Paleobiology and geographic range of the large-bodied Cretaceous theropod dinosaur Acrocanthosaurus atokensis

https://doi.org/10.1016/j.palaeo.2012.03.003Get rights and content

Abstract

A partial theropod skeleton from the Albian (ca. 105 ma) Cloverly Formation of Wyoming is shown to exhibit many features in common with members of Carcharodontosauria and is referred to Acrocanthosaurus atokensis on the basis of an autapomorphy and a unique combination of characters. The absence of neurocentral fusion in dorsal and caudal vertebrae and bone histology of the femur indicate that the specimen is a juvenile. The circumferences of lines of arrested growth were used to estimate mass over successive years of the animal's life. These mass estimates suggest that early in ontogeny, Acrocanthosaurus grew at rates on par with growth rates inferred in Allosaurus and most tyrannosaurid theropods, which are similar to rates expected for scaled-up precocial birds. Histological data from adult specimens suggest that Acrocanthosaurus reached adult body size in two to three decades. Gigantism in Acrocanthosaurus likely evolved via acceleration of growth rates relative to those of basal members of Allosauroidea, a transition also observed within tyrannosauroid theropods. Contrary to previous assessments, there is only evidence for one large-bodied theropod species in the Early Cretaceous of North America, though many fragmentary specimens are indeterminate to the genus level. Aptian–Albian and Maastrichtian-aged dinosaur communities were more similar to one another than to those of the intervening Campanian stage in that both seem to have featured a single, extremely large-bodied, fast growing, geographically widespread theropod dinosaur.

Highlights

► We present the first juvenile specimen of Acrocanthosaurus. ► We investigate the bone histology of juveniles and adults of Acrocanthosaurus. ► Acrocanthosaurus reached adult body size in about two decades. ► North American large-bodied theropod diversity was very low.

Introduction

The Lower Cretaceous Cloverly Formation of Wyoming and Montana records the presence of several abundant herbivorous dinosaurs such as the nodosaurid Sauropelta edwardsi, the ornithopod Tenontosaurus tilletti, and the sauropod Sauroposeidon proteles (Ostrom, 1970, D'Emic, in press). Several dinosaur taxa are shared between the Cloverly Formation and penecontemporaneous strata in Texas and Oklahoma, including Deinonychus antirrhopus, Sauroposeidon proteles, and different species of Tenontosaurus. In contrast, other Cloverly Formation dinosaur taxa are less well known and have not been a substantial source of data for studies of Cloverly Formation paleoecology or dinosaur paleoecology in general. For example, only single exemplars of the oviraptorosaur Microvenator celer and the ornithopod Zephyrosaurus schaffi have been described (Ostrom, 1970, Sues, 1980). Still other Cloverly Formation dinosaurs are only represented by remains that are indeterminate to the genus level, such as ornithomimids and large-bodied theropods (body mass > 1000 kg), which are limited to a handful of teeth and bones reported by Ostrom (1970).

The paucity of large-bodied theropod remains from this time on the continent is not limited to the Cloverly Formation. Only a single genus and species of large theropod has been named from the Lower Cretaceous of North America: the carcharodontosaurid Acrocanthosaurus atokensis (Stovall and Langston, 1950). Acrocanthosaurus is one of the largest known theropods, similar in size and weight to Tyrannosaurus rex (Bates et al., 2009) and Giganotosaurus carolinii (Calvo and Coria, 1998). All known definitive remains of Acrocanthosaurus are from the Aptian–Albian Trinity Group of Texas and laterally-equivalent Antlers Formation of Oklahoma (Eddy and Clarke, 2011).

Apart from material ascribed to Acrocanthosaurus, all other Lower Cretaceous North American large-bodied theropod remains are indeterminate to the genus level (Harris, 1998a). These include fragmentary teeth and bones from the Arundel clay of the Patuxent Formation of Maryland (Lull, 1911), the Cedar Mountain Formation of Utah (Kirkland et al., 1997), and the Cloverly Formation of Wyoming (Ostrom, 1970). Harris (1998a) suggested that some vertebrae from the Cloverly Formation and Arundel clay of the Patuxent Formation represent taxa distinct from Acrocanthosaurus, suggesting that more than one large-bodied theropod was present on the continent at the time. Several small- to medium-sized theropods were also present during the Early Cretaceous of North America, including tyrannosauroids (Cifelli et al., 1997, Zanno and Makovicky, 2011) and deinonychosaurs (Kirkland et al., 1993).

Recent fieldwork has yielded a partial skeleton of a juvenile theropod found in a bonebed in the Cloverly Formation, as well as some isolated large-bodied theropod material. Herein this partial skeleton and its bone histology are described, and its ontogenetic age and taxonomic affinity are discussed. Features supporting the referral of this skeleton to Acrocanthosaurus atokensis are demonstrated, and comparisons of its bone histology are made with that of adult individuals of the taxon. Histological data are used to estimate growth rate and longevity for Acrocanthosaurus. Finally, the taxonomic affinities of isolated large-bodied theropod remains from the Lower Cretaceous of North America are reviewed, and the bearing of this new information on dinosaur faunas of the continent at the time is discussed.

Institutional abbreviations: NCSM, North Carolina Museum of Natural Sciences, Raleigh, USA; SMU, Southern Methodist University, Dallas, USA; UM, University of Michigan Museum of Paleontology, Ann Arbor, USA; UMNH VP, Utah Museum of Natural History Vertebrate Paleontology Collection, Salt Lake City, USA; YPM, Yale Peabody Museum, New Haven, USA.

Section snippets

Systematic paleontology

DINOSAURIA Owen, 1842

THEROPODA Marsh, 1881

ALLOSAUROIDEA Currie and Zhao, 1993

CARCHARODONTOSAURIA Benson et al., 2010

CARCHARODONTOSAURIDAE Stromer, 1931

Acrocanthosaurus Stovall and Langston, 1950

Acrocanthosaurus atokensis Stovall and Langston, 1950

New referred material: UM 20796, a dorsal vertebral centrum, caudal vertebral neural arch, right and left pubes, right femur, proximal right fibula, and several fragments from site YPM 63–18 (see later for further locality information). Other materials

Description

The partial skeleton UM 20796 was collected by MDD in 2008 in an area less than 1 m2, and the bones were nearly in contact. For the following description, nomenclature for vertebral laminae and fossae follows Wilson (1999) and Wilson et al. (2011), respectively.

Discussion

Below, the taxonomic affinities of UM 20796 are discussed and estimates of its growth rate are made via bone histology. The implications of this new data and taxonomic revision of other specimens are discussed in the context of Cretaceous North American dinosaur communities.

Acknowledgements

Thanks to B. Dauksewicz, T. Churchill, B. Foreman, P. Gingerich, A. Hayden, D. Klein, S. Macone, C. Manz, A. Wood, D. Raisanen, A. Tillett, C. Youngs, P. Christenson, and the WY and MT Bureaus of Land Management (permits PA07-WY-155 and M 97866) for field assistance and support. G. Gunnell, A. Pan, L. Ballinger, W. Joyce, D. Brinkman, and V. Schneider are thanked for collection access and assistance. Thanks to R. Cifelli and V. Schneider for permission to thin section specimens. Thanks to S.

References (65)

  • G.M. Erickson et al.

    Growth curve of Psittacosaurus mongoliensis Osborn (Ceratopsia: Psittacosauridae) inferred from long bone histology

    Zoological Journal of the Linnean Society

    (2000)
  • T.A. Gates et al.

    Biogeography of terrestrial and freshwater vertebrates from the Late Cretaceous (Campanian) Western Interior of North America

    Palaeogeography, Palaeoclimatology, Palaeoecology

    (2010)
  • M.D. Abramoff et al.

    Image processing with ImageJ

    Biophotonics International

    (2004)
  • J.D. Archibald et al.

    Dinosaur extinction

  • K. Bates et al.

    Estimating mass properties of dinosaurs using laser imaging and 3D computer modelling

    PLoS One

    (2009)
  • R.B.J. Benson

    A description of Megalosaurus bucklandii (Dinosauria: Theropoda) from the Bathonian of the UK and the relationships of Middle Jurassic theropods

    Zoological Journal of the Linnean Society

    (2010)
  • R.B.J. Benson et al.

    A new clade of archaic large-bodied predatory dinosaurs (Theropoda: Allosauroidea) that survived to the latest Mesozoic

    Naturwissenschaften

    (2010)
  • R.C. Blakey

    Global paleogeographic views of earth history—late Precambrian to Recent

  • D.L. Brinkman et al.

    First occurrence of Deinonychus antirrhopus (Dinosauria: Theropoda) from the Antlers Formation (Lower Cretaceous, Aptian–Albian) of Oklahoma

    Oklahoma Geological Survey Bulletin

    (1998)
  • C. Brochu

    Closure of neurocentral sutures during crocodilian ontogeny: implications for maturity assessment in fossil archosaurs

    Journal of Vertebrate Paleontology

    (1996)
  • C. Brochu

    Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull

    Society of Vertebrate Paleontology Memoir

    (2003)
  • S.L. Brusatte et al.

    Phylogeny of Allosauroidea (Dinosauria: Theropoda): comparative analysis and resolution

    Journal of Systematic Palaeontology

    (2008)
  • S.L. Brusatte et al.

    The systematic utility of theropod enamel wrinkles

    Journal of Vertebrate Paleontology

    (2007)
  • S.L. Brusatte et al.

    The osteology of Neovenator salerii (Dinosauria: Theropoda) from the Wealden Group (Barremian) of the Isle of Wight

    Monograph of the Palaeontographical Society

    (2008)
  • S.L. Brusatte et al.

    Tyrannosaur paleobiology: new research on ancient exemplar organisms

    Science

    (2010)
  • P.J. Bybee et al.

    Sizing the Jurassic theropod dinosaur Allosaurus: assessing growth strategy and evolution of ontogenetic scaling of limbs

    Journal of Morphology

    (2006)
  • J.O. Calvo et al.

    New specimen of Giganotosaurus carolinii (Coria & Salgado, 1995), supports it as the largest theropod ever found

    Gaia

    (1998)
  • N.E. Campione et al.

    Cranial growth and variation in Edmontosaurs (Dinosauria: Hadrosauridae): implications for Latest Cretaceous megaherbivore diversity in North America

    PLoS One

    (2011)
  • T.D. Carr et al.

    Evidence for high taxonomic and morphologic tyrannosauroid diversity in the Late Cretaceous (Late Campanian) of the American Southwest and a new short-skulled tyrannosaurid from the Kaiparowits formation of Utah

    Naturwissenschaften

    (2011)
  • P. Christiansen

    Long bone scaling and limb posture in non-avian theropods: evidence for differential allometry

    Journal of Vertebrate Paleontology

    (1999)
  • P. Christiansen et al.

    Mass prediction in theropod dinosaurs

    Historical Biology

    (2004)
  • R.L. Cifelli et al.

    High-precision 40Ar/39Ar geochronology and the advent of North America's Late Cretaceous terrestrial fauna

    Proceedings of the National Academy of Sciences

    (1997)
  • P.J. Currie et al.

    A new specimen of Acrocanthosaurus atokensis (Theropoda, Dinosauria) from the Lower Cretaceous Antlers Formation (Lower Cretaceous, Aptian) of Oklahoma, USA

    Geodiversitas

    (2000)
  • P.J. Currie et al.

    A new large theropod (Dinosauria, Theropoda) from the Jurassic of Xinjiang, People's Republic of China

    Canadian Journal of Earth Sciences

    (1993)
  • F.L. DeCourten

    New data on Early Cretaceous dinosaurs from the Long Walk quarry and tracksite, Emery County, Utah

    Utah Geological Association Publication

    (1991)
  • D'Emic, M.D. in press. Revision of the sauropod dinosaurs of the Trinity Group (Comanchean Series, Early Cretaceous),...
  • D'Emic, M.D. and Foreman, B.Z. in press. The beginning of the sauropod dinosaur hiatus in North America: insights from...
  • D. Eddy et al.

    New information on the cranial anatomy of Acrocanthosaurus atokensis and its implications for the phylogeny of Allosauroidea (Dinosauria: Theropoda)

    PLoS One

    (2011)
  • G.M. Erickson et al.

    Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs

    Nature

    (2004)
  • G.M. Erickson et al.

    Was dinosaurian physiology inherited by birds? Reconciling slow growth in Archaeopteryx

    PLoS One

    (2009)
  • J.D. Harris

    Large, Early Cretaceous theropods in North America

  • J.D. Harris

    A reanalysis of Acrocanthosaurus atokensis, its phylogenetic status, and paleobiogeographic implications, based on a new specimen from Texas

    New Mexico Museum of Natural History and Science Bulletin

    (1998)
  • Cited by (0)

    View full text