Figure 1.
Volume-rendered CT-based reconstruction of the skull of the extinct turtle Plesiochelys etalloni (MH 435).
In the images of the left side the bone is rendered opaque, whereas in the right side the bone is rendered semitransparent to show the endocranial cavity. The bone is shown in green, the cranial endocast and inner ear in light blue, the internal carotid arteries in pink, and the columella in fuchsia. Skull in left lateral (A) dorsal (B) and ventral (C) views. Abbreviations: col, columella auris; endo, cranial endocast; fpcci, foramen posterius canalis caroticus internus; fst, foramen staedio-temporale. Scale bar equals 10 mm.
Figure 2.
Surface-rendered CT-based reconstructions of the cranial endocast and endosseous labyrinth of Plesiochelys etalloni (MH 435).
In dorsal (A–B), lateral (C–D), and ventral (E–F) views. The cavum acustico-jugulare is rendered opaque in (A, C, and E); to show the location of the columella it is rendered semitransparent in (B, F), and is absent in (D). The images show the cranial endocast in light blue, the inner ear in light violet, the cavum acustico-jugulare in purple, the columella in fuchsia, and internal carotids in pink. Abbreviations: asc, anterior semicircular canal; ca, cerebral artery; caj, cavum acustico-jugulare; ccv, canalis cavernosus; cer, cerebral hemisphere; col, columella auris; col. f, columellar foot; cr, cartilaginous ridge (= cartilaginous rider of [17,19]); cst, canalis stapedio-temporalis; fst, foramen stapedio-temporale; ic, internal carotid; ica, incisura columella auris; lab, endosseous labyrinth; lsc, lateral semicircular canal; med, medulla oblongata; nc, nasal cavity; ob, olfactory bulb; ot, olfactory tract; pa, palatine artery; pit, pituitary fossa; psc, posterior semicircular canal; sa, stapedial artery; V–VIII, cranial nerves. Scale bar equals 10 mm.
Figure 3.
Detail of posterior region of the CT-based reconstructions of the cranial endocast of Plesiochelys etalloni (MH 435) in left anteroventral view.
The figure shows the cranial endocast in light blue, the columella in fuchsia, the internal carotid arteries in pink, the CN VI in yellow, and the cavum acustico-jugulare and the canalis stapedio-temporalis (rendered semitransparent to show the Columella) in purple. Abbreviations: ca, cerebral artery; ccv, canalis cavernosus; col, columella auris; ic, internal carotid; pa, palatine artery; pit, pituitary fossa; sa, stapedial artery; V–VIII, cranial nerves. Scale bar equals 10 mm.
Figure 4.
Detail of posterior region of the CT-based reconstructions of the cranial endocast and inner ear of Plesiochelys etalloni (MH 435) showing cranial nerves VII and VIII.
The image shows the cranial endocast in light blue and the inner ear in light violet. Abbreviations: ccv, canalis cavernosus; lab, endosseous labyrinth; med, medulla oblongata; V–VIII, cranial nerves. Scale bar equals 10 mm.
Figure 5.
Digital reconstruction of the skull of Plesiochelys etalloni (MH 435) in lateroposteroventral view.
Detail of the posterior part of the middle ear showing the foramen for cranial nerve IX. The image shows the bone in green and the columella in fuchsia. Abbreviations: cavum acustico-jugulare; col. f, columellar foot; ct, cavum tympani; endo, endocranial cavity; fpcci, foramen posterius canalis caroticus internus; op, opisthotic; pal, palatine; pbs, parabasisphenoid complex; pt, pterygoid; sq, squamosal; IX, cranial nerve. Scale bar equals 10 mm.
Figure 6.
Digital reconstruction of the left inner ear of Plesiochelys etalloni (MH 435).
In lateral (A, E), dorsal (B, F), anterior (C) and posterior (D) views. The image shows the inner ear in light violet and the columella in fuchsia. The columella is shown in anatomical position (E, F) and isolated in posteroventral view (G). Abbreviations: aa, anterior ampulla; asc, anterior semicircular canal; cc, common crus; col, columella auris; col. f, columellar foot; dpl, ductus perilymphaticus; fo, fenestra ovalis; fpl, fenestra perylimphatica; lag, lagena; lsc, lateral semicircular canal; psc, posterior semicircular canal; Scale bar equals 10 mm.
Figure 7.
Brain endocasts and left endosseous inner ears of turtles available in the literature displayed in a simplified cladogram (based on Joyce [25]).
The black circle indicates a synapomorphy based clade definition while the white circle indicates a crown-group definition following Joyce et al. [54]. A, Brain endocasts comparison based on line drawings of extinct and extant turtles in right lateral view represented by (left to right) (1) Bothremys cooki (redrawn from [17]), (2) Podocnemis unifilis (after [33]), Chelidae Emydura macquarii (after [33]), Baenidae Plesiobaena antiqua (redrawn from [19]), Plesiochelys etalloni (this study), (3) Corsochelys haliniches (redrawn from [16]), (4) Chelonia mydas, (5) Eretmochelys imbricata, (6) Caretta caretta, (7) Lepidochelys kempi, (8) Dermochelys coriacea (after [23]), Chelydridae Macrochelys temminckii (after [33]), Emydidae Pseudemys concinna (after [33]), Testudinidae Chelonoidis chilensis (this study), Kinosternidae Sternotherus odoratus (after [33]), and Trionychia Apalone ferox (after [33]). Dashed line indicates the shape of the nasal cavity. Dotted line in Plesiochelys etalloni indicates reconstructed area of the endocast. Dark gray, extinct species. Light gray, extant species. Not to scale. B, Inner ear endocasts were redrawn from the following sources: Plesiochelys etalloni from this study and Chelydridae, Emydidae, Testudinidae, and Trionychia from Thewissen and Nummela [20] (Fig. 15.11 K-N). Chelydridae is represented by Macrochelys temminckii; Emydidae is represented by Trachemys scripta; Testudinidae is represented by Chelonoidis nigra; Trionychia is represented by Carettochelys insculpta. Proganochelys quenstedti, Meiolaniformes, and Plesiochelys etalloni are extinct taxa. Not to scale.