Origin and distribution of the brachial plexus in red-necked wallaby (Notamacropus rufogriseus, Marsupialia: Macropodidae).

Notamacropus rufogriseus (red-necked wallaby) are in the family Macropodidae, which is the second largest family of marsupials after the family Didelphidae. This study was conducted with the aim of providing a detailed description of the origin and distribution of the brachial plexus in N. rufogriseus. Two-year-old male and 3-year-old female red-necked wallabies were used for the study. The brachial plexus was formed by ventral rami of C4, C5, C6, C7, C8, and T1 spinal nerves. It is composed of three trunks that give rise to 12 principal nerves. The cranial trunk is formed by the combination of the rami C4-C7; the middle trunk is formed by the combination of the rami C6 and C7; and the caudal trunk is formed by the combination of the rami C8 and T1. Differences between left and right side of the plexus brachialis were not observed. C6 ventral spinal rami contribute the most to brachial plexus nerve formation, while C4 contributes the least. The formation and distribution of the plexus in N. rufogriseus exhibited more resemblance to the patterns observed in marsupial animals rather than placental mammals. Marsupial mammals demonstrate the involvement of C4 in the development of the brachial plexus. The formation and branching of the brachial plexus sequentially adapt in accordance with changes in their thoracic limb activities and innervation points. Anatomical data from brachial plexus studies optimizes thoracic limb clinical and surgical treatments. This work can provide baseline data for future marsupial brachial plexus studies and fill gaps in the scarce literature.