HERO IMAGE
Composite figure showing the growth series of Necrocarcinus sibiricus, from the smallest juvenile to the largest adult specimen, highlighting the gradual changes in carapace shape.
HIGHLIGHTS
A remarkable series of fossil crabs from Siberia captures different stages of growth within a single species. These specimens provide an exceptionally rare opportunity to study how extinct crabs changed as they developed from juveniles into adults.
overview
Understanding how extinct animals grew is often one of palaeontology’s greatest challenges. Most fossil species are known from only one or a few specimens, making it difficult to distinguish natural changes during growth from differences between species. An exceptional collection of Late Cretaceous crabs from northern Siberia has helped solve this problem.
The study describes the new species Necrocarcinus sibiricus from rocks deposited between the Cenomanian and Coniacian, approximately 95–86 million years ago. The available specimens represent several growth stages, allowing researchers to document how the animal’s carapace changed throughout its life. As the crabs matured, features such as the development of tubercles, the proportions of the carapace and the thickness of the cuticle changed progressively, producing adults that superficially resemble members of a different crab genus.
These observations demonstrate how growth-related changes can complicate the classification of fossil species when only isolated specimens are available. By documenting an almost complete ontogenetic sequence, the study provides rare insight into the development of extinct brachyuran crabs and highlights the importance of preserving specimens of different sizes. Beyond describing a new species, the research improves our understanding of crab evolution during the Late Cretaceous and offers a valuable framework for interpreting fossil diversity in other extinct crustacean groups.
REFERENCE
Kočová Veselská, M., Rogov, M., Gašparič, R., Hyžný, M., Ippolitov, A. P., Luque, J. & Košťák, M. 2025: A unique insight into the growth of necrocarcinoid crabs (Malacostraca: Decapoda: Brachyura): Evidence from the Upper Cretaceous of Siberia (Russia), with a description of a new species. Cretaceous Research, 168, 106053.
Read the publication on ResearchGate.
