|
|
Linia 183: |
Linia 183: |
| [[Kategoria:Kampan]] | | [[Kategoria:Kampan]] |
| [[Kategoria:Mastrycht]] | | [[Kategoria:Mastrycht]] |
− | <includeonly>
| |
− |
| |
− |
| |
− | Glut 1997
| |
− |
| |
− | Znane z lokacji: formacja Horseshoe Canyon (Alberta, Kanada)
| |
− | formacja Nemegt (Omnogov; Mongolia)
| |
− | neinazwana formacja w Heilungchang, Chiny
| |
− |
| |
− | znany materiał: 18 okazów (1997), kompletny szkielet, dwie kompletne izolowane czaszki, zarówno dojrzałych jak i młodocianych (juwenilnych) osobników.
| |
− |
| |
− | Holotyp: AMNH 5220, niemal kompletny szkielet z odcisiem skóry
| |
− | Paratyp: AMNH 5221 - nieartykułowana czaszka
| |
− | Plezjotyp: AMNH 5225 - kompletna k. kulszowa
| |
− |
| |
− | Diagnoza:
| |
− | S. osborni (Brown 1912b)
| |
− | czaszka z długim, tylnim kostnym grzebieniem tworzonym przez wydlużenie kosci czołowej i nosowej;
| |
− | k. lzowa bardzo długa, wyższy wyroste k. przedszczękowej wznosi się do tylnej granicy nozdrzy
| |
− | promieniowa i barkowa podobnej długości
| |
− | 8 kręgów krzyżowych
| |
− | kulszowa kończy się wznosząca "stopa"
| |
− | łonowa z któtkim wznoszącym się przednio ostrzem
| |
− | biodrowa silnie łukowata, przedni wyrostek zakrzywiony w dół, cienki płat
| |
− | czwarty krętarz k. udowej poniżej połowy trzony
| |
− | palce II i IV krótie
| |
− |
| |
− | S. angustirostris
| |
− | -węzsza czaszka i dłuższy grzebień (Rozhdestevensky 1957)
| |
− | Maryańska & Osmólska 1981a:
| |
− | -krósze nozdrza
| |
− | -krótsza i głębsza k. łzowa
| |
− | -przednia część żuchwy wydłużona w długi wyrostek, wchodzący klinem między k. szczękową i łzową
| |
− |
| |
− |
| |
− | Saurolophus to pierwszy kanadjski dinozaur znany z niemal kompletnego szkieletu.
| |
− |
| |
− |
| |
− | Historia odkrycia:
| |
− | 1911 - Amerykańskie Muzeum historii naturalnej z Horseshoe Canyon Formation, wówczas znane jako formacja Edmonton.
| |
− | 1912 - Barnum Brown opisuje holotyp i czasszkę; szkielet zostaje wypreparowany i wystawiony w amerykańskim muzeum historii naturalnej
| |
− | 1913 - Barnum Brown opisuje Saurolophus osborni.
| |
− |
| |
− |
| |
− | Saurolophus to duzy hadrozaur = holotypowysz szkielet mierzył ok. 8,4 m; 2 tony (Paul, 1988 - Glut, 1997)
| |
− |
| |
− |
| |
− |
| |
− | Najbardziej wyróżniającą się cechą zaurolofa był kostny grzebień, który wznosi się ponad kąt czaszki niczym kolec. Brown 1912b,1913a porównywał grzebień do tego, ubecnego u kameleona, sugerując, że służył on do jako miejsce przyczepu silnych mięśni.
| |
− | Dodson 1975 - sugeruje, że grzebienie mogły mieć znaczenie w identyfikacji płciowej.
| |
− |
| |
− | Pierścień sklerotyczny z holotypowej czaszki wykazuje, że oko było znacznie mniejsze niż oczodół. Ruszeel 1940a wykazal, że płyty pierścienia sklerotycznego nie są szeregowe w jednym kierunku, ale raczej mają jeden lub więcej segmentów w których płytki nachodzą na siebie w odwrotnym kierunu niż w innym segmencie/segmentach.
| |
− |
| |
− | w 1914 roku Brown utworzył podrodzinę Saurolophinae, zawierającą hadrozaurydy noszące szczątkowy grzebień
| |
− | Brett-Surman zauważył, że wszystkie hadrozaurydy mogą byc przyporządkowane do jednej z dwóch podrodzin - Hadrosaurinae lub Lambeosaurinae, gdzie Saurolophinae zawierajacym się w Hadrozaurynach.
| |
− |
| |
− | Duży okaz z Mongolii został wydobyty z formacji nemegt podczas Polsko-Mongolskich ekspedycji paleontologicznych. Przez Ryszarda Gradińskiego, Józefa Kazmierczaka i Jerzego Lefelda. Mierzył 12 metrów długości. S. angus to najbardziej obfity azjatycki hadrozaur, znany zarówno z Ałtan Uła jak i Tsagan hushu, i wydaje się być dominującym roślinożercą w formacji Nemegt
| |
− |
| |
− | Bazując na badaniach czaszi młodego osobnik s.angu m&o 1979 stwierdziły, że jak u innych ptasiomiednicsznych - dwie kości ponadoczodołwe są inkorporowane w górną granicę oczodołu czaszki. M&o 1979 zasugerowały rówmnjież, że utrata ponadoczodołowych jest obecna zarówno u prymitywncyh lambeozaurynow jak i hadrozaurynów, podczas gdy u bardziej zaawansowanych lambezoaurynów ponadoczodołwe mogły być początkowo częścią obręczy oczodołowej, ulegając fuzji z przedczołową i zaoczodołową w czasie ontogenezy.
| |
− | Wykazały również 1981, że wysotek k. nosowej jest prawdopodobnie wydrążony, a lity jedynie w szczytowym końcu. Zasugerowały, że grzebien służył do zwiększenia powierzchni oddechowej otworu nosowego, mając tym samym funkcję regulacji termicznej. Również do pewnego stopnia utrata u hadrozaurynów stawów pomiędzy częściami czaszki, zwłaszcza pomiędzy dolną gałęzią . przedszczękwoej i szczekową, służyła jako coś w rodzaju amortyzator wstrząsów, chroniacy delikatną struktruę nozdrzy przed uszkodzeniem w trakcie żucia.
| |
− |
| |
− | S. kryschtofovici - n.d. - opiera się na bliższym końcu lewej k. kulszowej, znalezionej w Beiliyie Kruchi, w północnym Heilungchiang w Chinach. Została opisana przez Riabinina w 1930b. Jest obecnie uznawany za synonim s. ang.
| |
− |
| |
− |
| |
− | Glut 2001
| |
− | w 1999 Ishigaki doniósł o odryciu ponad 600 dużych (25-155 cm długości), trójpalczastych tropów z późnej kredy w Bugeen Tsav i Gurilin Tsav w zachodniej części postyni Gobi.
| |
− | Zostały odryte w latach 1995-1998 przez Hayshsibara Museum of Natural Science-Mongolian Paleontological Center Joint Paleoncological Expedicion Team, zostały przypisane do zaurolofa, bazując na obfitości kościu należących do tego rodzaju na tym samym terenie w tym samym czasie.
| |
− | Jak twierdzi Ishigakio, ponad 15 000 tropów dinozaurów z 11 różnych lokacji na Gobi zopstały znalezionych podczas tej ekspedycji - również ankylozaurydów i teropodów.
| |
− |
| |
− | Ishigaki,S.
| |
− | Abundant Dinosaur Footprints from Upper Cretaceous of Gobi
| |
− | Desert, Mongolia
| |
− | Journal of Vertebrate Paleontology, Vol. 19, Supplement to Number
| |
− | 3, p. 54A, 1999
| |
− |
| |
− | Glut 1997
| |
− |
| |
− | Etymologia: z greckiego - "sauros" = "jaszczur" + "lophus" - grzebień. Grzebieniasty jaszczur
| |
− | Znane z lokacji: formacja Horseshoe Canyon (Alberta, Kanada)
| |
− | formacja Nemegt (Omnogov; Mongolia)
| |
− | neinazwana formacja w Heilungchang, Chiny
| |
− |
| |
− | znany materiał: 18 okazów (1997), kompletny szkielet, dwie kompletne izolowane czaszki, zarówno
| |
− |
| |
− | dojrzałych jak i młodocianych (juwenilnych) osobników.
| |
− |
| |
− | Holotyp: AMNH 5220, niemal kompletny szkielet z odcisiem skóry
| |
− | Paratyp: AMNH 5221 - nieartykułowana czaszka
| |
− | Plezjotyp: AMNH 5225 - kompletna k. kulszowa
| |
− |
| |
− | Diagnoza:
| |
− | S. osborni (Brown 1912b)
| |
− | czaszka z długim, tylnim kostnym grzebieniem tworzonym przez wydlużenie kosci czołowej i
| |
− |
| |
− | nosowej;
| |
− | k. lzowa bardzo długa, wyższy wyroste k. przedszczękowej wznosi się do tylnej granicy nozdrzy
| |
− | promieniowa i barkowa podobnej długości
| |
− | 8 kręgów krzyżowych
| |
− | kulszowa kończy się wznosząca "stopa"
| |
− | łonowa z któtkim wznoszącym się przednio ostrzem
| |
− | biodrowa silnie łukowata, przedni wyrostek zakrzywiony w dół, cienki płat
| |
− | czwarty krętarz k. udowej poniżej połowy trzony
| |
− | palce II i IV krótie
| |
− |
| |
− | S. angustirostris
| |
− | -węzsza czaszka i dłuższy grzebień (Rozhdestevensky 1957)
| |
− | Maryańska & Osmólska 1981a:
| |
− | -krósze nozdrza
| |
− | -krótsza i głębsza k. łzowa
| |
− | -przednia część żuchwy wydłużona w długi wyrostek, wchodzący klinem między k. szczękową i łzową
| |
− |
| |
− |
| |
− | Saurolophus to pierwszy kanadjski dinozaur znany z niemal kompletnego szkieletu.
| |
− |
| |
− |
| |
− | Historia odkrycia:
| |
− | 1911 - Amerykańskie Muzeum historii naturalnej z Horseshoe Canyon Formation, wówczas znane jako
| |
− |
| |
− | formacja Edmonton.
| |
− | 1912 - Barnum Brown opisuje holotyp i czasszkę; szkielet zostaje wypreparowany i wystawiony w
| |
− |
| |
− | amerykańskim muzeum historii naturalnej
| |
− | 1913 - Barnum Brown opisuje Saurolophus osborni.
| |
− |
| |
− |
| |
− | Saurolophus to duzy hadrozaur = holotypowysz szkielet mierzył ok. 8,4 m; 2 tony (Paul, 1988 -
| |
− |
| |
− | Glut, 1997)
| |
− |
| |
− |
| |
− |
| |
− | Najbardziej wyróżniającą się cechą zaurolofa był kostny grzebień, który wznosi się ponad kąt
| |
− |
| |
− | czaszki niczym kolec. Brown 1912b,1913a porównywał grzebień do tego, ubecnego u kameleona,
| |
− |
| |
− | sugerując, że służył on do jako miejsce przyczepu silnych mięśni.
| |
− | Dodson 1975 - sugeruje, że grzebienie mogły mieć znaczenie w identyfikacji płciowej.
| |
− |
| |
− | Pierścień sklerotyczny z holotypowej czaszki wykazuje, że oko było znacznie mniejsze niż
| |
− |
| |
− | oczodół. Ruszeel 1940a wykazal, że płyty pierścienia sklerotycznego nie są szeregowe w jednym
| |
− |
| |
− | kierunku, ale raczej mają jeden lub więcej segmentów w których płytki nachodzą na siebie w
| |
− |
| |
− | odwrotnym kierunu niż w innym segmencie/segmentach.
| |
− |
| |
− | w 1914 roku Brown utworzył podrodzinę Saurolophinae, zawierającą hadrozaurydy noszące szczątkowy
| |
− |
| |
− | grzebień
| |
− | Brett-Surman zauważył, że wszystkie hadrozaurydy mogą byc przyporządkowane do jednej z dwóch
| |
− |
| |
− | podrodzin - Hadrosaurinae lub Lambeosaurinae, gdzie Saurolophinae zawierajacym się w
| |
− |
| |
− | Hadrozaurynach.
| |
− |
| |
− | Duży okaz z Mongolii został wydobyty z formacji nemegt podczas Polsko-Mongolskich ekspedycji
| |
− |
| |
− | paleontologicznych. Przez Ryszarda Gradińskiego, Józefa Kazmierczaka i Jerzego Lefelda. Mierzył
| |
− |
| |
− | 12 metrów długości. S. angus to najbardziej obfity azjatycki hadrozaur, znany zarówno z Ałtan
| |
− |
| |
− | Uła jak i Tsagan hushu, i wydaje się być dominującym roślinożercą w formacji Nemegt
| |
− |
| |
− | Bazując na badaniach czaszi młodego osobnik s.angu m&o 1979 stwierdziły, że jak u innych
| |
− |
| |
− | ptasiomiednicsznych - dwie kości ponadoczodołwe są inkorporowane w górną granicę oczodołu
| |
− |
| |
− | czaszki. M&o 1979 zasugerowały rówmnjież, że utrata ponadoczodołowych jest obecna zarówno u
| |
− |
| |
− | prymitywncyh lambeozaurynow jak i hadrozaurynów, podczas gdy u bardziej zaawansowanych
| |
− |
| |
− | lambezoaurynów ponadoczodołwe mogły być początkowo częścią obręczy oczodołowej, ulegając fuzji z
| |
− |
| |
− | przedczołową i zaoczodołową w czasie ontogenezy.
| |
− | Wykazały również 1981, że wysotek k. nosowej jest prawdopodobnie wydrążony, a lity jedynie w
| |
− |
| |
− | szczytowym końcu. Zasugerowały, że grzebien służył do zwiększenia powierzchni oddechowej otworu
| |
− |
| |
− | nosowego, mając tym samym funkcję regulacji termicznej. Również do pewnego stopnia utrata u
| |
− |
| |
− | hadrozaurynów stawów pomiędzy częściami czaszki, zwłaszcza pomiędzy dolną gałęzią .
| |
− |
| |
− | przedszczękwoej i szczekową, służyła jako coś w rodzaju amortyzator wstrząsów, chroniacy
| |
− |
| |
− | delikatną struktruę nozdrzy przed uszkodzeniem w trakcie żucia.
| |
− |
| |
− | S. kryschtofovici - n.d. - opiera się na bliższym końcu lewej k. kulszowej, znalezionej w
| |
− |
| |
− | Beiliyie Kruchi, w północnym Heilungchiang w Chinach. Została opisana przez Riabinina w 1930b.
| |
− |
| |
− | Jest obecnie uznawany za synonim s. ang.
| |
− |
| |
− |
| |
− | Glut 2001
| |
− | w 1999 Ishigaki doniósł o odryciu ponad 600 dużych (25-155 cm długości), trójpalczastych tropów
| |
− |
| |
− | z późnej kredy w Bugeen Tsav i Gurilin Tsav w zachodniej części postyni Gobi.
| |
− | Zostały odryte w latach 1995-1998 przez Hayshsibara Museum of Natural Science-Mongolian
| |
− |
| |
− | Paleontological Center Joint Paleoncological Expedicion Team, zostały przypisane do zaurolofa,
| |
− |
| |
− | bazując na obfitości kościu należących do tego rodzaju na tym samym terenie w tym samym czasie.
| |
− | Jak twierdzi Ishigakio, ponad 15 000 tropów dinozaurów z 11 różnych lokacji na Gobi zopstały
| |
− |
| |
− | znalezionych podczas tej ekspedycji - również ankylozaurydów i teropodów.
| |
− |
| |
− | Ishigaki,S.
| |
− | Abundant Dinosaur Footprints from Upper Cretaceous of Gobi
| |
− | Desert, Mongolia
| |
− | Journal of Vertebrate Paleontology, Vol. 19, Supplement to Number
| |
− | 3, p. 54A, 1999
| |
− |
| |
− |
| |
− |
| |
− | ______________
| |
− | Barnum brown, 2010
| |
− |
| |
− | p.141
| |
− | While the rest of the crew quarried — including George Sternberg, who
| |
− | arrived on July 7 — Brown focused on prospecting. In all, he lists thirtysix
| |
− | major specimens, including fifteen hadrosaurs (such as Saurolophus),
| |
− | nine ceratopsians, three ankylosaurs, four ornithomimids (presumably
| |
− | Struthiomimus), and one plesiosaur.42 Although plesiosaur specimens are
| |
− | uncommon in these nonmarine sediments, they are not really unusual.
| |
− | Paleontologists now suspect that they swam up active river channels either
| |
− | in search of ballast stones or to shed parasites. In this early phase of the
| |
− | expedition, Brown downplayed the competition with Ottawa, reporting
| |
− | to Matthew: “The Ottawa party are somewhere . . . [on the river] in the
| |
− | Edmonton formation approximately at Drumheller twenty miles below
| |
− | which does not disturb me as that is in the lower part of the beds [which
| |
− | produce] chiefly quarry [i.e., bonebed] specimens. As long as they are there I
| |
− | shall concentrate the whole party in this formation where the exposures are
| |
− | best.” 43
| |
− |
| |
− | p. 151
| |
− | Brown’s discoveries continue to resonate. Today, paleontologists still recognize
| |
− | eight species of nonavian dinosaurs based on holotypes that Brown
| |
− | and his crews collected from the Dinosaur Park Formation, which he
| |
− | called the Belly River Beds: three horned dinosaurs, Chasmosaurus kaiseni
| |
− | (AMNH 5401), Monoclonius cutleri (AMNH 5427), and Styracosaurus
| |
− | parksi (AMNH 5372); two duckbills, Corythosaurus casuarius (AMNH
| |
− | 5240) and Prosaurolophus maximus (AMNH 5386); a small carnivorous
| |
− | theropod, Dromaeosaurus albertensis (AMNH 5356); and a dome-headed
| |
− | pacycephalosaur, Ornatotholus browni (AMNH 5450), which probably
| |
− | represents a juvenile Stegoceras.94 The collections of Brown’s crews from
| |
− | the Edmonton Group allowed Brown to describe four other new species as
| |
− | well: the horned dinosaurs Anchiceratops ornatus and Leptoceratops gracilis
| |
− | and two duckbilled dinosaurs, Hypacrosaurus altispinus and Saurolophus
| |
− | osborni. Today, Brown’s old quarries are being located, based on photos
| |
− | he took and using as evidence objects that he and his crews left behind,
| |
− | such as plaster, scrap lumber, and newspaper used to make the specimen
| |
− | casts.95 This project is being conducted in conjunction with GPS survey
| |
− | work in Dinosaur Provincial Park, to preserve not only the locality data
| |
− | for the specimens but also their stratigraphic context, which allows for a
| |
− | more comprehensive understanding of when the animals lived and how
| |
− | the fauna evolved some 75 million years ago.
| |
− |
| |
− |
| |
− | __________
| |
− | Chinese Fossil Vertebrates
| |
− |
| |
− | Nemegtian Vertebrates
| |
− | The vertebrate fossil assemblage of the Nemegt Formation in Mongolia is the
| |
− | basis of the Nemegtian land-vertebrate faunachron (Jerzykiewicz and Russell
| |
− | 1991: 370). Characteristic taxa are the theropod Tarbosaurus, the sauropods
| |
− | Nemegtosaurus (see figure 9-17) and Opisthocoelicaudia and the hadrosaurid
| |
− | Saurolophus. In northeastern China, Riabinin (1930) described Tarbosaurus?,
| |
− | Tanius, and Saurolophus from strata in Heilongjiang of Nemegtian age. In Xinjiang,
| |
− | the Subashi Formation yields Tarbosarus and Nemegtosaurus and thus is
| |
− | of Nemegtian age (Dong 1977, 1997f and h).
| |
− | I consider the vertebrate fauna of the upper Wangshi Formation of Shandong
| |
− | (see figure 9-6) (Z. Cheng et al. 1995; X. Wang 1996) to be of Nemegtian age,
| |
− | although this correlation is not certain. It has yielded the tyrannosaurid Chingkankousaurus
| |
− | fragilis Young, the hadrosaurids Tanius sinensis Wiman (= T. chingkankouensis
| |
− | Young, = T. laiyangensis Zhen), Shantungosaurus giganteus Hu, and
| |
− | Tsintaosaurus spinorhinus Young (see figure 9-18); the ankylosaur Pinacosaurus
| |
− | cf. P. grangeri Gilmore (see Buffetaut 1995); the pachycephalosaurid Micropachycephalosaurus
| |
− | hongtuyanensis Dong; and dinosaur eggs (Wiman 1929;
| |
− | Chow 1951; Young 1958b; Dong 1978, 1992). However, note that Pinacosaurus
| |
− | suggests that part of the Wangshi Series may be of Djadokhtan age (Buffetaut
| |
− | 1995; Buffetaut and Tong 1995), as does the suggestion that Bactrosaurus
| |
− | johnsoni from Iren Dabasu is a synonym of Tanius sinensis (Z. Cheng et al.
| |
− | 1995).
| |
− | What may be even younger dinosaur dominated assemblages from China
| |
− | must be assigned a Nemegtian age because they cannot at present be distin-
| |
− | guished from the classic Nemegtian assemblage. Nemegtian thus represents the
| |
− | last interval of Cretaceous time that can be recognized from fossil vertebrates in
| |
− | China. The Nemegtian hadrosaurid Saurolophus Brown is an early Maastrichtian
| |
− | genus in North America (Horshoe Canyon Formation, Alberta). This suggests
| |
− | an early Maastrichtian age for at least part of the Nemegtian.
| |
− |
| |
− |
| |
− | ______
| |
− | Flaming Cliffs
| |
− |
| |
− | 131-132
| |
− | At Altan Ula, Efremov's party found skeletons of seven giant
| |
− | hadrosaurs embedded in close association in a very hard red sandstone,
| |
− | seemingly the product of a mass death and burial. T h e site was called the
| |
− | "Dragons' Tomb." T h e skeletons turned out to be rather undragonly herbivores,
| |
− | the duckbill Saurolophus angustirostris, named for the solid crest on
| |
− | the back of the top of the head. Saurolophus was a big hadrosaur, with
| |
− | adults reaching lengths of forty feet and some individuals looming over
| |
− | twenty-five feet high.
| |
− | Hadrosaurs of the Cretaceous Gobi, as well as those in North America,
| |
− | were built to get around quite adeptly on land, but they also may have
| |
− | entered the water to feed on plants. T h e abundance of lacustrine and fluvial
| |
− | beds near the "Dragons' Tomb" probably provided a rich Saurolophus
| |
− | habitat. It is noteworthy that this locality contained not only skeletons but
| |
− | also remarkable fossil evidence for soft parts. Bubbly or pebbly impressions
| |
− | of skin were found in association with the skeletons. T h e fossilized "chunks
| |
− | of skin" are actually casts made from reverse-image molds pressed into the
| |
− | substrate by these ponderous hulks as they lay in the mud to rest, feed, or
| |
− | die. Skin impressions of hadrosaurs are known from other places, and in
| |
− | some cases they are truly spectacular. T h e world's premier specimen resides
| |
− | in the recently renovated dinosaur halls at the American Museum of Natural
| |
− | History, essentially a cast of the skin of the entire body—a complete
| |
− | mud "mummy"—of a North American Edmontosaurus, a distant relative of
| |
− | Saurolophus.
| |
− | All hadrosaurs have a distinctive battery of closely packed teeth,
| |
− | whose crown surfaces combine to form a mill. Ridges acted together like a
| |
− | rasping file that efficiently broke down tough vegetation. There are actually
| |
− | hundreds of teeth in a hadrosaur jaw but they work together as two sets
| |
− | of grinding mills, one set in each side of the upper and lower jaws. The
| |
− | skull roof and the back of the jaw show prominent struts and ledges of
| |
− | bone. These served as attachments for muscles whose contraction moved
| |
− | the jaws back and forth for effective milling. The skeleton itself is appointed
| |
− | with a rather short but very flexible and sinuous neck, small fore
| |
− | limbs, but large elongated hind limbs. The vertebrae of the massive and
| |
− | lengthy tail are equipped with extended splints or chevron bones, which
| |
− | project downward from the body of each tail (or caudal) vertebra. Covered
| |
− | with flesh, these would give the hadrosaur tail its notable flattened appearance.
| |
− | One of the most remarkable features of the vertebral column in
| |
− | hadrosaurs, as well as in certain other dinosaurs, is the intricate weaving of
| |
− | ossified tendons. These crisscross among the spines, extending above each
| |
− | vertebra in the back (lumbar) and the tail region. They seem to be there for
| |
− | support of the back; to prevent the trusswork of the vertebral column from
| |
− | sagging against that great mass of muscle, fat, and internal organs.
| |
− | Something, of course, had to feed on big herbivores like hadrosaurs,
| |
− | and the best candidate in the Gobi is the tyrannosaurid Tarbosaurus. During
| |
− | the expeditions of the 1940s the Russian team found three skeletons of
| |
− | Tarbosaurus in the Nemegt Formation at the Dragons' Tomb site, where
| |
− | several Saurolophus lay. Tarbosaurus (the name means alarming reptile) is
| |
− | very like the more familiar Tyrannosaurus and doubtless a close relative.
| |
− | Tarbosaurus is big. Some skeletons are up to forty-six feet long, longer than
| |
− | Tyrannosaurus by more than six feet (although apparently it stood a bit
| |
− | shorter than the tyrant king). Like sauropods, these animals required enormous
| |
− | amounts of food, in this case, meat. They were well built for the purpose.
| |
− | T h e skull of Tarbosaurus is more than four feet long. Its jaws are studded
| |
− | with recurved razor-edged teeth, some nearly six inches long. The
| |
− | three toes of the hind feet are appointed with viciously sharpened and
| |
− | curved claws. The lengthy hindlimb bones show scars for attachment of
| |
− | enormous muscles. Everything about it suggests power and agility, an animal
| |
− | capable of lunging its massive body at a hapless hadrosaur and disemboweling
| |
− | it in an instant.
| |
− |
| |
− | 167-169
| |
− | D R I F T I N G D I N O S A U R S
| |
− | This enrichment in the texture of landforms, oceans and seas, and certainly
| |
− | the isolation of many regions, fueled the momentum for evolution and divergence.
| |
− | Geographic isolation—by seas, rivers, mountain ranges, or contrasting
| |
− | climate—is a major driving force of speciation because populations
| |
− | that at one time exchanged genes are suddenly cut off from one another.
| |
− | They then evolve along their own pathways. Likewise, this differentiation
| |
− | can be expressed by the divergence among groups containing those species.
| |
− | So Cretaceous dinosaurs can be divided into various regional fiefdoms. To
| |
− | appreciate this, we must abandon a mind set that makes us view continents
| |
− | as they are today. Remember that in the Northern Hemisphere, eastern
| |
− | Asia and western North America were broadly connected in the region of
| |
− | the Bering Sea. On the other hand, eastern North America was cut off
| |
− | from this complex by a great seaway. It was, however, connected, at times,
| |
− | to broken-up parts of Europe in the North Atlantic region. Thus we can
| |
− | think of two continents—let's call them Asiamerica and Euroatlantis—instead
| |
− | of a single northern continent or the customary division of North
| |
− | America and Eurasia. Expectedly, dinosaur divergence mirrors this conti
| |
− | nental pattern. The armored ankylosaurids, the horned ceratopsians, and
| |
− | the more specialized hadrosaurs, like Saurolophus and the crested Corythosaurus,
| |
− | were evolving in the Gobi and the Rocky Mountain region and
| |
− | presumably parts in between. In contrast, primarily more generalized
| |
− | hadrosaurs claimed Europe and eastern North America. Although the
| |
− | dromaeosaurids (the group that includes Velociraptor) ranged broadly over
| |
− | the northern landmasses, they were virtually excluded from the southern
| |
− | continents. South of the equator there were a number of groups common
| |
− | to the northern continents—iguanodontids, hypsilophodontids, and
| |
− | sauropods—but these were distinctively different genera or even higher
| |
− | groups containing several genera. Also, our denizens of the Gobi, the protoceratopsids,
| |
− | as well as their ceratopsid relatives were notably absent from
| |
− | the southern continents.
| |
− | We see here, then, a picture of dinosaurs and continents that jives
| |
− | poorly with Osborn's and Andrews' concept of a center of origin for vertebrate
| |
− | evolution in Asia. What the pattern does suggest is a history of dinosaur
| |
− | differentiation that closely tracked the breakup of the continents.
| |
− | Originally, certain groups of dinosaurs ranged broadly over the sutured
| |
− | landmasses. Their descendants were allowed the opportunity of divergence
| |
− | once these landmasses were separated. Central Asia was certainly an im-
| |
− | portant region for the emergence of certain dinosaur groups, but it wasn't
| |
− | the only such region.
| |
− |
| |
− | T H E C O M F O R T A B L E C O R R I D O R
| |
− | Another point that has much interested paleontologists concerns the affinity
| |
− | of Cretaceous dinosaurs between two major regions of the world—
| |
− | Central Asia and western North America. At closer inspection, the resemblances
| |
− | between these two faunas are even more striking. Velociraptor is
| |
− | very much like another somewhat larger dromaeosaur from North America,
| |
− | Deinonychus. The hadrosaur Saurolophus is known from both regions.
| |
− |
| |
− |
| |
− | 194
| |
− | On July 27, the day after the departure of the BBC, a small team—
| |
− | Mark, Jim, Lowell, Dashzeveg, and I—struck out with two Mitsus and
| |
− | Mangal Jal's G A Z to a wholly new area. This sortie represented our farthest
| |
− | push westward—to a frontier as hot and windy and uninhabited as
| |
− | lonely Kheerman Tsav, a maze of sandstone cliffs and spires known as Bugin
| |
− | Tsav. T h e Russians and Mongolians had worked this place extensively,
| |
− | but we had never been there and we were anxious to see it. Bugin Tsav,
| |
− | whose baroquely intricate canyons exposed the multihued Nemegt Formation,
| |
− | had been declared a national park. The park lay about twenty miles
| |
− | west and slightly north of Naran Bulak, the lonely windswept complement
| |
− | to Kheerman Tsav directly to its south. Despite the seclusion of Bugin
| |
− | Tsav, we had no intention of removing dinosaur skeletons. We were simply
| |
− | interested in reconnoitering the place for skeletons that might warrant
| |
− | work there—pending permission for major excavation—the next field season.
| |
− | We did indeed find the myriad canyons, washes, cliffs, and hills of
| |
− | Bugin Tsav full of big bones. Some of these were the skeletons of lumbering
| |
− | sauropods or hadrosaurs. At one spot, I spied a long string of tail vertebrae
| |
− | snaking its way around the edge of a hill. As I walked around the
| |
− | other side of this knob, I was amazed to see more of the skeleton, part of
| |
− | the ribs and the neck vertebrae exposed. T h e beasts of Bugin Tsav were of
| |
− | mountain-sized proportions. They can be discovered from a distance. One
| |
− | especially hot July in the subsequent field season of 1993 we were driving
| |
− | through these extensive badlands when Mark suddenly told me to stop the
| |
− | car. Fifty yards back, the giant skeleton of a Saurolophus, a forty-foot-long
| |
− | duck-billed dinosaur, was exposed on top of a small sand hill. A Tarbosaurus
| |
− | foot, with its distinctive tripod of digits and its long claws, rested
| |
− | on top of the duck-billed skeleton, as if the carnosaur were staking a claim
| |
− | to the carcass.
| |
− |
| |
− | 215
| |
− | This pattern of head accouterments and their possible bearing on social
| |
− | rank or role is not confined to ceratopsians. The duck-billed
| |
− | hadrosaurs are differentiated mainly by the development (or lack thereof)
| |
− | of their emblematic head crests. Some forms have virtually no crest at all.
| |
− | This may have been a primitive feature of the group, which is found in
| |
− | both early and later hadrosaurs (remember, the fossil record doesn't always
| |
− | perfectly mirror the advancement of steps in evolution). In crested forms
| |
− | the name of the game is weird elaboration and variation. Saurolophus, our
| |
− | beast from the Gobi (also known from North America), has a prominent
| |
− | bony ridge on top of the snout and face that ends behind in a small spike.
| |
− | The Gobi species of this group shows some distinctiveness in its somewhat
| |
− | longer and more fan-shaped head spike. But the really bizarre species are
| |
− | some of the North American forms. An extremely broad platelike crest is
| |
− | known in Corythosaurus, and there is a long bony tube that extends backward
| |
− | nearly three and a half feet from the skull of Parasaurolophus. Stranger
| |
− | still is the fact that the nasal passages actually extend for some distance into
| |
− | these hollow crests. Their caliber and design vary, just like the differences
| |
− | one sees in the passageways of trombones, saxophones, and tubas. Not all
| |
− | these crests are hollow; for example, hadrosaurines, which include the
| |
− | Gobi beast Saurolophus, lacked such passageways.
| |
− | These crests have excited some paleontologists to a considerable degree
| |
− | and there is no shortage of speculation on their function. As with
| |
− | many reconstructions of fossils, none of these explanations can be decisively
| |
− | verified, nor are any of them necessarily false. To complicate matters,
| |
− | the crests may have taken on different functions in different species. Yet it
| |
− | is possible to determine which of these ideas make more sense. The suggested
| |
− | use of the crests for breathing, air storage, or air trapping while underwater
| |
− | seems on the whole rather unlikely. These beasts were adept in
| |
− | water, and they might have retreated to lakes, rivers, and seas to escape a
| |
− | rapacious Tarbosaurus or Tyrannosaurus. Nonetheless, their well-supported
| |
− | bodies and their tooth batteries indicate that hadrosaurs probably spent
| |
− | most of their time on land, eating relatively tough branches and leaves of
| |
− | trees and bushes. Fossilized conifer needles, branches, deciduous foliage,
| |
− | and numerous small seeds and fruits have been claimed to be the "stomach
| |
− | contents" of a hadrosaur Edmontosaurus. If this identity is correct, one can
| |
− | assume that the duckbills did not have an overpowering need to feed underwater
| |
− | for long periods of time.
| |
− | For lack of a better notion, the correlation between the hadrosaur
| |
− | crest development and a signaling function endures. T h e idea was refined
| |
− | starting with some thoughts expressed by the paleontologist James Hopson
| |
− | at the University of Chicago and later elaborated by Peter Dodson at
| |
− | the University of Pennsylvania and Dave Weishampel at Johns Hopkins
| |
− | University. Animals that use such obvious cues today often share a number
| |
− | of qualities. They have a keen sense of eyesight and/or hearing. They are
| |
− | often social and sexually dimorphic (males are larger and more aggressively
| |
− | built and armed than females, or vice versa), with individuals in frequent
| |
− | threatening behavior or combat for competition for mates of the opposite
| |
− | sex. Finally, species living in the same area that rely on such signals, like the
| |
− | antelopes of the Serengeti, often have very distinctive, highly different
| |
− | head ornaments like horns, to cue their own species.
| |
− | Hadrosaurs in a broad sense fit this picture. They have large eye sock
| |
− | ets and intricate ear bones, indicating acute vision and hearing. Weishampel
| |
− | developed some ingenious experiments to suggest that the hollow
| |
− | tubular crests of Parasaurolophus and other hadrosaurs were effective sound
| |
− | resonators. Moreover, Dodson's studies have shown that crests are accentuated
| |
− | in adults and, even in the case of adults, both big-crested and
| |
− | smaller-crested individuals are found in samples representing the same
| |
− | species. As in the case of the ceratopsians, this suggests a difference in the
| |
− | sexes pertaining to social behavior. Either the males or the females were establishing
| |
− | mating hierarchies or involved in rituals of signaling threats and
| |
− | combat. Finally, in a few localities in North America more than six different
| |
− | species are found together and most of these are easily discriminated
| |
− | by their varying head crests.
| |
− | What about our Gobi creature Saurolophus} One might conjure up a
| |
− | picture of massive animals feeding in the marshes and deeps of a lake.
| |
− | Crests on some individuals may have indicated their position in the mating
| |
− | hierarchy, a signal backed up by the honking sounds of protective
| |
− | males. Is this vision the reality of seventy-five million years before Efremov
| |
− | and his band came upon hadrosaur skeletons in the Nemegt Valley? We'll
| |
− | never know. Some ideas, like the use of crests for visual cues, seem to match
| |
− | some circumstantial evidence. Elaboration of the scene is not so easy however.
| |
− | The myriad published color schemes for dinosaur crests, shields,
| |
− | trunks, and tails are purely imaginary. At any rate it's fun to think about
| |
− | them.
| |
− |
| |
− |
| |
− | ____________
| |
− | Dragon Hunter
| |
− | 374
| |
− | After their five years of work in both hemispheres, the Canadians
| |
− | and Chinese were able to demonstrate that large sections of the continental
| |
− | masses were not covered by oceans during the late Cretaceous
| |
− | and were connected in their northernmost latitudes by land bridges. As
| |
− | Michael J. Novacek has pointed out, a fairly wide variety of dinosaurs
| |
− | made use of these intercontinental links to travel between Asia and
| |
− | North America. For example, the hadrosaur Saurolophus is found in
| |
− | both regions; Velociraptor, ankylosaurs, and Oviraptor had close relatives
| |
− | in North America, as did larbosaurus, a slightly smaller version of
| |
− | Tyrannosaurus, which are so much alike that some paleontologists believe
| |
− | they should both be classified as a single species. And a theropod
| |
− | found in the Gobi, Sauromithoides, has a counterpart known as
| |
− | Troodon that inhabited Alberta, Wyoming, and Montana.
| |
− |
| |
− |
| |
− |
| |
− | ____________________---
| |
− | Currie
| |
− |
| |
− | American Dinosaurs
| |
− | A close relationship, possibly at the species
| |
− | level, of Tyrannosaurus with the Asiatic Tarbosaurus
| |
− | is recognized. Other evidence for exchange is better
| |
− | documented by Canadian dinosaurs, notably the ha-
| |
− | drosaurine Saurolophus. Due to the relatively impoverished
| |
− | faunas of the Judith River Formation and
| |
− | dearth of early Maastrichtian dinosaurs in the United
| |
− | States, coupled with the relatively restricted area of
| |
− | late Maastrichtian strata in Alberta and Saskatchewan,
| |
− | faunal overlap between the United States and
| |
− | Canada is not as great as expected, and the greater
| |
− | diversity and completeness of specimens favors Canada.
| |
− |
| |
− | American Museum of Natural History
| |
− | In 1902 Barnum Brown led an AMNH expedition
| |
− | to the Cretaceous beds of the HELL CREEK region
| |
− | of Montana. This resulted in the first known specimen
| |
− | of Tyrannosaurus rex, in 1902, and a second,
| |
− | more highly preserved specimen in approximately
| |
− | 1908. This second specimen is generally regarded
| |
− | as the most famous dinosaur fossil in the world
| |
− | and has long been a centerpiece of the AMNH.
| |
− | Brown went on to lead museum-sponsored expeditions
| |
− | in 1910–1915 to the Red Deer River region of
| |
− | Alberta, Canada. These also yielded rich discoveries,
| |
− | especially of hadrosaurs such as Saurolophus and
| |
− | Corythosaurus. In the 1930s another AMNH expedition
| |
− | led by Brown excavated a large collection of
| |
− | Jurassic fossils from the Howe Ranch site in
| |
− | Wyoming.
| |
− |
| |
− | Canadian Dinosaurs
| |
− | The late Campanian–early Maastrichtian beds of
| |
− | the Horseshoe Canyon Formation near Drumheller
| |
− | are also rich with skeletons of indeterminate theropods
| |
− | (Richardoestesia), dromaeosaurids (Dromaeosaurus
| |
− | and Saurornitholestes), caenagnathids (Chirostenotes),
| |
− | tyrannosaurids (Aublysodon, Albertosaurus,
| |
− | and Daspletosaurus), ornithomimids (Struthiomimus,
| |
− | Dromicieomimus, and Ornithomimus), troodontids
| |
− | (Troodon), hypsilophodontids (Parksosaurus), hadrosaurs
| |
− | (Edmontosaurus, Saurolophus, and Hypacrosaurus),
| |
− | pachycephalosaurids (Stegoceras), ceratopsids
| |
− | (Anchiceratops, Arrhinoceratops, and Pachyrhinosaurus),
| |
− | and ankylosaurs (Edmontonia and Euoplocephalus)
| |
− |
| |
− | Edmonton Group 230
| |
− | The Edmonton Group is an important dinosaurand
| |
− | coal-bearing unit in the south-central portion
| |
− | of the Alberta Basin that ranges in age from latest
| |
− | Campanian to early Danian (Early Paleocene) and
| |
− | thus spans the Cretaceous–Paleogene boundary. It
| |
− | comprises a southeastward-thinning, largely nonmarine
| |
− | to shallow marine clastic wedge that is exposed
| |
− | in modern drainages throughout south-central Alberta.
| |
− | It conformably overlies and interfingers with
| |
− | marine shales of the late Campanian Bearpaw Formation
| |
− | and is overlain unconformably by sandstones of
| |
− | the Late Paleocene Paskapoo Formation. It has been
| |
− | a source of important dinosaur and other fossil vertebrate,
| |
− | invertebrate, and plant discoveries since the
| |
− | early part of the 20th century and, recently, has figured
| |
− | importantly in studies of terminal Cretaceous
| |
− | extinctions.
| |
− |
| |
− | Mesozoic 450
| |
− | The Laurasian continents appeared to
| |
− | continue biotic exchange through the Mesozoic, but
| |
− | the faunas are not cosmopolitan; seemingly they were
| |
− | interrupted either by marine excursions (eastern and
| |
− | western North America; North America–Europe) or
| |
− | by ecological barriers (North America–Asia) at least
| |
− | from time to time. For example, congeneric hadrosaurs
| |
− | (Saurolophus) are known in both North America
| |
− | and Asia in the Maastrichtian; different genera of
| |
− | closely related pachycephlosaurs are known from the
| |
− | Campanian and Maastrichtian of both continents;
| |
− | basal ceratopsians (Psittacosaurus) are known from
| |
− | Asia but not North America, protoceratopsids are
| |
− | known from both continents, but Ceratopsidae are
| |
− | restricted to the Western Hemisphere.
| |
− |
| |
− | Mongolian Dinosaurs 480
| |
− | Only two hadrosaurs have been described so far.
| |
− | Saurolophus angustirostris was a huge animal, up to 14
| |
− | m long. Like the North American species, the nasals
| |
− | extend posterodorsally above the orbit to form a solid
| |
− | crest, which is supported from behind by upraised
| |
− | frontal buttresses. This is one of the most common
| |
− | Mongolian dinosaurs from the latest Cretaceous beds,
| |
− | and there are many fine specimens that even include
| |
− | abundant skin impressions. Barsboldia sicinskii is a
| |
− | lambeosaurine with very long and club-shaped neural
| |
− | spines in the dorsal vertebrae.
| |
− |
| |
− | formacja Nemegt 472
| |
− | The assemblage of dinosaurs found in the Nemegt
| |
− | Formation contains theropods, sauropods, hadrosaurids,
| |
− | pachycephalosaurs, and ankylosaurs. A distinctive
| |
− | character of this fauna is the unusually high
| |
− | diversity of theropods, which includes 14 monospecific
| |
− | genera belonging to at least six families. Among
| |
− | these theropods, Tarbosaurus bataar and Gallimimus
| |
− | bullatus are represented by 10 or more specimens,
| |
− | whereas there are only single specimens for most
| |
− | other species. Among herbivorous dinosaurs, the
| |
− | large hadrosaurid Saurolophus angustirostris is as common
| |
− | as T. baatar, whereas other species are rare. Another
| |
− | striking feature of the dinosaur assemblage of
| |
− | the Nemegt Formation is the lack of neoceratopsians,
| |
− | although their primitive representatives (Protoceratopsidae)
| |
− | occurred in the older Barun Goyot and Djadokhta
| |
− | formations. In contrast, the advanced neo-
| |
− | ceratopsians of the Ceratopsidae are common in contemporaneous
| |
− | North American strata.
| |
− |
| |
− | Orlov Museum 518
| |
− | The Mesozoic hall is divided into main space and
| |
− | upper gallery. The hall is decorated with monumental
| |
− | color murals about Mesozoic life, and the gallery is
| |
− | decorated with bas-relief. The largest specimen in the
| |
− | hall is the cast of Diplodocus presented by the United
| |
− | States, but most of the exposition comprises specimens
| |
− | from Mongolia and Middle Asia. Among these
| |
− | are skeletons of the iguanodontid Probactrosaurus, the
| |
− | hadrosaurs Corythosaurus, Arstanosaurus, and Saurolophus,
| |
− |
| |
− | Paleontological Museum of the
| |
− | Mongolian Academy of Sciences,
| |
− | Ulaan Baatar 556
| |
− | and skeletons
| |
− | of hadrosaur and protoceratopsian embryos and
| |
− | hatchlings, Gallimimus, Protoceratops, Psittacosaurus,
| |
− | Saichania, and Saurolophus.
| |
− |
| |
− | Polish–Mongolian
| |
− | Paleontological Expeditions 605
| |
− | The 1965 expedition (23 participants) was one of
| |
− | the largest. Most of the time the expedition team
| |
− | worked in two groups. Nine people spent a month
| |
− | at Bayn Dzak, discovering some new sites with small
| |
− | vertebrates and significantly augmenting the mammal
| |
− | and lizard collection. Dinosaur skeletons, including
| |
− | Protceratops and Pinacosaurus juveniles, numerous
| |
− | dinosaur eggs and nests, tortoises, and a previously
| |
− | unknown, small crocodile (Gobiosuchus) were also
| |
− | found. The second, larger group (14 people) worked
| |
− | in the Nemegt Basin, mainly at Altan Ula IV and
| |
− | Nemegt, but also visited Altan Ula III and Tsagan
| |
− | Khushu localities. Numerous skeletons of dinosaurs,
| |
− | tortoises, and crocodiles were found, as well as fish
| |
− | remains, ostracodes, tree trunks, and charophyte oogonia.
| |
− | Except for numerous Tarbosaurus and Saurolophus
| |
− | skeletons previously found by the Soviet Expeditions,
| |
− | the dinosaur skeletons collected represented
| |
− | new taxa of ornithomimids, sauropods, and pachycephalosaurids.
| |
− | In the middle of July, the Bayn Dzak
| |
− | group joined the Nemegt team for several days and
| |
− | then headed toward the Lakes Valley in the west of
| |
− | Mongolia to look at Tertiary deposits.
| |
− | After completion of the expedition of 1965, fieldwork
| |
− | in Mongolia was suspended for 1 year. In 1967
| |
− | and each of the successive three years, a group of
| |
− | five Polish and Mongolian paleontologists stayed for
| |
− | several weeks in the Bayn Dzak region to search for
| |
− | small Late Cretaceous vertebrates but no excavations
| |
− | were undertaken.
| |
− | The 1970 expedition was also a larger one and
| |
− | included 15 participants. At the beginning, the entire
| |
− | team worked at Bayn Dzak, enlarging the mammal
| |
− | and lizard collection but also investigating outcrops
| |
− | in the vicinity. When the camp at Bayn Dzak was
| |
− | closed, the expedition headed south to the Nemegt
| |
− | Basin. The main camp was set up at Nemegt (Northern
| |
− | Sayr). The outcrops at Altan Ula II and III and
| |
− | the Shiregin Gashun (� Shiregeen Gashoon) Basin
| |
− | north of the Nemegt range were also visited. In addition
| |
− | to several Tarbosaurus and Saurolophus skeletons,
| |
− | oviraptorid and pachycephalosaurid skulls and ornithomimid
| |
− | and ankylosaurid skeletons were discovered.
| |
− |
| |
− | Soviet–Mongolian
| |
− | Paleontological Expeditions 723
| |
− | the American Expeditions could have done.
| |
− | The first excavations of 1948 were opened up in
| |
− | the southeastern Gobi at a locality called Sayn Shand.
| |
− | Here, several skeletons of the new ankylosaurid Talarurus
| |
− | plicatospineous and fragmentary material of Talarurus
| |
− | disparoserratus were recovered from the Upper
| |
− | Cretaceous strata. The expedition then turned westward
| |
− | to Bayn Dzak, where the Central Asiatic Expeditions
| |
− | had made dramatic discoveries in the 1920s. As
| |
− | the Americans had found a quarter century before,
| |
− | the Soviets found abundant Protoceratops skeletons
| |
− | and dinosaur eggs. Additional finds included a wellpreserved
| |
− | large ankylosaurid, Syrmosaurus vimicaudus
| |
− | (a junior synonym of Pinacosaurus grangeri).
| |
− | As the Soviet team moved south toward the border
| |
− | with China, they came upon a broad depression surrounded
| |
− | by an expanse of trackless, shifting desert.
| |
− | The Nemegt Valley extends 180 km east to west, and
| |
− | up to 70 km north to south. Within the confines of this
| |
− | isolated area the crew located numerous Cretaceous
| |
− | ‘‘dinosaur cemeteries’’ scattered across the valley
| |
− | floor. These deposits included hadrosaurs, carnosaurs,
| |
− | sauropods, ankylosaurs, and ornithomimids.
| |
− | Among the inhospitable gorges of red sandstone the
| |
− | expedition found seven skeletons of Tarbosaurus bataar,
| |
− | a new large theropod closely related to the North
| |
− | American genus Tyrannosaurus.
| |
− | At a Nemegt locality near Altan Ula, the team
| |
− | discovered a dense burial of large hadrosaurs (>12
| |
− | m long and 7.7 m tall), some with skin impressions,
| |
− | which Rozhdestvensky (1960) described as Saurolophus
| |
− | angustirostris. So productive was the locality that
| |
− | it was christened ‘‘Dragon’s Tomb.’’ Certainly the
| |
− | most puzzling animal recovered from the Nemegt by
| |
− | the Soviet–Mongolian expeditions was Therizinosaurus
| |
− | cheloniformis, originally thought to be a gigantic
| |
− | turtle, represented by unguals varying from 30 to
| |
− | more than 60 cm in length. Therizinosauridae were
| |
− | eventually recognized as similar to the dinosaurs
| |
− | known as segnosaurs, and these are now regarded
| |
− | as coelurosaurian theropods.
| |
− |
| |
− | University of California Museum
| |
− | of Paleontology 802
| |
− | Ornithischian dinosaurs are also well represented
| |
− | in the UCMP(...)These include incomplete skeletal remains of
| |
− | the questionably basal hypsilophodontid Thescelosaurus;
| |
− | a fully preserved skull of Edmontosaurus annectens
| |
− | and other hadrosaurs, including an undescribed
| |
− | skull of Parasaurolophus from Utah; an ontogenetic
| |
− | series of Edmontosaurus collected from the North
| |
− | Slope of Alaska (in trust from the University of
| |
− | Alaska); extensive ceratopsian material including
| |
− | skulls of Triceratops, plus skull and postcranial remains
| |
− | of the pachycephalosaurs Stegoceras, Ornatotholus,
| |
− | Pachycephalosaurus, Stygimoloch, and additional
| |
− | new and indeterminate material (Goodwin, 1990).
| |
− | Among an extensive collection of mostly marine
| |
− | vertebrates (plesiosaurs, mosasaurs, etc.) from the
| |
− | Panoche Hills of the Central Valley of California is a
| |
− | skull and relatively complete skeleton of a hadrosaurine
| |
− | allied to Saurolophus, although badly damaged
| |
− | by gypsum.
| |
− |
| |
− | _______________
| |
− | Martin, 2006
| |
− |
| |
− | 94
| |
− | In the late 1940s, Russian expeditions to Mongolia followed the American efforts
| |
− | through the auspices of the Russian Paleontological Institute, led by paleontologist
| |
− | (and famed Russian science-fiction writer) Ivan A. Efremov (1907–72) and herpetologist
| |
− | Anatole K. Rozhdestvensky. In these excursions they found more
| |
− | examples of the previously discovered Cretaceous dinosaurs of that region, as well
| |
− | as some important new finds, such as the ankylosaur Pinacosaurus (Chapter 12),
| |
− | hadrosaur Saurolophus (Chapter 11), and the large theropod Tarbosaurus, which is
| |
− | so similar to Tyrannosaurus that it is now considered an Asian variant of the species
| |
− | (Chapter 9). The continued success of the Russian expeditions ensured that more investigators
| |
− |
| |
− | would follow; a Polish–Mongolian research group returned to the area
| |
− | in the 1960s, as did American Museum paleontologists in the 1990s. Renowned
| |
− | paleontologist Zofia Kielan-Jaworowska led the Polish–Mongolian expedition,
| |
− | which also included participants Teresa Maryanska and Halszka Osmólska, who
| |
− | are still considered to be Poland’s leading experts on dinosaurs.
| |
− |
| |
− | 363
| |
− | Solid-crested forms, such as Saurolophus, have large nasal chambers
| |
− | under the solid bone; non-crested hadrosaurids (such as Edmontosaurus and
| |
− | Kritosaurus) have a similar anatomical situation. In contrast, the hollow-crested forms,
| |
− | represented by the lambeosaurines, have tube-like structures that emanate from the
| |
− | nasal cavities and extend dorsally and posteriorly.
| |
− |
| |
− | __________________________
| |
− | TARusMon
| |
− |
| |
− | 254
| |
− | The great Nemegt plain
| |
− | As a result of the digging here, at least ten complete
| |
− | skeletons of dinosaurs were recovered, not to mention
| |
− | numerous other fossils representative of these ancient
| |
− | reptiles. There was a gigantic carnivorous dinosaur,
| |
− | closely related to if not identical with the well-known
| |
− | giant predator from the Cretaceous beds of Montana,
| |
− | Tyrannosaurus. There was also found the gigantic
| |
− | duck-billed dinosaur Saurolophus, hitherto known from
| |
− | North America. These dinosaurs, as well as various
| |
− | other dinosaurian genera, including some of the small
| |
− | ostrich-like dinosaurs, indicate quite clearly the
| |
− | nature of the close connections that bound central
| |
− | Asia to western North America during Cretaceous
| |
− | times. As mentioned previously, the continental
| |
− | regions now separated by the Bering Straits were then
| |
− | one great tropical land, a broad lowland across which
| |
− | numerous dinosaurian giants and their lesser brethren
| |
− | wandered far and wide, from east to west, with great
| |
− | facility.
| |
− |
| |
− | 255
| |
− | One interesting aspect of the Russian explorations
| |
− | in the Gobi, especially in the Nemegt Basin, is the
| |
− | manner in which the discovery of late Cretaceous
| |
− | dinosaurs, especially the giant duck-billed dinosaur
| |
− | Saurolophus, fulfilled in part a prophecy made by
| |
− | Professor Osborn in 1930.
| |
− |
| |
− | 491
| |
− | Genus Saurolophus Brown, 19 12
| |
− | Typespecies. S. osborni Brown, 191 2.
| |
− | Saurolophus angustirostrir Rozhdestvenskii, 195 7
| |
− | (subjective validity)
| |
− | Holotype. PIN 55 118.
| |
− | Diagnosis. Skull narrow, especially across the snout;
| |
− | external narial opening short, its caudal border lies
| |
− | vertically above the first maxillary tooth; frontal with
| |
− | long vertical anterior process which provides a caudal
| |
− | prop to the lower half of the nasal crest; prefrontal
| |
− | props the base of the nasal crest caudolaterally; rostra1
| |
− | surface of nasal (within the crest) bears a longitudinal
| |
− | ridge or is covered with irregular, bony chambers (?);
| |
− | two supraorbitals identifiable, but fused in the orbital
| |
− | rim; jugal elongated rostrally into a sharp process
| |
− | wedged between maxilla and lacrimal; (lacrimal short
| |
− | compared to S. osborni); quadrate strongly bowed caudally;
| |
− | sacral neural spines perpendicular to long axis
| |
− | of sacrum, first two sacral ribs reinforce the pubo-iliac
| |
− | contact; scapula curved; radius shorter than humerus;
| |
− | postacetabular process of ilium broad and subrectangular;
| |
− | pes about a quarter of femur length (?); length
| |
− | ratios oE Mt 111 to femur = 0.27; pedal phalanx 11-2 to
| |
− | pedal phalanx 11-1 =0.23 (from Maryanska and
| |
− | Osmblska, 1984: 132).
| |
− | Comments. While this might seem an impressive list of
| |
− | diagnostic characters, the detailed cranial anatomy of
| |
− | the type species of S. osborni has never been described,
| |
− | and it will be clear to all workers on hadrosaurs that
| |
− | many of the anatomical characters listed for S. angustirostris
| |
− | may well fall within the normal range of
| |
− | intraspecific variability. The type species is wallmounted
| |
− | in the ornithischian gallery at the American
| |
− | Museum of Natural History and this, along with comparable
| |
− | material from the collections, will need to be
| |
− | re-studied before the status of the Mongolian taxon
| |
− | can be assessed confidently. A simple examination of
| |
− | the skull of S. angustirostris described by Maryariska
| |
− | and Osm6lska (1981a, b) (Figure 24.44) confirms, as
| |
− | they suggested, that this is a juvenile (smaller size, relatively
| |
− | larger orbital cavity, less extensive development
| |
− | of the facial muzzle). Growth and differentiation
| |
− | of the skull to that seen in the example of S. angustirostrisillustrated
| |
− | in Figure 24.4B seems to have produced
| |
− | a form virtually indistinguishable from the North
| |
− | American species (Figure 24.4C); immaturity of the
| |
− | smaller form (Figure 24.4A) may also account for
| |
− | the greater clarity in suture pattern between many of
| |
− | the facial bones that probably underlie differences
| |
− | in the descriptive accounts of the two currently recognized
| |
− | species.
| |
− | The postcranial skeleton is typical of that of hadrosaurine
| |
− | ornithopods (notably the structure of the
| |
− | ischium, the shaft of which is straight and lacks the
| |
− | distal expansion seen in lambeosaurines - see Figure
| |
− | 24.5). The pelvic girdle of S. angustirostrisillustrated in
| |
− | Figure 24.7C was held by Maryanska and Osm6lska
| |
− | (1984) to be specifically distinct from that of S. osborni
| |
− | particularly in details of the shape of the ilium and
| |
− | pubis. However, comparison with Rozhdestvenskii's
| |
− | 1957 illustration (Figure 24.5) of the same species
| |
− | would appear to offer a broadly comparable number of
| |
− | anatomical differences. For the moment we remain
| |
− | unconvinced by these apparent differences.
| |
− | S. angustirostris is known from the skeletal remains
| |
− | of at least 15 individuals, including articulated cranial
| |
− | and postcranial material from the Nemegt Formation
| |
− | (Late Cretaceous: CarnpanianlMaastrichtian;
| |
− | Weishampel and Horner, 1990; Jerzykiewicz and
| |
− | Russell, 1991) of the Altan Uul and North Nemegt
| |
− | localities (Figure 24.1; locations 7 and 9), of the
| |
− | Nemegt Basin, Gobi Desert, Mongolia. S. angustirostrir
| |
− | is very similar in general anatomy to the type-species
| |
− | of the genus, S. osborni Brown, 1912 (see also Brown,
| |
− | 191 3), from the Late Cretaceous (Early Maastrichtian;
| |
− | Weishampel and Horner, 1990) Horseshoe Canyon
| |
− | Formation of Alberta (Canada). Both of Brown's
| |
− | papers represent brief descriptive announcements
| |
− | rather than full osteological descriptions of this
| |
− | species; and, in the absence of more detailed work, it
| |
− | has proved impossible (within the scope of this
| |
− | review) to resolve the taxonomy of these two species
| |
− | further.
| |
− | For the present it is probably prudent to consider S.
| |
− | angustirostris as a distinct species of Saurolophus,
| |
− | however, the possibility that the Mongolian species is
| |
− | conspecific with the North American form S. osborni
| |
− | should be considered, and is a matter that needs to be
| |
− | resolved. This problem of taxonomic distinction of
| |
− | forms in the Late Cretaceous of Asia and western
| |
− | North America has a bearing on evolutionary modelling
| |
− | and biogeographical dispersal patterns, not to
| |
− | mention its significance for biostratigraphic correlations
| |
− | between localities in the western North
| |
− | American and Asian provinces. Similar taxonomic
| |
− | observations can be made on other faunal elements
| |
− | such as the validity of the taxonomic distinctions
| |
− | claimed for Tyrannosaurus and Tarbosaurus, Troodon
| |
− | and Saurornithoides, Deinonychus and Velociraptor, and
| |
− | others.
| |
− |
| |
− | Conclusions 500
| |
− | The fossil record of ornithopods in Mongolia and
| |
− | adjacent parts of the former Soviet Union is confined
| |
− | to (:retaceous exposures, and is of restricted utility,
| |
− | largely as a consequence of the poor preservation of
| |
− | material and the relatively low abondance of ornithopods
| |
− | at localities discovered to date. '4 notable
| |
− | exception is Saurolophus angu.rtirostri.r whose remains
| |
− | have heen discovered in sonie abundance at the
| |
− | 'Dragons' Grave' locality of .\ltan Uul I 1 in the Gobi
| |
− | Desert.
| |
− |
| |
− |
| |
− | ____________
| |
− | Dinosaur heresies
| |
− |
| |
− | 435
| |
− | ecosystem,
| |
− | one of the most even ever evolved. But the next layer up,
| |
− | the Scollard, is very uneven. One genus of duckbill, Saurolophus,
| |
− | made up 75 percent of all the big specimens, and others were quite
| |
− | rare. Simpson's index for this time falls to 1.4, a low score. Something
| |
− | was happening—new species were not evolving adaptations
| |
− | fast enough to permit them to take a more even share of the ecosystem.
| |
− | And similar low evenness continued through the next formation,
| |
− | the Edmonton—Hell Creek, for which Simpson's index is
| |
− | only 1.3. One genus, Triceratops, made up 70 to 80 percent of the
| |
− | finds of large dinosaurs. This unbalanced situation endured for two
| |
− | million years before the final extinction.
| |
− |
| |
− | ______----
| |
− | The Dinosauria
| |
− |
| |
− | 460p
| |
− |
| |
− | Saurolophus Brown, 1912
| |
− | S. osborni Brown, 1912 Horseshoe Canyon early Complete skull and skeleton,
| |
− | Formation (Alberta), Maastrichtian 2 complete skulls,
| |
− | Canada disarticulated skull material
| |
− | S. angustirostris Rozhdestvensky, 1952 Nemegt Formation, White ?late Campanian At least 15
| |
− |
| |
− | specimens,
| |
− | Beds of Hermiin Tsav or early including articulated skull
| |
− | (Ömnögov’), Nemegt Maastrichtian and postcranial skeleton
| |
− | Svita (Bayankhongor),
| |
− | Mongolia
| |
− |
| |
− | 463
| |
− | In Saurolophus, the caudal
| |
− | portion of the nasals is elongated into a solid spikelike crest that
| |
− | projects caudodorsally from the skull roof. In all nonlambeosaurine
| |
− | hadrosaurids, the solid crests are not involved with the
| |
− | narial passages and are solely ornamental in nature.
| |
− |
| |
− | 464
| |
− | The maxilla is one of the largest bones of the skull. Its triangular
| |
− | outline derives from a broad base formed by the tooth
| |
− | row and an apex formed by its dorsal process. The tooth row is
| |
− | inset from the lateral margin of the maxilla. The row is either
| |
− | straight or slightly concave in the buccal direction. The maxilla
| |
− | forms a transversely convex and broad articular surface for reception
| |
− | of the undersurface of the body and lateral process of the
| |
− | premaxilla. In Edmontosaurus, Brachylophosaurus, Saurolophus,
| |
− | and Gryposaurus, the front of the rostral process of the maxilla
| |
− | makes a spheroid contact with the premaxillary body. Medial to
| |
− | this articulation is the median rostral process (Weishampel
| |
− | 1984a; anterior maxillary process of Heaton [1972] and Horner
| |
− | [1983, 1992]) that fits into a notch on the premaxilla of all nonlambeosaurine
| |
− | hadrosaurids (Horner 1992). It is sufficiently
| |
− | long that it can be seen through the external naris in Edmontosaurus,
| |
− | Maiasaura, and Brachylophosaurus and represents the
| |
− | primitive condition for hadrosaurines.
| |
− |
| |
− | 466
| |
− | In all hadrosaurids, the large jugal is thin, flat, and elongate
| |
− | and forms the ventral margin of the orbit and infratemporal fenestra
| |
− | as well as the ventral half of the postorbital bar. Rostrally,
| |
− | the jugal is expanded dorsoventrally, forming an extensive articulation
| |
− | with the maxilla and the rostroventral margin of the
| |
− | orbit. In all lambeosaurines except Parasaurolophus, the rostral
| |
− | margin is broadly convex, whereas in the remaining hadrosaurids,
| |
− | it is distinctly angular and rostrally pointed, extending
| |
− | along the maxilla-lacrimal contact (figs. 20.6B, 20.7). This
| |
− | angular process is large, long, and symmetrically triangular in
| |
− | species of Maiasaura, Brachylophosaurus, and Telmatosaurus, but
| |
− | asymmetrical in Prosaurolophus, Saurolophus, and Edmontosaurus,
| |
− | (figs. 20.2–20.5). The jugal flange immediately ventral to the
| |
− |
| |
− | 468
| |
− | The squamosals contact one another along the dorsal
| |
− | midline in Maiasaura, Saurolophus, and all lambeosaurines;
| |
− | they nearly contact one another in all the remaining taxa except
| |
− | Telmatosaurus, in which the intervening parietal creates a significant
| |
− | separation between them. The internal surface of the
| |
− | squamosal acts as the attachment site for Mm. adductor mandibulae
| |
− | externus superficialis et medialis
| |
− |
| |
− | The frontal is the largest element of the skull roof, extending
| |
− | broadly between the orbits and the nasal (rostrally) and parietal
| |
− | (caudally). It is rostrocaudally shorter in hadrosaurids with
| |
− | supracranial crests (i.e., lambeosaurines and the hadrosaurines
| |
− | Prosaurolophus, Saurolophus, Brachylophosaurus, and Maiasaura)
| |
− | than in flat-headed forms. In lambeosaurines (see fig. 20.6C),
| |
− | the rostrodorsal surface forms a broad, excavated, deeply striated
| |
− | base for the crest, contacting the nasals rostrally and the
| |
− | caudolateral process of the premaxilla laterally (in adult Lambeosaurus,
| |
− | only the latter forms the base of the crest). Only the caudalmost margin of the frontal can be seen in articulate
| |
− | lambeosaurine skulls. In hadrosaurines, the rostrodorsal surface
| |
− | of the frontal is broadly excavated for reception of the
| |
− | nasal and more lateral prefrontal. In some hadrosaurines, a
| |
− | small gap or opening is occasionally present on the midline between
| |
− | the frontals and the nasals. Laterally, the frontal participates
| |
− | to a variable degree in the dorsal orbital rim in many
| |
− | hadrosaurids, but in others such as Naashoibitosaurus, Saurolophus,
| |
− | “Kritosaurus” australis, and the lambeosaurines it is entirely
| |
− | excluded from the orbit by a prefrontal-postorbital contact
| |
− | (Horner 1992). The frontal forms a complex interdigitate
| |
− | joint with the postorbital from the dorsal rim of the orbit to the
| |
− | supratemporal fenestra (often obscured in adult lambeosaurines
| |
− | due to the development of the crest). In addition, the frontal
| |
− | articulates with the parietal along a nearly transverse interdigitate
| |
− | joint, often accompanied by a median projection of the
| |
− | parietal into the interfrontal joint (the interparietal process of
| |
− | Lull and Wright [1942], see below). The paired frontals contact
| |
− | each other along a simple butt joint in juveniles, which later
| |
− | becomes complexly interdigitate in adults, especially near the
| |
− | parietal. The frontal exhibits an upward doming in adult lambeosaurines,
| |
− | and sometimes in juvenile nonlambeosaurine hadrosaurids
| |
− | (e.g., Lophorhothon). The frontal also rises to help buttress
| |
− | the rear of the crest in lambeosaurines. Ventrally, the frontal
| |
− | contacts the laterosphenoid and orbitosphenoid portions of
| |
− | the braincase.
| |
− |
| |
− | 470
| |
− | The mandible of all hadrosaurids is both long and massive,
| |
− | forming at least two-thirds of the length of the lower jaw. The
| |
− | dentary amounts to more than 75% the total mandibular length
| |
− | in Edmontosaurus. In lambeosaurines, it is often strongly ventrally
| |
− | deflected at its rostral margin. The dentary bears a conspicuously
| |
− | high, laterally offset coronoid process that is well
| |
− | separated from the tooth row, which extends medial to and as
| |
− | far back as the caudal margin of the process. Distally the coronoid
| |
− | process is greatly expanded rostrally. The coronoid process
| |
− | extends into the adductor chamber medial to the jugal. The
| |
− | dorsal and caudal surfaces of the coronoid process serve for the
| |
− | attachment of most of the adductor musculature (e.g., Mm. adductor
| |
− | mandibulae externus, pseudopterygoideus). The lateral
| |
− | dentary surface is smooth and prominently convex along its
| |
− | length. There are several foramina for vessels and nerves to the
| |
− | face and buccal cavity along this surface. The medial aspect of
| |
− | the dentary is slightly convex and marked by a series of neurovascular
| |
− | foramina at the base of the mandibular alveoli. The
| |
− | mandibular symphysis is linear and slightly inclined to the long
| |
− | axis of the mandible; well-striated grooves attest to the presence
| |
− | of well-developed symphyseal ligaments. The caudal margin of
| |
− | the mandibular canal along the base of the medial dentary
| |
− | served as the insertion site for M. adductor mandibulae caudalis.
| |
− | The rostral region of the dentary is edentulous, shortest in
| |
− | lambeosaurines and basal hadrosaurids and longest in Edmontosaurus,
| |
− | Shantungosaurus, Saurolophus, and Prosaurolophus. The
| |
− | mandibular dentition is emarginated from the lateral aspect
| |
− | of the dentary.
| |
− | The single, median predentary is fitted across the rostral
| |
− | mandibular symphysis; it is a flat, scoop-shaped element bearing
| |
− | two lateral processes that contact the lateral margins of the
| |
− | dentaries, a dorsal median process articulating with the dorsal
| |
− | margin of the mandibular symphysis, and a bilobate ventral
| |
− | median process that underlies the symphysis. The oral margin
| |
− | of the predentary bears broad, triangular denticles; below the
| |
− | denticles is a row of large vascular foramina and pits. In life, this
| |
− | surface was surrounded by a cornified rhamphotheca (Cope
| |
− | 1883; Versluys 1923; Sternberg 1935; Morris 1970). The rostral
| |
− | margin of the predentary is nearly straight transversely in most
| |
− | hadrosaurids, but rounded in Saurolophus.
| |
− |
| |
− | 472
| |
− | The sacrum in adult hadrosaurids consists of 9–12 vertebrae,
| |
− | including single dorsosacral and caudosacral contributions.
| |
− | Fusion of the sacrum varies both ontogenetically and between
| |
− | species. In Gryposaurus notabilis and Brachylophosaurus canadensis,
| |
− | there are nine fused sacrals, whereas Maiasaura peeblesorum
| |
− | has a sacrum formed of ten vertebrae, of which the first seven
| |
− | are fused and separated from a subsequent fusion of three. The
| |
− | seven cranial sacrals in both species possess parapophyses that
| |
− | extend laterally to support the iliac plate formed of the sacral
| |
− | ribs. This iliac plate, in turn, contacts the inner surface of the
| |
− | ilium; the first and second sacral ribs that contribute to the iliac
| |
− | plate also extend ventrally to provide additional contact
| |
− | with the iliac peduncle of the pubis (Marya´nska and Osmólska
| |
− | 1983, 1984b). The eighth sacral, whether fused or unfused, possesses
| |
− | massive transverse processes that extend laterally to meet
| |
− | the caudal blade of the ilium. The remaining sacrals possess
| |
− | transverse processes that abruptly decrease in lateral extent caudally.
| |
− | These processes seldom reach the ilium. In Saurolophus
| |
− | angustirostris, the ends of the transverse processes are placed on
| |
− | the dorsal margin of the ilium (Marya´nska and Osmólska
| |
− | 1984b). Neural spine height in the dorsals as well as the sacrals
| |
− | is species dependent. In Barsboldia sicinskii, the neural spines
| |
− | are especially long, robust, and club-shaped at their termini
| |
− | (Marya´nska and Osmólska 1981b). Sacral centra vary in shape,
| |
− | being more or less heart-shaped cranially, dorsoventrally compressed
| |
− | centrally, and rounded caudally. In juveniles, the dorsoventrally
| |
− | compressed sacrals possess an extremely large neural
| |
− | canal, which becomes increasingly smaller with age. Fusion of
| |
− | the sacrum begins at the junction of the second and third sacrals
| |
− | and progresses caudally. Fusion of the first and second sacrals
| |
− | apparently takes place at the same time as fusion of the sixth and
| |
− | seventh sacrals. The sacrum of many hadrosaurines has a median
| |
− | ventral groove that extends axially along at least the caudalmost
| |
− | four or five centra. The lambeosaurine sacrum usually has
| |
− | a ventral ridge (see Young 1958a). Ventral sacral morphology has
| |
− | been used in hadrosaurid systematics by a number of authors
| |
− | (e.g., Brett-Surman 1977; Weishampel and Horner 1990); however,
| |
− | variation in this general Bauplan is known. For example,
| |
− | some individuals lack either a ridge or a groove, whereas others
| |
− | possess both morphologies. Further research is needed before
| |
− | ventral sacral morphology can be determined to be phylogenetically
| |
− | informative.
| |
− |
| |
− | 473
| |
− | The ulna is straight in nearly all hadrosaurids and expanded
| |
− | only at the proximal end. The exception is Saurolophus angustirostris,
| |
− | whose robust ulna is distinctly bowed. A small olecranon
| |
− | process extends a short distance above the proximal articular
| |
− | surface. The proximal end is triangular in caudal view,
| |
− | possessing a grooved depression below the olecranon on the
| |
− | cranial face for the proximal end of the radius. Distally, the ulna
| |
− | is subtriangular in shape, with a flattened cranial face for the
| |
− | distal end of the radius
| |
− |
| |
− | 478
| |
− | Hadrosaurines display a high degree of homoplasy, and resolution
| |
− | within this clade is not particularly strong. Hadrosaurinae
| |
− | itself is united by eight characters, only one of which is unambiguous:
| |
− | the presence of a caudal margin on the circumnarial
| |
− | fossa. Lophorhothon is placed as the sister taxon to all other
| |
− | hadrosaurines in our analysis. This latter clade is supported unambiguously
| |
− | by having an outer narial fossa demarcated from
| |
− | the circumnarial fossa by a strong ridge. This unnamed clade of
| |
− | non-Lophorhothon hadrosaurines consists of two subclades. The
| |
− | first, formed of Naashoibitosaurus, “Kritosaurus” australis, and
| |
− | Saurolophus, are united by having a jugal whose pointed rostral
| |
− | process is symmetrically triangular in shape (a feature also
| |
− | found in the lambeosaurine clade of Parasaurolophus + Hypacrosaurus+
| |
− | Corythosaurus+Lambeosaurus). Of these three taxa, Saurolophus
| |
− | and “K.” australis may be most closely related to each other,
| |
− | but only weakly so (low zygapophyseal peduncles on the cervical
| |
− | vertebrae, also found in Gryposaurus and considered a reversal of
| |
− | the condition found basally among hadrosaurids). “K.” australis,
| |
− | from the Los Alamitos Formation of Argentina, was originally
| |
− | referred to Kritosaurus by Bonaparte et al. (1984) as Kritosaurus
| |
− | australis.We find no compelling characters, however, that place
| |
− | this taxon within Kritosaurus, otherwise known solely from
| |
− | North America. Recent discoveries of additional hadrosaurids
| |
− | in Argentina will likely reveal the systematic significance of
| |
− | “Kritosaurus” australis (Calvo, pers. comm.).
| |
− |
| |
− | 480
| |
− | Based solely on the geographic distribution of the two most
| |
− | proximal outgroups of, and the cladistically analyzed members
| |
− | within, Hadrosauridae, it is most parsimonious to hypothesize
| |
− | a North American origin for the clade. This assessment differs
| |
− | from that presented by Milner and Norman (1984), who hypothesize
| |
− | an Asian origin, and Brett-Surman (1979), who suggested
| |
− | that their area of origin cannot be determined. With a
| |
− | North American origin, the presence of Telmatosaurus in Europe
| |
− | then requires a dispersal event there sometime in the mid-
| |
− | Cretaceous. Thereafter, the split between Hadrosaurinae and
| |
− | Lambeosaurinae probably took place within North America, also
| |
− | in the mid-Cretaceous. Two dispersal events in the history of
| |
− | Hadrosaurinae, one to Asia no later than the early Maastrichtian
| |
− | (Saurolophus angustirostris) and the other to South America no
| |
− | later than the late Campanian (“Kritosaurus” australis). All other
| |
− | diversification events within this clade took place in North
| |
− | America. Similarly, Lambeosaurinae has a North American origin,
| |
− | with a dispersal event to Asia no later than the Campanian,
| |
− | as indicated by the presence of Tsintaosaurus there. Although
| |
− | these dispersal scenarios are suggested by our present phylogenetic
| |
− | understanding, they may easily change as the phylogeny
| |
− | is amended with other materials.
| |
− |
| |
− | considerable amount of work has been accomplished in the collection
| |
− | of Campanian-age hadrosaurid specimens, there is some
| |
− | habitat differentiation among hadrosaurid species (Russell 1967;
| |
− | Dodson 1971; Horner 1983; Horner et al. 2001; see also Lucas
| |
− | [1981] and Lehman [1987] on similar habitat partitioning in the
| |
− | southwestern United States). For instance, hadrosaurines such
| |
− | as Gryposaurus incurvimanus (as well as the pachycephalosaur
| |
− | Stegoceras validum) are found in fluvial and associated environments
| |
− | represented by the Judith River Formation during the
| |
− | transgressive phases of the Bearpaw Sea. The same is said to be
| |
− | true of Hypacrosaurus stebingeri, which is known from the Bearpaw
| |
− | transgression at the top of the Two Medicine Formation. In
| |
− | contrast, Brachylophosaurus canadensis (and the ceratopsid Avaceratops
| |
− | lammersi) is known from regressive units near the bottom
| |
− | of the Judith River Formation or near the distal components
| |
− | of the clastic wedge in near-coastal environment deposits. A
| |
− | similar situation apparently occurred among the Maastrichtian
| |
− | faunas of North America, where the hadrosaurine Edmontosaurus
| |
− | regalis is found in near-marine environments, and the
| |
− | Saurolophus osborni and the lambeosaurine Hypacrosaurus altispinus
| |
− | are found in marginally more continental lowlands (Russell
| |
− | and Chamney 1967). Other species, such as the hadrosaurine
| |
− | Maiasaura peeblesorum,were apparently endemic to upper coastal
| |
− | plain environments (regressive sediments) during the Campanian
| |
− | (Horner 1983). To date, upper coastal plain hadrosaurines
| |
− | have not yet been found or recognized from Maastrichtian-age
| |
− | sediments of North America.
| |
− |
| |
− |
| |
− | __________
| |
− | Evolution and exc
| |
− |
| |
− | 227
| |
− | The years since 1950 have been marked by a healthy mixture of
| |
− | discovery, reflection, and revision on a worldwide scale. Beginning in
| |
− | fuia, studies published in the early 1950sb y A. K. Rozhdestvenskyi ntro
| |
− | duced a new specieso f Saurolophu.tsh,i s time from Mongolia, and a new
| |
− | iguanodontian from the Ear$ Cretaceous, also from Mongolia.
| |
− | Originally named Iguanodon onentalis, this form is now known as
| |
− | Alnrhinus, thanks to research by Norman published in 1998. Also from
| |
− | fuia came Tsintaosauru(sf rom Tsintao), described by C.-CY. oung 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.
| |
− |
| |
− | _
| |
− | PFGD
| |
− |
| |
− | 299
| |
− | Saurolophus (=Lophorthothon) atopus
| |
− | Adult size not certain
| |
− | FOSSIL REMAINS Minority of skull and majority of
| |
− | skeletons.
| |
− | ANATOMICAL CHARACTERISTICS Shallow transverse
| |
− | crest over orbits.
| |
− | AGE Late Cretaceous, Campanian.
| |
− | DISTRIBUTION AND FORMATIONS Alabama, North
| |
− | Carolina; Mooreville Chalk, Black Creek.
| |
− | 299
| |
− | G E N A S A U R S
| |
− | Saurolophus (=Prosaurolophus)
| |
− | blackfeetensis
| |
− | Adult size not certain
| |
− | FOSSIL REMAINS Several partial skulls
| |
− | and skeletons, large juveniles.
| |
− | ANATOMICAL CHARACTERISTICS Beak spoon shaped,
| |
− | shallow transverse crest over orbits.
| |
− | AGE Late Cretaceous, Middle and/or Late Campanian.
| |
− | DISTRIBUTION AND FORMATION Montana; upper Two
| |
− | Medicine.
| |
− | HABITAT Seasonally dry upland woodlands.
| |
− |
| |
− | Saurolophus (=Prosaurolophus) maximus
| |
− | 8.5 m (27 ft) TL, 3 tonnes
| |
− | FOSSIL REMAINS Numerous skulls and skeletons,
| |
− | completely known.
| |
− | ANATOMICAL CHARACTERISTICS Beak spoon shaped,
| |
− | shallow transverse crest over orbits.
| |
− | AGE Late Cretaceous, Late Campanian.
| |
− | DISTRIBUTION AND FORMATION Alberta; upper
| |
− | Dinosaur Park.
| |
− | HABITAT Well-watered, forested floodplain with coastal
| |
− | swamps and marshes, cool winters.
| |
− | NOTES Shared its habitat with Hypacrosaurus intermedius
| |
− | and H. lambei; main enemy Albertosaurus libratus.
| |
− | Saurolophus osborni
| |
− | 8.5 m (27 ft) TL, 3 tonnes
| |
− | FOSSIL REMAINS Two complete skulls and a nearly
| |
− | complete skeleton, almost completely known.
| |
− | ANATOMICAL CHARACTERISTICS Beak spoon shaped,
| |
− | spike-shaped crest over orbits.
| |
− | AGE Late Cretaceous, Early Maastrichtian.
| |
− | DISTRIBUTION AND FORMATION Alberta; lower
| |
− | Horseshoe Canyon.
| |
− | HABITAT Well-watered, forested floodplain with coastal
| |
− | swamps and marshes, cool winters.
| |
− | NOTES May be the direct descendent of S. maximus.
| |
− | Shared its habitat with Hypacrosaurus altispinus.
| |
− | Saurolophus angustirostris
| |
− | 12 m (40 ft) TL, 9 tonnes
| |
− | FOSSIL REMAINS Complete skull and numerous
| |
− | skeletons, almost completely known.
| |
− | ANATOMICAL CHARACTERISTICS Beak spoon shaped,
| |
− | spike-shaped crest over orbits.
| |
− | AGE Late Cretaceous, Late Campanian and/or Early
| |
− | Maastrichtian.
| |
− | DISTRIBUTION AND FORMATION Mongolia; Nemegt.
| |
− | HABITAT Well-watered woodland with seasonal rain.
| |
− | NOTES Main enemy Tyrannosaurus bataar.
| |
− | </includeonly>
| |