Variation in Numbers of Scleral Ossicles and Thier Phylogenetic Transformations Within the Pelecaniformes
Year: 1989
Type: article
Abstract: We examined scleral rings from 44 species of Pelecaniformes and found nonrandom variation in numbers of scleral ossicles among genera, but little or no variability within genera.Phaethon, Fregata, and Pelecanus retain the primitive 15 ossicles per ring, while the most recent common ancestor of the Sulae (Phalacrocoracidae, Anhinga, and Sulidae) is inferred to have had a derived reduction to 12 or 13 ossicles.Within the Sulidae, Sula (sensu stricto) exhibits further reduction to 10 ossicles.These patterns of ossicle reduction are congruent with both Cracraft's hypothesis of pelecaniform relationships (1985) and that of Sibley et al. (1988).The presence of scleral rings in museum specimens is significantly greater for Phaethon and Fregata, and less for Pelecanus, than would be expected from a random distribution.We conclude that the scleral ring is of potential systematic importance, and we make recommendations for its preservation in museum collections.
Language: English
Subfield: Anatomy
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W26534498