dinosaur renaissance

{{short description|Acceptance of dinosaurs as warm-blooded and birds as avian-dinosaurs}}

File:Bob Bakker lecture.jpg lecturing at the Houston Museum of Natural Science]]

The dinosaur renaissanceThe term has entered into common usage after an article of the same name by paleontologist Robert T. Bakker in Scientific American, in April 1975. Examples can be found [http://www.citypaper.com/news/story.asp?id=11282 here] {{webarchive|url=https://web.archive.org/web/20070927205753/http://www.citypaper.com/news/story.asp?id=11282 |date=2007-09-27 }} and [https://web.archive.org/web/20060110100858/http://www.geotimes.org/jan06/feature_threedinofaces.html here]. was a highly specified scientific revolution that began in the late 1960s and led to renewed academic and popular interest in dinosaurs. It was initially spurred by research indicating that dinosaurs may have been active warm-blooded animals, rather than sluggish cold-blooded lizard-like reptilians as had been the prevailing view and description during the first half of the twentieth century.

This new view of dinosaurs was championed particularly by John Ostrom, who argued that birds evolved from coelurosaurian dinosaurs,{{cite journal |last1=Ostrom |first1= J. |year=1974 |title=Archaeopteryx and the Origin of Flight |journal=The Quarterly Review of Biology |volume= 49 |issue= 1 | pages=27–47 | jstor=2821658 |doi=10.1086/407902 |s2cid= 85396846 }} and Robert Bakker, who argued that dinosaurs were warm-blooded in a way similar to modern mammals and birds.{{cite book |last1=Bakker |first1= R.T. |year=1986 |title=The Dinosaur Heresies |publisher= William Morrow |location= New York |isbn=0-8217-5608-7 | oclc=36439291 |author-link=Robert T. Bakker}} Bakker frequently portrayed his ideas as a "renaissance" akin to those in the late nineteenth century, referring to the period in between the Dinosaur Wars and the dinosaur renaissance as "the dinosaur doldrums".

The dinosaur renaissance led to a profound shift in thinking on nearly all aspects of dinosaur biology, including physiology, evolution, behaviour, ecology and extinction. It also sparked public imagination and inspired many cultural depictions of dinosaurs.

Dinosaurs and the origin of birds

In the mid and latter parts of the nineteenth century, some scientists thought there was a close relationship between birds and dinosaurs—and that dinosaurs represented an intermediate stage between "reptiles" and birds.

File:Archaeo-deinony hands.svg (left) and Archaeopteryx (right) led John Ostrom to revive the link between non-avian dinosaurs and avian dinosaurs, birds.]]

Shortly after the 1859 publication of Charles Darwin's The Origin of Species, British biologist and evolution-defender Thomas Henry Huxley proposed that birds were descendants of dinosaurs. He cited skeletal similarities, particularly among dinosaurs, the "first bird"—Archaeopteryx—and modern birds.{{cite journal |last= Huxley|first= T.H. |author-link=Thomas Henry Huxley |year=1868|title= On the animals which are most nearly intermediate between birds and reptiles |journal=Annals and Magazine of Natural History |volume=2 |pages=66–75 |series=4th |url=https://www.biodiversitylibrary.org/page/22247928}}{{cite wikisource | last1=Huxley | first1=Thomas H. | title=Further Evidence of the Affinity between the Dinosaurian Reptiles and Birds | wslink=Quarterly Journal of the Geological Society of London/Volume 26/Further Evidence of the Affinity between the Dinosaurian Reptiles and Birds | work=Quarterly Journal of the Geological Society of London | volume=26 | year=1870 | doi=10.1144/GSL.JGS.1870.026.01-02.08 | pages=12–31 | firsticon=yes | noicon=yes }} However, in 1926, Gerhard Heilmann wrote his influential book The Origin of Birds,Heilmann, G. 1926: The Origin of Birds. Witherby, London. {{ISBN|0-486-22784-7}} (1972 Dover reprint) in which he dismissed the dinosaur–bird link, based on the dinosaurs' supposed lack of a furcula.An assumption which is now known to have been incorrect. Thereafter, the accepted hypothesis was that birds evolved from crocodylomorph and thecodont ancestors, rather than from dinosaurs. This removed dinosaurs from a central role in debates about the origin of living species, and may have contributed to the decline of academic interest in dinosaur evolution.{{fact|date=May 2023}}

This situation persisted until 1964, when John Ostrom discovered a small carnivorous dinosaur which he named Deinonychus antirrhopus,{{cite journal |last1=Ostrom |first1=J. H. |year=1969 |title=Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana |journal=Peabody Museum of Natural History Bulletin |volume=30 |pages=1–165 |url=http://peabody.yale.edu/scipubs/bulletins_postillas/ypmB30_1969.pdf |access-date=2011-01-02 |archive-date=2010-06-27 |archive-url=https://web.archive.org/web/20100627151832/http://www.peabody.yale.edu/scipubs/bulletins_postillas/ypmB30_1969.pdf |url-status=dead }} a theropod whose skeletal resemblance to birds seemed unmistakable. This led Ostrom to argue that Huxley had been right, and that birds had indeed evolved from dinosaurs. Although it was Deinonychus that inspired Ostrom to connect birds with dinosaurs, very similar birdlike dinosaurs, such as Velociraptor, had been known for many decades,{{cite journal |last1=Osborn |first1= H.F. |year=1924 |title=Three new Theropoda, Protoceratops zone, central Mongolia |journal=American Museum Novitates |issue= 144 |pages= 1–12 |hdl=2246/3223 }} but no connection had been made. After Ostrom's discoveries, the idea that birds are dinosaurs gained support among palaeontologists, and today it is almost universally accepted.Darren Naish, 2021, "Ostrom, John", in Dinopedia - A Brief Compendium of Dinosaur Lore, Princeton University Press

Dinosaur monophyly

Around 1880, dinosaurs were largely treated as a monophyletic group (i.e. having a last common ancestor not shared with other reptiles). However, Harry Seeley disagreed with this interpretation, and split the Dinosauria into two orders, the Saurischia ("lizard-hipped") and the Ornithischia ("bird-hipped"), which were seen as members of the Archosauria with no special relationship to each other.{{cite journal |last1=Seeley |first1=H.G. |year=1887 |title= On the classification of the fossil animals commonly named Dinosauria |journal= Proceedings of the Royal Society |volume= 43 |pages= 165–171 | bibcode = 1887RSPS...43..165S | doi = 10.1098/rspl.1887.0117 | issue=258–265 | jstor=114526 |doi-access= free }}{{cite journal | last1 = Seeley | first1 = H.G. | year = 1888 | title = The classification of the Dinosauria | journal = Rep Br Assoc Adv Sci | volume = 1887 | pages = 698–699 }} As such, the Dinosauria was no longer seen as a scientific grouping, and "dinosaur" was reduced to being a popular term, without scientific meaning. This became the standard interpretation throughout much of the twentieth century.Romer A.S. 1956. Osteology of the Reptiles. Chicago: University Chicago. 772 p.

This changed in 1974, when Bakker and Peter Galton published a paper in Nature, arguing that not only were dinosaurs a natural monophyletic group, but that they should be raised to the status of a new class, which would also contain birds.{{cite journal | pages=168–172 | year=1974 | volume=248 | last1=Bakker | doi = 10.1038/248168a0 | journal=Nature |bibcode=1974Natur.248..168B | first1=Robert T. | last2=Galton | first2=Peter M. | title=Dinosaur Monophyly and a New Class of Vertebrates | issue=5444| s2cid=4220935 }} Although initially this revival of dinosaur monophyly was controversial,{{cite book |last1=Charig |first1=A. |year=1976 |chapter= Dinosaur monophyly and a new class of vertebrates: a critical review. |editor1-last= Bellairs |editor1-first=AA |editor2-last =Cox |editor2-first=B |title=Morphology and Biology of Reptiles. Linnean Society Symposium| volume=3|pages= 65–104 | isbn = 0-12-085850-9 }} the idea did gain acceptance, and since the rise of cladistic methodology, it has been nearly universally supported.{{cite journal |doi=10.1080/02724634.1996.10011361 |last1=Novas |first1= F.E. |year=1996 |title= Dinosaur monophyly |journal=Journal of Vertebrate Paleontology |volume= 16 |pages= 723–741 |jstor=4523770 |issue=4 }}

Warm-bloodedness and activity levels

File:Laelaps-Charles Knight-1897.jpg) by Charles R. Knight. Bakker pointed to such restorations to demonstrate that in the 19th century it was widely accepted that dinosaurs may have been active and agile animals.]]

In a series of scientific papers, books, and popular articles in the 1970s and 1980s, beginning with his 1968 paper "The superiority of dinosaurs",{{cite journal | last1 = Bakker | first1 = R.T. | year = 1968 | title = The superiority of dinosaurs | journal = Discovery | volume = 3 | issue = 2| pages = 11–22 }} Robert Bakker argued strenuously that dinosaurs were warm-blooded and active animals, capable of sustained periods of high activity. In most of his writings Bakker framed his arguments as new evidence leading to a revival of ideas popular in the late 19th century, frequently referring to an ongoing "dinosaur renaissance". He used a variety of anatomical and statistical arguments to defend his case,{{cite book |last1= Bakker |first1= R. T. |year= 1987 |chapter= The Return of the Dancing Dinosaurs |title= Dinosaurs Past and Present, vol. I |editor1-first= S. J. |editor1-last= Czerkas |editor2-first= E. C. |editor2-last= Olson |isbn= 0-295-96541-X |publisher= University of Washington Press |url-access= registration |url= https://archive.org/details/dinosaurspastpre0000unse }}{{cite journal | pages=81–85 | last1=Bakker | volume=238 | journal=Nature | first1=Robert T. | year=1972 | title=Anatomical and ecological evidence of endothermy in dinosaurs | doi = 10.1038/238081a0 | bibcode = 1972Natur.238...81B | issue=5359| s2cid=4176132 }} the methodology of which was fiercely debated among scientists.{{cite book |first1=R.D.K. |last1=Thomas |first2= E.C. |last2= Olson |year= 1980 |title=A Cold Look at the Warm-Blooded Dinosaurs | isbn=0-89158-464-1 | publisher= Westview Press }}

These debates sparked interest in new methods for ascertaining the palaeobiology of extinct animals, such as bone histology, which have been successfully applied to determining the growth-rates of many dinosaurs. Today, it is generally thought that many or perhaps all dinosaurs had higher metabolic rates than living reptiles, but also that the situation is more complex and varied than Bakker originally proposed. For example, while smaller dinosaurs may have been true endotherms, the larger forms could have been inertial homeotherms,{{cite book |last1=Benton |first1= M.J. |year=2005 |title=Vertebrate Palaeontology | pages= 221–223 |chapter=Were the Dinosaurs Warm-Blooded or Not? | chapter-url=https://books.google.com/books?id=P1LkOL1CijEC&pg=PA221 |isbn=0-632-05637-1 | publisher=Wiley-Blackwell | edition=3rd}}{{cite journal | last1=Paladino | first1=Frank V. | last2=O'Connor | first2=Michael P. | last3=Spotila | first3=James R. | title=Metabolism of leatherback turtles, gigantothermy, and thermoregulation of dinosaurs | journal=Nature | volume=344 | pages=858–860 | year=1990 | doi=10.1038/344858a0 | issue=6269 | bibcode=1990Natur.344..858P| s2cid=4321764 }} or many dinosaurs could have had intermediate metabolic rates.{{cite journal |last1= Barrick |first1= R. E. |last2= Showers |first2= W. J. |last3= Fischer |first3= A. G. |title= Comparison of Thermoregulation of Four Ornithischian Dinosaurs and a Varanid Lizard from the Cretaceous Two Medicine Formation: Evidence from Oxygen Isotopes |journal= PALAIOS |volume= 11 |issue= 4 |pages= 295–305 |year= 1996 |doi=10.2307/3515240 |jstor= 3515240 |bibcode= 1996Palai..11..295B }}

New theories on dinosaur behaviour

The late 1960s also saw several new theories on the way dinosaurs behaved, often involving sophisticated social behaviour. On the basis of trackways, Bakker argued that sauropod dinosaurs moved in structured herds, with the adults surrounding the juveniles in a protective ring. However, shortly afterwards this particular interpretation was challenged by Ostrom{{cite journal |last1=Ostrom |first1= J.H. |year=1972 |title= Were some dinosaurs gregarious? |journal=Palaeogeography |volume= 11 |pages= 287–301 | doi=10.1016/0031-0182(72)90049-1 |issue=4 |bibcode=1972PPP....11..287O }} among others, although the venerable dinosaur track expert Roland T. Bird apparently agreed with Bakker.{{cite book |last1=Bird |first1=R.T. |year=1985 |title=Bones for Barnum Brown |location=Fort Worth |publisher=Texas Christian University Press |isbn=0-87565-007-4 |url=https://archive.org/details/bonesforbarnumbr00rola }}

The first rigorous study of dinosaur nesting behaviour came in the late 1970s, when palaeontologist Jack Horner showed that the duckbilled dinosaur Maiasaura cared for its young.{{cite journal | last1= Horner | first1= John R. | last2= Makela | first2= Robert | title= Nest of Juveniles Provides Evidence of Family-Structure Among Dinosaurs | journal= Nature | volume= 282|pages=296–298 | year= 1979 | doi=10.1038/282296a0 | issue=5736 | bibcode=1979Natur.282..296H| s2cid= 4370793 }}

Changing portrayal of dinosaurs

The dinosaur renaissance changed not only scientific ideas about dinosaurs, but also their portrayal by artists. Bakker, himself a talented artist, often illustrated his ideas in a lively fashion. Indeed, [https://web.archive.org/web/20090228070415/http://www.lindahall.org/events_exhib/exhibit/exhibits/dino/ost1969_l.shtml Bakker's illustration] of Deinonychus, made for Ostrom's 1969 description, has become one of the most recognisable and iconic of dinosaur restorations.Darren Naish, 2021, "Deinonychus", in Dinopedia - A Brief Compendium of Dinosaur Lore, Princeton University Press

During the 1970s, restorations of dinosaurs shifted from being lizard-like, to being more mammal- and bird-like. Artists started to show dinosaurs in more active poses, and incorporating newer theories of dinosaur locomotion and behaviour. Tails that were widely shown as having been dragged behind a creature, were now shown uplifted, in order to balance the huge bodies while active.{{fact|date=May 2023}}

Besides Bakker, key artists in this "new wave" were first Mark Hallett, Gregory S. Paul in the 1970s, and during the 1980s Doug Henderson and John Gurche.{{fact|date=May 2023}}

Gregory Paul in particular defended and expanded on Bakker's ideas on dinosaur anatomy. He expounded a rigorous and detailed approach to dinosaur restoration, in which he often criticised the errors of the traditionalist approach.{{cite book |last1= Paul |first1= G. S. |year= 1987 |chapter= The science and Art of Restoring the Life Appearance of Dinosaurs and Their Relatives; a Rigorous How-to Guide |title= Dinosaurs Past and Present, vol. II |editor1-first= S. J. |editor1-last= Czerkas |editor2-first= E. C. |editor2-last= Olson |isbn= 0-295-96570-3 |publisher= University of Washington Press |url-access= registration |url= https://archive.org/details/dinosaurspastpre0000unse }} He also produced a large number of restorations showing small dinosaurs with feathers, and defended the idea in a number of articles and his book Predatory Dinosaurs of the World.{{cite book |last1=Paul |first1=G.S. |author-link=Gregory S. Paul |year=1988 |title=Predatory Dinosaurs of the World |location=New York |publisher=Simon & Schuster |isbn=0-671-61946-2 |edition=1st |url=https://archive.org/details/predatorydinosau00paul }} His view was proven largely correct in the late 1990s with the discovery of several feathered dinosaurs. Paul's ideas and style have had a significant impact on dinosaur art.Darren Naish, 2021, "Paul, Greg", in Dinopedia - A Brief Compendium of Dinosaur Lore, Princeton University Press

New extinction theories, the meteor impact

Traditionally paleontology had followed geology in preferring uniformitarian mechanisms, despite the promotion by Eugene Merle Shoemaker of the importance of catastrophic impacts. During the renaissance period Walter Alvarez and others found iridium in the Cretaceous–Tertiary boundary layer. Also the Chicxulub Crater, was identified and determined to be due to a meteor impact. These discoveries led to the acceptance and popularisation of the idea that the extinction had been caused by an impact event. This in turn undermined the assumption that dinosaurs had become extinct because they were inferior to mammals. Instead it suggested they had fallen prey to a random event which no large animal could have survived.

Cultural impacts

Bakker's non-technical articles and books, particularly The Dinosaur Heresies, have contributed significantly to the popularization of dinosaur science.Darren Naish, 2021, "Bakker, Robert (or Bob)", in Dinopedia - A Brief Compendium of Dinosaur Lore, Princeton University Press

The 1993 film version of Jurassic Park was perhaps the most significant event in raising public awareness of dinosaur renaissance theories. For the first time in a major film, dinosaurs were portrayed as intelligent, agile, warm-blooded animals, rather than lumbering monsters more common to older films. Jack Horner was a consultant, and the artwork of Gregory Paul, Mark Hallett, Doug Henderson, and John Gurche were used in pre-production.Darren Naish, 2021, "Jurassic Park", in Dinopedia - A Brief Compendium of Dinosaur Lore, Princeton University Press While the dinosaurs eventually shown in the films had various anatomical inaccuracies, all four of these artists are in the on-screen credits as "Dinosaur Specialists". Bakker himself was not consulted or credited, but his research is referenced by one of the characters in the film, and a Bakker look-alike appears in the sequel The Lost World.{{fact|date=May 2023}}