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

• Published in: Cretaceous research 2025-04, Vol.168, p.106053, Article 106053
• Main Authors: Kočová Veselská, Martina, Rogov, Mikhail, Gašparič, Rok, Hyžný, Matúš, Ippolitov, Alexey P., Luque, Javier, Košťák, Martin
• Format: Article
• Language: English
• Subjects: Camarocarcinus; Cenomanian; Coniacian; Necrocarcinus; Taymyr Peninsula; Turonian
• ISSN: 0195-6671
• DOI: 10.1016/j.cretres.2024.106053

The Upper Cretaceous (Cenomanian to Coniacian, 100.5–86.3 Ma) strata of the northern Krasnoyarsk Krai (Russia) yielded new fossil brachyuran crab material, based on which a new species, Necrocarcinus sibiricus, is described. Although the specimens come from settings of slightly different ages, all of them display dorsal carapace characteristics consistent with variation attributable to ontogenetic changes related to growth, for instance, the narrowing of the orbitofrontal margin, and a continuous smoothing and widening of the carapace. Interestingly, due to these ontogenetic changes, the largest of the studied specimens exhibits a morphology close to that previously described in Camarocarcinus, a related necrocarcinoid crab genus known from Paleocene strata. The newly described species shows that the dorsal carapace morphology typical for Camarocarcinus can be observed in at least some fully grown necrocarcinids, prompting a re-evaluation of the relationship between Necrocarcinidae and Camarocarcinidae. We propose that camarocarcinids may be derived from within Necrocarcinidae, with the particular morphology of Camarocarcinus resulting from heterochronous developmental processes, i.e., peramorphosis. •A new species of, Necrocarcinus sibiricus, is described from the Upper Cretaceous of Krasnoyarsk Krai (Russia).•The geographic range of the family Necrocarcinidae is extended into the high latitudes in the Arctic region.•Observed variations in dorsal carapace features are attributed to ontogenetic changes related to growth.•Morphologically, N. sibiricus sp. nov. represents a link between Camarocarcinidae and Necrocarcinidae as currently construed.