Saurolophus
To jest wstępna wersja artykułu.
| Autor: |
| Łukasz Czepiński |
| Saurolophus (zaurolof) | |
|---|---|
| Długość: | do 12 m |
| Masa: | 3 t |
| Miejsce występowania: | Kanada
(formacja Horseshoe Canyon; Alberta) |
| Czas występowania | 83,5-65,5 Ma |
| Systematyka | Dinosauria |
Ryc. 1. Rekonstrukcje przyżyciowe S. osborni (A) i S. angustirostris (B), | |
| Mapa znalezisk: | |
|
Wczytywanie mapy…
Mapa 1. Występowanie Saurolophus osborni.Wczytywanie mapy…
Mapa 2. Występowanie Saurolophus angustirostris i S. kryschtofovici.Wczytywanie mapy… Mapa 3. Występowanie Saurolophus sp.
| |
Wstęp
Saurolophus osborni
Historia odkrycia
Materiał kopalny
Diagnoza
Etymologia
Nazwa rodzajowa Saurolophus oznacza "grzebieniasty jaszczur" (z greckiego sauros - jaszczur i lophus - grzebień)[1]. Epitet gatunkowy - osborni - honoruje zasłużonego amerykańskiego paleontologa - Henry'ego Fairfielda Osborna.
S. angustirostris
Historia odkryć
Materiał kopalny
Diagnoza
Porównanie z S. osborni
Tropy
Etymologia
Jak podaje Anatoly Konstantinovich Rozhdestvensky w oryginalnej, rosyjskiej publikacji z 1952 roku, S. angustirostris oznacza "зауролоф узкомордый", czyli "wąskopyski zaurolof"[2].
S. morrisi
Historia odkrycia
Materiał kopalny
Diagnoza
Etymologia
S. morrisi honoruje paleontologa Williama J. Morrisa, który wsławił się badaniami nad morfologią funkcjonalną i historią ewolucyjną hadrozaurydów z wybrzeża Pacyfiku i Środkowego Zachodu Ameryki Północnej[3].
S. kryschtofovici
W 1930 roku rosyjski paleontolog, Anatoly Nikolaevich Riabinin opisał fragment lewej kości kulszowej (dokładnie jej bliższy koniec; ryc. XX) jako nowy gatunek zaurolofa - S. kryschtofovici (najprawdopodobniej na cześć kogoś o nazwisku Kryschtofovic). Skamieniałość została znaleziona w Beilyie Kruchi, na północy Heilungchiang w Chinach[4]. Obecnie gatunek ten jest uznawany za nomen dubium i zazwyczaj łączony z S. angustitornis, m.in. ze względu na bliskość ich występowania (patrz: Mapa 2)[5].
Spis gatunków
| Saurolophus | Brown, 1912 | |
|---|---|---|
| S. osborni | Brown, 1912 | |
| S. angustirostris | Rozhdestvensky, 1952 | |
| S. morrisi | Prieto-Márquez i Wagner, 2012 | |
| S. kryschtofovici | Riabinin, 1930 | nomen dubium |
Bibliografia
- ↑ Barnum Brown, 1912. A crested dinosaur from the Edmonton Cretaceous. Bulletin of the American Museum of Natural History 31 (14): 131–136.
- ↑ Рождественский, A.K. 1952. Новый представитель утконосых динозавров из Верхнемеловых отложений монголии. Доклады Академии Наук СССР 86: 405-408.
[Rozhdestvensky, A.K. 1952. A new representative of the duck-billed dinosaurs from the Upper Cretaceous deposits of Mongolia. Doklady Akademii Nauk S.S.S.R. 86: 405–408.] - ↑ Prieto-Márquez, A., Wagner, J.R. 2012. Saurolophus morrisi, a new species of hadrosaurid dinosaur from the Late Cretaceous of the Pacific coast of North America. Acta Palaeontologica Polonica (w druku)
- ↑ Riabinin, A.N. 1930. On the age and fauna of the dinosaur beds on the Amur River. Mémoir, Société Mineral Russia 59: 41–51.
- ↑ Glut, D.F. 1997. Saurolophus. "Dinosaurs: The Encyclopedia". McFarland & Co. pp. 788–789.
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>
