Figure 1.
Partial premaxillae and partial right nasal of Tsintaosaurus spinorhinus (IVPP V829).
Specimen in (A) dorsal, (C) right lateral, (D) left lateral, (E) ventral, (F) rostroventral, and (G) rostral views. B. Insert of our reconstruction of the skull of T. spinorhinus showing the position of the prefrontal (solid black).
Figure 2.
Rhomboid distal nasal process of the crest of Tsintaosaurus spinorhinus.
A. Partial distal nasal process of IVPP V725 in right lateral view. B. Lateral view of composite skull (reversed). C. partial premaxillonasal complex of IVPP V829 in right lateral view. D. Line drawing of (C) showing nasal-premaxilla articulation, and the displacement (arrow) experienced by the distal nasal process relative to its articular position. E. Mounted holotype skull (IVPP V725) of T. spinorhinus in left lateral view (reversed). F. Partial right distal nasal process (although catalogued as IVPP V725, this element corresponds to a different specimen than the type; reversed).
Figure 3.
Nasal anatomy of Tsintaosaurus spinorhinus (IVPP V725).
A. Paired depressions for the nasal passage in rostroventral view. B. Distal rhomboid processes of the nasal of IVPP V725 in rostroventral view, showing areas of missing bone (white rectangle) and medial post-depositional displacement of the right process (double arrow). C. Composite skull in left lateral view. D. Rostral view of the sagittal ridge present on the rostral surface of the tubular processes of the fused nasals, interpreted here as the articular surface for the lateral process of the premaxilla.
Figure 4.
Nasofrontal articulation of Tsintaosaurus spinorhinus.
Paratype partial skull, IVPP 818. A. Rostral view. B. Rostrodorsal view. C. Dorsal view; note that the nasofrontal articulation is covered by the ecotcranial surface of the frontal. D. Left rostrodorsolateral view.
Figure 5.
Left premaxilla of Tsintaosaurus spinorhinus (IVPP K107).
Premaxilla in (A) rostrodorsal and (C) rostral views. B. Insert of our reconstruction of the skull of T. spinorhinus showing the position of the prefrontal (solid black).
Figure 6.
Left prefrontal of Tsintaosaurus spinorhinus (IVPP V725).
Prefrontal in (A) dorsal, (B) lateral, (D) medial, and (E) medioventral views. C. Insert of our reconstruction of the skull of T. spinorhinus showing the position of the prefrontal (solid black).
Figure 7.
Anatomical model of the cranium and supracranial crest of Tsintaosaurus spinorhinus.
A. Model of the skull in rostrolateral view. B. Lateral view of the model based on IVPP V723, V725, V829, and K107. C. Caudal view of the dorsal region of the crest. In B and C, grey areas indicate the available bones; white areas are missing bones and hypothesized reconstructions of missing parts of bones.
Figure 8.
Model of internal crest anatomy of Tsintaosaurus spinorhinus.
Based on the model in Fig. 7. Red indicates cut bone; arrows indicate hypothetical direction of airflow. A. Air enters the nasal passage through the left pseudonaris. B. Air passes dorsally into the crest from the left pseudonaris. C. Air from the right pseudonaris enters the common median chamber and passes caudally. D. Air from the left pseudonaris passes ventrally along the caudal margin of the crest into the cranial cavity.
Figure 9.
Nasofrontal articulation of selected hadrosaurids in phylogenetic context.
For each terminal taxon, the lower figure is a reconstruction of the skull roof in dorsal view and the upper figure is a schematic cross-section along the line of section (LOS) indicated. The frontal has been highlighted in dark blue for clarity, the nasal is orange in cross-sections (and omitted from dorsal view for clarity), and the nasofrontal/nasoprefrontal articulation surface is in light blue. Cut bone is red and missing bone is cross-hatched. Gryposaurus notabilis, AMNH 5350; Tsintaosaurus spinorhinus, combination of IVPP 725 and 818; Jaxartosaurus aralensis, PIN (Paleontological Institute, Moscow, Russia) 1/5009; Amurosaurus riabinini, AENM (Amur Natural History Museum, Blagoveschensk, Russia) 1/232; and Parasaurolophus tubicen, PMU (Paleontological Museum, Uppsala, Sweden) R222.
Figure 10.
Simplified time-calibrated phylogram of Lambeosaurinae.
Topology based on [14], with characters discussed in text optimized. In each hadrosaurid skull, light grey indicates premaxilla and black denotes nasal. The literature sources for each of the taxon’s datings are as follows: Aralosaurus tuberiferus [60,61], Jaxartosaurus aralensis [62], Pararhabdodon isonensis [21], Tsintaosaurus spinorhinus [33], and Lambeosaurini (oldest recorded age being that of Corythosaurus casuarius) and Parasaurolophini (oldest recorded age being that of Parasaurolophus walkeri) [63]. Geochronological ages are from [64].