This study identifies three new neoselachian tooth taxa from the Middle and Upper Triassic. On the basis of morphological and histological characters, Rhomaleodus budurovi, nov. gen. et sp. (Anisian of Bulgaria), is resolved as stem selachimorph, with an additional specimen from the same stratigraphic level assigned to Synechodus sp. Selachimorph grade of enameloid microstructural organization (crystalline bundles) was also identified during examination of the dental tissues of “Polyacrodus” holwellensis (Rhaetian of England), necessitating its transfer to the new genus Duffinselache. The present data reveal several levels of increasing architectural complexity in the arrangement of the enameloid crystalline bundles of stem selachimorphs, which are argued to convey a phylogenetic signal that can be used to establish relationships within the group. It is suggested that the evolution of the hypermineralized enameloid cover of neoselachian teeth progressed from a plesiomorphic single crystalline state, through amalgamation of individual crystals into loosely defined bundles (marking the appearance of Selachimorpha), and their subsequent differentiation into a highly ordered parallel bundles, followed by the development of an inner layer of haphazardly oriented bundles. The superficial shiny-layered enameloid of Neoselachii is interpreted as remnant of a much reduced single crystalline layer.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.