Tyrannosaurus rex Osborn 1905
Most known T. rex crania containing teeth were examined (Supplementary Data 1, available online at www.vertpaleo.org/ jvp/JVPcontents.html). Tarbosaurus Maleev, 1955, was excluded as there is no consensus on its taxonomy and it appears to be a distinct species (Holtz, 2001; Hurum and Sabath, 2003; C...
| Main Author: | |
|---|---|
| Format: | Text |
| Language: | unknown |
| Published: |
Zenodo
2005
|
| Subjects: | |
| Online Access: | https://dx.doi.org/10.5281/zenodo.4323776 https://zenodo.org/record/4323776 |
| Summary: | Most known T. rex crania containing teeth were examined (Supplementary Data 1, available online at www.vertpaleo.org/ jvp/JVPcontents.html). Tarbosaurus Maleev, 1955, was excluded as there is no consensus on its taxonomy and it appears to be a distinct species (Holtz, 2001; Hurum and Sabath, 2003; Carr and Williamson, 2004). Data from Dilophosaurus Welles, 1970; Liliensternus Welles, 1984; Ceratosaurus dentisulcatus Madsen and Welles, 2000 (?= Ceratosaurus nasicornis Marsh, 1884); Masiakasaurus Sampson et al. 2001; ‘ Indosuchus ’; Majungatholus Sues and Taquet, 1979; Baryonyx Charig and Milner, 1986; Suchomimus Sereno et al., 1998; Allosaurus Marsh 1877; Acrocanthosaurus Stovall and Langston, 1950; Carcharodontosaurus Stromer, 1931; Gorgosaurus Lambe, 1914; Daspletosaurus Russell, 1970; Tyrannosaurus rex Troodon Leidy, 1856; Saurornithoides junior Barsbold, 1974; Bambiraptor Burnham et al., 2000; Deinonychus Ostrom, 1969 a; Dromaeosaurus Matthew and Brown, 1922; and Velociraptor Osborn, 1924 were used to provide context for teeth of Tyrannosaurus rex within theropod dental morphospace (see Smith et al., 2005, for data). Growth-related change is important in paleobiology (e.g., Currie, 2003b). However, as ontogeny in Tyrannosaurus rex is currently poorly understood, data were excluded from problematic specimens (see Molnar and Carpenter, 1989; Carr, 1999; Brochu, 2002; Carr and Williamson, 2004), such as LACM 28741 (‘ Aublysodon ’) and CMNH 7541 (‘ Nanotyrannus ’), to be dealt with separately. These specimens are likely juveniles of T . rex (see Carr, 1999; Holtz, 2001), and have been synonymized as such (Carr and Williamson, 2004). However, a consensus is lacking (see Currie, 2003a; Currie et al., 2003), and there are new data (J. Peterson, pers. comm., 2002) that merit consideration. I am not comfortable coding teeth as pertaining to T . rex unless there is general agreement that they are such, nor is it wise to use data from a problematic specimen to support or refute a T. rex affinity for that individual. Therefore, I included only those data that are currently unquestioned as pertaining to T. rex . As tyrannosaurid taxonomy becomes clearer, the dentitions of problematic specimens should be compared against those of well-supported taxa. In the absence of this and in the absence of data for proven juvenile teeth for T. rex , discussions of ontogenetic change in its dentition are premature (e.g., Senter and Robins, 2003). Measurements and Counts Measurements were made directly with electronic calipers or on digital images using SigmaScan®. Denticles were counted with a Hensoldt-Wetzlar 8X lens possessing a mm-scale reticle. Data cases are averages of five replicate measurements (measurement repeatability was assessed by Smith, 2002). Data were included from teeth regarded as being fully erupted (teeth that are erupting, are reconstructed, or are not accessible because the specimen is on display were omitted). Orientation terminology (Fig. 1A) follows Smith and Dodson (2003). Studies of tyrannosaurid dentitions must pay particular attention to the premaxillary and first dentary teeth. The basal short axes of these crowns are mesiodistal rather than labiolingual in orientation (as in most theropods), and the long axes (sensu the basoapical axis in human incisors, see Minagi et al., 1999) are oriented labiolingually rather than mesiodistally (Fig. 1B, C). The variables used in this article (Fig. 1D, E) were derived or discussed in detail by Smith et al. (2005); they are noted briefly here. Size was described using crown base length (CBL), crown base width (CBW), crown height (CH), and apical length (AL). CBL and CBW were measured in a horizontal plane referenced approximately to point B of Smith et al. (2005). Basal shape was described using the crown base ratio (CBR = CBW/CBL); crown “squatness” was assessed using the crown height ratio (CHR = CH/CBL). Apex displacement from the crown base center and crown curvature were described using the crown angle (CA). Crown angle values were calculated using the Law of Cosines and solving for: where a = CBL, b = AL, and c = CH. Denticle size and spacing was quantified by determining the number of denticles per 5 mm of carina length (see Farlow and Brinkman, 1987), counted as close to the base, mid point, and apex as possible (see Chandler, 1990), thus generating the basal (MB and DB), mid-crown (MC and DC), and apical densities (MA and DA). For very small teeth (e.g., Bambiraptor ), counts were taken over 2 mm and then adjusted to 5 mm after Farlow et al. (1991). Five counts of each variable were taken, the means of which yielded average densities for the mesial and distal carinae (MAVG, DAVG, after Chandler, 1990). The ratio of MAVG to DAVG generated the denticle size density index (DSDI), devised and discussed by Rauhut and Werner (1995). Analyses Statistical analyses were run with SPSS, SigmaStat®, and Stat- View and were illustrated using SigmaPlot®. Factors that might have a significant effect on the variability within the data were examined using analysis of variance (ANOVA). As biogeography (concept after Carrasco, 2000a, b; Lieberman et al., 2002) showed no significant effect on the observed variation (Smith et al., 2005) and sexing and aging of tyrannosaurs is problematic (Larson, 1994; Chapman et al., 1997; Galton, 1999), tooth position is the main factor that might account for a significant proportion of the observed variation. ANOVA was employed to test this hypothesis using variability profiles sensu Yablokov (1974) but modified after Smith (2002) to show positional variation within tooth rows (sensu Williamson, 1996). As the variables were compared with tooth position rather than with coefficients of variation (see Yablokov, 1974), raw data were analyzed instead of following Sokal and Braumann (1980). The results were examined using post-hoc tests that compared the means of the dependent variables with respect to tooth position: Fisher’s PLSD (see Sokal and Rolf, 1995) and Tukey-Kramer (Kramer, 1956). Raw data were used for AL, CA, CBL, CBR, CBW, CH, CHR, MAVG, and DAVG. CA and DAVG were also compared after removing size as a confounding variable (see Marko and Jackson, 2001). Smith et al. (2005) log-transformed the data and ran a principal-components analysis. The data for DAVG were then regressed on PC1, which explained 84.4% of the observed variation; the residuals from these regressions constitute the sizecorrected variables CA2 and DAVG2. MORPHOLOGY AND POSITIONAL VARIATION Osborn’s (1912) study remains the best prior treatment of Tyrannosaurus dentition, although other works have briefly discussed the teeth (e.g., Brochu, 2002; Hurum and Sabath, 2003). Osborn (1912) focused on CM 9380, AMNH 5027, 5117, 5866, and CM 9379. He reported a dental formula of 4 premaxillary, 12 maxillary, and 13–14 dentary teeth, for 58–60 total positions. Molnar (1991) found 4/11–12/? from these specimens and LACM 23844 and SDSM 12047. Currie et al. (2003) reported 4/11–12/ 12–14, but from which specimens these data came is not clear. Table 2 provides an updated list of tooth counts. Theropods are not usually considered to be heterodont taxa, but this view is too simple (see Currie, 1987). Tyrannosaurus rex in particular exhibits as much heterodonty (see Stromer, 1934) as do taxa acknowledged as having distinctive dentitions, such as Eoraptor Sereno et al., 1993, Troodon , and Masiakasaurus . Preliminarily, T. rex appears to be more heterodont than Daspletosaurus or Albertosaurus it possesses tooth morphologies that we can regard as classes at the element level (see Peyer, 1968; Zhao et al., 2000) and as sets sensu Hungerbühler (2000) at the intraelement level. These sets differ in concept from the ontogenetic tooth families of Edmund (1969) and Osborn (1973). Broadly, T . rex follows the ‘typical’ theropod pattern (see Holtz and Osmólska, 2004) of ‘recurved’ crowns possessing longer base lengths than widths (Molnar and Carpenter, 1989). However, T. rex teeth are less curved than those of many theropods (an obvious exception to this are the dentitions of certain spinosaurids; see Sereno et al., 1998; Sues et al., 2002). The Premaxillary Dentition There are four teeth in all known premaxillae of T. rex , a feature that is robust for the Tyrannosauridae (see Osborn, 1905, 1906, 1912; Carpenter, 1990, 1992; Molnar, 1991; Brochu, 2002; Currie, 2003a; Hurum and Sabath, 2003). Premaxillary tooth count is constant for most theropods (see Lamanna, 1998). Currie (pers. comm., 1998; see also Ji and Ji, 1997) noted a discrepancy in tooth count in a specimen of Sinosauropteryx Ji and Ji, 1996 (NIGP 127586), but the lack of variation in other theropods suggests that this might be a specimen-specific or taxon-specific anomaly (assuming the individuals all represent one species). Currie and Chen (2001) reported that preparation issues confound tooth counts in Sinosauropteryx . Baryonyx might possess six left and seven right premaxillary teeth in BMNH R9951 (see Charig and Milner, 1997). However, Rpm6 and 7 appear to be crowded into one alveolus, suggesting that BMNH R9951 could also be anomalous. Such anomalies are common in mammals (P. Dodson, pers. comm., 2004) and should not affect the stability of theropod counts. It is also possible that tooth-count variation increases with decreasing crown size (J. D. Harris, pers. comm., 2004). Crown Size —The premaxillary class is significantly smaller than the maxillary class in CBL, CBW, CH, and AL (Table 1, Fig. 2), as in other tyrannosaurids (Russell, 1970; Holtz, 2001; Currie, 2003a; Hurum and Sabath, 2003) and some ceratosaurs (Rauhut, 2004). There are trends of increasing size along the tooth row for CBL, CBW, CH, and AL (Fig. 2). The first tooth (mean pm1 CBL = 28.61 mm) is significantly smaller than that for pm3 (pm3 CBL = 33.96; ANOVA with pm1: F = 2.92, p .0346), but the remaining teeth are not significantly different from each other in size. The fourth tooth is slightly smaller than pm3 in all size variables, but the differences are not significant. A similar decrease in size toward the premaxillary-maxillary suture (premaxilla-maxilla joint sensu Molnar, 1991) occurs in Coelophysis Cope, 1889, Dilophosaurus , and Eoraptor (Welles, 1984; Colbert, 1989; Sereno and Novas, 1993). Crown Shape and Carina Morphologies —Theropod crown basal cross sections are often ovals that taper to points corresponding to the locations of the carinae (Fig. 1B). The basal long axis (generally oriented mesiodistally) can be twice the length of the short axis (usually oriented labiolingually). In the premaxilla of T. rex however, although the crown bases are narrow ovals, the long axes are oriented labiolingually (Fig. 1C). The labial faces are ovals that are convex toward the rostral end of the snout (Fig. 3A). The lingual faces form very weakly convex curves (e.g., AMNH 5027), which are more pronounced basally, creating a shallow wide ridge (contra Molnar and Carpenter, 1989); apically the faces are almost flat (Fig. 3B). The curves of the lingual faces flatten out proximal to the carinae, which are located at the mesiolingual and distolingual corners of the crowns. The flattening is more pronounced distal to pm1 where the very slightly convex mesial and distal faces curve into the lingual face. A number of theropods exhibit positional variation with respect to carina placement. Tyrannosaurus rex exhibits dramatic changes in this feature along the maxillary and dentary tooth rows, but virtually none within the premaxilla: the carinae are all located at the corners of the teeth, as in other tyrannosaurids (Russell, 1970; Currie, 2003a). In labial view, the denticles are often just visible along the mesial and distal edges of the labial faces. The carinae start from lingual points on the apices and extend basally along the mesial and distal faces to the bases, exhibiting slight labial convexity. They cross the apices with a surface expression of one carina wrapping over the tip rather than two distinct carinae, although each is discussed separately here. The mesial carinae are ̴2–5 mm shorter than the distal and often do not extend to the bases. Both carinae in pm3 of BHI 3033 terminate before reaching the base. Often premaxillary mesial carinae of T. rex are slightly shorter than the distal carinae, so it might be possible to discriminate left and right crowns by identifying the distal carina. Similar morphologies occur in the premaxillae of other tyrannosaurids (Russell, 1970; Carr, 1999; Currie, 2003a), leading to the premaxillary crowns being referred to as ‘incisiform,’ ‘U-shaped,’ or ‘D-shaped in cross section’ (see Russell, 1970; Currie et al., 1990; Carpenter, 1992; Holtz, 1994, 1998; Carr, 1999; Ford and Chure, 2001; Brochu, 2002; Currie, 2003a; Carr and Williamson, 2004). Given the convexity of the lingual face and the oval shapes of the crown bases, these descriptors are somewhat inaccurate, but do get the general meaning across (at least colloquially; better descriptions might be desired when using this feature as a systematic character). Although theropod teeth in general tend to be more circular mesially and more bladelike distally (see Smith et al., 2005), T. rex exhibits a reverse trend. The premaxillary teeth are significantly more blade-like than those in the maxilla or dentary (Table 1, Fig. 4A). This might be initially surprising, but T. rex premaxillary crown bases are very elongate. The first two teeth are significantly less circular than are than are pm3 and 4 (pm2 CBR = 0.57; pm3 = 0.64, F = 14.06, p .0128). The premaxillary teeth are more ‘squat’ than in the maxilla or dentary (Table 1, Fig. 4B). Along the tooth row, the crowns become increasingly, but not significantly, more elongated (CHR values of 1.52, 1.52, 1.64, and 1.74, from p1–pm4, respectively). The rostral end of the snout in T. rex is more squared off than in many theropods (Fig. 5A), so that the tooth row curves away from the midline. This, along with the derived crown shapes, produces the distinctive tyrannosaurid premaxillary dentition. Carina placement and lingual face morphology in T. rex are similar to those of pm1 of Allosaurus (e.g., YPM 1333 and 4933, MOR 693, and UMNH 1251) and pm1–3 in Majungatholus (e.g., FMNH PR2100). In all three taxa the carinae form the mesial and distal edges of the lingual faces in lingual view (Figs. 5 B–D). However, this resemblance of Allosaurus and Majungatholus premaxillary teeth with those of T. rex is only valid mesially. By the distal ends of the tooth rows in both of these taxa, the crowns are distinctly different from the premaxillary condition in T. rex . By pm4 in Allosaurus (YPM 1333), the mesial carina, in mesial view, begins at the apex and curves lingually such that it forms the lingual edge of the mesial face at about the mid-crown point. In pm5 the distal carina essentially defines the distal keel of the crown, showing only a very slight labial convexity along its length. Crown Curvature —That crown curvature is taxonomically variable in theropods has been suggested (Gilmore, 1920; Russell, 1970; Madsen, 1976). Within-taxon variation takes the form of increasingly curved crowns along the length of the tooth row (see Smith 2002), often accompanied by a decrease in size (Chandler, 1990). However, some taxa, such as Spinosaurus Stromer, 1915, and Irritator Martill et al., 1996, exhibit very little mesial curvature (see Sues et al., 2002). This curvature can be seen indirectly in the CA data generated by equation (1). In general, CA values closer to 90° indicate more centrally positioned apices, a condition that usually correlates with less curved mesial profiles. Lower CA values usually correlate with more strongly curved mesial profiles. In T. rex , curvature decreases from pm1–4 (Fig. 4C), but the differences are not significant (mean CA values of 84.7°, 85.1°, 85.9°, and 85.9° from pm1–4). The CA values in the premaxillary dentition versus those in the maxilla and dentary are also not significant (Table 1, Fig. 4C). Denticles —The mesial premaxillary denticles range in size from ̴9–̴11/5 mm (Table 1), with a weak trend of increasing size along the tooth row (Fig. 6A), although differences between adjacent teeth are mostly not significant. Premaxillary MAVG values are not significantly larger than those of the maxillary or dentary teeth (Table 1). In examining the components from which MAVG is generated, the MA data range from 8.4–10.9/5 mm, the MC data from 7–9.5/5 mm, and the MB data from 9–12.5/5 mm. There is no significant size trend along the tooth row in the apical denticles, but the mid-crown denticles show a very weak increasing trend. The MB data show no clear trends. The apical mesial denticles (10.3/5 mm) are significantly smaller than those of the maxilla (7.9/5 mm, p <.0001) and dentary (8.5/5 mm, p .0245), but the mid-crown and basal denticles are not. Overall, the components of MAVG and DAVG mimic the trends illustrated in Figure 6. As Smith (2002) provided variability plots of these variables and they are not substantially more informative for understanding the dentition of T. rex , MA, MC, MB, DA, DC, and DB plots have been omitted here. The distal denticles display similar patterns of variation to that seen in MAVG data (Fig. 6B); premaxillary DAVG values are not significantly different in size from those of the maxilla or dentary (Table 1). The apical distal denticles (10.3/5 mm) are significantly smaller than those of the maxilla (8.3/5 mm, p .0003), but not those of the dentary (9.4/5 mm, p .0890). There are no significant differences in size between the dentigerous bones of T. rex for the mid-crown or basal distal denticles. When premaxillary DSDI data are examined for T. rex , posi- tional variation in the denticles largely disappears (Fig. 6C). The range of premaxillary DSDI variation is well within the range of DSDI variability for the mouth as a whole. Indeed, while there is some noise within the data, there is little positional influence for this feature in any of three tooth classes. Thus, DSDI does not appear to be particularly useful in examining T . rex teeth. However, the lack of positional variation suggests that DSDI data might have some systematic utility. The Maxillary Dentition The maxillary class of T. rex contains an average of 12 teeth, including the largest in the dental arcade and some of the smallest (Fig. 2). It is significantly larger than the premaxillary and dentary classes in CBL, CH, and AL and significantly larger than the premaxillary class in CBW (Table 1). Indeed, mx3 and mx4 are large enough that it might be possible to distinguish them from dentary crowns using CH (mx3: 111.30 mm; mx4: 105.34 mm versus d4: 90.14 mm). The teeth in the maxillary dentition are different from those in the premaxillary class in : Published as part of Joshua B. Smith, 2005, Heterodonty in Tyrannosaurus rex: Implications for the taxonomic and systematic utility of theropod dentitions, pp. 865-887 in Journal of Vertebrate Paleontology 25 (4) on pages 866-884, DOI: 10.1671/0272-4634(2005)025[0865:HITRIF]2.0.CO;2, http://zenodo.org/record/3942994 : {"references": ["Maleev, E. A. 1955. [Carnivorous dinosaurs of Mongolia]. Priroda 1955 (6): 112 - 115. [Russian]", "Holtz, T. R., Jr. 2001. The phylogeny and taxonomy of the Tyrannosauridae; pp. 64 - 75 in D. H. Tanke and K. Carpenter (eds.), Mesozoic Vertebrate Life. Indiana University Press, Bloomington, Indiana.", "Hurum, J. H., and K. Sabath. 2003. Giant theropod dinosaurs from Asia and North America: Skulls of Tarbosaurus bataar and Tyrannosaurus rex compared. Acta Palaeontologica Polonica 48: 161 - 190.", "Carr, T. D., and T. E. Williamson. 2004. Diversity of late Maastrichtian Tyrannosauridae (Dinosauria: Theropoda) from western North America. Zoological Journal of the Linnean Society 142: 479 - 523.", "Welles, S. P. 1970. Dilophosaurus (Reptilia: Saurischia), a new name for a dinosaur. Journal of Paleontology 44: 989.", "Welles, S. P. 1984. Dilophosaurus wetherilli (Dinosauria, Theropoda). Osteology and comparisons. Palaeontographica Abteilung A 185: 85 - 180.", "Madsen, J. H., Jr., and S. P. Welles. 2000. Ceratosaurus (Dinosauria, Theropoda): a revised osteology. Utah Geological Survey Miscellaneous Publication 00 - 2: 1 - 80.", "Marsh, O. C. 1884. Principal characters of American Jurassic dinosaurs. Part VIII. The Order Theropoda. American Journal of Science (ser. 3) 28: 161 - 162.", "Sampson, S. D., M. T. Carrano, and C. A. Forster. 2001. A bizarre predatory dinosaur from the Late Cretaceous of Madagascar. Nature 409: 504 - 506.", "Sues, H. - D., and P. Taquet. 1979. A pachycephalosaurid dinosaur from Madagascar and a Laurasia-Gondwanaland connection in the Cretaceous. Nature 279: 633 - 635.", "Charig, A. J., and A. C. Milner. 1986. Baryonyx, a remarkable new theropod dinosaur. Nature 324: 359 - 361.", "Sereno, P. C., A. L. Beck, D. B. Dutheil, B. Gado, H. C. E. Larsson, G. H. Lyon, J. D. Marcot, O. W. M. Rauhut, R. W. Sadleir, C. A. Sidor, D. J. Varricchio, G. P. Wilson, and J. A. Wilson. 1998. A long-snouted predatory dinosaur from Africa and the evolution of spinosaurids. Science 282: 1298 - 1302.", "Marsh, O. C. 1877 a. Notice of new dinosaurian reptiles from the Jurassic formation. American Journal of Science (series 3) 14: 514 - 516.", "Stovall, J. W., and W. Langston, Jr. 1950. Acrocanthosaurus atokensis, a new genus and species of Lower Cretaceous Theropoda from Oklahoma. American Midland Naturalist 43: 696 - 728.", "Stromer, E. 1931. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wusten Agyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 10. Ein Skelett-Rest von Carcharodontosaurus nov. gen. Abhandlungen der Bayerischen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Abteilung N. F. 9: 1 - 23.", "Lambe, L. M. 1914. On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of Stephanosaurus marginatus from the same horizon. Ottawa Naturalist 28: 13 - 20.", "Russell, D. A. 1970. Tyrannosaurs from the Late Cretaceous of western Canada. National Museum of Natural Science, Publications in Paleontology 1: 1 - 34.", "Leidy, J. P. 1856. Notices of the remains of extinct reptiles and fishes discovered by Dr. F. V. Hayden in the badlands of the Judith River, Nebraska Territory. Proceedings of the Academy of Natural Sciences of Philadelphia 8: 72 - 73.", "Barsbold, R. 1974. Saurornithoididae, a new family of small theropod dinosaurs from central Asia and North America. Palaeontologia Polonica 30: 5 - 22.", "Burnham, D. A., K. L. Derstler, P. J. Currie, R. T. Bakker, Z. Zhou, and J. H. Ostrom. 2000. Remarkable new birdlike dinosaur (Theropoda: Maniraptora) from the Upper Cretaceous of Montana. University of Kansas Paleontological Contributions 13: 1 - 12.", "Ostrom, J. H. 1969. A new theropod dinosaur from the Lower Cretaceous of Montana. Postilla 128: 1 - 17.", "Matthew, W. D., and B. Brown. 1922. The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta. Bulletin of the American Museum of Natural History 46: 367 - 385.", "Osborn, H. F. 1924. Three new Theropoda, Protoceratops zone, central Mongolia. American Museum Novitates 144: 1 - 12.", "Smith, J. B., D. R. Vann, and P. Dodson. 2005. Dental morphology and variation in theropod dinosaurs: implications for the taxonomic identification of isolated teeth. The Anatomical Record Part A 285: 699 - 736.", "Currie, P. J. 2003 b. Allometric growth in tyrannosaurids (Dinosauria, Theropoda) from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences 40: 651 - 665.", "Molnar, R. E., and K. Carpenter. 1989. The Jordan theropod (Maastrichtian, Montana, U. S. A.) referred to the genus Aublysodon. Geobios 22: 445 - 454.", "Carr, T. D. 1999. Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria). Journal of Vertebrate Paleontology 19: 497 - 520.", "Brochu, C. A. 2002. Osteology of Tyrannosaurus rex: insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull. Society of Vertebrate Paleontology Memoir 7: 1 - 138.", "Currie, P. J. 2003 a. Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada. Acta Palaeontologica Polonica 48: 191 - 226.", "Currie, P. J., J. H. Hurum, and K. Sabath. 2003. Skull structure and evolution in tyrannosaurid dinosaurs. Acta Palaeontologica Polonica 48: 227 - 234.", "Senter, P., and J. H. Robins. 2003. Taxonomic status of the specimens of Archaeopteryx. Journal of Vertebrate Paleontology 23: 961 - 965.", "Smith, J. B. 2002. An examination of dental morphology and variation in theropod dinosaurs: implications for the identification of isolated teeth. Unpublished Ph. D. dissertation, University of Pennsylvania, Philadelphia, Pennsylvania, 617 pp.", "Smith, J. B., and P. Dodson. 2003. A proposal for a standard terminology of anatomical notation and orientation in fossil vertebrate dentitions. Journal of Vertebrate Paleontology 23: 1 - 14.", "Minagi, S., T. Hara, T. Sato, N. Natsuaki, and Y. - T. Akamatsu. 1999. Relationship between anterior guidance and mesiodistal inclination of lower incisor in human subject with or without TMJ noise. Journal of Oral Rehabilitation 26: 781 - 785.", "Farlow, J. O., and D. L. Brinkman. 1987. Serration coarseness and patterns of wear of theropod dinosaur teeth. Geological Society of America Abstracts with Programs 19: 151.", "Chandler, C. L. 1990. Taxonomic and functional significance of serrated tooth morphology in theropod dinosaurs. Unpublished M. S. thesis, Yale University, New Haven, Connecticut, 163 pp.", "Farlow, J. O., D. L. Brinkman, W. L. Abler, and P. J. Currie. 1991. Size, shape, and serration density of theropod dinosaur lateral teeth. Modern Geology 16: 161 - 198.", "Rauhut, O. W. M., and C. Werner. 1995. First record of the family Dromaeosauridae (Dinosauria: Theropoda) in the Cretaceous of Gondwana (Wadi Milk Formation, northern Sudan). Palaontologische Zeitshrift 69: 475 - 489.", "Carrasco, M. A. 2000 a. Variation in the dentition of kangaroo rats (genus Dipodomys) and its implications for the fossil record. The Southwestern Naturalist 45: 490 - 507.", "Lieberman, D. E., B. M. McBratney, and G. Krovitz. 2002. The evolution and development of cranial form in Homo sapiens. Proceedings of the National Academy of Sciences 99: 1134 - 1139.", "Larson, P. L. 1994. Tyrannosaurus sex; pp. 147 - 157 in G. E. Nelson (ed.), The Dinosaurs of Wyoming. Wyoming Geological Association, Casper.", "Chapman, R. E., D. B. Weishampel, G. Hunt, and D. Rasskin-Gutman. 1997. Sexual dimorphism in dinosaurs; pp. 83 - 93 in D. L. Wolberg, E. Stump, and G. D. Rosenberg (eds.), Dinofest International. Academy of Natural Sciences, Philadelphia.", "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: 19 - 55.", "Yablokov, A. V. 1974. Variability of Mammals. Amerind, New Delhi, India, 350 pp.", "Williamson, T. E. 1996.? Brachychampsa sealeyi, sp. nov., (Crocodylia, Alligatoroidea) from the Upper Cretaceous (lower Campanian) Menefee Formation, northwestern New Mexico. Journal of Vertebrate Paleontology 16: 421 - 431.", "Sokal, R. R., and C. A. Braumann. 1980. Significance tests for coefficients of variation and variability profiles. Systematic Zoology 29: 50 - 66.", "Kramer, C. Y. 1956. Extension of multiple range tests to group means with unequal numbers of replications. Biometrics 12: 307 - 310.", "Marko, P. B., and J. B. C. Jackson. 2001. Patterns of morphological diversity among and within arcid bivalve species pairs separated by the Isthmus of Panama. Journal of Paleontology 75: 590 - 606.", "Sues, H. - D. 1978. A new small theropod dinosaur from the Judith River Formation (Campanian) of Alberta, Canada. Zoological Journal of the Linnean Society 62: 381 - 400.", "Osborn, H. F. 1912. Crania of Tyrannosaurus and Allosaurus. Memoirs of the American Museum of Natural History 1: 3 - 30.", "Molnar, R. E. 1991. The cranial morphology of Tyrannosaurus rex. Palaeontographica Abteilung A 217: 137 - 176.", "Currie, P. J. 1987. Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). Journal of Vertebrate Paleontology 7: 72 - 81.", "Stromer, E. 1934. Die zahne des Compsognathus und bemerkungen uber das gebiss der Theropoda. Centralblatt fur Mineralogie, Geologie, und Palaontologie, Arbeit B 2: 74 - 85.", "Sereno, P. C., and F. E. Novas. 1993. The skull and neck of the basal theropod Herrerasaurus ischigualastensis. Journal of Vertebrate Paleontology 13: 451 - 476.", "Peyer, B. 1968. Comparative Odontology (translated and edited by R. Zangerl). University of Chicago Press, Chicago, 347 pp.", "Zhao, Z., K. M. Weiss, and D. W. Stock. 2000. Development and evolution of dentition patterns and their genetic basis; pp. 152 - 172 in M. F. Teaford, M. M. Smith, and M. J. W. Ferguson (eds.), Development, Function, and Evolution of Teeth. Cambridge University Press, Cambridge, England.", "Hungerbuhler, A. 2000. Heterodonty in the European phytosaur Nicrosaurus kapffi and its implications for the taxonomic utility and functional morphology of phytosaur dentitions. Journal of Vertebrate Paleontology 20: 31 - 48.", "Edmund, A. G. 1969. Dentition; pp. 117 - 200 in C. Gans, A. d. A. Belairs, and T. S. Parsons (eds.), Biology of the Reptilia. Academic Press, London.", "Osborn, J. W. 1973. The evolution of dentitions. American Scientist 61: 548 - 559.", "Holtz, T. R., Jr., and H. Osmolska. 2004. Saurischia; pp. 21 - 24 in D. B. Weishampel, P. Dodson, and H. Osmolska (eds.), The Dinosauria, Second Edition. University of California Press, Berkeley.", "Sues, H. - D., E. Frey, D. M. Martill, and D. M. Scott. 2002. Irritator challengeri, a spinosaurid (Dinosauria: Theropoda) from the Lower Cretaceous of Brazil. Journal of Vertebrate Paleontology 22: 535 - 547.", "Osborn, H. F. 1905. Tyrannosaurus and other Cretaceous carnivorous dinosaurs. Bulletin of the American Museum of Natural History 21: 259 - 265.", "Osborn, H. F. 1906. Tyrannosaurus, Upper Cretaceous carnivorous dinosaur. (Second communication). Bulletin of the American Museum of Natural History 22: 281 - 296.", "Carpenter, K. 1990. Variation in Tyrannosaurus rex; pp. 141 - 145 in K. Carpenter and P. J. Currie (eds.), Dinosaur Systematics: Perspectives and Approaches. Cambridge University Press, Cambridge, England.", "Carpenter, K. 1992. Tyrannosaurids (Dinosauria) of Asia and North America; pp. 250 - 268 in N. Mateer and P. J. Chen (eds.), Aspects of Nonmarine Cretaceous Geology. China Ocean Press, Beijing.", "Lamanna, M. C. 1998. Addressing uncertainty in theropod dinosaur systematics: an example using premaxillary tooth count; p. 34 in D. L. Wolberg, K. Gittis, S. Miller, L. Carey, and A. Raynor (eds.), The Dinofest \u2122 Symposium, Abstracts with Program 3. The Academy of Natural Sciences, Philadelphia, Pennsylvania.", "Ji, Q., and S. - A. Ji. 1997. Advance in the study of the avian Sinosauropteryx prima. Chinese Geology 242: 30 - 32.", "Ji, Q., and S. - A. Ji. 1996. On discovery of the earliest bird fossil in China and the origin of birds. Chinese Geology 233: 30 - 33.", "Currie, P. J., and P. - J. Chen. 2001. Anatomy of Sinosauropteryx prima from Liaoning, northeastern China. Canadian Journal of Earth Sciences 38: 1705 - 1727.", "Charig, A. J., and A. C. Milner. 1997. Baryonyx walkeri, a fish-eating dinosaur from the Wealden of Surrey. Bulletin of the Natural History Museum of London 53: 11 - 70.", "Rauhut, O. W. M. 2004. Provenance and antomy of Genyodectes serus, a large-toothed ceratosaur (Dinosauria: Theropoda) from Patagonaia. Journal of Vertebrate Paleontology 24: 894 - 902.", "Cope, E. D. 1889. On a new species of Triassic Dinosauria. American Naturalist 23: 626.", "Colbert, E. H. 1989. The Triassic dinosaur Coelophysis. Museum of Northern Arizona Bulletin 57: 1 - 160.", "Currie, P. J., J. K. Rigby, Jr., and R. E. Sloan. 1990. Theropod teeth from the Judith River Formation of southern Alberta, Canada; pp. 107 - 125 in K. Carpenter and P. J. Currie (eds.), Dinosaur Systematics: Perspectives and Approaches. Cambridge University Press, Cambridge, England.", "Holtz, T. R., Jr. 1994. The phylogenetic position of the Tyrannosauridae: implications for theropod systematics. Journal of Paleontology 68: 1100 - 1117.", "Holtz, T. R., Jr. 1998. A new phylogeny of the carnivorous dinosaurs; pp. 5 - 61 in B. P. Perez-Moreno, T. Holtz, J. L. Sanz, and J. J. Moratalla (eds.), Gaia 15: Aspects of Theropod Paleobiology. Museu Nacional de Historia Natural, Lisbon, Portugal.", "Ford, T. L., and D. J. Chure. 2001. Ghost lineages and the paleogeographic and temporal distribution of tyrannosaurids. Journal of Vertebrate Paleontology 21: 50 A- 51 A.", "Gilmore, C. W. 1920. Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus. United States National Museum Bulletin 110: 1 - 159.", "Madsen, J. H., Jr. 1976. Allosaurus fragilis: a revised osteology. Utah Geological Survey Bulletin 109: 1 - 163.", "Stromer, E. 1915. Ergebnisse der Forschungsreisen Prof. E. Stromers in den Wusten Agyptens. II. Wirbeltier-Reste der Baharije-Stufe (unterstes Cenoman). 3. Das Original des Theropoden Spinosaurus aegyptiacus nov. gen., nov. spec. Abhandlungen der Koniglich Bayerischen Akademie der Wissenschaften, Mathematisch-physikalische Classe 28 (3): 1 - 32.", "Martill, D. M., A. R. I. Cruickshank, E. Frey, P. G. Small, and M. Clarke. 1996. A new crested maniraptoran dinosaur from the Santana Formation (Lower Cretaceous) of Brazil. Journal of the Geological Society of London 153: 5 - 8.", "Molnar, R. E. 1998. Mechanical factors in the design of the skull of Tyrannosaurus rex (Osborn, 1905); pp. 193 - 218 in B. P. Perez- Moreno, T. Holtz, J. L. Sanz, and J. J. Moratalla (eds.), Gaia 15: Aspects of Theropod Paleobiology. Museu Nacional de Historia Natural, Lisbon, Portugal.", "Currie, P. J. 1995. New information on the anatomy and relationships of Dromaeosaurus albertensis (Dinosauria: Theropoda). Journal of Vertebrate Paleontology 15: 576 - 591.", "Carr, T. D., T. E. Williamson, and D. R. Schwimmer. 2005. A new genus and species of tyrannosauroid from the Late Cretaceous (Middle Campanian) Demopolis Formation of Alabama. Journal of Vertebrate Paleontology 25: 119 - 143.", "Currie, P. J. 1997 a. Theropods; pp. 216 - 233 in J. O. Farlow and M. K. Brett-Surman (eds.), The Complete Dinosaur. Indiana University Press, Bloomington.", "Molnar, R. E. 1978. A new theropod dinosaur from the Upper Cretaceous of central Montana. Journal of Paleontology 52: 73 - 82.", "Gilmore, C. W. 1933. On the dinosaurian fauna of the Iren Dabasu Formation. Bulletin of the American Museum of Natural History 67: 23 - 78.", "Hutt, S., D. Naish, D. M. Martill, M. J. Barker, and P. Newberry. 2001. A preliminary account of a new tyrannosaurid theropod from the Wessex Formation (Early Cretaceous) of southern England. Cretaceous Research 22: 227 - 242.", "Hutt, S., D. M. Martill, and M. J. Barker. 1996. The first European allosaurid dinosaur (Lower Cretaceous, Wealden Group, England). Neues Jahrbuch fur Geologie und Palaontologie Monatschefte 1996: 635 - 644.", "Harris, J. D. 1998. 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 13: 1 - 75.", "Currie, P. J., and K. Carpenter. 2000. A new specimen of Acrocanthosaurus atokensis (Theropoda, Dinosauria) from the Lower Cretaceous Antlers Formation (Lower Cretaceous, Aptian) of Oklahoma, USA. Geodiversitas 22: 207 - 246.", "Sereno, P. C., D. B. Dutheil, M. Iarochene, H. C. E. Larsson, G. H. Lyon, P. M. Magwene, C. A. Sidor, D. J. Varricchio, and J. A. Wilson. 1996. Predatory dinosaurs from the Sahara and Late Cretaceous faunal differentiation. Science 272: 986 - 991.", "Chure, D. J., M. Manabe, M. Tanimoto, and Y. Tomida. 1999. An unusual theropod tooth from the Mifune Group (late Cenomanian to early Turonian), Kumamoto, Japan; pp. 291 - 296 in Y. Tomida, T. H. Rich, and P. Vickers-Rich (eds.), Proceedings of the Second Gondwana Dinosaur Symposium. National Science Museum, Tokyo, Tokyo.", "Coria, R. A., and L. Salgado. 1995. A new giant carnivorous dinosaur from the Cretaceous of Patagonia. Nature 377: 224 - 226.", "Erickson, G. M. 1995. Split carinae on tyrannosaurid teeth and implications of their development. Journal of Vertebrate Paleontology 15: 268 - 274.", "McIntosh, J. S. 1981. Annotated catalog of the dinosaurs (Reptilia, Archosauria) in the collections of Carnegie Musuem of Natural History. Bulletin of the Carnegie Museum of Natural History 18: 1 - 67.", "Slaughter, R. W., W. J. Hickerson, and W. R. Hammer. 1994. Analysis of Antarctic theropod teeth based on serration densities and patterns. Geological Society of America Abstracts with Program 26: 61 A.", "Baszio, S. 1997. Investigations on Canadian dinosaurs: systematic palaeontology of isolated dinosaur teeth from the Latest Cretaceous of south Alberta, Canada. Courier Forschungsinstitut Senckenberg 196: 33 - 77.", "Holtz, T. R., Jr., D. L. Brinkman, and C. L. Chandler. 1998. Denticle morphometrics and a possibly omnivorous feeding habit for the theropod dinosaur Troodon; pp. 159 - 166 in B. P. Perez-Moreno, T. Holtz, J. L. Sanz, and J. J. Moratalla (eds.), Gaia 15: Aspects of Theropod Paleobiology. Museu Nacional de Historia Natural, Lisbon, Portugal.", "Abler, W. L. 1992. The serrated teeth of tyrannosaurid dinosaurs, and biting structures in other animals. Paleobiology 18: 161 - 183.", "Gauthier, J. 1986. Saurischian monophyly and the origin of birds; pp. 1 - 55 in K. Padian (ed.), The Origin of Birds and the Evolution of Flight. California Academy of Sciences, San Francisco, California.", "Auffenberg, W. 1981. The Behavioral Ecology of the Komodo Monitor. University Presses of Florida, Gainesville, 406 pp.", "Currie, P. J. 1998. Possible evidence of gregarious behavior in tyrannosaurids; pp. 271 - 277 in B. P. Perez-Moreno, T. Holtz, J. L. Sanz, and J. J. Moratalla (eds.), Gaia 15: Aspects of Theropod Paleobiology. Museu Nacional de Historia Natural, Lisbon, Portugal.", "Carpenter, K. 1982. Baby dinosaurs from the Late Cretaceous Lance and Hell Creek Formations and a description of a new species of theropod. University of Wyoming Contributions to Geology 20: 123 - 134.", "Bakker, R. T., M. Williams, and P. Currie. 1988. Nanotyrannus, a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana. Hunteria 1: 2 - 30.", "Farlow, J. O., and D. L. Brinkman. 1994. Wear surfaces on the teeth of tyrannosaurs; pp. 165 - 175 in G. D. Rosenberg and D. L. Wolberg (eds.), Dino Fest. The Paleontological Society, Knoxvill |
|---|