Fig 1.
Dinosaur specimens preserved in articulation, showing that the glenoid is anteroventral to the ribcage and the scapular blades lie along the sides of the ribcage.
A. CMN cast of AMNH 5351, Centrosaurus apertus. B. Psittacosaurus mongoliensis, AMNH 6254. C. Velociraptor mongoliensis, IGM 100/25, after reference [9]. See Table 1 for institutional abbreviations.
Fig 2.
AMNH 5339, Struthiomimus altus, illustrating angles used in the study of resting scapular orientation.
Solid straight line follows longitudinal axis of first dorsal vertebra, broken line with small dashes follows axis of scapular blade, and broken line with large dashes follows axis of sacrum. Angle A = angle between long axes of scapular blade and first dorsal centrum (116° in this case). Angle B = angle between long axes of scapular blade and sacrum (9° in this case). Angle C = angle between long axes of sacrum and first dorsal vertebra (107° in this case).
Fig 3.
Ceratopsid skeletons preserved in articulation, showing that the ceratopsid sacrum is horizontal (parallel with the ground) when the humerus is held horizontally.
The line through the long axis of the sacrum is subparallel with the line that serves as a proxy for the horizontal by connecting the tips of the metapodials of the right forelimb (with horizontal humerus) and an outline of those of the right hindlimb, with the latter rotated to simulate a normal standing pose. A. CMN cast of AMNH 5351, Centrosaurus apertus. B. AMNH 5372, Styracosaurus albertensis. See Table 1 for institutional abbreviations.
Table 1.
Data used in correlation analyses that tested hypotheses of resting scapular orientation in bipedal saurischians.
See Materials and Methods section for descriptions of angles A, B, and C. Asterisked scapulae exhibit a scapular tip that extends high above the vertebral column. For angles A and B, a negative number represents an orientation in which the tip of the scapular blade is further from the vertebral column than the acromion is (in most dinosaurs, the opposite is the case). Institutional abbreviations (for this and subsequent tables): AM = Amherst College Museum, Amherst, Massachusetts. AMNH = American Museum of Natural History, New York City, New York, United States. BHI = Black Hills Institute of Geological Research, Hill City, South Dakota, United States. BMMS = Bürgermeister Müller MuseumSolnhofen, Solnhofen, Germany. BSP = Bayerische Staatsammlung für Paläontologie und Historische Geologie, Munich, Germany. CAGS = China Academy of Geological Sciences, Beijing, China. CHG = Chengdu College of Geology, Sichuan Province, China. CM = Carnegie Museum of Natural History, Pittsburgh, Pennsylvania. CMN = Canadian Museum of Nature, Ottawa, Ontario, Canada. DINO = Dinosaur National Monument, Jensen, Utah, United States. HMN = Museum für Naturkunde, Berlin, Germany. IGM = Mongolian Institute of Geology, Ulaan Bator, Mongolia. IRSNB = Institut Royal des Sciences Naturelles de Belgique, Brussels, Belgium. IVPP = Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China. JM = Jura Museum, Eichstätt, Germany. LH = Long Hao Institute for Paleontology, Hohhot, Nei Mongol Autonomous Region, China. LH = Universidad Autónoma de Madrid, Madrid, Spain. LPM = Liaoning Paleontological Museum, Liaoning Province, China. MCF = Museo Carmen Funes, Plaza Huincul, Argentina. MCZ = Museum of Comparative Zoology, Cambridge, Massachusetts, United States. MNA = Museum of Northern Arizona, Flagstaff, Arizona, United States. MNHN = Muséum National d’Histoire Naturelle, Paris, France. MOR = Museum of the Rockies, Bozeman, Montana, United States. NGMC = National Geological Museum of China, Beijing, China. NIGP = Nanking Institute of Geology and Paleontology, Beijing, China. PVSJ = Museo de San Juan, San Juan, Argentina. ROM = Royal Ontario Museum, Toronto, Ontario, Canada. SAM = South African Museum, Cape Town, South Africa. SBA = Sopritendeza per i Beni Archeologici di Salerno, Avellino, Benevento e Caserta, Italy. SC = Italian state collections (no associated city). SMNS = Staatliches Museum für Naturkunde, Stuttgart, Germany. STM = Shandong Tianyu Museum of Nature, Pingyi, Shandong, China. TMP = Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada. UCMZ = University of Calgary Museum of Zoology, Calgary, Alberta, Canada. ULR = Museo de Ciencias Naturales de la Universidad de La Rioja, La Rioja, Argentina. YFGP = Yizhou Fossil and Geology Park, Liaoning, China. YPM = Yale Peabody Museum, New Haven Connecticut, United States.
Table 2.
Data used to calculate mean resting orientations of ornithischian scapular angles in lateral view.
See Materials and Methods section for description of angle B. Group means shown without confidence intervals are those for which sample size is too small to derive 95% confidence intervals (n < 8). See Table 1 for institutional abbreviations.
Table 3.
Data used to calculate mean resting orientations of dinosaurian forelimb joints in lateral view.
l = left, r = right, S = shoulder angle, E = elbow angle, W = wrist angle. See Materials and Methods section for descriptions of angles. See Table 1 for institutional abbreviations.
Table 4.
Mean resting orientations of dinosaurian scapulae in lateral view, with 95% confidence intervals (L1 and L2) for the mean of the one group with a large enough sample size to calculate confidence intervals, and with n in parentheses.
See Materials and Methods section for description of angle B.
Fig 4.
Pectoral girdles and forelimbs of dinosaurs in left lateral view, depicting resting scapular and forelimb orientations in different dinosaurian groups as recommended according to the results of this study.
In each case, solid horizontal line is parallel to long axis of sacrum. A. theropods without semilunate carpals (Dilophosaurus wetherilli, UCMP 37302). B. theropods with semilunate carpals other than Caudipteryx (Velociraptor mongoliensis, after reference [60]). C. Caudipteryx (C. sp., after reference [8]). D. ceratopsids (Styracosaurus albertensis, NMC 344). E. basal sauropodomorphs (Plateosaurus engelhardti, AMNH 6810). F. non-hadrosaurian ornithopods (Thescelosaurus neglectus, reference [62]). G. hadrosaurids (Parasaurolophus walkeri, after reference [48]). Angle labels: B = scapular orientation relative to long axis of sacrum. E = elbow angle. S = shoulder angle. W = wrist angle. See Materials and Methods section for descriptions of angles.
Table 5.
Mean resting orientations of dinosaurian forelimb joints in lateral view, with 95% confidence intervals (L1 and L2) of the means of the groups and combined groups with large enough sample sizes, and with n in parentheses.
S = shoulder angle, E = elbow angle, W = wrist angle. See Materials and Methods section for descriptions of angles.
Table 6.
Recommended orientations of dinosaurian scapulae and forelimb joints in lateral view, for use in reconstructions and skeletal mounts, based on results of this study.
See Materials and Methods for descriptions of each angle.
Fig 5.
Reconstructions of dinosaurs from Fig 4 standing with the forelimb in resting pose, left lateral view.
A. Dilophosaurus wetherilli. B. Velociraptor mongoliensis. C. Caudipteryx sp. D. Plateosaurus engelhardti. E. Thescelosaurus neglectus. H. Parasaurolophus walkeri. All images in this figure are reprinted from original, previously-unpublished artwork by Leandra Walters under a CC BY license, with permission from Leandra Walters, original copyright 2015.