DOCSLIB.ORG

New Tyrannosaur from the Mid-Cretaceous of Uzbekistan Clarifies Evolution of Giant Body Sizes and Advanced Senses in Tyrant Dinosaurs

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
New Tyrannosaur from the Mid-Cretaceous of Uzbekistan Clarifies Evolution of Giant Body Sizes and Advanced Senses in Tyrant Dinosaurs New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs Stephen L. Brusattea,1, Alexander Averianovb,c, Hans-Dieter Suesd, Amy Muira, and Ian B. Butlera aSchool of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, United Kingdom; bZoological Institute, Russian Academy of Sciences, St. Petersburg 199034, Russia; cDepartment of Sedimentary Geology, Saint Petersburg State University, St. Petersburg 199178, Russia; and dDepartment of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560 Edited by Neil H. Shubin, The University of Chicago, Chicago, IL, and approved January 29, 2016 (received for review January 5, 2016) Tyrannosaurids—the familiar group of carnivorous dinosaurs in- We here report the first diagnostic tyrannosauroid from the mid- cluding Tyrannosaurus and Albertosaurus—were the apex predators Cretaceous, a new species from the Turonian (ca. 90–92 million in continental ecosystems in Asia and North America during the years ago) Bissekty Formation of Uzbekistan. This formation has latest Cretaceous (ca. 80–66 million years ago). Their colossal sizes recently emerged as one of the most important records of mid- and keen senses are considered key to their evolutionary and eco- Cretaceous dinosaurs globally (9–11). Possible tyrannosauroid logical success, but little is known about how these features devel- specimens from the Bissekty Formation were reported more than oped as tyrannosaurids evolved from smaller basal tyrannosauroids a half century ago (12), and, more recently, several isolated fossils that first appeared in the fossil record in the Middle Jurassic (ca. 170 were assigned to the group (9, 13), but none of these has been million years ago). This is largely because of a frustrating 20+ million- particularly complete or diagnostic at the species level, and their year gap in the mid-Cretaceous fossil record, when tyrannosauroids phylogenetic relationships have been difficult to assess. We de- transitioned from small-bodied hunters to gigantic apex predators scribe a remarkably preserved and highly diagnostic braincase that but from which no diagnostic specimens are known. We describe the links together these specimens and reveals the existence of a mid- first distinct tyrannosauroid species from this gap, based on a highly sized species phylogenetically intermediate between the oldest, derived braincase and a variety of other skeletal elements from the smallest tyrannosauroids and the largest, last-surviving tyran- ca. – Turonian ( 90 92 million years ago) of Uzbekistan. This taxon is phy- nosaurids, which had already developed many of the apomorphic logenetically intermediate between the oldest basal tyrannosauroids features of the tyrannosaurid brain and ear but not the cranial and the latest Cretaceous forms. It had yet to develop the giant size sinus system. and extensive cranial pneumaticity of T. rex and kin but does possess the highly derived brain and inner ear characteristic of the latest Systematic Paleontology Cretaceous species. Tyrannosauroids apparently developed huge Dinosauria Owen, 1842; Theropoda Marsh, 1881; Coelurosauria size rapidly during the latest Cretaceous, and their success in the Huene, 1914; Tyrannosauroidea Osborn, 1905; Timurlengia euotica top predator role may have been enabled by their brain and keen EARTH, ATMOSPHERIC, gen. et sp. nov. AND PLANETARY SCIENCES senses that first evolved at smaller body size. Holotype dinosaur | Tyrannosauroidea | Uzbekistan | phylogenetics | evolution ZIN PH (Paleoherpetological Collection, Zoological Institute, Russian Academy of Sciences, Saint Petersburg, Russia) 1146/16, yrannosaurs were at their heyday during the final ∼20 million a well-preserved braincase missing only the paroccipital processes years of the Age of Dinosaurs. Iconic taxa like Tyrannosau- T and much of the parabasisphenoid (Figs. 1 and 2 and Figs. S1−S3). EVOLUTION rus, Tarbosaurus, and Albertosaurus reigned at the top of the food chain in Asia and North America, endowed with colossal size Significance and sophisticated senses that set them apart from other carniv- orous dinosaurs (1, 2). These multiton, ecologically dominant Tyrannosaurs—the iconic group of dinosaurian carnivores that latest Cretaceous species (tyrannosaurids) evolved from an an- Tyrannosaurus rex— cestral lineage of basal tyrannosauroids, which originated more includes dominated latest Cretaceous than 100 million years before T. rex but for most of their history ecosystems with their colossal sizes and sophisticated senses. A gap in the mid-Cretaceous fossil record between these giant remained second-tier predators, rarely with a mass exceeding apex predators and their older, smaller relatives makes it dif- that of a horse (2–4). The ascent of tyrannosaurs from these early ficult to understand how the characteristic body size and eco- species to the latest Cretaceous giants was one of the seminal logical habits of T. rex and kin developed. A new species from events in dinosaur evolution, establishing the final dinosaur- Uzbekistan fills this gap. This horse-sized animal shows that dominated faunas that flourished before the end-Cretaceous tyrannosaurs had yet to achieve huge size at this time but had mass extinction (5). already evolved key brain and sensory features of the gigantic Little is known, however, about how tyrannosaurids developed latest Cretaceous species. Tyrannosaurs apparently developed many of their signature features, such as their gigantic sizes, giant body size rapidly, late in the Cretaceous, and their success highly unusual brains, ears attuned to low-frequency sounds, and may have been enabled by their early-evolving keen senses. extensively pneumatized skulls. This is due to a vexing gap in the fossil record that has long frustrated attempts to understand ty- Author contributions: S.L.B., A.A., and H.-D.S. designed research; S.L.B., A.A., H.-D.S., A.M., rannosaur evolution. There are hundreds of specimens of large- and I.B.B. performed research; S.L.B. contributed new reagents/analytic tools; S.L.B., A.M., bodied latest Cretaceous tyrannosaurids (1), and now a growing and I.B.B. analyzed data; and S.L.B., A.A., and H.-D.S. wrote the paper. record of smaller and more primitive Middle Jurassic−Early Cre- The authors declare no conflict of interest. taceous tyrannosauroids (2, 6–8). However, there are no diagnostic This article is a PNAS Direct Submission. fossils from the intervening 20+ million years of the mid-Cretaceous, 1To whom correspondence should be addressed. Email: [email protected]. the time when tyrannosauroids transitioned from marginal hunters This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. to apex predators (1, 2). 1073/pnas.1600140113/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1600140113 PNAS | March 29, 2016 | vol. 113 | no. 13 | 3447–3452 Downloaded by guest on September 26, 2021 Fig. 1. Skeletal reconstruction of T. euotica, with known bones colored in red. Individual bones come from different individuals, as they were surface- collected as isolated specimens in the Bissekty Formation of Uzbekistan. The proportions of the skeleton are based on an intermediate body type between Xiongguanlong and Tyrannosaurus but should be considered provisional until associated material is found. Bones are as follows: A, left frontal, ZIN PH 2330/ 16; B, holotypic braincase, ZIN PH 1146/16; C, cervical vertebra, ZIN PH 671/16; D, cervical vertebra, USNM (National Museum of Natural History) 538131; E, dorsal neural arch, USNM 538132; F, dorsal vertebra, CCMGE (Chernyshev’s Central Museum of Geological Exploration) 432/12457; G, anterior caudal ver- tebra, ZIN PH 951/16; H, middle caudal vertebra, ZIN PH 120/16; I, distal caudal vertebra, ZIN PH 507/16; J, pedal ungual, USNM 538167; K, manual ungual,ZINPH 619/16; L, right articular and surangular (reversed), ZIN PH 1239/16; M, left quadrate, ZIN PH 2296/16; N, right dentary, ZIN PH 15/16; and O, right maxilla (reversed), ZIN PH 676/16. (Individual scale bars, 2 cm.) Skeletal drawing courtesy of Todd Marshall. Etymology Body Size Timurlengia, in reference to the fourteenth-century Central Asian The holotypic braincase of T. euotica is nearly identical in size to ruler Timurleng (English: Tamerlane), and euotica, meaning “well- that of the holotype of Xiongguanlong baimoensis (based on eared” in reference to the large inner ear of the holotype. nearly equal widths of the occipital condyle and supraoccipital above the foramen magnum, and depth of the proximal end of Referred Specimens the paroccipital process). Along with the phylogenetic proximity ZIN PH 854/16 is the right side of a partial braincase that shares of the two taxa, this suggests that the holotypic individual of unique apomorphies with, and is otherwise identical to, the ho- T. euotica was roughly the same body size as Xiongguanlong, lotype (Fig. S4). We also refer to T. euotica a series of isolated whose mass has been estimated at 170–270 kg (14, 15). Al- cranial and postcranial bones described by Averianov and Sues though most sutures on the holotype of T. euotica are fused, part (9) and identified as belonging to indeterminate tyrannosauroids of the broken parabasisphenoid was not fused to the remainder (Fig. 1). These bones possess tyrannosauroid characters, are of the braincase, perhaps suggesting that the individual was not from the same horizon as the holotype of T. euotica, and belong yet osteologically mature and adults of the species may have to individuals of approximately the same body size. Furthermore, been somewhat larger. However, almost all other tyrannosau- separate phylogenetic analyses place the braincase and the series roid specimens from the Bissekty Formation are of the same of additional bones in the same position as an “intermediate”- size, or smaller, than corresponding bones in the holotype of grade tyrannosauroid (see Systematics). We therefore consider it X. baimoensis (9). The one possible exception is a fragment of most parsimonious that all of these specimens belong to the the posterior end of the lower jaw that was described as be- same taxon.
Load more

Recommended publications
  • PALEONTOLOGY and BIOSTRATIGRAPHY of MONGOLIA the JOINT SOVIET-MONGOLIAN PALEONTOLOGICAL EXPEDITION (Transactions, Vol
    PALEONTOLOGY AND BIOSTRATIGRAPHY OF MONGOLIA THE JOINT SOVIET-MONGOLIAN PALEONTOLOGICAL EXPEDITION (Transactions, vol. 3) EDITORIAL BOARD: N. N. Kramarenko (editor-in-chief) B. Luvsandansan, Yu. I. Voronin, R. Barsbold, A. K. Rozhdestvensky, B. A. Trofimov, V. Yu. Reshetov 1976 S. M. Kurzanov A NEW CARNOSAUR FROM THE LATE CRETACEOUS OF NOGON-TSAV, MONGOLIA* The Upper Cretaceous locality of Nogon-Tsav, located in the Zaltaika Gobi, 20 km NW of Mt. Ongon-Ulan-Ula, was discovered by geologists of the MNR. Then, in a series of years (1969–1971, 1973) the joint Soviet-Mongolian Geological Expedition investigated the site. According to the oral report of B. Yu. Reshetova, the deposits in this region are composed basically of sandstone and clay, clearly subdivided into two deposits. The lower great thickness contains many complete skulls, separate bones of tarbosaurs, ornithomimids, and claws of therizinosaurs. The upper red-colored beds are characterized only by scattered fragments of skulls. The fragments described below are of a new carnivorous dinosaur, Alioramus remotus (coll. South Goby region), from the family Tyrannosauridae, which occurs in the lower gray beds. Genus Alioramus Kurzanov, gen. nov. G e n u s n a m e from alius (Lat.) – other, ramus (Lat.) – branch; masc. G e n o t y p e — A. remotus Kurzanov, sp. nov., Upper Cretaceous, Nemegetinskaya suite, southern Mongolia. D i a g n o s i s . Tyrannosaurid of average size. Skull low, with highly elongated jaws. Nasals with well-developed separate crests of 1–l.5 cm height. Second antorbital fenestrae displaced forward, reaching the anterior end of the 5th tooth.
    [Show full text]
  • A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus Rex with Implications for Locomotion, Ontogeny, and Growth
    A Computational Analysis of Limb and Body Dimensions in Tyrannosaurus rex with Implications for Locomotion, Ontogeny, and Growth John R. Hutchinson1*, Karl T. Bates2, Julia Molnar1, Vivian Allen1, Peter J. Makovicky3 1 Structure and Motion Laboratory, Department of Veterinary Basic Sciences, The Royal Veterinary College, Hatfield, Hertfordshire, United Kingdom, 2 Department of Musculoskeletal Biology, Institute of Aging and Chronic Disease, University of Liverpool, Liverpool, United Kingdom, 3 Department of Geology, Field Museum of Natural History, Chicago, Illinois, United States of America Abstract The large theropod dinosaur Tyrannosaurus rex underwent remarkable changes during its growth from ,10 kg hatchlings to .6000 kg adults in ,20 years. These changes raise fascinating questions about the morphological transformations involved, peak growth rates, and scaling of limb muscle sizes as well as the body’s centre of mass that could have influenced ontogenetic changes of locomotion in T. rex. Here we address these questions using three-dimensionally scanned computer models of four large, well-preserved fossil specimens as well as a putative juvenile individual. Furthermore we quantify the variations of estimated body mass, centre of mass and segment dimensions, to characterize inaccuracies in our reconstructions. These inaccuracies include not only subjectivity but also incomplete preservation and inconsistent articulations of museum skeletons. Although those problems cause ambiguity, we conclude that adult T. rex had body masses around 6000–8000 kg, with the largest known specimen (‘‘Sue’’) perhaps ,9500 kg. Our results show that during T. rex ontogeny, the torso became longer and heavier whereas the limbs became proportionately shorter and lighter. Our estimates of peak growth rates are about twice as rapid as previous ones but generally support previous methods, despite biases caused by the usage of scale models and equations that underestimate body masses.
    [Show full text]
  • A New Raptorial Dinosaur with Exceptionally Long Feathering Provides Insights Into Dromaeosaurid flight Performance
    ARTICLE Received 11 Apr 2014 | Accepted 11 Jun 2014 | Published 15 Jul 2014 DOI: 10.1038/ncomms5382 A new raptorial dinosaur with exceptionally long feathering provides insights into dromaeosaurid flight performance Gang Han1, Luis M. Chiappe2, Shu-An Ji1,3, Michael Habib4, Alan H. Turner5, Anusuya Chinsamy6, Xueling Liu1 & Lizhuo Han1 Microraptorines are a group of predatory dromaeosaurid theropod dinosaurs with aero- dynamic capacity. These close relatives of birds are essential for testing hypotheses explaining the origin and early evolution of avian flight. Here we describe a new ‘four-winged’ microraptorine, Changyuraptor yangi, from the Early Cretaceous Jehol Biota of China. With tail feathers that are nearly 30 cm long, roughly 30% the length of the skeleton, the new fossil possesses the longest known feathers for any non-avian dinosaur. Furthermore, it is the largest theropod with long, pennaceous feathers attached to the lower hind limbs (that is, ‘hindwings’). The lengthy feathered tail of the new fossil provides insight into the flight performance of microraptorines and how they may have maintained aerial competency at larger body sizes. We demonstrate how the low-aspect-ratio tail of the new fossil would have acted as a pitch control structure reducing descent speed and thus playing a key role in landing. 1 Paleontological Center, Bohai University, 19 Keji Road, New Shongshan District, Jinzhou, Liaoning Province 121013, China. 2 Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, USA. 3 Institute of Geology, Chinese Academy of Geological Sciences, 26 Baiwanzhuang Road, Beijing 100037, China. 4 University of Southern California, Health Sciences Campus, BMT 403, Mail Code 9112, Los Angeles, California 90089, USA.
    [Show full text]
  • Implications for Predatory Dinosaur Macroecology and Ontogeny in Later Late Cretaceous Asiamerica
    Canadian Journal of Earth Sciences Theropod Guild Structure and the Tyrannosaurid Niche Assimilation Hypothesis: Implications for Predatory Dinosaur Macroecology and Ontogeny in later Late Cretaceous Asiamerica Journal: Canadian Journal of Earth Sciences Manuscript ID cjes-2020-0174.R1 Manuscript Type: Article Date Submitted by the 04-Jan-2021 Author: Complete List of Authors: Holtz, Thomas; University of Maryland at College Park, Department of Geology; NationalDraft Museum of Natural History, Department of Geology Keyword: Dinosaur, Ontogeny, Theropod, Paleocology, Mesozoic, Tyrannosauridae Is the invited manuscript for consideration in a Special Tribute to Dale Russell Issue? : © The Author(s) or their Institution(s) Page 1 of 91 Canadian Journal of Earth Sciences 1 Theropod Guild Structure and the Tyrannosaurid Niche Assimilation Hypothesis: 2 Implications for Predatory Dinosaur Macroecology and Ontogeny in later Late Cretaceous 3 Asiamerica 4 5 6 Thomas R. Holtz, Jr. 7 8 Department of Geology, University of Maryland, College Park, MD 20742 USA 9 Department of Paleobiology, National Museum of Natural History, Washington, DC 20013 USA 10 Email address: [email protected] 11 ORCID: 0000-0002-2906-4900 Draft 12 13 Thomas R. Holtz, Jr. 14 Department of Geology 15 8000 Regents Drive 16 University of Maryland 17 College Park, MD 20742 18 USA 19 Phone: 1-301-405-4084 20 Fax: 1-301-314-9661 21 Email address: [email protected] 22 23 1 © The Author(s) or their Institution(s) Canadian Journal of Earth Sciences Page 2 of 91 24 ABSTRACT 25 Well-sampled dinosaur communities from the Jurassic through the early Late Cretaceous show 26 greater taxonomic diversity among larger (>50kg) theropod taxa than communities of the 27 Campano-Maastrichtian, particularly to those of eastern/central Asia and Laramidia.
    [Show full text]
  • Postcranial Skeletal Pneumaticity in Sauropods and Its
    Postcranial Pneumaticity in Dinosaurs and the Origin of the Avian Lung by Mathew John Wedel B.S. (University of Oklahoma) 1997 A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Integrative Biology in the Graduate Division of the University of California, Berkeley Committee in charge: Professor Kevin Padian, Co-chair Professor William Clemens, Co-chair Professor Marvalee Wake Professor David Wake Professor John Gerhart Spring 2007 1 The dissertation of Mathew John Wedel is approved: Co-chair Date Co-chair Date Date Date Date University of California, Berkeley Spring 2007 2 Postcranial Pneumaticity in Dinosaurs and the Origin of the Avian Lung © 2007 by Mathew John Wedel 3 Abstract Postcranial Pneumaticity in Dinosaurs and the Origin of the Avian Lung by Mathew John Wedel Doctor of Philosophy in Integrative Biology University of California, Berkeley Professor Kevin Padian, Co-chair Professor William Clemens, Co-chair Among extant vertebrates, postcranial skeletal pneumaticity is present only in birds. In birds, diverticula of the lungs and air sacs pneumatize specific regions of the postcranial skeleton. The relationships among pulmonary components and the regions of the skeleton that they pneumatize form the basis for inferences about the pulmonary anatomy of non-avian dinosaurs. Fossae, foramina and chambers in the postcranial skeletons of pterosaurs and saurischian dinosaurs are diagnostic for pneumaticity. In basal saurischians only the cervical skeleton is pneumatized. Pneumatization by cervical air sacs is the most consilient explanation for this pattern. In more derived sauropods and theropods pneumatization of the posterior dorsal, sacral, and caudal vertebrae indicates that abdominal air sacs were also present.
    [Show full text]
  • Prootic Anatomy of a Juvenile Tyrannosauroid from New Jersey and Its Implications for the Morphology and Evolution of the Tyrannosauroid Braincase
    Prootic anatomy of a juvenile tyrannosauroid from New Jersey and its implications for the morphology and evolution of the tyrannosauroid braincase Chase D Brownstein Corresp. 1 1 Collections and Exhibitions, Stamford Museum & Nature Center, Stamford, Connecticut, United States Corresponding Author: Chase D Brownstein Email address: [email protected] Among the most recognizable theropods are the tyrannosauroids, a group of small to large carnivorous coelurosaurian dinosaurs that inhabited the majority of the northern hemisphere during the Cretaceous and came to dominate large predator niches in North American and Asian ecosystems by the end of the Mesozoic era. The clade is among the best-represented of dinosaur groups in the notoriously sparse fossil record of Appalachia, the Late Cretaceous landmass that occupied the eastern portion of North America after its formation from the transgression of the Western Interior Seaway. Here, the prootic of a juvenile tyrannosauroid collected from the middle-late Campanian Marshalltown Formation of the Atlantic Coastal Plain is described, remarkable for being the first concrete evidence of juvenile theropods in that plain during the time of the existence of Appalachia and the only portion of theropod braincase known from the landmass. Phylogenetic analysis recovers the specimen as an “intermediate” tyrannosauroid of similar grade to Dryptosaurus and Appalachiosaurus. Comparisons with the corresponding portions of other tyrannosauroid braincases suggest that the Ellisdale prootic is more similar to Turonian forms in morphology than to the derived tyrannosaurids of the Late Cretaceous, thus supporting the hypothesis that Appalachian tyrannosauroids and other vertebrates were relict forms surviving in isolation from their derived counterparts in Eurasia.
    [Show full text]
  • Immigrant Species, Or Native Species?
    The Journal of Paleontological Sciences: JPS.C.2017.01 TESTING THE HYPOTHESES OF THE ORIGIN OF TYRANNOSAURUS REX: IMMIGRANT SPECIES, OR NATIVE SPECIES? __________________________________________________________________________________________________________________ Chan-gyu Yun Vertebrate Paleontological Institute of Incheon, Incheon 21974, Republic of Korea & Biological Sciences, Inha University, Incheon 22212, Republic of Korea [email protected] __________________________________________________________________________________________________________________ Abstract: It is an undoubtable fact that Tyrannosaurus rex is the most iconic dinosaur species of all time. However, it is currently debatable whether this species has a North American origin or Asian origin. In this paper, I test these two hypotheses based on current fossil records and former phylogenetic analyses. Phylogenetic and fossil evidence, such as derived tyrannosaurine fossils of Asia, suggests that the hypothesis of an Asian origin of Tyrannosaurus rex is the most plausible one, but this is yet to be certain due to the scarcity of fossil records. INTRODUCTION The most famous and iconic dinosaur of all time, Tyrannosaurus rex, is only known from upper Maastrichtian geological formations in Western North America (e.g. Carr and Williamson, 2004; Larson, 2008). However, older relatives of Tyrannosaurus rex (e.g. Daspletosaurus, Tarbosaurus) are known from both Asia and North America. This leads to an evolutionary question: is the origin of Tyrannosaurus rex from Asia, or North America? About six of the currently valid tyrannosaurine taxa were described in the twenty-first century (based on parsimony analysis of Brusatte and Carr, 2016), with new species which are being described (Sebastian Dalman, Pers. Comm., 2016; Thomas Carr, Pers. Comm., 2016). It can be said that "now" is the "golden age” for studying tyrannosaurine evolution.
    [Show full text]
  • Nanotyrannus’ As a Valid Taxon Of
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Queen Mary Research Online Dentary groove morphology does not distinguish ‘Nanotyrannus’ as a valid taxon of tyrannosauroid dinosaur. Comment on: “Distribution of the dentary groove of theropod dinosaurs: implications for theropod phylogeny and the validity of the genus Nanotyrannus Bakker et al., 1988” Stephen L. Brusatte1*, Thomas D. Carr2, Thomas E. Williamson3, Thomas R. Holtz, Jr.4,5, David W. E. Hone6, Scott A. Williams7 1 School of GeoSciences, University of Edinburgh, Grant Institute, James Hutton Road, Edinburgh, EH9 3FE, United Kingdom, [email protected] 2Department of Biology, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140, USA 3New Mexico Museum of Natural History and Science, 1801 Mountain Road, NW, Albuquerque, NM 87104, USA 4Department of Geology, University of Maryland, 8000 Regents Drive, College Park, MD 20742, USA 5Department of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA 6School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, United Kingdom. 7Burpee Museum of Natural History, 737 North Main Street, Rockford, IL 60115, USA *Corresponding author ABSTRACT: There has been considerable debate about whether the controversial tyrannosauroid dinosaur ‘Nanotyrannus lancensis’ from the uppermost Cretaceous of North America is a valid taxon or a juvenile of the contemporaneous Tyrannosaurus rex. In a recent Cretaceous Research article, Schmerge and Rothschild (2016) brought a new piece of evidence to this discussion: the morphology of the dentary groove, a depression on the lateral surface of the dentary that houses neurovascular foramina.
    [Show full text]
  • Limb Design, Function and Running Performance in Ostrich-Mimics and Tyrannosaurs
    GAIA Nº 15, LISBOA/LISBON, DEZEMBRO/DECEMBER 1998, pp. 257-270 (ISSN: 0871-5424) LIMB DESIGN, FUNCTION AND RUNNING PERFORMANCE IN OSTRICH-MIMICS AND TYRANNOSAURS Gregory S. PAUL 3109 N Calvert St. Side Apt., BALTIMORE MD 21218. USA ABSTRACT: Examination of the limb morphology of small ornithomimids and large tyranno- saurids shows that they remained remarkably constant in design regardless of size. The changes that were present were consistent with maintaining limb strength and function constant with size. It is concluded that ornithomimid and tyrannosaurid legs functioned in a similar manner, and always exhibit the features normally associated with a fast running gait. This is in contrast to modern animals, in which elephants as gigantic as large tyranno- saurids have limbs that are modified for a slow walking gait. INTRODUCTION to run observed in elephants. The hypothesis can be challenged if it can be shown that at least some ex- Because they had long, gracile, bird-like legs, it tinct giants retained the skeletal adaptations for run- has long been accepted that the smaller predatory ning observed in smaller species, and in their own dinosaurs were swift runners (O [& GREG- SBORN offspring. In turn, the hypothesis that giants can run ], 1916; COLBERT, 1961; RUSSELL, 1972; ORY fast if they retain limbs similar to smaller runners can C , 1978; THULBORN, 1982; PAUL, 1988; OOMBS be challenged if it is shown that the skeleton is too H , 1994). Much more controversial has been OLTZ vulnerable to structural failure. the locomotory abilities of their giant relatives, which have been restored as no faster than elephants BODY MASSES (LAMBE, 1917; HALSTEAD &HALSTEAD, 1981; THUL- BORN, 1982; BARSBOLD, 1983), able to run at only Sources for mass data for extinct and extant ani- modest speeds (COOMBS, 1978; MOLNAR &FAR- mals include PAUL (1988, 1997), NOWAK (1991) and LOW, 1990; HORNER &LESSEM, 1993; FARLOW, MATTHEWS (1994).
    [Show full text]
  • Cranial Anatomy of Allosaurus Jimmadseni, a New Species from the Lower Part of the Morrison Formation (Upper Jurassic) of Western North America
    Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America Daniel J. Chure1,2,* and Mark A. Loewen3,4,* 1 Dinosaur National Monument (retired), Jensen, UT, USA 2 Independent Researcher, Jensen, UT, USA 3 Natural History Museum of Utah, University of Utah, Salt Lake City, UT, USA 4 Department of Geology and Geophysics, University of Utah, Salt Lake City, UT, USA * These authors contributed equally to this work. ABSTRACT Allosaurus is one of the best known theropod dinosaurs from the Jurassic and a crucial taxon in phylogenetic analyses. On the basis of an in-depth, firsthand study of the bulk of Allosaurus specimens housed in North American institutions, we describe here a new theropod dinosaur from the Upper Jurassic Morrison Formation of Western North America, Allosaurus jimmadseni sp. nov., based upon a remarkably complete articulated skeleton and skull and a second specimen with an articulated skull and associated skeleton. The present study also assigns several other specimens to this new species, Allosaurus jimmadseni, which is characterized by a number of autapomorphies present on the dermal skull roof and additional characters present in the postcrania. In particular, whereas the ventral margin of the jugal of Allosaurus fragilis has pronounced sigmoidal convexity, the ventral margin is virtually straight in Allosaurus jimmadseni. The paired nasals of Allosaurus jimmadseni possess bilateral, blade-like crests along the lateral margin, forming a pronounced nasolacrimal crest that is absent in Allosaurus fragilis. Submitted 20 July 2018 Accepted 31 August 2019 Subjects Paleontology, Taxonomy Published 24 January 2020 Keywords Allosaurus, Allosaurus jimmadseni, Dinosaur, Theropod, Morrison Formation, Jurassic, Corresponding author Cranial anatomy Mark A.
    [Show full text]
  • New Tyrannosaur from the Mid-Cretaceous of Uzbekistan Clarifies Evolution of Giant Body Sizes and Advanced Senses in Tyrant Dinosaurs
    New tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies evolution of giant body sizes and advanced senses in tyrant dinosaurs Stephen L. Brusattea,1, Alexander Averianovb,c, Hans-Dieter Suesd, Amy Muira, and Ian B. Butlera aSchool of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, United Kingdom; bZoological Institute, Russian Academy of Sciences, St. Petersburg 199034, Russia; cDepartment of Sedimentary Geology, Saint Petersburg State University, St. Petersburg 199178, Russia; and dDepartment of Paleobiology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560 Edited by Neil H. Shubin, The University of Chicago, Chicago, IL, and approved January 29, 2016 (received for review January 5, 2016) Tyrannosaurids—the familiar group of carnivorous dinosaurs in- We here report the first diagnostic tyrannosauroid from the mid- cluding Tyrannosaurus and Albertosaurus—were the apex predators Cretaceous, a new species from the Turonian (ca. 90–92 million in continental ecosystems in Asia and North America during the years ago) Bissekty Formation of Uzbekistan. This formation has latest Cretaceous (ca. 80–66 million years ago). Their colossal sizes recently emerged as one of the most important records of mid- and keen senses are considered key to their evolutionary and eco- Cretaceous dinosaurs globally (9–11). Possible tyrannosauroid logical success, but little is known about how these features devel- specimens from the Bissekty Formation were reported more than oped as tyrannosaurids evolved from smaller basal tyrannosauroids a half century ago (12), and, more recently, several isolated fossils that first appeared in the fossil record in the Middle Jurassic (ca. 170 were assigned to the group (9, 13), but none of these has been million years ago).
    [Show full text]
  • A Century of Spinosaurs - a Review and Revision of the Spinosauridae
    View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Queen Mary Research Online A century of spinosaurs - a review and revision of the Spinosauridae with comments on their ecology HONE David William Elliott1, * HOLTZ Thomas Richard Jnr2 1 School of Biological and Chemical Sciences, Queen Mary University of London, London, E1 4NS, UK 2 Department of Geology, University of Maryland, College Park, MD 20742 USA Abstract: The spinosaurids represent an enigmatic and highly unusual form of large tetanuran theropods that were first identified in 1915. A recent flurry of discoveries and taxonomic revisions of this important and interesting clade had added greatly to our knowledge, however, spinosaur body fossils are generally rare and most species are known from only limited skeletal remains. Their unusual anatomical adaptations to the skull, limbs and axial column all differ from other large theropods and point to an unusual ecological niche and a lifestyle intimately linked to water. Keywords: Theropoda, Megalosauroidea, Baryonychinae, Spinosaurinae, palaeoecology E-mail: [email protected] 1 Introduction The Spinosauridae is an enigmatic clade of large and carnivorous theropods from the Jurassic and Cretaceous that are known from both Gondwana and Laurasia (Holtz et al., 2004). Despite their wide temporal and geographic distribution, the clade is known primarily from teeth and the body fossil record is extremely limited (Bertin, 2010). As such, relatively little is known about this group of animals, although their unusual morphology with regard to skull shape, dentition, dorsal neural spines and other features mark them out as divergent from the essential bauplan of other non-tetanuran theropods (Fig 1).
    [Show full text]