Endocranial Anatomy of Lambeosaurine Hadrosaurids (Dinosauria: Ornithischia): A Sensorineural Perspective on Cranial Crest Function

Abstract

Brain and nasal cavity endocasts of four corythosaurian lambeosaurines (Dinosauria: Ornithischia) were investigated to test hypotheses of cranial crest function related to sensorineural systems. Endocasts were generated through computed tomography and three-dimensional rendering and visualization software. The sample comprises a range of ontogenetic stages from the taxa Lambeosaurus, Corythosaurus, and Hypacrosaurus. Results show that the morphology of brain endocasts differs little from that of hadrosaurines. The strikingly convoluted nasal vestibule of Hypacrosaurus altispinus, when interpreted in the context of lambeosaurine phylogeny, suggests selective pressure for nasal cavity function independent from changes in the external shape of the crest and associated visual display function. The plesiomorphically small olfactory bulbs and apparently small olfactory region of the nasal cavity argues against the hypothesis that increased olfactory acuity played a causal role in crest evolution. The elongate cochlea of the inner ear reveals that hearing in lambeosaurines emphasized low frequencies consistent with the hypothesized low-frequency calls made by the crests under the resonation model of crest function. The brain is relatively large in lambeosaurines compared with many other large dinosaurs, and the cerebrum is relatively larger than that of all non-hadrosaurian ornithischians and large theropods, but compares favorably with hadrosaurine hadrosaurids as well as some maniraptoran theropods. It is concluded that the large brains of lambeosaurines are consistent with the range of social behaviors inferred when the crest is interpreted as an intraspecific signaling structure. Anat Rec, 292:1315Rec, 292: -1337Rec, 292: , 2009. V V C 2009 Wiley-Liss, Inc.

Modern Imaging Techniques as a Window to Prehistoric Auditory Worlds

“…4h) should have been able to hear frequencies up to 6.9 kHz, with a best hearing range of 2.4-3.2 kHz. Evans et al (2009) later extended these results to the hadrosaurian dinosaurs Lambeosaurus, Corythosaurus, and Hypacrosaurus, and found those taxa to also have been limited to a frequency range of less than 3.0 kHz.…”

Remarkable preservation of brain tissues in an Early Cretaceous iguanodontian dinosaur

“…Previous measurements of dinosaur endocast volumes estimate them to have contained as little as 50% of actual brain (Hopson 1979;Evans et al 2009). Exceptions to this general assumption have been proposed: hadrosaurs (lambeosaurines, derived iguanodontian ornithopods) have been argued to have had brain tissues that filled rather more of the endocranial cavity (Evans 2005, cited in Evans et al 2009), especially in the anterior and ventral regions of the endocasts where more detailed lobelike structures (e.g.…”

“…cerebral hemispheres and the hypothalamus) are discernible to the naked eye. More posterior regions of the endocranium in dinosaurs, adjacent to the cerebellum and medulla, are, by contrast, relatively poorly defined and may indeed have been overlain by extensive sinuses, as is the case in extant crocodilians (Ostrom 1961;Hopson 1979;Evans et al 2009).…”

A sub-adult skull ofHypacrosaurus stebingeri(Ornithischia: Lambeosaurinae): anatomy and comparison

“…Areas of the bone surface and tooth enamel were damaged during preparation, and the specimen contains many fresh breaks. CT scans of the skull show crushed narial passages and do not appear to differ from the typical 'S-loop' known for H. stebingeri (Horner et al 2001;Evans et al 2009). …”