Redescription and anatomical investigation of Schroederichthys maculatus Springer, 1966 and S. saurisqualus Soto, 2001 with comments on their systematics (Chondrichthyes: Carcharhiniformes: Atelomycteridae)

Abstract

Schroederichthys maculatus and S. saurisqualus together with S. tenuis present an elongated postpelvic trunk region and are usually referred as the neotenic species group of the genus Schroederichthys. The original morphological description of the two former species was mainly focused on external morphology and detailed information on anatomical structures such as neurocranium and teeth are lacking. This study aims, therefore, to present further information on external morphology, teeth and dermal denticles and to reappraise and illustrate skeletal structures of Schroederichthys maculatus and S. saurisqualus. Ethanol-preserved specimens of both species were measured and dissected for the examination of internal anatomical structures, such as neurocranium, teeth, dermal denticles and visceral arches. Three new tooth measurements are proposed herein. Neurocranial measurements, disposition of orbital foramina and tooth characters vary among neotenic species of Schroederichthys and should be included in future cladistic analyses. A detailed anatomical investigation of S. bivius and S. chilensis is also recommended in order to shed light on the interrelationships within the genus.