Exploring ancestral phenotypes and evolutionary development of the mammalian middle ear based on Early Cretaceous Jehol mammals

We report a new Cretaceous multituberculate mammal with 3D auditory bones preserved. Along with other fossil and extant mammals, the unequivocal auditory bones display features potentially representing ancestral phenotypes of the mammalian middle ear. These phenotypes show that the ectotympanic and the malleus-incus complex changed notably during their retreating from the dentary at various evolutionary stages and suggest convergent evolution of some features to extant mammals. In contrast, the incudomalleolar joint was conservative in having a braced hinge configuration, which narrows the morphological gap between the quadroarticular jaw joint of non-mammalian cynodonts and the incudomalleolar articulations of extant mammals. The saddle-shaped and abutting malleus-incus complexes in therians and monotremes, respectively, could have evolved from the braced hinge joint independently. The evolutionary changes recorded in the Mesozoic mammals are largely consistent with the middle ear morphogenesis during the ontogeny of extant mammals, supporting the relation between evolution and development.     

Regular class teachers' perceptions of transition programs for EMR students and their impact on the students

This study was designed to obtain the perceptions of regular class teachers who taught children who had been in EMR programs, but had been decertified (D) and returned to regular classes in response to court cases and recent legislation. A cohort of regular class (RC) students were selected for comparative purposes. It was found that D students were placed into low ability classes; yet, teachers perceived D subjects to be significantly lower than RC students in both academic achievement and social acceptance. Only a small proportion of teachers indicated that the enrollment of D students had much impact on the regular class instructional program. However, the teachers were rather critical of the services received under the auspices of a transitional program, indicating in large part that the services were either not apparent or ineffective.