Scale morphology and squamation pattern of Guiyu oneiros provide new insights into early osteichthyan body plan

Abstract

Scale morphology and squamation play an important role in the study of fish phylogeny and classification. However, as the scales of the earliest osteichthyans or bony fishes are usually found in a disarticulated state, research into squamation patterns and phylogeny has been limited. Here we quantitatively describe the scale morphology of the oldest articulated osteichthyan, the 425-million-year-old Guiyu oneiros, based on geometric morphometrics and high-resolution computed tomography. Based on the cluster analysis of the scales in the articulated specimens, we present a squamation pattern of Guiyu oneiros, which divides the body scales into 4 main belts, comprising 16 areas. The new pattern reveals that the squamation of early osteichthyans is more complicated than previously known, and demonstrates that the taxa near the crown osteichthyan node in late Silurian had a greater degree of squamation zonation compared to more advanced forms. This study offers an important reference for the classification of detached scales of early osteichthyans, provides new insights into the early evolution of osteichthyan scales, and adds to our understanding of the early osteichthyan body plan.

Comparative ultrastructure and ornamentation characteristics of scales in gobiid species (Teleostei: Gobiidae) using the scanning electron microscope

“…Surfaces are a crucial and fundamental feature of life allowing organisms to interact with the world around them (Wainwright, 2019). Scales that cover the external fish body provide an interesting surface with numerous characteristics in their structures which can be used to study fish taxonomy (at the species and higher ranks), sexual dimorphism, age determination and growth, past environment experienced by fish, discriminating between hatchery‐reared and wild populations, migration, environmental pollution of the water, and phylogenetic studies (Chu, 1935; Cui, Qiao, & Zhu, 2019; Dapar, Torres, Fabricante, & Demayo, 2012; Das, 1959; Esmaeili, Hojat Ansari, & Teimory, 2007; Esmaeili, Zarei, Vahed, & Masoudi, 2019; Ferrito, Corsaro, & Tigano, 2003; Jawad, 2005; Lanzing & Higginbotham, 1974; Seshappa, 1999). The use of scanning electron microscopy (SEM) has greatly increased the importance of scale morphology in ichthyological studies (Esmaeili et al, 2007; Esmaeili et al, 2019; Esmaeili, Baghbani, Zareian, & Shahryari, 2009; Jawad, 2005).…”

Fish Species Identification Using the Rhombic Squamation Pattern

“…Scale morphology and squamation have been used to study scale morphology in different parts of the body (Chen et al, 2012;Mondéjar-Fernández and Clément, 2012), to describe the squamation pattern of osteichthyans providing new insights into the early evolution of osteichthyan scales, to understand the early osteichthyan body plan (Cui et al, 2019), and to study the morphology and articulated squamations of extinct species (Žigaite and Goujet, 2012). However, to our knowledge, no other analysis has used the rhombic lamination pattern to discriminate between species as is presented in this study.…”

A microanatomical and histological study of the scales of the Devonian sarcopterygian Miguashaia bureaui and the evolution of the squamation in coelacanths

“…Gess & Coates, 2015;Lu et al, 2017). Styloichthys displays shared derived characters of the lower jaw, braincase and dermal skull with coelacanths (Friedman, 2007), however, as opposed to other actinistians, Styloichthys presents rhombic cosmoid scales (Cui et al, 2019;Lu & Zhu, 2008), similar in shape to those of early dipnomorphs (e.g.…”