Rapid Radiation of Zeiformes Revealed Through Comparison of Jaw Morphologies

Date: Friday, August 12th 11:00 AM Central Time (U.S. and Canada)

Location: Zoom

ABSTRACT

Zeiformes (e.g., Dories, Lookdown dories, Tinselfishes, Oreos) are a deep (1000 m) to mid-water (100 m) marine order of acanthomorph fishes with a circumpolar distribution, and a fossil record extending back to the Late Cretaceous. The order consists of 33 species across six families. The phylogenetic placement of the Zeiformes within Teleostei has been debated, but more recent studies based on both molecular and morphological data place Zeiforms within Paracanthopterygii closely related to Gadiformes. Zeiformes are characterized by anal and dorsal profiles that contain a variable number of fin rays and spines. They are mostly deep bodied, highly compressed fishes that exhibit a unique type of jaw protrusibility. This type of jaw protrusibility enables these fishes to capture smaller and more elusive prey and could be an important factor in their evolutionary success. This study investigates the jaw morphologies among zeiform families, the variation in jaw protrusion among the taxa, and the evolution of jaw protrusion in the various zeiform lineages compared to previous overall body shape data. Micro CT- scanning technology and three-dimensional geometric morphometrics was employed to observe jaw variation across taxa by using landmarks. Morphospace data showed a similar trend of a star-shaped radiation from an ancestral form like that of Grande et al. (2018), but with differing taxa converging and diverging on each other due to jaw morphologies. This is mostly likely due to modularity of zeiform morphology and developmental constraints since body form responds to a different set of selective pressures than the jaws do. Furthermore, zeiform taxa showed considerable variation among taxa with respect to specific bones of the jaw, possibly the result of submodulization and heterochronic shifts in development within the entire craniofacial area. This study was able to offer new methods for 3D geometric morphometric studies and revealed new evolutionary insights into the complex relationships of zeiforms.