Such examples of juvenile dinosaurs are rare, the museum tells us; it also says there is nothing like this display appearing anywhere else. That may be true of other aspects of this hall as well. This redesign doubles the size of the display space (to 14,000 square feet), showing 300 fossils and 20 complete mounts of dinosaurs and sea creatures in two long galleries, each with a mezzanine level, spanning two of the museum’s buildings.

There is a 68-foot-long Mamenchisaurus found in China, and a 28-inch-long Fruitadens haagarorum, the smallest dinosaur ever found in North America. (The museum tells us it holds the only specimens.) A 43-foot wall shows 100 miscellaneous dinosaur specimens, ranging from footprints to fossilized droppings, with identifications and elaborations offered by touch-screen monitors. And the new hall is a major milestone in a seven-year $135 million transformation of the museum (including new exhibitions, new gardens and outdoor displays), to be completed by its centennial in 2013.

Many of the hall’s objects are also recent finds, discovered by the Dinosaur Institute, a research arm of the museum directed by the hall’s main curator, the paleontologist Luis M. Chiappe. This means that what we see reflects the latest preservation techniques (more clearly revealing texture than the old coatings did); the latest research on mounting (altering the posture and poses of several species); and the latest ideas about the goals of dinosaur displays (created by the Brooklyn-based Evidence Design). These changes (like others apparent in recent dinosaur exhibitions at the American Museum of Natural History in New York) highlight a transformation that has taken place in natural history museums since the age of the diorama.

In those traditional glass-enclosed scenes, which can be sampled in some of the stunning older galleries in the museum here, animals are evoked not with fossilized bones but with preserved skin and fur. Taxidermic specimens are posed in re-creations of their natural habitats, against meticulously painted backdrops showing, perhaps, the expanse of the veldt or the dense growth of a rain forest. The goal of this artifice is realism, bringing the visitor to an imagined spot, granting a glimpse of the natural world without humans.

There are vestiges of that approach in the new Dinosaur Hall’s murals, which try to imagine these creatures’ habitats and long-lost skin, fur or feathers. But that isn’t the point. When we look around here, we are not seeing the natural world or its ancient relics stripped of human presence; instead, we are reminded repeatedly that these dinosaurs might as well be posing with their once-unnoticed re-creators.