Abstract
The number of thoracic vertebrae and the presence of the notarium were examined with the naked eye for 353 bleached skeletal specimens of birds belonging to 18 orders, 42 families, 105 genera and 147 species and subspecies. The results are as follows.
(1) The number of thoracic vertebrae of the skeletons examined varied from 6 to 12. Interspecific variations of the numbers of thoracic vertebrae were observed in Nycticorax nycticorax nycticorax, Melopsittacus undulatus etc. Anatid birds exhibited a very large coefficient of variation in the number of thoracic vertebrae, i.e. 14.0%. These results suggest that the number of thoracic vertebrae would be of little value as a differential character for species and genera of birds.
(2) The notarium has been observed in 103 species and subspecies of birds.
(3) The birds examined exhibited a great variation in the presence of the notarium, as well as the number and positions of thoracic vertebrae constituting the notarium. They also showed a variation in the number of thoracic vertebrae joining in the synsacrum.
(4) The notarium was observed in both terrestrial species (e.g. Phasianus) and arboreal species with a high flying power (e.g. Columbidae, Falconidae). It also occurs in the Fruidae and Phoenicop teridae, which are good flyers. Therefore it is suggested that the presence of the notarium may not be related to flyight style.
