| Hadrosaurus | |
|---|---|
 | |
| Reconstructed skeleton, Academy of Natural Sciences | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Ornithopoda |
| Family: | †Hadrosauridae |
| Subfamily: | †Hadrosaurinae |
| Genus: | †Hadrosaurus Leidy,1858 |
| Type species | |
| †Hadrosaurus foulkii Leidy, 1858 | |
| Synonyms | |
| |
Hadrosaurus (/ˌhædrəˈsɔːrəs/;lit. 'bulky lizard') is agenus ofhadrosauridornithopoddinosaurs that lived inNorth America during theLate CretaceousPeriod in what is now theWoodbury Formation inNew Jersey about 83.6 to 77.9 million years ago. Theholotype specimen was found in fluvial marine sedimentation, meaning that the corpse of the animal was transported by a river and washed out to sea. Some fossils are found in theTar Heel/Coachman Formation.[1]
They were large animals ranging from 7 to 8 m (23 to 26 ft) in length and 2 to 4 t (2.2 to 4.4 short tons) in weight. Most of the preserved elements are very robust, unusual traits in hadrosaurs.Hadrosaurus were ponderously built animals equipped withkeratinous beaks for cropping foliage and a specialized and complex dentition for food processing.Hadrosaurus foulkii, the onlyspecies in thisgenus, is known from a single specimen consisting of much of the skeleton and parts of the skull. The specimen was collected in 1858 and represents the first dinosaur species known from more than isolated teeth to be identified in North America. Usingradiometric dating ofbivalve shells from the Woodbury Formation, the sedimentary rocks where theHadrosaurus fossil was found have beendated at some time during theCampanian stage. In 1868, the only known specimen became the first-ever dinosaur skeleton to be mounted. In 1991,Hadrosaurus became the officialstate dinosaur of New Jersey.[2][3][4][5]
In 1838, John Estaugh Hopkins was digging in amarl pit (on a small tributary of theCooper River inHaddonfield, New Jersey, and part of theCampanian-ageWoodbury Formation) when he uncovered large bones. He put them on display at his home, also in Haddonfield. In 1858, the bones sparked the interest of a visitor,William Parker Foulke, who dug out the rest of the bones from the marl pit in the same year. The excavation site, known as theHadrosaurus foulkii Leidy Site, is now aNational Historic Landmark.
Foulke contactedpaleontologistJoseph Leidy, and together they recovered eightteeth from themaxillar anddentary areas,dental battery fragments, left maxilla fragments, three partialdorsal vertebrae, 13 caudalcentra, including an almost complete middlecaudal vertebra. Other fragments included a partial rightcoracoid, lefthumerus, leftradius, leftulna, leftilium, rightischium, right partialpubis, the left hindlimb composed by thefemur,tibia,fibula withmetatarsals II and IV and the first pedalphalanx from the thirddigit. Foulke and Leidy studied the fossils together and, in 1858, Leidy formally described and namedHadrosaurus foulkii in honor of his collaborator. While originally a portmanteau of Haddonfield, the location of its discovery with the accepted suffix for dinosaurs -saurus, the nameHadrosaurus was scientifically justified as deriving from theGreekἁδρός,hadros, meaning "bulky" or "large", andσαῦρος,sauros, meaning "lizard". The name was an additional play on words by Leidy since it translates from Greek asFoulke's big lizard.
Leidy recognized that the bones were from a dinosaur because of their similarity to those ofIguanodon, discovered in England some decades before but, at the time, the skeleton ofHadrosaurus was one of the most complete dinosaur skeletons known. Leidy's monographCretaceous Reptiles of the United States, describingHadrosaurus more completely, and with illustrations, was written in 1860, but theAmerican Civil War delayed its publication until 1865.[6]
Leidy reconstructedHadrosaurus as a biped, in contrast to the view at the time that such dinosaurs werequadrupedal. The entire skeleton was completely assembled in 1868 by a team including Englishsculptor andnaturalistBenjamin Waterhouse Hawkins and was put on display atPhiladelphia Academy of Natural Sciences. It was the first-ever mounted dinosaur skeleton. When the skeleton was first put together, it was displayed with a plaster skull sculpted by Hawkins. Many other artists have recreatedHadrosaurus with skulls from other, related species such asGryposaurus andBrachylophosaurus. A statue ofHadrosaurus, sculpted by Haddonfield resident John Giannotti, now stands in the center of the town of Haddonfield, commemorating its discovery there. Thanks to Joyce Berry and her fourth-grade classes (1988–1991) at Strawbridge Elementary School inHaddon Township, New Jersey, theHadrosaurus was named the state dinosaur[7] ofNew Jersey in 1991. It is one of the most celebrated dinosaurs ever and is of great historic importance.[6] The skeleton is usually kept out of sight in the Academy's collections. However, from November 22, 2008, to April 19, 2009, a fully assembled cast of the skeleton, and an exhibit about the science and culture surrounding the dinosaur's discovery, was open to the public.[citation needed]
Hadrosaurus were large-sized animals growing up to 7–8 metres (23–26 ft) and weighing as much as 2 to 4 t (2.2 to 4.4 short tons).[8][9] According to Prieto-Márquez,Hadrosaurus can be distinguished in having a shortened pectoral crest that is slightly over 40% of the totalhumeral length, a deltopectoral crest that is developed from the humeral shaft causing the laterodistal border to display a broad lateral facet, a lower greatest point of the supraacetabular crest located above lateral edge from the rear to the bottom on the posterior tuberosity of the ischial peduncle of the ilium, a shortened supraacetabular crest from the front to the rear with its breadth being half the length of the middle iliac plate.[10]
As in most hadrosaurs, the forelimbs were not as heavily built as the hindlimbs, but were long enough to be used in standing or movement.[6][9][11] The holotype specimen was a relatively large animal at the time of death with a 1.05-meter-long (105 cm)femur and 93.3-centimeter-long (933 mm)tibia. Most of the preserved elements feature a marked robust composition with thefibula being one of the most robust among hadrosaurs.[6]
Despite the fact that the familyHadrosauridae hasHadrosaurus as itstype genus, the skeleton lacks a skull and was long viewed as too incomplete to compare to other hadrosaurs for classification purposes, leading most scientists to consider it anomen dubium, or dubious name.[10] However, a re-evaluation of the fossil material in 2011 noted several distinct characteristics of the skeleton that could allow the genusHadrosaurus and speciesH. foulkii to remain in use as validtaxa.[10]
Hadrosaurus has also traditionally served as the basis for a large subfamily called Hadrosaurinae, which was seen as a group of largely crestless hadrosaurs related to the crested subfamilyLambeosaurinae. However, the changing view ofHadrosaurus classification in relation to other hadrosaurs has led some scientists to rename these subfamilies. In a 2008 study,Hadrosaurus was found to be more primitive than either lambeosaurines or other "hadrosaurines", and not a particularly close relative of classic "hadrosaurines" such asEdmontosaurus andSaurolophus. As a result of this, the name Hadrosaurinae was restricted toHadrosaurus alone, and the subfamily comprising the traditional "hadrosaurines" was renamed theSaurolophinae.[12]
Below is a simplifiedcladogram recovered by Ramírez-Velascoet al. in 2012 in their description ofHuehuecanauhtlus. This topology was recovered using an extensive sampling of 60hadrosauroid species, and two outgroup taxa, which were scored based on 287 morphological traits,[13] and included data from two recent redescriptions ofHadrosaurus by Prieto-Márquezet al. (2006)[6] and Prieto-Márquez (2011).[10]
| Hadrosauroidea |
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In 2003, Rothschild and colleagues performed a study looking for epidemiology oftumors in dinosaurs. Evidence of tumors, includinghemangiomas,desmoplastic fibroma,metastatic cancer andosteoblastoma were discovered in specimens ofHadrosaurus by analyzing dinosaur vertebrae usingcomputerized tomography andfluoroscope screening. Several other hadrosaurids, includingBrachylophosaurus,Edmontosaurus andGilmoreosaurus, also tested positive. Although more than 10,000fossils were examined in this manner, the tumors were limited toHadrosaurus and other hadrosaurs. The tumors were only found on caudal vertebrae and they may have been caused by environmental factors or genetic inheritance.[14]
The holotype ofHadrosaurus was found in marine sediments, which suggests the skeleton was transported by a river and then deposited in the Cretaceous sea. TheHadrosaurus remains all persist to theWoodbury Formation.[6] Through theradiometric dating ofbivalve shells known from the formation, the sedimentary rocks where the holotype specimen ofHadrosaurus was found have beendated from 80.5 million to 78.5 million years ago.[15] However, a more accurate date make range from 83.6 to around 77.9 mya.[16]
