Palaeoecology and evolutionary implications of enrolled trilobites from the Kushan Formation, Guzhangian of North China

Abstract

Damesella paronai is the earliest enrolled odontopleurid trilobite to be found in the fossil record. Whereas its interlocking devices were very poorly developed, its trunk shows advanced articulations, which only lack an articulating facet, though an anterior notch is present in the outer part of each pleura. Its body pattern and structures did not allow it an encapsulated enrolment style. On the other hand, it is coeval with the early asaphid Monkaspis daulis, found in the same beds and at the same level. This co-inhabiting trilobite had a more advanced structure that enabled it to achieve a fully enrolled, encapsulated style. These superior structures enhance the preservation of enrolled specimens of M. daulis, and it seems to be generally the case that more elegant structures actually improve preservation. The evolutionary trends of the lineages of these two trilobites show that while odontopleurids were very conservative, using the same enrolment style throughout their history, the asaphids developed different enrolment styles, which was one factor in giving them a capacity to occupy different ecological niches and a greater range of environments.

Keywords:

• Cambrian
• ecology
• functional morphology
• arthropods

Acknowledgements

Jorge Esteve is supported by the Spanish MINECO (Ref. FPDI-2013-17337). This research is a contribution to the project CGL2013-48877-P from Spanish MINECO and EU–FEDER. Jin-Liang Yuan is supported by the 973 Project of National Ministry of Sciences and Technology (2013CB835000), the National Natural Science Foundation of China (41362002; 41402011). We are grateful to Isabel Pérez (Universidad de Zaragoza, Spain) for her technical support with the figures of this manuscript. We are grateful to Nigel Hughes (UCR) and one anonymous reviewer for their review and helpful suggestions, which improved this manuscript. We also thank to David Bruton for his discussion about functional morphology of the double spine in derivate odontopleurids.

Funding

This work was supported by the Consejo Superior de Investigaciones Científicas [grant number CGL2013-48877-P]; Secretaría de Estado de Investigación, Desarrollo e Innovación [grant number FPDI-2013-17337]; 973 Project of National Ministry of Sciences and Technology [grant number 2013CB835000]; and National Natural Science Foundation of China [grant number 41362002], [grant number 41402011].