Osteological development of the surf silverside (Notocheirus hubbsi) (Teleostei: Atheriniformes: Notocheiridae)

The surf silverside (Notocheirus hubbsi) is a rare and poorly known species within Notocheiridae. However, 2 collections of larval and juvenile specimens in Chile provided an opportunity to study unknown aspects of its morphological development and early life history. This study describes the ossification process and provides a detailed osteological description of the juvenile stage which is compared with adult descriptions available from the literature. Features are described in detail for comparative purposes with members of other atheriniform species, especially of the genus Iso. A single epural is present in larval stages of Notocheirus but is absent in juvenile and adult stages, hence, Iso and Notocheirus share the presence of a single epural, whereas other atheriniforms have 2 epurals. The pattern of Notocheirus supraorbital sensory canal pores is shared with that of Atherinopsinae. Our expectation is that similarities such as these may be tested as homologies, aiding in the resolution of competing hypotheses of relationships and family-level classification. Spinoid scales and odontodes associated with dermal bones of the head are unique for Notocheirus, however they not always present in juvenile and adult specimens. The crown of odontodes on the snout are not associated to any bones and appear to be unique for Notocheirus as well.