2004/07/01 by R. Robert Tyson, John P. Graham, Patrick T. Colahan +1 · 1 citation
Veterinary · Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · Medicine · #Veterinary Equine Medical Research #Botanical Studies and Applications #Genetic and phenotypic traits in livestock #Horse #Medicine #Anatomy #Biology #Paleontology
paper · doi:10.1111/j.1740-8261.2004.04060.x
openalex publication_date 2004/07/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/23
An 8-month-old miniature horse filly was presented for evaluation of severe rotational and angular limb deformities of the thoracic and pelvic limbs. On radiographic examination, complete ulnas and fibulas were identified. These findings are consistent with a condition previously described as a form of atavism. The term atavism is used to describe the reappearance of a trait or character that was seen in all earlier evolutionary specimens of a particular species, but has not been seen in recent ancestors. The atavistic traits of complete ulnas and fibulas have previously been described in Welsh and Shetland Ponies, all of which had severe rotational and angular limb deformities. In this horse, bilateral osteochondritis dissecans of the medial trochlear ridge of the talii were also identified. To the authors' knowledge, this is the first report of the atavistic traits of complete ulnas and fibulas seen in the miniature horse.