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Leaellynasaura amicagraphica, dinosaur, skull. Holotype. [P 185991]

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).

Xenovenator espinosai, holotype braincase CPC 2973. In (A) left lateral; (B) right lateral; (C) dorsal; (D) ventral; (E) anterior; (F) posterior. Abbreviations: bo, basicoccipital; bul, parabasisphenoid bulla; ex, exoccipital; fr, frontal; lad, lateral depression; lac, lacrimal articulation; lat, laterosphenoid; osp, orbitosphenoid; par, parietal; pbs, parabasisphenoid; po, postorbital; ri, median ridge; sk, skull; stf, supratemporal fossa.

Skull of Dromiceiomimus

Skull of Saichania, Warsaw Museum of Evolution

Skull of Oohkotokia horneri, gen. et sp. nov. (MOR 433, holotype)

The incomplete skull and vertebrae of the holotype of Omphalosaurus nevadanus, seen in dorsal (left) and ventral view (right). This image was derived by combining plates 8 and 9 of Merriam (1906), done by an uncredited artist. Legend: A - angular D - dentary Pl - palatine Pt - pterygoid Sa - surangular Sp - splenial V - vertebrae a, b, c - "doubtful elements"

Restored Placochelys placodonta skull at the Museum für Naturkunde, Berlin.

Restored Placochelys placodonta skull at the Museum für Naturkunde, Berlin.

Comparison of cranial features between closely related southern Laramidian taxa; (A), Akainacephalus johnsoni (UMNH VP 20202) from the Late Cretaceous Kaiparowits Formation of Utah; and (B), Nodocephalosaurus kirtlandensis (SMP VP-900) from the Late Cretaceous Kirtland Formation of New Mexico, in left lateral views. Various synapomorphies are shared with N. kirtlandensis (highlighted in black and white arrows) and includes “flaring nostrils”; enlarged, laterally projecting, loreal osteoderms that are situated directly dorsal to the external nares. Other synapomorphies include pyramid-shaped nasal and frontal osteoderms positioned on the dorsal regions of the skull. A number of significant differences have been observed between both specimens; in A. johnsoni, the anterior, and posterior supraorbital bosses form an enlarged element that is somewhat backswept, whereas in N. kirtlandensis, the posterior and anterior supraorbital bosses are clearly defined as individual osteoderms, and are much smaller in size. Additionally, the squamosal horn in Akainacephalus is very small but is prominent and tetrahedrally shaped in Nodocephalosaurus. The quadratojugal horn in Akainacephalus is massive, has a subtriangular morphology in lateral view and projects almost entirely ventral, whereas in Nodocephalosaurus, the quadratojugal horn is smaller and has a typical fin-shaped morphology. Study sites: asob, anterior supraorbital boss; ext naris, external naris; laca, lacrimal caputegulum; loca, loreal caputegulum; naca, nasal caputegulae; orb, orbit; psob, posterior supraorbital boss; qjh, quadratojugal horn; sqh, squamosal horn.

Riojasaurus skull cast, Copenhagen.

Riojasaurus skull cast, Copenhagen.

Skull of Pistosaurus longaevus (cast - USNM 16107) in right, left and posterior views.

Skull of Pistosaurus longaevus (cast - USNM 16107) in right, left and posterior views.

Skull replica of Vagaceratops at Canadian Museum of Nature

Skull cast of Anchiceratops ornatus (original specimen: TMP 1983.001.0001) on display at the University of Michigan Museum of Natural History.