Spines and baskets in apex predatory sea scorpions uncover unique feeding strategies using 3D-kinematics

Michel Schmidt; Roland R Melzer; Roy E Plotnick; Russell D C Bicknell

doi:10.1016/j.isci.2021.103662

Spines and baskets in apex predatory sea scorpions uncover unique feeding strategies using 3D-kinematics

iScience. 2021 Dec 21;25(1):103662. doi: 10.1016/j.isci.2021.103662. eCollection 2022 Jan 21.

Authors

Michel Schmidt^{1

2}, Roland R Melzer^{1

2

3}, Roy E Plotnick⁴, Russell D C Bicknell⁵

Affiliations

¹ Bavarian State Collection of Zoology, Bavarian Natural History Collections, Munich, Germany.
² Department Biology II, Ludwig-Maximilians-Universität München, Munich, Germany.
³ GeoBio-Center, Ludwig-Maximilians-Universität München, Munich, Germany.
⁴ Department of Earth and Environmental Sciences, University of Illinois at Chicago, Chicago, IL, USA.
⁵ Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, Australia.

Abstract

Megalograptidae and Mixopteridae with elongate, spinose prosomal appendages are unique early Palaeozoic sea scorpions (Eurypterida). These features were presumably used for hunting, an untested hypothesis. Here, we present 3D model-based kinematic range of motion (ROM) analyses of Megalograptus ohioensis and Mixopterus kiaeri and compare these to modern analogs. This comparison confirms that the eurypterid appendages were likely raptorial, used in grabbing and holding prey for consumption. The Megalograptus ohioensis model illustrates notable Appendage III flexibility, indicating hypertrophied spines on Appendage III may have held prey, while Appendage II likely ripped immobilized prey. Mixopterus kiaeri, conversely, constructed a capture basket with Appendage III, and impaled prey with Appendage II elongated spines. Thus, megalograptid and mixopterid frontalmost appendages constructed a double basket system prior to moving dismembered prey to the chelicerae. Such 3D kinematic modeling presents a more complete understanding of these peculiar euchelicerates and highlights their possible position within past ecosystems.

Keywords: Animals; Biological sciences; Evolutionary biology; Paleobiology; Zoology.