A muscle that originates via thin tendons from the distal and dorsal aspects of the neural spines. The tendons course proximomedially to distolaterally and give rise to fleshy fibers that insert onto the lateral aspect of the neural arches of each of the vertebrae it crosses. The m. extensor caudae medialis is a continuation of m. semispinalis dorsi into the tail. [ http://www.ncbi.nlm.nih.gov/pubmed/22753107 ]