2022/12/19 by Aleksandr A. Mironenko, S. V. Naugolnykh · 1 citation
Earth and Planetary Sciences · Agricultural and Biological Sciences · #Paleontology and Stratigraphy of Fossils #Paleontology and Evolutionary Biology #Cephalopods and Marine Biology
paper · doi:10.18261/let.55.4.2
openalex publication_date 2022/12/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
Ammonoids – cephalopod molluscs with external shells that existed from the Early Devonian up to the end of the Cretaceous – had well-developed jaws. During ammonoid evolution, several different types of their jaw apparatus arose, the study of which is of undoubted interest since it allows researchers to draw conclusions about the feeding strategies of ammonoids and their position in trophic chains. However, there is a lack of findings relating to the evolution of ammonoid jaws during the Permian. Here we describe a collection of almost thirty of cephalopod jaws from the Divjinskian Formation (Artinskian Stage, Cisuralian, Lower Permian), from the Sverdlovsk region of Russia. Most likely, these jaws belong to goniatitid ammonoid Uraloceras , the most abundant cephalopod mollusc in the Divjinskian (Divya) Formation. Uraloceras lower jaws are typical ammonoid anaptychi which have a rounded, wide and convex shape with smooth or slightly ribbed surface. They have a large inner lamella with a trapezoidal platform in the central part. One of the jaws bears a possible bite trace of a predator or scavenger. The upper jaws, described here for the first time, are slightly smaller than the lower jaws, their shape is narrow and pointed. Originally, both jaws were completely organic without calcareous elements. The absence of sculpture, consisting of frequent ribs and growth lines, characteristic of the more ancient Carboniferous goniatitid jaws, makes the jaws of the Uraloceras closer to the structure of the jaw apparatus of Triassic ammonoids. Judging by the pointed shape of the tips of both jaws, Uraloceras were active predators. Keywords Permian Cephalopoda Ammonoidea jaw apparatus anaptychi Artinskian