139 Evolution of Life in the Cambrian Seas: Biotic, Biogeochemical, and Sedimentological Contexts, Part II

This session is dedicated to studies that illuminate the biotic, geobiological, sedimentological, and geochemical contexts of the evolution of early animal life in the oceans, with a particular focus on the Cambrian Period.

Monday, 20 October 2025
1:30 PM - 5:30 PM
HBGCC, 304B

A hypersegmented Kylinxia-like Arthropod from the middle Cambrian Marjum Formation (Utah): Insights into arthropod early Evolution and Phylogeny

Paper number: 139-9
Program: Technical Sessions
Time: 3:25 PM – 3:40 PM

Authors

Abstract

The lower Cambrian arthropod Kylinxia zhangi is widely regarded as bridging a key morphological gap in the arthropod stem lineage between radiodonts and deuteropods. It was originally described as combining five eyes (as in Opabinia), radiodont-like raptorial frontal appendages, and an arthrodized body composed of a four-segmented head, a long articulated anterior trunk (25 segments), a five-segmented non-articulated posterior trunk (“pygidium”), and a trilobed tail fan. A recent revision, however, proposed a more deuteropod-like morphology, with a six-segmented head and only three eyes.

 

We report the discovery of a Kylinxia-like arthropod in the middle Cambrian Marjum Lagerstätte in western Utah. Shared features with the Chinese taxon include a large anteromedian eye flanked by smaller lateral eyes, upward-directed radiodont-like frontal appendages, and a body divided into a six-segmented head, a multisegmented articulated anterior trunk, and a short non-articulated posterior trunk bearing caudal outgrowths. This rare Marjum arthropod differs from Kylinxia in having spiniform (rather than triangular) endites on the frontal appendages, spine-like (rather than flap-like) caudal outgrowths, and a much higher number of articulated trunk segments (>60 vs. 25 or 26). It also possesses complex digestive glands reminiscent of leanchoiliid megacheirans. The implications of this significant finding for the phylogenetic placement of Kylinxia and the evolutionary history of arthropods are discussed.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-412981

© Copyright 2025 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.