Neurovascular anatomy of dwarf dinosaur implies precociality in sauropods.

Macronaria, a group of mostly colossal sauropod dinosaurs, comprised the largest terrestrial vertebrates of Earth's history. However, some of the smallest sauropods belong to this group as well. The Late Jurassic macronarian island dwarf Europasaurus holgeri is one of the most peculiar and best-studied sauropods worldwide. So far, the braincase material of this taxon from Germany pended greater attention. With the aid of micro-computed tomography (microCT), we report on the neuroanatomy of the nearly complete braincase of an adult individual, as well as the inner ears (endosseous labyrinths) of one other adult and several juveniles (the latter also containing novel vascular cavities). The presence of large and morphologically adult inner ears in juvenile material suggests precociality. Our findings add to the diversity of neurovascular anatomy in sauropod braincases and buttress the perception of sauropods as fast-growing and autonomous giants with manifold facets of reproductive and social behaviour. This suggests that - apart from sheer size - little separated Europasaurus from its large-bodied relatives.

Dinosaurs, like all animals with spines, had their main sensory organs ­ the organs that allowed them to listen, taste, see, smell, think and even keep their balance ­ on their heads. This means that studying their fossilized skulls can provide a wealth of information about how these animals perceived their environment through so-called 'endocasts' (digital models of the cavities within the skull). Endocasts of the skulls of many different dinosaur species already exist, but a small species called Europasaurus holgeri had so far not received this treatment. This sauropod lived in what is now northern Germany during the Late Jurassic period (154 million years ago), and it owed its reduced size to having become isolated on an island, where it became smaller after many generations. Schade et al. wanted to gain a better understanding of certain lifestyle aspects of the biology of E. holgeri, and to be able to compare the endocast anatomy of this species to other dinosaurs. To do this, the team studied the braincases of both very young and mature E. holgeri individuals using a technique called computer tomography. The approach taken by Schade et al. allowed them to examine and describe in detail the inner cavities that once contained the brain, inner ears, nerves and blood supply of eight different E. holgeri individuals. They found that the inner ears of small and young E. holgeri individuals were almost as large as those of their adult counterparts, and very similar in shape. Given that inner ears have roles in both audition and the sense of equilibrium, this suggests that E. holgeri babies were able to leave their nest very soon after hatching. This makes it likely that the babies of the species were highly developed when they hatched, and could probably feed themselves almost immediately, possibly similar to chickens. Furthermore, the relatively large size of the part of the inner ear responsible for hearing hints at E. holgeri being well able to communicate with other members of the species using sound. The findings of Schade et al. add to the diversity of the record on the anatomy of the braincases of dinosaurs. Additionally, the results support the idea that sauropods may have been herd-living animals with social interactions that grew very fast and had to be light on their feet very early in life. Finally, comparing the endocasts of E. holgeri to those of other dinosaurs suggests that, beyond a discrepancy in body size, this species was very similar to its larger relatives on the Jurassic mainland.

Neuroanatomy of the nodosaurid Struthiosaurus austriacus (Dinosauria: Thyreophora) supports potential ecological differentiations within Ankylosauria.

Nodosauridae is a group of thyreophoran dinosaurs characterized by a collar of prominent osteoderms. In comparison to its sister group, the often club-tailed ankylosaurids, a different lifestyle of nodosaurids could be assumed based on their neuroanatomy and weaponry, e.g., regarding applied defensive strategies. The holotype of the nodosaurid Struthiosaurus austriacus consists of a single partial braincase from the Late Cretaceous of Austria. Since neuroanatomy is considered to be associated with ecological tendencies, we created digital models of the braincase based on micro-CT data. The cranial endocast of S. austriacus generally resembles those of its relatives. A network of vascular canals surrounding the brain cavity further supports special thermoregulatory adaptations within Ankylosauria. The horizontal orientation of the lateral semicircular canal independently confirms previous appraisals of head posture for S. austriacus and, hence, strengthens the usage of the LSC as proxy for habitual head posture in fossil tetrapods. The short anterior and angular lateral semicircular canals, combined with the relatively shortest dinosaurian cochlear duct known so far and the lack of a floccular recess suggest a rather inert lifestyle without the necessity of sophisticated senses for equilibrium and hearing in S. austriacus. These observations agree with an animal that adapted to a comparatively inactive lifestyle with limited social interactions.

Neuroanatomy of the spinosaurid Irritator challengeri (Dinosauria: Theropoda) indicates potential adaptations for piscivory.

Spinosauridae, a theropod group characterized by elongated snouts, conical teeth, enlarged forelimbs, and often elongated neural spines, show evidence for semiaquatic adaptations and piscivory. It is currently debated if these animals represent terrestrial carnivores with adaptations for a piscivorous diet, or if they largely lived and foraged in aquatic habitats. The holotype of Irritator challengeri, a nearly complete skull from the late Early Cretaceous Santana Formation of northeastern Brazil, includes one of the few preserved spinosaurid braincases and can provide insights into neuroanatomical structures that might be expected to reflect ecological affinities. We generated digital models of the neuroanatomical cavities within the braincase, using computer tomography (CT) data. The cranial endocast of Irritator is generally similar to that of other non-maniraptoriform theropods, with weakly developed distinctions of hindbrain and midbrain features, relatively pronounced cranial flexures and relatively long olfactory tracts. The endosseous labyrinth has a long anterior semicircular canal, a posteriorly inclined common crus and a very large floccular recess fills the area between the semicircular canals. These features indicate that Irritator had the ability for fast and well-controlled pitch-down head movements. The skull table and lateral semicircular canal plane are strongly angled to one another, suggesting a downward angling of approximately 45° of the snout, which reduces interference of the snout with the field of vision of Irritator. These neuroanatomical features are consistent with fast, downward snatching movements in the act of predation, such as are needed for piscivory.

Response of villin headpiece-capped gold nanoparticles to ultrafast laser heating.

The integrity of a small model protein, the 36-residue villin headpiece HP36, attached to gold nanoparticles (AuNP) is examined, and its response to laser excitation of the AuNPs is investigated. To that end, it is first verified by stationary IR and CD spectroscopy, together with denaturation experiments, that the folded structure of the protein is fully preserved when attached to the AuNP surface. It is then shown by time-resolved IR spectroscopy that the protein does not unfold, even upon the highest pump fluences that lead to local temperature jumps on the order of 1000 K of the phonon system of the AuNPs, since that temperature jump persists for too short a time of a few nanoseconds only to be destructive. Judged from a blue shift of the amide I band, indicating destabilized or a few broken hydrogen bonds, the protein either swells, becomes more unstructured from the termini, or changes its degree of solvation. In any case, it recovers immediately after the excess energy dissipates into the bulk solvent. The process is entirely reversible for millions of laser shots without any indication of aggregation of the protein or the AuNPs and with only a minor fraction of broken protein-AuNP thiol bonds. The work provides important cornerstones in designing laser pulse parameters for maximal heating with protein-capped AuNPs without destroying the capping layer.

Vibrational energy transport through a capping layer of appropriately designed peptide helices over gold nanoparticles.

We design and characterize spherical gold nanoparticles, which are covalently linked to and completely covered by 3(10)-helical peptides. These helices provide a scaffold to place (13)C=O isotope labels at defined distances from the gold surface, which we employ as local thermometers. Probing these reporter groups with transient infrared spectroscopy, we monitor the vibrational energy flow across the peptide capping layer following excitation of the nanoparticle plasmon resonance.

Vibrational energy transport in peptide helices after excitation of C-D modes in Leu-d10.

Vibrational energy transport in a short 3(10)-helical peptide is studied by time-resolved femtosecond infrared spectroscopy. The C-D vibrations of decadeuterated leucine incorporated in the helical chain are excited, and the subsequent flow of vibrational energy through the helix is monitored by employing C horizontal lineO probes at various distances from the heat source as local thermometers. The C-D modes are not resonant to the C horizontal lineO modes, neither directly nor through any Fermi resonance, thereby suppressing resonant energy transfer directly along the C horizontal lineO oscillators of the peptide backbone. In contrast to our previous work (J. Phys. Chem. B 2008, 112, 9091), we no longer find any substantial difference in the vibrational energy transport efficiency after high- or low-energy excitation. That is, the heat diffusion constant of (2.0 +/- 0.5) A(2) ps(-1) is the same as that after depositing vibrational energy through the ultrafast internal conversion of a covalently bound chromophore.

Vibrational energy transport in the presence of intrasite vibrational energy redistribution.

The mechanism of vibrational energy flow is studied in a regime where a diffusion equation is likely to break down, i.e., on length scales of a few chemical bonds and time scales of a few picoseconds. This situation occurs, for example, during photochemical reactions in protein environment. To that end, a toy model is introduced that on the one hand mimics the vibrational normal mode distribution of proteins, and on the other hand is small enough to numerically time propagate the system fully quantum mechanically. Comparing classical and quantum-mechanical results, the question is addressed to what extent the classical nature of the molecular dynamics simulations (which would be the only choice for the modeling of a real molecular system) affects the vibrational energy flow mechanism. Small differences are found which are due to the different ways classical and quantum mechanics distribute thermal energy over vibrational modes. In either case, a ballistic and a diffusive phase can be identified. For these small length and time scales, the latter is governed by intrasite vibrational energy redistribution, since vibrational energy does not necessarily thermalize completely within individual peptide units. Overall, the model suggests a picture that unifies many of the observations made recently in experiments.

Femtosecond midinfrared study of the photoinduced Wolff rearrangement of diazonaphthoquinone.

Time-resolved vibrational femtosecond spectroscopy is employed to investigate the photoinduced Wolff rearrangement reaction of diazonaphthoquinone (DNQ) dissolved in different solvents (methanol and water). DNQ is an important compound in commercial Novolak photoresists. Upon photoexcitation the ketene intermediate appears within 300 fs, indicating that the ketene is formed in a very fast concerted process involving N(2) loss and rearrangement. The strong shift of the vibrational band, assigned to the ketene by density functional theory calculations and experimental infrared spectra, toward higher wavenumbers is attributed to vibrational cooling. The relaxation time depends on the solvent (10 ps in methanol and 3 ps in water). However, the spectroscopic data show that the indirect ketene formation via a carbene intermediate might also be involved in the reaction process contributing to the ketene formation on the 10 ps time scale.