Dolichocebus gaimanensis Is Not a Stem Platyrrhine.

The lower molars of the early Miocene New World monkey Dolichocebus gaimanensis from Patagonia, considered by some to be a stem platyrrhine, are for all intents and purposes indistinguishable from the same teeth preserved in the type specimen of the middle Miocene Laventiana annectens from Colombia. Canine morphology further indicates that Dolichocebus is a cebine, closely related to living Saimiri. The phenetic and phyletic continuity of these extinct species, here classified as congeners, means they are the first fossil platyrrhines that link South America's southern and northern Miocene monkey faunas, possibly as vicariant communities or with ancestral-descendant species that evolved by phyletic evolution. These findings further refute the hypothesis that early Miocene platyrrhines are (1) monophyletic and (2) outside the so-called crown platyrrhine radiation. The connection between these species is additional evidence supporting the hypothesis that the pattern of platyrrhine evolution is notably distinct for the predominance of low-level taxonomic clades (genera, tribes, subfamilies) of prolonged ecophylogenetic stability, which is the essence of the Long-Lineage Hypothesis.

The Crista Fenestra and Its Impact on the Surgical Approach to the Scala Tympani during Cochlear Implantation.

OBJECTIVE: The aim of this work was to describe the dimensions of the crista fenestra and determine its presence by means of high-resolution computed tomography (CT) for the purpose of cochlear implantation via the round window approach. METHODS: A series of 10 adult human temporal bones underwent high-resolution CT scanning and were further dissected for microscopic study of the round window niche. RESULTS: In all of the specimens, the round window membrane was fully visualized after the complete removal of bony overhangs. The crista fenestra was identified as a sharp bony crest located in the anterior and inferior borders of the niche; its area ranged from 0.28 to 0.80 mm2 (mean 0.51 ± 0.18). The proportion of the area occupied by the crista fenestra in the whole circumference of the round window ranged from 23 to 50% (mean 36%). We found a moderate positive correlation between the area of the niche and the dimensions of the crista fenestra (Spearman rho: 0.491). In every case, high-resolution CT scanning was unable to determine the presence of the crista fenestra. CONCLUSION: The crista fenestra occupies a variable but expressive area within the bony round window niche. Narrower round window niches tended to house smaller crests. The presence of the crista fenestra is an important obstacle to adequate access to the scala tympani. Nevertheless, a high-resolution CT scan provides no additional preoperative information with regard to its presence for the purpose of surgical access to the scala tympani via the round window niche.

Redescrição e osteologia de Bryconamericus exodon Eigenmann, 1907 (Ostariophysi, Characiformes, Characidae) / Redescription and osteology of Bryconamericus exodon Eigenmann, 1907 (Ostariophysi, Characiformes, Characidae)

Apresenta-se a redescrição de Bryconamericus exodon Eigenmann (1907), espécie-tipo do gênero, uma descrição osteológica da espécie, uma comparação com outras espécies de Characiformes e comentários sobre seu relacionamento com outros caracídeos. Bryconamericus exodon é facilmente distinta de todas as demais espécies do gênero por possuir os lobos superior e inferior da nadadeira caudal castanho-escuros; aproxima-se das espécies de Bryconamericus com corpo alongado e baixo, menos de 30 por cento do comprimento padrão, boca terminal e dentes da série externa do pré-maxilar desalinhados. Compartilha com outros Characidae um palatino fenestrado, perfurado ou adelgaçado, em sua porção médio-anterior, e um pós-cleitro 3 alongado e com aproximadamente a mesma largura em toda sua extensão, sinapomorfias adicionais para os Characidae com ii, 8 raios na nadadeira dorsal e quatro dentes na série interna do pré-maxilar.

The redescription of B. exodon Eigenmann (1907), type species of Bryconamericus, an osteological description for the species, a comparison with other characiform fishes, and comments about its relationships among other characids are presented. Bryconamericus exodon is easily distinguished from other species in the genus by possessing upper and lower caudal-fin lobes dark brown; it is proximate to other Bryconamericus species that possess: an elongated and low body, its depth less than 30 percent of standard length, mouth terminal, and teeth of external premaxillary series not aligned. Furthermore it shares with other Characidae a palatine fenestrate, perforated or shallowed in its medial, anterior, portion, and a third postcleithrum elongated and equally wide along its entire length, character states proposed as additional synapomorphies for the characids with ii, 8 dorsal-fin rays and four teeth in the internal premaxillary series.