Article: Allometry in Late Devonian Podocopa ostracods (Crustacea) and its implications for ostracod ontogeny

Abstract Podocopa ostracods have abounded in various marine and non-marine habitats since the early Palaeozoic and left a diverse fossil record in strata worldwide. This is particularly useful for stratigraphic correlation and palaeoenvironmental and palaeogeographical reconstructions. However, despite being the most numerous ostracods during the Palaeozoic, their origins, evolution, ontogeny and phylogeny remain poorly defined. This paper represents the first study of morphological variation in Devonian Platycopida ostracods (an order of Podocopa) using a geometric morphometric approach. Our results identify substantial shape variation in Cribroconcha honggulelengensis Song \& Crasquin from the Upper Devonian Hongguleleng Formation of western Junggar, northwest China, demonstrating a remarkable change in juveniles between stages A-3 and A-2. Using linear regressions between principal component scores from right lateral view and carapace length, we demonstrate allometric growth patterns for this species. The body plan of C. honggulelengensis developed along an ontological variable: from an ovate outline with rare pores to an oblong outline with dense and large pores. Environmental factors should play an important role in shape determination during ontogeny of C. honggulelengensis.