Skip to main content
×
×
Home

Recognizing sexual dimorphism in the fossil record: lessons from nonavian dinosaurs

  • Jordan C. Mallon (a1)
Abstract
Abstract

The demonstration of sexual dimorphism in the fossil record can provide vital information about the role that sexual selection has played in the evolution of life. However, statistically robust inferences of sexual dimorphism in fossil organisms are exceedingly difficult to establish, owing to issues of sample size, experimental control, and methodology. This is particularly so in the case of dinosaurs, for which sexual dimorphism has been posited in many species, yet quantifiable data are often lacking. This study presents the first statistical investigation of sexual dimorphism across Dinosauria. It revisits prior analyses that purport to find quantitative evidence for sexual dimorphism in nine dinosaur species. After the available morphological data were subjected to a suite of statistical tests (normality and unimodality tests and mixture modeling), no evidence for sexual dimorphism was found in any of the examined taxa, contrary to conventional wisdom. This is not to say that dinosaurs were not sexually dimorphic (phylogenetic inference suggests they may well have been), only that the available evidence precludes its detection. A priori knowledge of the sexes would greatly facilitate the assessment of sexual dimorphism in the fossil record, and it is suggested that unambiguous indicators of sex (e.g., presence of eggs, embryos, medullary bone) be used to this end.

Copyright
References
Hide All
Akaike H. 1973. Information theory and an extension of the maximum likelihood principle. Pp. 267281 in B. N. Petrov, and F. Csáki, eds. Proceedings of the Second International Symposium on Information Theory. Akadémiai Kiadó, Budapest.
Allsteadt J., and Lang J. W.. 1995. Sexual dimorphism in the genital morphology of young American alligators, Alligator mississippiensis . Herpetologica 51:314325.
Anderson T. W., and Darling D. A.. 1952. Asymptotic theory of certain “goodness-of-fit” criteria based on stochastic processes. Annals of Mathematical Statistics 23:193212.
Andersson M. 1994. Sexual selection. Princeton University Press, Princeton, N.J.
Asher R. J., Lin K. H., Kardjilov N., and Hautier L.. 2011. Variability and constraint in the mammalian vertebral column. Journal of Evolutionary Biology 24:10801090.
Barden H. E., and Maidment S. C. R.. 2011. Evidence for sexual dimorphism in the stegosaurian dinosaur Kentrosaurus aethiopicus from the Upper Jurassic of Tanzania. Journal of Vertebrate Paleontology 31:641651.
Benton M. J., Juul L., Storrs G. W., and Galton P. M.. 2000. Anatomy and systematics of the prosauropod dinosaur Thecodontosaurus antiquus from the Upper Triassic of southwest England. Journal of Vertebrate Paleontology 20:77108.
Bonnan M. F., Farlow J. O., and Masters S. L.. 2008. Using linear and geometric morphometrics to detect intraspecific variability and sexual dimorphism in femoral shape in Alligator mississippiensis and its implications for sexing fossil archosaurs. Journal of Vertebrate Paleontology 28:422431.
Bonucci E., and Gherardi G.. 1975. Histochemical and electron microscope investigations on medullary bone. Cell and Tissue Research 163:8197.
Borkovic B., and Russell A.. 2014. Sexual selection according to Darwin: a response to Padian and Horner’s interpretation. Comptes Rendus Palevol 13:701707.
Brown B., and Schlaikjer E. M.. 1940. The structure and relationships of Protoceratops . Annals of the New York Academy of Sciences 40:133265.
Brown B., and Schlaikjer E. M.. 1943. A study of the troodont dinosaurs with the description of a new genus and four new species. American Museum of Natural History Bulletin 82:121149.
Brown C. M., Arbour J. H., and Jackson D. A.. 2012. Testing of the effect of missing data estimation and distribution in morphometric multivariate data analyses. Systematic Biology 61:941954.
Bryant H. N., and Russell A. P.. 1992. The role of phylogenetic analysis in the inference of unpreserved attributes of extinct taxa. Philosophical Transactions of the Royal Society of London B 337:405418.
Caldwell M. W., and Lee M. S. Y.. 2001. Live birth in Cretaceous marine lizards (mosasauroids). Proceedings of the Royal Society of London B 268:23972401.
Callomon J. H. 1963. Sexual dimorphism in Jurassic ammonites. Transactions of the Leicester Literary and Philosophical Society 57:2156.
Carpenter K. 1990a. Variation in Tyrannosaurus rex. Pp. 141–145 in Carpenter and Currie 1990.
Carpenter K. 1990b. Ankylosaur systematics: example using Panoplosaurus and Edmontonia (Ankylosauria: Nodosauridae). Pp. 281–298 in Carpenter and Currie 1990.
Carpenter K. 1999. Eggs, nests, and baby dinosaurs: a look at dinosaur reproduction. Indiana University Press, Bloomington.
Carpenter K. 2010. Variation in a population of Theropoda (Dinosauria): Allosaurus from the Cleveland-Lloyd Quarry (Upper Jurassic), Utah, USA. Paleontological Research 14:250259.
Carpenter K., and Currie P. J., eds. 1990. Dinosaur systematics: approaches and perspectives. Cambridge University Press, Cambridge.
Carpenter K., and Smith M.. 2001. Forelimb osteology and biomechanics of Tyrannosaurus rex . Pp. 90116 in D. H. Tanke, and K. Carpenter, eds. Mesozoic vertebrate life. Indiana University Press, Bloomington.
Carpenter K., Hayashi S., Kobayashi Y., Maryańska T., Barsbold R., Sato K., and Obata I.. 2011. Saichania chulsanensis (Ornithischia, Ankylosauridae) from the Upper Cretaceous of Mongolia. Palaeontographica Abteilung A 294:161.
Chapman R. E., Galton P. M., Sepkoski J. J. Jr., and Wall W. P.. 1981. A morphometric study of the cranium of the pachycephalosaurid dinosaur Stegoceras . Journal of Paleontology 55:608618.
Chapman R. E., Weishampel D. B., Hunt G., and Raskin-Gutman D.. 1997. Sexual dimorphism in dinosaurs. Pp. 8393 in D. L. Wolberg, E. Stump, and G. D. Rosenberg, eds. Dinofest International: Proceedings of a Symposium Sponsored by Arizona State University. Academy of Natural Sciences, Philadelphia.
Cheng Y.-N., Wu X.-C., and Ji Q.. 2004. Triassic marine reptiles gave birth to live young. Nature 432:383386.
Cheng Y.-N., Holmes R., Wu X.-C., and Alfonso N.. 2009. Sexual dimorphism and life history of Keichousaurus hui (Reptilia: Sauropterygia). Journal of Vertebrate Paleontology 29:401408.
Chinsamy A., and Tumarkin‐Deratzian A.. 2009. Pathologic bone tissues in a turkey vulture and a nonavian dinosaur: implications for interpreting endosteal bone and radial fibrolamellar bone in fossil dinosaurs. Anatomical Record 292:14781484.
Chinsamy A., Chiappe L. M., Marugán-Lobón J., Chunling G., and Fengjiao Z.. 2013. Gender identification of the Mesozoic bird Confuciusornis sanctus . Nature Communications 4:1381.
Colbert E. H. 1989. The Triassic dinosaur Coelophysis . Museum of Northern Arizona Bulletin 57:1160.
Colbert E. H. 1990. Variation in Coelophysis bauri. Pp. 81–90 in Carpenter and Currie 1990.
Cunningham J. T. 1900. Sexual dimorphism in the animal kingdom: a theory of the evolution of secondary sexual characters. Adam and Charles Black, London.
Currie P. J., and Russell D. A.. 1988. Osteology and relationships of Chirostenotes pergracilis (Saurischia, Theropoda) from the Judith River (Oldman) Formation of Alberta, Canada. Canadian Journal of Earth Sciences 25:972986.
Currie P. J., Rigby J. K. Jr., and Sloan R. E.. 1990. Theropod teeth from the Judith River Formation of southern Alberta, Canada. Pp. 107–125 in Carpenter and Currie 1990.
Currie P. J., Langston W. Jr., and Tanke D. H.. 2008. A new species of Pachyrhinosaurus (Dinosauria, Ceratopsidae) from the Upper Cretaceous of Alberta, Canada. Pp. 1108 in P. J. Currie, W. Langston, Jr., and D. H. Tanke, eds. A new horned dinosaur from an Upper Cretaceous bone bed in Alberta. NRC Research Press, Ottawa.
Danforth C. H. 1930. Numerical variation and homologies in vertebrae. American Journal of Physical Anthropology 14:463481.
Darwin C. 1871. The descent of man, and selection in relation to sex. J. Murray, London.
Deng T. 2005. New discovery of Iranotherium morgani (Perissodactyla, Rhinocerotidae) from the late Miocene of the Linxia Basin in Gansu, China, and its sexual dimorphism. Journal of Vertebrate Paleontology 25:442450.
Dodson P. 1975. Taxonomic implications of relative growth in lambeosaurine hadrosaurs. Systematic Biology 24:3754.
Dodson P. 1976. Quantitative aspects of relative growth and sexual dimorphism in Protoceratops . Journal of Paleontology 50:929940.
Dodson P. 1990. On the status of the ceratopsids Monoclonius and Centrosaurus. Pp. 231–243 in Carpenter and Currie 1990.
Dodson P. 2011. Sex in the Cretaceous—how to tell the girls from the boys. American Paleontologist 19(3):2124.
Dong Z. 1997. Mixture analysis and its preliminary application in archaeology. Journal of Archaeological Science 24:141161.
Evans D. C. 2007. Ontogeny and evolution of lambeosaurine dinosaurs (Ornithischia: Hadrosauridae). Unpublished Ph.D. dissertation. University of Toronto, Toronto.
Farlow J. O. 1990. Review: dynamic dinosaurs. Paleobiology 16:234241.
Galton P. M. 1982a. Juveniles of the stegosaurian dinosaur Stegosaurus from the Upper Jurassic of North America. Journal of Vertebrate Paleontology 2:4762.
Galton P. M. 1982b. The postcranial anatomy of stegosaurian dinosaur Kentrosaurus from the upper Jurassic of Tanzania, East Africa. Geologica et Palaeontologica 15:139160.
Galton P. M. 1985. British plated dinosaurs (Ornithischia, Stegosauridae). Journal of Vertebrate Paleontology 5:211254.
Galton P. M. 1990. Stegosauria. Pp. 435455 in D. B. Weishampel, P. Dodson, and H. Osmólska, eds. The Dinosauria. University of California Press, Berkeley.
Galton P. M. 1991. Postcranial remains of stegosaurian dinosaur Dacentrurus armatus from upper Jurassic of France and Portugal. Geologica et Palaeontologica 25:299327.
Galton P. M. 1997. Comments on sexual dimorphism in the prosauropod dinosaur Plateosaurus engelhardti (Upper Triassic, Trossingen). Neues Jahrbuch für Geologie und Paläontologie, Monatshefte 1997:674682.
Galton P. M. 1999. Sex, sacra and Sellosaurus gracilis (Saurischia, Sauropodomorpha, Upper Triassic, Germany)—or why the character “two sacral vertebrae” is plesiomorphic for Dinosauria. Neues Jahrbuch fur Geologie und Palaontologie-Abhandlungen 213:1956.
Galton P. M., and Upchurch P.. 2004. Stegosauria. Pp. 343362 in D. B. Weishampel, P. Dodson, and H. Osmólska, eds. The Dinosauria, 2nd ed. University of California Press, Berkeley.
Gangloff R. A. 1995. Edmontonia sp., the first record of an ankylosaur from Alaska. Journal of Vertebrate Paleontology 15:195200.
Gingerich P. 1981. Cranial morphology and adaptations in Eocene Adapidae. 1. Sexual dimorphism in Adapis magnus and Adapis parisiensis . American Journal of Physical Anthropology 56:217234.
Godfrey L. R., Lyon S. K., and Sutherland M. R.. 1993. Sexual dimorphism in large-bodied primates: the case of the subfossil lemurs. American Journal of Physical Anthropology 90:315334.
Goodwin W. B. 1990. Morphometric landmarks of pachycephalosaurid cranial material from the Judith River Formation of northcentral Montana. Pp. 189–201 in Carpenter and Currie 1990.
Gow C. E., Kitching J. W., and Raath M. A.. 1990. Skulls of the prosauropod dinosaur Massospondylus carinatus Owen in the collections of the Bernard Price Institute for Palaeontological Research. Palaeontologia africana 27:4558.
Goymann W., Makomba M., Urasa F., and Schwabl I.. 2015. Social monogamy vs. polyandry: ecological factors associated with sex roles in two closely related birds within the same habitat. Journal of Evolutionary Biology 28:13351353.
Gregory W. K., and Mook C. C.. 1925. On Protoceratops, a primitive ceratopsian dinosaur from the Lower Cretaceous of Mongolia. American Museum Novitates 156:19.
Gross J., and Ligges U.. 2015. nortest: tests for normality. R package, Version 1:04.
Hammer Ø., and Harper D. A.. 2001. Paleontological data analysis. Blackwell Publishing: Malden, Mass.
Hammer Ø., Harper D. A. T., and Ryan P. D.. 2001. PAST: Paleontological Statistics software package for education and data analysis. Palaeontologia Electronica 4(1):1–9. http://palaeo-electronica.org/2001_1/past/issue1_01.htm.
Handa N., Watabe M., and Tsogtbaatar K.. 2012. New specimens of Protoceratops (Dinosauria: Neoceratopsia) from the Upper Cretaceous in Udyn Sayr, southern Gobi area, Mongolia. Paleontological Research 16:179198.
Handley W. D., Chinsamy A., Yates A. M., and Worthy T. H.. 2016. Sexual dimorphism in the late Miocene mihirung Dromornis stirtoni (Aves: Dromornithidae) from the Alcoota Local Fauna of central Australia. Journal of Vertebrate Paleontology 36:e1180298. doi: 10.1080/02724634.2016.1180298.
Hartigan J. A., and Hartigan P. M.. 1985. The dip test of unimodality. Annals of Statistics 13:7084.
Hedrick A. V., and Temeles E. J.. 1989. The evolution of sexual dimorphism in animals: hypotheses and tests. Trends in Ecology and Evolution 4:136138.
Hone D. W., Naish D., and Cuthill I. C.. 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia 45:139156.
Hone D. W., Farke A. A., and Wedel M. J.. 2016a. Ontogeny and the fossil record: what, if anything, is an adult dinosaur? Biology Letters 12:20150947. doi: 10.1098/rsbl.2015.0947.
Hone D. W., Wood D., and Knell R. J.. 2016b. Positive allometry for exaggerated structures in the ceratopsian dinosaur Protoceratops andrewsi supports socio-sexual signaling. Palaeontologia Electronica 19(1):113.
Hopson J. A. 1975. The evolution of cranial display structures in hadrosaurian dinosaurs. Paleobiology 1:2143.
Horner J. R., and Padian K.. 2004. Age and growth dynamics of Tyrannosaurus rex . Proceedings of the Royal Society of London B 271:18751880.
Hübner T. R. 2012. Bone histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia)–variation, growth, and implications. PLoS ONE 7:e29958. doi: 10.1371/journal.pone.0029958.
Isles T. E. 2009. The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour. Historical Biology 21:139214.
Josephson S. C., Juell K. E., and Rogers A. R.. 1996. Estimating sexual dimorphism by method‐of‐moments. American Journal of Physical Anthropology 100:191206.
Klein N., and Sander P. M.. 2007. Bone histology and growth of the prosauropod dinosaur Plateosaurus engelhardti von Meyer, 1837 from the Norian bonebeds of Trossingen (Germany) and Frick (Switzerland). Special Papers in Palaeontology 77:169206.
Klein N., and Sander P. M.. 2008. Ontogenetic stages in the long bone histology of sauropod dinosaurs. Paleobiology 34:247263.
Knell R. J., and Fortey R. A.. 2005. Trilobite spines and beetle horns: sexual selection in the Palaeozoic? Biology Letters 1:196199.
Knell R. J., and Sampson S.. 2011. Bizarre structures in dinosaurs: species recognition or sexual selection? A response to Padian and Horner. Journal of Zoology 283:1822.
Knell R. J., Naish D., Tomkins J. L., and Hone D. W.. 2013a. Is sexual selection defined by dimorphism alone? A reply to Padian and Horner. Proceedings of the Zoological Society of London 35:491562.
Knell R. J., Naish D., Tomkins J. L., and Hone D. W.. 2013b. Sexual selection in prehistoric animals: detection and implications. Trends in Ecology and Evolution 28:3847.
Kościński K., and Pietraszewski S.. 2004. Methods to estimate sexual dimorphism from unsexed samples: a test with computer-generated samples. Przegląd Antropologiczny—Anthropological Review 67:3355.
Kurzanov S. M. 1972. Sexual dimorphism in protoceratopsians. Palaeontological Journal 1:9197.
Lambert O., Godefroit P., Li H., Shang C. Y., and Dong Z.-M.. 2001. A new species of Protoceratops (Dinosauria, Neoceratopsia) from the Late Cretaceous of Inner Mongolia (PR China). Bulletin de l’Institut Royal des Sciences Naturelles de Belgique. Sciences de la Terre, Supplément 71:528.
Larson P. L. 1994. Tyrannosaurus sex. Paleontological Society Special Publication 7:139155.
Larson P. L. 1997. The king’s new clothes: a fresh look at Tyrannosaurus rex . Pp. 6571 in D. L. Wolberg, E. Stump, and G. D. Rosenberg, eds. Dinofest lnternational: Proceedings of a Symposium Sponsored by Arizona State University. Academy of Natural Sciences, Philadelphia.
Larson P. L. 2008. Variation and sexual dimorphism in Tyrannosaurus rex . Pp. 103128 in P. Larson, and K. Carpenter, eds. Tyrannosaurus rex: the tyrant king. Indiana University Press, Bloomington.
Lee A. H., and Werning S.. 2008. Sexual maturity in growing dinosaurs does not fit reptilian growth models. Proceedings of the National Academy of Sciences of the USA 105:582587.
Lehman T. M. 1990. The ceratopsian subfamily Chasmosaurinae: sexual dimorphism and systematics. Pp. 211–229 in Carpenter and Currie 1990.
Livezey B. C., and Humphrey P. S.. 1984. Sexual dimorphism in continental steamer-ducks. Condor 86:368377.
Loewen M. A. 2009. Variation in the late Jurassic theropod dinosaur Allosaurus: ontogenetic, functional, and taxonomic implications. Unpublished Ph.D. dissertation. University of Utah, Salt Lake City.
J., Unwin D., Deeming D. C., Jin X., Liu Y., and Ji Q.. 2011. An egg-adult association, gender and reproduction in pterosaurs. Science 331:321324.
Maechler M. 2015. diptest: Hartigan’s dip test statistic for unimodality—corrected R Package. Version 0:7577.
Maiorino L., Farke A. A., Kotsakis T., and Piras P.. 2015. Males resemble females: re-evaluating sexual dimorphism in Protoceratops andrewsi (Neoceratopsia, Protoceratopsidae). PLoS ONE 10:e0126464. doi: 10.1371/journal.pone.0126464.
Mallon J. C., and Holmes R. B.. 2006. A reevaluation of sexual dimorphism in the postcranium of the chasmosaurine ceratopsid Chasmosaurus belli (Dinosauria: Ornithischia). Canadian Field-Naturalist 120:403412.
Mendelson T. C., and Shaw K. L.. 2013. Further misconceptions about species recognition: a reply to Padian and Horner. Trends in Ecology and Evolution 28:252253.
Nopcsa F.. 1929. Sexual differences in ornithopodous dinosaurs. Palaeobiologica 2:187201.
O’Harra C. C. 1930. A fossil mammal with unborn twins. Science 71:341342.
Padian K., and Horner J. R.. 2011a. The evolution of “bizarre structures” in dinosaurs: biomechanics, sexual selection, social selection or species recognition? Journal of Zoology 283:317.
Padian K., and Horner J. R.. 2011b. The definition of sexual selection and its implications for dinosaurian biology. Journal of Zoology 283:2327.
Padian K., and Horner J. R.. 2013. Misconceptions of sexual selection and species recognition: a response to Knell et al. and to Mendelson and Shaw. Trends in Ecology and Evolution 28:249250.
Padian K., and Horner J. R.. 2014a. The species recognition hypothesis explains exaggerated structures in non-avian dinosaurs better than sexual selection does. Comptes Rendus Palevol 13:97107.
Padian K., and Horner J. R.. 2014b. Darwin’s sexual selection: understanding his ideas in context. Comptes Rendus Palevol 13:709715.
Penkalski P. 2001. Variation in specimens referred to Euoplocephalus tutus . Pp. 261298 in K. Carpenter, ed. The armored dinosaurs. Indiana University Press, Bloomington.
Persons W. S. IV, Funston G. F., Currie P. J., and Norell M. A.. 2015. A possible instance of sexual dimorphism in the tails of two oviraptorosaur dinosaurs. Scientific Reports 5:9472.
Platt S. G., Rainwater T. R., Thorbjarnarson J. B., Finger A. G., Anderson T. A., and McMurry S. T.. 2009. Size estimation, morphometrics, sex ratio, sexual size dimorphism, and biomass of Morelet’s crocodile in northern Belize. Caribbean Journal of Science 45:8093.
Plavcan J. M. 1994. Comparison of four simple methods for estimating sexual dimorphism in fossils. American Journal of Physical Anthropology 94:465476.
Prieto-Marquez A., Gignac P. M., and Joshi S.. 2007. Neontological evaluation of pelvic skeletal attributes purported to reflect sex in extinct non-avian archosaurs. Journal of Vertebrate Paleontology 27:603609.
Raath M. A. 1990. Morphological variation in small theropods and its meaning in systematics: evidence from Syntarsus. Pp. 91–105 in Carpenter and Currie 1990.
Rinehart L. F., Lucas S. G., Heckert A. B., Spielmann J. A., and Celeskey M. D.. 2009. The paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin 45:1260.
Rothschild B. M., and Berman D. S.. 1991. Fusion of caudal vertebrae in Late Jurassic sauropods. Journal of Vertebrate Paleontology 11:2936.
Rowe T. 1989. A new species of the theropod dinosaur Syntarsus from the Early Jurassic Kayenta Formation of Arizona. Journal of Vertebrate Paleontology 9:125136.
Rozhdestvensky A. K. 1965. Growth changes in Asian dinosaurs and some problems of their taxonomy. Paleontologičeskij Žurnal 3:95109 [In Russian.]
R Core Team. 2014. R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. https://www.R-project.org.
Ryan M. J., and Evans D. C.. 2005. Ornithischian dinosaurs. Pp. 312348 in P. J. Currie, and E. B. Koppelhus, eds. Dinosaur Provincial Park: a spectacular ancient ecosystem revealed. Indiana University Press, Bloomington.
Saitta E. T. 2015. Evidence for sexual dimorphism in the plated dinosaur Stegosaurus mjosi (Ornithischia, Stegosauria) from the Morrison Formation (Upper Jurassic) of western USA. PLoS ONE 10:e0123503. doi: 10.1371/journal.pone.0123503.
Sanchez I., Quiralte V., Morales J., Azanza B., and Pickford M.. 2010. Sexual dimorphism of the frontal appendages of the early Miocene African pecoran Prolibytherium Arambourg, 1961 (Mammalia, Ruminantia). Journal of Vertebrate Paleontology 30:13061310.
Sander P. M. 2000. Long bone histology of the Tendaguru sauropods: implications for growth and biology. Paleobiology 26:466488.
Sato T., Cheng Y.-N., Wu X.-C., Zelenitsky D. K., and Hsiao Y.-F.. 2005. A pair of shelled eggs inside a female dinosaur. Science 308:375.
Schoener T. W. 1967. The ecological significance of sexual dimorphism in size in the lizard Anolis conspersus . Science 155:474477.
Schott R. K., Evans D. C., Goodwin M. B., Horner J. R., Brown C. M., and Longrich N. R.. 2011. Cranial ontogeny in Stegoceras validum (Dinosauria: Pachycephalosauria): a quantitative model of pachycephalosaur dome growth and variation. PLoS ONE 6:e21092. doi: 10.1371/journal.pone.0021092.
Schweitzer M. H., Wittmeyer J. L., and Horner J. R.. 2005. Gender-specific reproductive tissue in ratites and Tyrannosaurus rex . Science 308:14561460.
Schweitzer M. H., Elsey R. M., Dacke C. G., Horner J. R., and Lamm E.-T.. 2007. Do egg-laying crocodilian (Alligator mississippiensis) archosaurs form medullary bone? Bone 40:11521158.
Schweitzer M. H., Zheng W., Zanno L., Werning S., and Sugiyama T.. 2016. Chemistry supports the identification of gender-specific reproductive tissue in Tyrannosaurus rex . Scientific Reports 6:23099.
Shapiro S. S., and Wilk M. B.. 1965. An analysis of variance test for normality (complete samples). Biometrika 52:591611.
Shine R. 1989. Ecological causes for the evolution of sexual dimorphism: a review of the evidence. Quarterly Review of Biology 64:419461.
Smith D. K. 1998. A morphometric analysis of Allosaurus . Journal of Vertebrate Paleontology 18:126142.
Stacklies W., Redestig H., Scholz M., Walther D., and Selbig J.. 2007. pcaMethods—a bioconductor package providing PCA methods for incomplete data. Bioinformatics 23:11641167.
Sternberg C. M. 1927. Horned dinosaur group in the National Museum of Canada. Canadian Field-Naturalist 41:6773.
Tereshchenko V. S. 2001. Sexual dimorphism in the postcranial skeleton of protoceratopsids (Neoceratopsia, Protoceratopsidae) from Mongolia. Paleontological Journal 35:415425.
Thulborn R. A. 1974. A new heterodontosaurid dinosaur (Reptilia: Ornithischia) from the Upper Triassic Red Beds of Lesotho. Zoological Journal of the Linnean Society of London 55:151175.
Thulborn R. A. 1994. Dimorphic jaw bones in the theropod Allosaurus fragilis . Association of Australian Palaeontologists, Sydney, Australasian Palaeontological Convention Abstracts and Programme 94:54.
Tomkins J. L., LeBas N. R., Witton M. P., Martill D. M., and Humphries S.. 2010. Positive allometry and the prehistory of sexual selection. American Naturalist 176:141148.
VanBuren C. S., and Evans D. C.. In press. Evolution and function of anterior cervical vertebral fusion in tetrapods. Biological Reviews. doi: 10.1111/brv.12245.
Van Valkenburgh B., and Sacco T.. 2002. Sexual dimorphism, social behavior, and intrasexual competition in large Pleistocene carnivorans. Journal of Vertebrate Paleontology 22:164169.
Ward P. 1965. Feeding ecology of the black‐faced dioch Quelea quelea in Nigeria. Ibis 107:173214.
Webb G. J. W., and Messel H.. 1978. Morphometric analysis of Crocodylus porosus from the north coast of Arnhem Land, northern Australia. Australian Journal of Zoology 26:127.
Weishampel D. B. 1981. Acoustic analyses of potential vocalization in lambeosaurine dinosaurs (Reptilia: Ornithischia). Paleobiology 7:252261.
Weishampel D. B., and Chapman R. E.. 1990). Morphometric study of Plateosaurus from Trossingen (Baden-Württemberg, Federal Republic of Germany). Pp. 43–51 in Carpenter and Currie 1990.
Westermann G. E. G. ed. 1969. Sexual dimorphism in fossil Metazoa and taxonomic implications. E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart.
Witmer L. M. 1995. The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils. Pp. 1933 in J. J. Thomason, ed. Functional morphology in vertebrate paleontology. Cambridge University Press, Cambridge.
Woodward H. N., Freedman Fowler E. A., Farlow J. O., and Horner J. R.. 2015. Maiasaura, a model organism for extinct vertebrate population biology: a large sample statistical assessment of growth dynamics and survivorship. Paleobiology 41:503527.
Zelenitsky D. K., Therrien F., Joyce W. G., and Brinkman D. B.. 2008. First fossil gravid turtle provides insight into the evolution of reproductive traits in turtles. Biology Letters 4:715718.
Recommend this journal

Email your librarian or administrator to recommend adding this journal to your organisation's collection.

Paleobiology
  • ISSN: 0094-8373
  • EISSN: 1938-5331
  • URL: /core/journals/paleobiology
Please enter your name
Please enter a valid email address
Who would you like to send this to? *
×

Metrics

Altmetric attention score

Full text views

Total number of HTML views: 358
Total number of PDF views: 766 *
Loading metrics...

Abstract views

Total abstract views: 3087 *
Loading metrics...

* Views captured on Cambridge Core between 27th March 2017 - 16th December 2017. This data will be updated every 24 hours.