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history tools tools move to sidebar hide actions read edit view history general what links here related changes upload file permanent link page information cite this page get shortened url switch to legacy parser print export download as pdf printable version in other projects wikimedia commons wikispecies wikidata item appearance move to sidebar hide from wikipedia the free encyclopedia redirected from maiasaura peeblesorum extinct genus of reptiles maiasaura temporal range late cretaceous santonian campanian 86 3 70 6 ma preꞓ ꞓ o s d c p t j k pg n b v h b apt albian c t c s cam m mounted cast brussels natural history museum scientific classification kingdom animalia phylum chordata class reptilia clade dinosauria clade ornithischia clade ornithopoda family hadrosauridae subfamily saurolophinae tribe brachylophosaurini genus maiasaura horner makela 1979 type species maiasaura peeblesorum horner makela 1979 maiasaura from greek μαῖα a lit good mother and greek σαύρα the feminine form of saurus lit reptile is a large herbivorous saurolophine hadrosaurid duck billed dinosaur genus that lived in the area currently covered by the state of montana and the canadian province of alberta 1 in the upper cretaceous mid to late campanian from 86 3 to 70 6 million years ago 2 discovered in 1978 during the dinosaur renaissance the species description of maiasaura first came in 1979 from paleontologists jack horner and bob makela following the discovery of a site located south of choteau montana they named the new genus and species maiasaura peeblesorum with the genus name maiasaura good mother lizard referring to makela and horner s conclusion that this species took care of their offspring collected data at the site indicated that maiasaura fed its young while they were in the nest the first instance of parental and social behavior in dinosaurs 3 this was in contradiction with the common idea of the 1970s that dinosaurs laid eggs and abandoned them immediately afterwards providing no parental care in 1979 one year after the discovery of the nests and juveniles maiasaura eggs were unearthed the first discovery of dinosaur eggs both on the american continent and in the western hemisphere further work in the area led to the discovery of more dinosaur eggs leading to the area being named egg mountain computed tomography scans showed embryos at a very early stage of development inside some of the eggs because of these elements maiasaura is considered one of the most significant discoveries in the history of dinosaur research 4 5 6 maiasaura whose bones have been found by hundreds in the state of montana has been chosen as montana s state fossil description edit skull cast royal ontario museum size comparison with human maiasaura peeblesorum were large attaining a maximum known length of about 9 metres 30 ft and an approximate body mass measured at up to 4 metric tons 4 4 short tons 7 they had a large duck billed mouth structure and rows of hundreds of teeth typical of hadrosaurids while hadrosaurids have very similar post cranial body plans 8 the distinguishing characteristic of maiasaura peeblesorum is a prominent short solid crest like structure situated between the eyes this crest may have been used in headbutting contests between males during the breeding season citation needed maiasaura were herbivorous terrestrial dinosaurs they were capable of walking both on two bipedal or four quadrupedal legs studies of the stress patterns of healed bones show that juveniles under four years old walked mainly bipedally switching to a mainly quadrupedal style of walking when they grew larger 9 maiasaura like most other hadrosaurs possessed little in the way of obvious weaponry though likely could defend themselves with kicks stomps or their muscular tails it is likely that they primarily resorted to fleeing in the face of danger using the vast sizes of their herds to be less likely to be targeted mass bone beds discovered in the two medicine formation show that herds could be extremely large and comprise as many as 10 000 individuals 10 hundreds of specimens have been found throughout all stages of life allowing for m peeblesorum to be used for understanding how hadrosaurids grew 11 discovery edit map of brachylophosaurini saurolophinae specimen discoveries in alberta and montana the first remains of maiasaura have been found south of choteau visible on the map for years until the 1960s and 1970s anyone who has traveled through the area south of choteau montana might have come across maiasaura remains whether such remains have been or have not been attributed to a dinosaurian origin the first people who are confirmed as having found maiasaura remains laying on the egg mountain area as it is called today are two homestead families of bynum montana the brandvolds and the trexlers marion kathryn brandvold 1912 2014 née nehring had inherited the rock shop trex agate shop that had been founded in 1937 by her first husband clifford trex trexler 1908 1962 in the years that preceded 1978 she and her second husband john brandvold 1937 2020 12 had been finding small bones and they had been trying to put them together 13 but in 1978 paleontologist bob makela had been told by fellow berkeley paleontologist bill clemens that the state of montana had called him about a north western montana woman who had found bones which she wanted to identify 14 makela informed his research partner jack horner and both went to the trex agate shop in bynum there marion brandvold showed them some dinosaur bones which the paleontologists could identify but also two tiny bones that horner identified as baby hadrosaur bones brandvold said she had more at her place so they followed her to the brandvolds house where she d been keeping the remains of at least four individuals in a coffee can 14 15 two weeks later brandvold took makela and horner to the site in choteau where she have found the remains there bones were visible on the surface not even needing to dig during the same summer of 1978 makela and horner excavated the spot and noticed that they were excavating a nest where in the end they found a total of 15 baby dinosaurs 14 that was their first excavated nest but subsequently the site delivered more nests and juveniles all of them of a till then unknown species of hadrosaur the next year in july 1979 during the second summer dig a lady student named fran tannenbaum under the direction of jack horner discovered the first whole dinosaur egg ever found in north america 16 and in the western hemisphere with time more eggs were discovered and the site of this discovery earned the name of egg mountain because of the abundance of hadrosaur eggs and eggshell pieces found in it 17 18 a skull of maiasaura specimen pu 22405 now in the collections of the yale peabody museum of natural history as ypm pu 22405 following the transfer of the princeton university vertebrate paleontology collections was discovered by david trexler s wife laurie trexler in 1979 trexler partially broke the skull as a consequence of her lack of appropriate excavating tools but after informing jack horner and robert makela both paleontologists managed to extract the whole remaining part of the fossil 14 it is the specimen that makela and horner had used the same year as the holotype of the new species which they described and named as the type species maiasaura peeblesorum the generic name maiasaura means good mother lizard and the specific name peeblesorum honours the families of john and james peebles on whose land the finds were made 19 3 david trexler the second son of clifford trexler and marion brandvold grew up in such a context that he ended up by becoming a paleontologist himself in 1995 he founded in bynum the montana dinosaur center that center plays an important role in connexion with the first identified remains of maiasaura because during the years that spanned from 1998 to 2004 david trexler s mother marion brandvold led a legal fight with the yale and princeton universities in order to recover the bones of the baby maiasauras that she had found back in the 1970s in 2004 she obtained a satisfactory issue and since then these historically important fossils are preserved at the montana dinosaur center in bynum 20 over 200 specimens in all age ranges have been found 21 the announcement of the discovery of maiasaura attracted renewed scientific interest to the two medicine formation and many other new kinds of dinosaurs were discovered as a result of the increased attention 22 choteau maiasaura remains are found in higher strata than their two medicine river counterparts 23 the sites that close to choteau contain maiasaura remains of adults juveniles nests and eggs have been preserved in the rock as if a rapid event had frozen the area it is assumed that such event was the eruption of a volcano located among the nearby elkhorn mountains nests eggs and animals were covered by ash and once they fossilised they remained almost perfectly preserved until they were discovered in 1978 17 18 in 1985 the nature conservancy purchased the site of egg mountain from the james and marian peebles family the original owners of the land leasing the property to the peebles for cattle grazing and allowing curator jack horner and the museum of the rockies to run a paleontology field camp in 2004 the museum of the rockies purchased the property and now the museum gives egg mountain the name of museum of the rockies beatrice r taylor paleontology research site honouring beatrice taylor whose family donated the money for the purchase 24 classification edit cast of a juvenile skeleton life restorations of an adult and juvenile maiasaura peeblesorum is in the tribe brachylophosaurini along with these related taxa acristavus gagslarsoni 25 brachylophosaurus canadensis 26 ornatops incantatus 27 probrachylophosaurus bergei 28 the following cladogram of hadrosaurid relationships was published in 2013 by albert prieto márquez et al 29 saurolophinae brachylophosaurini acristavus gagslarsoni brachylophosaurus canadensis maiasaura peeblesorum shantungosaurus giganteus edmontosaurus edmontosaurus regalis edmontosaurus annectens saurolophini kerberosaurus manakini sabinas otu prosaurolophus maximus saurolophus saurolophus morrisi saurolophus osborni saurolophus angustirostris kritosaurini wulagasaurus dongi kritosaurus navajovius aquilarhinus secernosaurus koerneri willinakaqe salitralensis gryposaurus gryposaurus latidens gryposaurus notabilis gryposaurus monumentensis paleobiology edit reconstructed cast by jack horner of a maiasaura emerging from its egg maiasaura lived in herds and it raised its young in nesting colonies the nests in the colonies were packed closely together like those of modern seabirds with the gap between the nests being around 7 metres 23 ft less than the length of the adult animal 30 the nests were made of earth and contained 30 to 40 eggs laid in a circular or spiral pattern the eggs were about the size of ostrich eggs and are oval shaped with one slightly more pointed end 31 fossilized m peeblesorum eggs are black in color and have high prominent ridges on the outer surface 31 the eggs were incubated by the heat resulting from rotting vegetation placed into the nest by the parents rather than a parent sitting on the nest upon hatching fossils of baby maiasaura show that their legs were not fully developed and thus they were incapable of walking fossils also show that their teeth were partly worn which means that the adults brought food to the nest 32 reconstruction of a nest with eggs baby maiasaura casts on display at royal ontario museum the hatchlings grew from a size of 41 to 147 centimetres 16 to 58 in long in the span of their first year at this point or perhaps after another year the animal left the nest this high rate of growth may be evidence of warm bloodedness the hatchlings had different facial proportions from the adults with larger eyes and a shorter snout 32 these features are associated with cuteness and commonly elicit care from parents in animals dependent on their parents for survival during the early stages of life based on metabolic growth rates and age estimations of juvenile specimens both in and outside the nests it is suggested that infant maiasaura were altricial and left the confines of their nests after 40 75 days or roughly a little over 1 2 months old these studies also were compared to the related lambeosaurine hadrosaur hypacrosaurus for which neonates are also known these analyses suggest hypacrosaurus was more precocial than maiasaura based on its ecological traits 33 studies led by holly woodward jack horner freedman fowler et al have given insight into the life history of maiasaura resulting in what is perhaps the most detailed life history of any dinosaur known and to which all others can be compared from a sample of fifty individual maiasaura tibiae it was found that maiasaurs had a mortality rate of about 89 9 in their first year of life if the animals survived their second year their mortality rate would drop to 12 7 the animals would spend their next six years maturing and growing sexual maturity was found to occur in their third year while skeletal maturity was attained at eight years of age in their eighth year and beyond the mortality rate for maiasaura would spike back to around 44 4 the studies that followed also found that maiasaurs were primarily bipedal as juveniles and switched to a more quadrupedal stance as they aged it was also found that maiasaura also included rotting wood in its diet as well that its environment had a long dry season prone to drought the results of the study were published in the journal palaeobiology on september 3 2015 34 35 diet edit a paper from 2007 showed that maiasaura had a diet consisting of fibrous plants wood rotting wood tree bark leaves branches ferns angiosperms and possibly grasses this would imply that maiasaura was both a browser and a grazer 36 37 38 analysis of its dental wear patterns show that juvenile m peeblesorum exhibited more crush wear than adults which displayed more shear wear than juveniles this suggests that adults fed more on tough fibrous vegetation while juveniles fed more on hard brittle objects like nuts seeds or berries 39 sexual dimorphism edit studies of maiasaura by saitta et al suggest that one sex was roughly 45 larger than the other according to the mathematical analysis known as size statistics however it cannot be ascertained at this time whether the larger sex was male or female 40 41 palaeoecology edit illustration of a herd of maiasaura walking along a creekbed as found in the semi arid two medicine formation fossil bed this region was characterized by volcanic ash layers and conifer fern and horsetail vegetation maiasaura is a characteristic fossil of the middle portion lithofacies 4 of the two medicine formation dated from about 86 3 to 70 6 million years ago 2 maiasaura lived ...
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