Absolute axial growth and trunk segmentation in the early Cambrian trilobite Oryctocarella duyunensis

Article Type

Research Article

Publication Title

Paleobiology

Abstract

A short stratigraphic interval near Bulin in western Hunan (China) yields multiple specimens of the ~514-Myr-old oryctocarine trilobite Oryctocarella duyunensis. Size data obtained from these specimens indicate that, from meraspid degree 1 onward, degrees represent successive instars. Meraspid growth persisted until a terminal stage was reached, providing the first example of determinate growth in trilobites and, notably, in an early Cambrian species. The sample contains three varieties of such terminal stages, recognized as holaspids, with 9, 10, or 11 thoracic segments, respectively. During the meraspid phase, growth rates were not constant in this species. The pattern of growth seen in the Bulin assemblage differs modestly from that reported in the same species from two other localities, attesting to microevolutionary variation in developmental patterns among these collections.

First Page

517

Last Page

532

DOI

10.1017/pab.2020.63

Publication Date

8-1-2021

Comments

Open Access, Hybrid Gold, Green

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