Dozo M T
División Paleontología Vertebrados, Facultad de Ciencias Naturales yMuseo, Universidad Nacional de La Plata Argentina.
J Hirnforsch. 1987;28(4):397-406.
A natural endocranial cast which represents a complete brain of a specimen of Hapalops indifferens is described. Comparing this cast to brains of actual Tardigrada, it shows a telencephalic morphology and a pattern of neocortical sulci that resemble more the brain of Bradypus rather than that of Choloepus. The neocortical sulci homologate the lateral or corono-lateral, suprasylvian and pseudosylvian sulci. Taking into account the studies of cortical maps in Bradypus and the notable similitude of the pattern of neocortical sulci between Bradypus and H. indifferens, the possible representation of the primary sensitive and motor somatic areas, secondary sensitive somatic area, visual and auditory areas are inferred. As in Bradypus, the primary sensitive and motor somatotopic organizations would be overlapped and would not be mirror images; they would show a predominance of the area of the forelimb. The relative brain size of H. indifferens is similar or higher than that of sloths of the genus Bradypus. The close resemblance between Bradypus and Hapalops, with respect to its brain morphology and relative brain size. is congruent with the current hypothesis of the phylogenetic relations between fossil and recent Tardigrada.
本文描述了一个天然颅内铸型，它代表了一种无区别扁爪水熊（Hapalops indifferens）标本的完整大脑。将这个铸型与实际缓步动物的大脑进行比较，结果显示其端脑形态和新皮质沟回模式更类似于三趾树懒（Bradypus）的大脑，而非二趾树懒（Choloepus）的大脑。新皮质沟回与外侧或冠状外侧沟、颞上沟和假颞沟相对应。考虑到对三趾树懒皮质图谱的研究以及三趾树懒和无区别扁爪水熊之间新皮质沟回模式的显著相似性，推断出了初级感觉和运动躯体区域、次级感觉躯体区域、视觉和听觉区域的可能表征。与三趾树懒一样，初级感觉和运动躯体定位组织会相互重叠，且不是镜像关系；它们会以前肢区域占优势。无区别扁爪水熊的相对脑容量与三趾树懒属的树懒相似或更大。三趾树懒和扁爪水熊在大脑形态和相对脑容量方面的密切相似性，与当前关于化石和现代缓步动物系统发育关系的假设相一致。
