Angular cartilage structure and variation in Neotropical freshwater stingrays (Chondrichthyes: Myliobatiformes: Potamotrygonidae), with comments on their function and evolution. Issue 1 (19th October 2017)

• Record Type: Journal Article
• Authors: Fontenelle, João Pedro; Loboda, Thiago S; Kolmann, Matthew; de Carvalho, Marcelo R
• Is Part Of: Zoological journal of the Linnean Society. Volume 183:Issue 1(2018)
• Page Start: 121
• Page End: 142
• Publication Date: 2017-10-19
• Subjects: fibrocartilage -- hyomandibulae -- hyomandibular -- Meckelian ligament -- jaws -- jaw suspension; Zoology -- Periodicals; 590
• DOI: 10.1093/zoolinnean/zlx054
• Languages: English
• ISSNs: 0024-4082

Abstract

Abstract: The various configurations of the jaws, anterior branchial arches and neurocranium provide some of the fundamental synapomorphies, distinguishing the major lineages of sharks, rays and ratfishes. For the Neotropical freshwater stingrays (family Potamotrygonidae), putatively unique skeletal elements, the angular cartilages, are intermediate between the hyomandibula and the lower jaw. These skeletal elements have been proposed as a synapomorphy for the potamotrygonids, but confidence in this character has been limited by poor sampling and taxonomic uncertainty, particularly regarding their ontogeny and homology. The morphology of the angular cartilages across the family is described, and the nomenclature of these structures is standardized. In addition, developmental and functional hypotheses for the origins of the angular cartilages are proposed. These cartilages, formed within the hyomandibular–Meckelian ligament, are suggested to be fibrocartilaginous in origin and aid in jaw kinesis. The angular cartilages are corroborated as a synapomorphy for Potamotrygonidae, although there is great variation within the family and similar structures have arisen independently in other extinct and extant batoid lineages. In potamotrygonines, the angular cartilages appear to have been lost in piscivorous Heliotrygon and Paratrygon, while additional angular cartilages were gained, typically one at a time, in some lineages of Potamotrygon .