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A hemivertebra in a temnospondyl amphibian: the oldest record of scoliosis

2007; Taylor & Francis; Volume: 27; Issue: 4 Linguagem: Inglês

10.1671/0272-4634(2007)27[1043

1937-2809

Florian Witzmann,

Connective tissue disorders research

Scoliosis is a lateral or rotational curvature of the vertebral column that can be traced back to different underlying reasons. The majority of scolioses are 'idiopathic,' that is, the cause is not known (Asher and Burton, 2006). Idiopathic scoliosis in humans develops most often during phases of intensive growth of the vertebral column in children and during adolescence. In other cases, postnatal development of scoliosis can be attributed, for example, to trauma, cancer, neuromuscular disease, or inflammation of the vertebral column (Asher and Burton, 2006). In few cases, scoliosis is caused by congenital vertebral malformations that develop very early during human embryogenesis (McMaster and Ohtsuka, 1982; Erol et al., 2004). Most congenital scolioses in humans are produced by one or more lateral hemivertebrae in the vertebral column. Thereby, a hemivertebra acts as a wedge and leads often to an excessive curvature of the column (McMaster and Ohtsuka, 1982). The incidence of hemivertebrae is estimated at 5-10 in 10.000 births in humans (Wynne-Davies, 1975). Apart from humans, hemivertebrae have been described in horses, dogs (Ettinger and Feldman, 2005), rabbits, and snakes (Baur, 1891 and references therein). In fossil animals, the occurrence of hemivertebrae is known only in two cases. Lydekker (1889) mentioned a cervical hemivertebra in the Upper Jurassic plesiosaur Cimoliasaurus plicatus, and Janensch (1934) in the Upper Jurassic ornithischian dinosaur Dysalotosaurus lettowvorbecki. In this paper, a hemivertebra causing a scoliosis is described in a temnospondyl amphibian from the early Middle Triassic of New Mexico. This is the basalmost and geologically oldest vertebrate in which this pathology is demonstrated so far. The formation of hemivertebrae with respect to the special vertebral morphology and ontogeny in temnospondyl amphibians and the implications of this disease for this animal are discussed.