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Tsintaosaurus (hadrosaur) reconstructed with large, hollow lambeosaurine crest



From: Ben Creisler
bcreisler@gmail.com


New in PLoS ONE:

Albert Prieto-Márquez & Jonathan R. Wagner (2013)
The ‘Unicorn’ Dinosaur That Wasn’t: A New Reconstruction of the Crest
of Tsintaosaurus and the Early Evolution of the Lambeosaurine Crest
and Rostrum.
PLoS ONE 8(11): e82268.
doi:10.1371/journal.pone.0082268
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0082268


The lambeosaurine Tsintaosaurus spinorhinus has traditionally been
reconstructed with an elevated, hollow, spike-like crest composed
entirely of the nasal bones, although this has been disputed. Here, we
provide a new reconstruction of the skull of this species based on
reexamination and reinterpretation of the morphology and articular
relationships of the type and Paratype skulls and a fragmentary crest.
We confirm the presence of a supracranial crest composed of the
elevated nasal bones, but also including the premaxillae. We
hypothesize that the crest is a tall, lobate, hollow structure that
projects dorsally and slightly caudally a distance greater than the
height of the skull along the quadrate. In our reconstruction, the
nasal passage passes through the crest, but enters the skull rostral
to the tubular process of the nasals, not through it. Tsintaosaurus
spinorhinus is rediagnosed on the basis of a suite of cranial
autapomorphies including a circumnarial fossa subdivided into three
accessory fossae, prefrontal with ascending rostral process and
lateral flange, nasals fused sagittally to form elongate tubular
process that rises dorsally from skull roof, each nasal being expanded
rostrocaudally into a rhomboid distal process, and medial processes of
premaxillae at the summit of the cranial crest inserted between
rhomboid processes of nasals. Tsintaosaurus spinorhinus lacks
characters that are present in more derived lambeosaurines
(parasaurolophins and lambeosaurins), such as rotation of the caudal
margin of the crest to an acute angle with the skull roof, lateral
processes of the nasals that enclose part of the intracranial cavity
and participate in the formation of the walls of the common median
chamber, and a smooth narial fossa lacking ridges and accessory
fossae. We hypothesize that ancestrally the rostrum of lambeosaurines
may have been more similar to that in Saurolophinae, and became
subsequently reduced in complexity during evolution of the group.