We have analyzed the internal structure of the brain of the microbiotherian marsupial Dromiciops gliroides and compared it with the brains of American and Australian marsupials. Dromiciops does not have a fasciculus aberrans, but does exhibit other features of brain structure that are similar to diprotodontid metatherians (e.g., lamination of the lateral geniculate nucleus of the dorsal thalamus). Cortical organization in Dromiciops shows some similarities with that in Australian marsupial carnivores in that the proportional areas of isocortex devoted to somatosensory and visual function are similar in size to each other, and greater in area than that devoted to olfactory or auditory function. This points to similar sensory requirements for the foraging lifestyle of Dromiciops and small Australian marsupial carnivores, with isocortical specialization for somatosensation and vision. We also examined phylogenetic relationships of Dromiciops with extant marsupials based on maximum parsimony analysis using a soft body brain morphology-only matrix, representing 93 extant marsupial taxa. The results recovered Dromiciops as a sister group to the Australasian marsupial clade Diprotodontia.

中文翻译：

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Dromiciops gliroides 的大脑和行为

我们分析了微生物有袋动物 Dromiciops gliroides 大脑的内部结构，并将其与美国和澳大利亚有袋动物的大脑进行了比较。Dromiciops 没有 fasciculus aberrans，但确实表现出类似于双原齿类后兽类的其他脑结构特征（例如，背侧丘脑外侧膝状体核的分层）。Dromiciops 的皮层组织与澳大利亚有袋食肉动物的皮层组织有一些相似之处，即用于躯体感觉和视觉功能的等皮层的比例区域在大小上彼此相似，并且比用于嗅觉或听觉功能的区域大。这表明 Dromiciops 和澳大利亚小型有袋类食肉动物对觅食生活方式的感官要求相似，具有躯体感觉和视觉的等皮质专业化。我们还使用代表 93 个现存有袋类动物的软体大脑形态矩阵，基于最大简约分析，研究了 Dromiciops 与现存有袋动物的系统发育关系。结果恢复了 Dromiciops 作为澳大利亚有袋动物进化枝 Diprotodontia 的姊妹组。