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Many well-preserved silicified megalodontids found from the Jiapila Formation of the Upper Triassic in western China show great variations in the amorphous teeth and the massive hinge plate, making the internal molds vary greatly in size and shape. Thus, the internal molds of megalodontids do not always provide reliable taxonomic characters. As a result, about 3/4 of the 132 species and 6 of 9 genera of Triassic Megalodontidae erected on the basis of internal molds have to be revised. The revised definitions of genera Neomegalodon, Triadomegalodon, and Conchodon are given in this paper. [ABSTRACT FROM AUTHOR]

As a contribution to investigate the interspecific diversity in the large genus Mecisrocephalus Newport, 1843 with respect to these centipedes' predatonal role in soil tropical communities, we compared the patterns of maxillipede denticles in 32 species of the genus, and studied all published relevant information. All Mecisrocephalus species share a conservative pattern of six distinct denticles on the mesal side of the four articles of each maxillipede. Current views on centipede phylogeny suggest that the basic pattern in Mecistocephalus originated from an ancestral array of fewer denticles, by addition of other denticles on the first and fourth articles of the maxillipede. These patterns are not affected by sexual dimorphism, and intraspecific variation for denticle position, size and shape is negligible, but for minor allometry determining a relative increase of the size of some denticles with respect to the maxillipedes during growth. Species differ mainly in size, shape, and orientation of most denticles. Remarkably larger and unusually shaped denticles are found in a hitherto undescribed species from the Seychelles, which is described in this paper as M. megalodon n. sp. [ABSTRACT FROM AUTHOR]