Evolution of the Dentition in Holocephalans (Chondrichthyes) Through Tissue Disparity

The Holocephali is a major group of chondrichthyan fishes, the sister taxon to the sharks and rays (Elasmobranchii). However, the dentition of extant holocephalans is very different from that of the elasmobranchs, lacking individual tooth renewal, but comprising dental plates made entirely of self-renewing dentine. This renewal of all tissues occurs at the postero-lingual plate surface, as a function of their statodont condition. The fossil record of the holocephalans illuminates multiple different trends in the dentition, including shark-like teeth through to those with dentitions completely lacking individual teeth. Different taxa illustrate developmental retention of teeth but with fusion in their serial development. Dentine of different varieties comprises these teeth and composite dental plates, whose histology includes vascularized tubes within coronal dentine, merging with basal trabecular dentine. In this coronal vascularized dentine, extensive hypermineralization forms a wear resistant tissue transformed into a variety of morphologies. Through evolution, hypermineralized dentine becomes enclosed within the trabecular dentine, and specialized by reduction into specific zones within a composite dental plate, with these increasing in morphological disparity, all reflecting loss of defined teeth but retention of dentine production from the inherited developmental package.

Dental Impaction in the Cecum: Case Report and Review of Gastrointestinal Foreign Body Impactions

Approximately 20% of the adult population in the United States wears dentures. Foreign body ingestions, including dentures, are not uncommon. Although the majority of all ingested foreign bodies pass spontaneously through the gastrointestinal tract, impaction may occur, especially with physiologic constrictions, angulations, or stenosis. The esophagus is the most common site of impaction, whereas colonic impaction is extremely uncommon. We present a case of an 84-year-old male who was referred to the gastroenterology clinic for denture impaction, which lasted for two weeks. The patient had already failed to pass the denture following conservative treatment with laxatives, and repeated abdominal imaging showed the dental plate in the cecum. Colonoscopy was performed three weeks after the ingestion of his dentures, and tripod forceps were used to dislodge the end of the dental plate and ultimately remove it. The patient was asymptomatic for the entire period.

Feeding structures in the ray-finned fish Eurynotus crenatus (Actinopterygii: Eurynotiformes): implications for trophic diversification among Carboniferous actinopterygians

ABSTRACTThe Permo-Carboniferous eurynotiforms show conspicuous modifications to postcranial and cranial morphology relative to primitive actinopterygian conditions, and represent an important early example of functional experimentation within ray-finned fishes. Although eurynotiforms are represented by abundant articulated fossil material, the internal anatomy of the group is not well known. Microcomputed tomography (μCT) of Eurynotus crenatus from the early Carboniferous (Viséan) Wardie Shales Member of the Gullane Formation of Wardie, Scotland provides detailed information on the jaws, palate and dentition. The lower jaw is deep and bears a well-developed convex dental plate on the prearticular/coronoids. The dentary bears a dorsally directed posterior process and lacks any obvious marginal dentition. The prearticular bears a low coronoid process. Apart from the first and second dermopalatines, and a likely accessory vomer, bones of the palate are tightly sutured or fused. The upper dental plate comprises a longitudinal, concave horizontal dental surface that occludes with the convex lower toothplate, and a more vertical region consisting of anastomosing ridges. The parasphenoid has a narrow anterior corpus and a broad posterior stalk that bears a pronounced midline notch. The smooth, irregularly punctated surfaces of the dental plates are formed by closely packed teeth with conjoined crowns, providing clues to the evolution of the more monolithic toothplates of Amphicentrum from the peg-like teeth reported in the earliest and most anatomically generalised eurynotiforms. The feeding apparatus shows many qualitative and quantitative features consistent with the processing of hard prey items. Eurynotus and its relatives show the first clear example of jaw and dental structures consistent with durophagy among actinopterygians. The origin of the group in the early Carboniferous is suggestive of diversification into newly available ecological roles in the aftermath of the end-Devonian extinction.

DEVELOPMENT OF DENTAL GEL FORMULATION CONTAINING MICROCAPSULES WITH EXTRACT OF Aster lanceolatus Willd. (ASTERACEAE) TO EVALUATE ITS EFFECT ON DENTAL PLATE

Este trabalho teve como objetivo desenvolver uma formulação de gel dental contendo microcápsulas com extrato de flores, folhas e caules de Aster lanceolatus Willd. para avaliar sua atividade sobre o biofilme dental, visto que estudos anteriores demonstraram sua atividade contra diversas cepas bacterianas. O microencapsulamento através de gelificação externa foi escolhido por apresentar inúmeras vantagens, como inibição da degradação do extrato por fatores ambientais. Foram desenvolvidas sete formulações base e a que apresentou melhor aspecto, foi submetida à análise sensorial, que apesar de demonstrar problemas com a cor e consistência mostrou aceitação. Concluiu-se que a incorporação de extratos ativos em formulações, como o microencapsulamento, é uma área que ainda pode ser muito explorada.

A new species of chimaeriform (Chondrichthyes, Holocephali) from the uppermost Cretaceous of the López de Bertodano Formation, Isla Marambio (Seymour Island), Antarctica

We describe a new chimaeriform fish, Callorhinchus torresi sp. nov., from the uppermost Cretaceous (late Maastrichtian) of the López de Bertodano Formation, Isla Marambio (Seymour Island), Antarctica. The material shows it is distinct from currently known fossil and extant species of the genus, whereas the outline of the tritors (abrasive surfaces of each dental plate) shows an intermediate morphology between earlier records from the Cenomanian of New Zealand and those from the Eocene of Isla Marambio. This suggests an evolutionary trend in tritor morphology in the lineage leading to modern callorhynchids, during the Late Cretaceous-Palaeogene interval.