Research ArticlePALEONTOLOGY

The anatomy, paleobiology, and evolutionary relationships of the largest extinct side-necked turtle

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Science Advances  12 Feb 2020:
Vol. 6, no. 7, eaay4593
DOI: 10.1126/sciadv.aay4593
  • Fig. 1 New specimen and reconstruction of S. geographicus from Venezuela.

    (A and B) CIAAP-2002-01 carapace in dorsal view. (C) Close-up of the left horn in CIAAP-2002-01 [see red square in (B)]. (D) Medial-right view of the left horn showing its ventral projection. (E and F) Close-up of one of bone surface of the carapace showing the pitted sculpture [see red circle in (B)]. (G) General reconstruction of CIAAP-2002-01 including the horns covered with keratinous sheath (light gray). co, costal bone; M, marginal scute; P, pleural scute; pe, peripheral bone; py, pygal bone; sp., suprapygal; V, vertebral scute. Blue lines indicate sulci. Photo credit: Edwin-Alberto Cadena, Universidad del Rosario.

  • Fig. 2 Male and female shell anatomy of S. geographicus.

    (A) Reconstruction of S. geographicus male (front) and female (middle-left), together with the giant caimanine Purussaurus mirandai and the large catfish Phractocephalus nassi. (B and C) AMU-CURS-85 nearly complete carapace in ventral view. (D and E) AMU-CURS-1098 nearly complete plastron in ventral view. (F to N) Female shell anatomy of S. geographicus MPV-0001 from Colombia. (F and G) Carapace in dorsal view. (H and I) Plastron in ventral view. (J and K) Close-up of the right anterior portion of the carapace in dorsoposterior view, showing bite marks and punctured bone [(J) and rectangle in (G)]. (L and M) Nuchal-anterior peripheral in dorsomedial view, showing thickened and moderately to strongly upturned (arrows) [(L) and circle in (G)]. (N) Close-up of the bone surface of one of the costal bones [(N) and circle in (G)], exhibiting microvermiculation sculpturing pattern. Abd, abdominal scute; Ana, anal scute; bm, bite mark; bp, bridge peripheral; co, costal bone; ent, entoplastron; epi, epiplastron; Ext, extragular scute; Fem, femoral scute; Hum, humeral scute; hyo, hyoplastron; hyp, hypoplastron; Int, intergular scute; isc, ischium scar; Lpg, left pelvic girdle; M, marginal scute; mes, mesoplastron; ne, neural bone; nu, nuchal bone; pe, peripheral bone; Pec, pectoral scute; pub, pubis bone; py, pygal bone; Rco, right coracoid; Rpg, right pelvic girdle; Rsc, right scapula; sp., suprapygal; tv, thoracic vertebra; V, vertebral scute; xip, xiphiplastron. Blue lines indicate sulci. Art: Jaime Chirinos. Photo credit: Edwin-Alberto Cadena, Universidad del Rosario.

  • Fig. 3 New humeri and bone histology of a partial femur of S. geographicus.

    (A to D) AMU-CURS-85 left humerus in ventral (A), medial (B), dorsal (C), and proximal (D) views. (E to H) OL-1820 left humerus in ventral (E), lateral (F), dorsal (G), and proximal (H) views. (I and J) AMU-CURS-233 partial femur in ventral (I) and dorsal (J) views. (K) Outline of the femur indicating the region where the thin section was elaborated. (L) Thin section of the partial femur, indicating the close-up presented in (M) to (P). (M) Close-up of the cortical region of the bone. (N) Close-up of the deeper part of the cortex. (O) Close-up of the central region of the bone. (P) Close-up of the transitional region of the bone. Outlines of the largest extant and extinct turtles ever, indicating their maximum carapace length (see table S2): (Q) S. geographicus. (R) A. ischyros. (S) D. coriacea (extant). (T) M. cf. sivalensis. (U) R. swinhoei (extant). (V) C. niger (extant). pco, primary cortex; SO, secondary osteon. Photo credit (A to H): Edwin-Alberto Cadena, Universidad del Rosario; (I to P): Torsten Scheyer, University of Zurich.

  • Fig. 4 Skull DNPM-MCT-1496-R and new lower jaws of S. geographicus.

    (A to D) DNPM-MCT-1496 skull described by Meylan et al. (8), from Acre, Brazil in dorsal (A), ventral (B), and right lateral (C) views. (D) Composite skull and lower jaw (not a scale) of S. geographicus using relief images of DNPM-MCT-1496 skull and VPPLT-979 lower jaw. (E to L) VPPLT-979 lower jaw from La Tatacoa Desert, Colombia in dorsal (E and F), ventral (G and H), and right-lateral (I and J) views. (K and L) VPPLT-979 articular bone and facet in posterior view, exhibiting the foramen posterius chorda tympani. (M to T) Right articular region of the lower jaw, Podocnemis expansa NHMW-137 (M and N), S. geographicus VPPLT-979 (O and P), S. geographicus AMU-CURS-706 (Q and R), P. dumerilianus AMNH-1886 (S and T). (U) Lower jaw of P. dumerilianus AMNH-1886 in dorsal view. (V) P. expansa NHMW-137 lower jaw in dorsal view. ang, angular; arf, articular facet; art, articular; cor, coronoid; den, dentary; fm, fossa Meckelii; fna, foramen nervi auriculotemporalis; fos, fossa articularis mandibularis; fpc, foramen posterius chorda tympani; pra, processus retroarticularis; pre, prearticular; sr, symphisis ridge; sur, surangular. Photo credit (A to C): Orangel Aguilera-Socorro, Universidade Federal Fluminense; (E to V): Edwin-Alberto Cadena, Universidad del Rosario.

  • Fig. 5 Phylogenetic relationships and geographic-temporal occurrences of S. geographicus.

    (A) The phylogeny is based on the single MPT, resulting from the analysis of 245 characters [L = 1180, consistency index (CI) = 0.319, and retention index (RI) = 0.748]. Bremer support indices are indicated next to the internodes. (B) A time-calibrated cladogram of South American Erymnochelyinae; the bars indicate the stratigraphic occurrence of taxa; internode length is hypothetical. (C) Paleogeographic reconstruction of northern South America during the late Miocene (10 Ma), including the localities with fossil record of S. geographicus and extension of the Pebas system, modified from Hoorn (44). (D) General stratigraphic column of Urumaco Formation, including the four localities where the new fossils of S. geographicus described here were found. (E) Excavation of AMU-CURS-85 carapace from Tío Gregorio locality. H, Holocene; L, tree length; Oligo, Oligocene; Paleo, Paleocene; Pleisto, Pleistocene; Plio, Pliocene. Pr, present.

  • Fig. 6 Climate and geological events versus size of Neogene to present tropical South American turtles and crocodilians.

    Deep-sea benthic foraminifer oxygen isotope curve for 0 to 23 Ma, redraw from Zachos et al. (46), showing major global climatic events (left). Major geological and geographical events for northern South America (light brown bars). Maximum skull or lower jaw (green values) and carapace (black values) for turtles and crocodylians from northern South American fossil sites. Formations are represented by yellow stars: 1, Barzalosa Fm., early Miocene, Colombia; 2, Castillo Fm., early Miocene, Venezuela; 3, Castilletes Fm., early-middle Miocene, Colombia; 4, La Victoria and Villavieja Fms., middle-late Miocene, Colombia; 5, Pebas Fm., middle Miocen, Peru; 6, Urumaco Fm., late Miocne, Venezuela; 7, Madre de Dios and Ipururo Fms., late Miocene, Brazil; 8, Pisco Fm., late Miocene, Peru; 9, Solimões Fm., late Miocene-Pliocene, Brazil; 10, San Gregorio Fm., early Pliocene, Venezuela; 11, Ware Fm., Pliocene-Pleistocene, Colombia; 12, Mesa Fm., Pleistocene, Venezuela. Carap, carapace; MMCO, middle Miocene climatic optimum; MMCT, middle Miocene climatic transition; Magda, Magdalena; Pleist; Pleistocene. Detailed information on localities, specimens, and sources are in table S3.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/7/eaay4593/DC1

    Supplementary Text

    Fig. S1. S. geographicus CIAAP-2002-01 details.

    Fig. S2. Outlines and indication of the measurements of the new specimens described here and reported in tables S1 and S2.

    Fig. S3. S. geographicus CIAAP-2002-01 carapace.

    Fig. S4. AMU-CURS-85 carapace of S. geographicus from Venezuela.

    Fig. S5. Details of S. geographicus AMU-CURS-1098 from Venezuela.

    Fig. S6. Lower jaws of S. geographicus from Venezuela, Colombia, and extant podocnemidids.

    Fig. S7. Additional strict consensus trees.

    Fig. S8. A. angulata from the Cretaceous of Japan.

    Fig. S9. Phylogeny versus skull–lower jaw length for Miocene neotropical crocodylians.

    Table S1. Measurements and body mass estimation for S. geographicus and other extant and extinct giant turtles as preserved in centimeters and kilograms.

    Table S2. Specific measurements and thickness (see fig. S2) of new specimens of S. geographicus.

    Table S3. Data on size for the Neogene to extant neotropical turtles and crocodylians.

    Data file S1. Body mass estimation calculations.

    Data file S2. Bone compactness calculations using Bone Profiler.

    Data file S3. Character-taxon matrix Nexus file raw data.

    Data file S4. Character-taxon matrix Nexus file final version.

    Movie S1. Video of CIAAP-2002-01 specimen.

    Movie S2. Video of the excavation of AMU-CURS-85 specimen.

    References (6893)

  • Supplementary Materials

    The PDF file includes:

    • Supplementary Text
    • Fig. S1. S. geographicus CIAAP-2002-01 details.
    • Fig. S2. Outlines and indication of the measurements of the new specimens described here and reported in tables S1 and S2.
    • Fig. S3. S. geographicus CIAAP-2002-01 carapace.
    • Fig. S4. AMU-CURS-85 carapace of S. geographicus from Venezuela.
    • Fig. S5. Details of S. geographicus AMU-CURS-1098 from Venezuela.
    • Fig. S6. Lower jaws of S. geographicus from Venezuela, Colombia, and extant podocnemidids.
    • Fig. S7. Additional strict consensus trees.
    • Fig. S8. A. angulata from the Cretaceous of Japan.
    • Fig. S9. Phylogeny versus skull–lower jaw length for Miocene neotropical crocodylians.
    • Table S1. Measurements and body mass estimation for S. geographicus and other extant and extinct giant turtles as preserved in centimeters and kilograms.
    • Table S2. Specific measurements and thickness (see fig. S2) of new specimens of S. geographicus.
    • Table S3. Data on size for the Neogene to extant neotropical turtles and crocodylians.
    • References (6993)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Data file S1 (Microsoft Excel format). Body mass estimation calculations.
    • Data file S2 (Microsoft Word format). Bone compactness calculations using Bone Profiler.
    • Data file S3 (.nex format). Character-taxon matrix Nexus file raw data.
    • Data file S4 (.nex format). Character-taxon matrix Nexus file final version.
    • Movie S1 (.mp4 format). Video of CIAAP-2002-01 specimen.
    • Movie S2 (.mp4 format). Video of the excavation of AMU-CURS-85 specimen.

    Files in this Data Supplement:

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