurosaurus''
★
★
★ ''Microhadrosaurus''
★
★
★ ''Orthomerus''
★
★
★ ''Pteropelyx''
★
★
★ ''Thespesius''
★
★
★ ''Trachodon''
Phylogeny
Hadrosauridae was first defined as a clade, by Forster in a 1997 abstract, as simply "Labeosaurinae plus Hadrosaurinae and their most recent common ancestor." In 1998, Paul Sereno defined the clade Hadrosauridae as the most inclusive possible group containing ''Saurolophus'' (a well-known hadrosaurine) and ''Parasaurolophus'' (a well-known lambeosaurine), later emending the definition to include ''Hadrosaurus'', the type geus of the family, which ICZN rules state must be included, despite its status as a ''nomen dubium''. According to some studies, Sereno's definition would place a few other well-known hadrosaurs (such as ''Telmatosaurus'' and ''Bactrosaurus'') outside the family, which led Horner ''et al.'' (2004) to define the family to include ''Telmatosaurus'' by default.
The following cladogram is after the 2004 review by Jack Horner, David B. Weishampel, and Catherine Forster, in the second edition of ''The Dinosauria''.
Lambeosaurinae cladogram
The following cladogram is after the 2007 redescription of ''Lambeosaurus magnicristatus'' (Evans and Reisz, 2007):
References
1. Fassett, J, Zielinski, R.A., and Budahn, J.R. (2002). Dinosaurs that did not die; evidence for Paleocene dinosaurs in the Ojo Alamo Sandstone, San Juan Basin, New Mexico. In: Koeberl, C., and MacLeod, K. (eds.). ''Catastrophic events and mass extinctions: impacts and beyond.'' ''Special Paper - Geological Society of America'' '356':307-336.
External links
★ UCMP Tree of Life
★ Trachodon
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