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Thyreophoran dinosaurs have spike- and club-shaped osteoderms probably used for defensive weapons. The structural and histological variations have been little known. Here, we provide the comparisons of the internal structures in defensive weapons of ankylosaurs and stegosaurs, using spikes of a polacanthid (Gastonia) and a nodosaurid (Edmontonia), clubs of ankylosaurids (Saichania and Ankylosauridae indet. from Canada), and spikes of stegosaurids (Stegosaurus and Dacentrurus), which sheds light on understandings of evolutionary history and functional implications of defensive weapons in thyreophorans. In ankylosaurs, the structural and histological features of spikes and clubs are similar with those of small osteoderms in having thin compact bones, thick cancellous bones with large vascular canals, and abundant collagen fibers. A previous study demonstrated that each of three groups of ankylosaurs (polacanthid, nodosaurid, and ankylosaurid) has distinct characteristic arrangements of collagen fibers in small osteoderms. This study shows that spikes and clubs of ankylosaurs maintain the same characteristic features for each group despite of the differences in shapes and sizes. Conversely, the spike-shaped osteoderms in primitive (Dacentrurus) and derived (Stegosaurus) stegosaurids have similar structure to each other and are significantly different from the other types of stegosaur osteoderms (throat bony ossicles and plates) in having thick compact bones with a medullary cavity. These lack abundant collagen fibers unlike ankylosaur osteoderms. The spikes of ankylosaurs and stegosaurs are similar in shape, but their structural and histological features are different in having unique structures of collagen fibers for ankylosaurs and thick compact bones for stegosaurs, providing enough strength to have large spikes and to use them as defensive weapons. Although the shapes of ankylosaur clubs are different from spikes, the internal structures are similar, suggesting that ankylosaurs maintain similar structures despite of different shapes in osteoderms. These results indicate that ankylosaurs and stegosaurs used different strategies independently to evolve defensive weapons.

Two techniques (stone-splitters and demolition agents) are revealed to be efficient methods for breaking large stone blocks in extreme paleontological excavation. In certain conditions – where security factors, permission issues, terrain conditions, rock properties are problematic – the traditional methods for breaking large rock blocks cannot be applied (e.g. crane trucks or explosives). Using an expansive demolition agent or stone-splitters after drilling equidistant holes not only allows a cheap, quick and safe solution but also permits precise removal of up to 9 ton blocks. Stone-splitters are a three-part tool that when inserted linearly and equidistantly along a brittle rock mass cause a precise fracture.

dinosaur genera Diceratops Lull, 1905 and Microceratops Bohlin, 1953 are preoccupied by the Hymenoptera insects, Diceratops Foerster, 1868 and Microceratops Seyrig, 1952, respectively. Therefore, the name of the ceratopsian dinosaur Diceratops Lull, 1905 from the Late Cretaceous of United States is a junior homonym of the hymenoptera Diceratops Foerster, 1868. Diceratus n. gen. (Greek di ‘‘two,’’ Greek ceratos ‘‘horned’’) is proposed as the replacement name of Diceratops Lull, 1905. Some workers have considered Diceratops synonymous with Triceratops (e.g., Dodson and Currie, 1990) but it was reinstated by Forster (1996) after analysis of the characteristics of all existing ceratopsid skulls, and recent reviews (e.g., Dodson et al., 2004) have considered Diceratops a valid genus.
Due to preoccupation, the name of the ceratopsian dinosaur Microceratops Bohlin, 1953 from the Cretaceous of the Gobi is
a junior homonym of the insect Microceratops Seyrig, 1952. Microceratus n. gen. (Greek micro ‘‘small,’’ Greek ceratos ‘‘horned’’) is proposed as the replacing name of Microceratops Bohlin, 1953.
Sereno (2000:489) has declared Microceratops a nomen dubium since the holotype material lacks any diagnostic features, a
convention followed by You and Dodson (2004:480). However, the name is still used by Le Loeuff et al. (2002), Lucas (2006),
Alifanov (2003) and Xu et al. (2002), and such practice justifies the renaming of the genus.
In order to preserve some stability, the names chosen here deliberately preserve the same prefixes.