A reappraisal of Paleozoic horseshoe crabs from Russia and Ukraine
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ORIGINAL PAPER
A reappraisal of Paleozoic horseshoe crabs from Russia and Ukraine Russell D. C. Bicknell 1
&
Serge V. Naugolnykh 2 & Tom Brougham 1
Received: 25 April 2020 / Revised: 8 September 2020 / Accepted: 17 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Xiphosura are extant marine chelicerates that have displayed apparent morphological conservatism and remarkable survivorship across their ~ 480 Ma fossil record. The easily recognisable features that are known to even the earliest xiphosurans—a crescentic prosoma and often trapezoidal thoracetron (opisthosoma)—have generated debate surrounding their origins and taxonomic significance. This interest resulted in the description of numerous horseshoe crab species during the early to mid-twentieth century, particularly in Russia, that have remained unrevised since their original publications and unconsidered in the light of recent phylogenetic hypotheses. Here, we re-examine the non-belinurid taxa housed within the Chernyshev Central Museum for Geological Exploration in Saint Petersburg. We present the first formal diagnosis of Bellinuroopsis rossicus, erect Shpineviolimulus jakovlevi (Glushenko and Ivanov, 1961) comb. nov., to contain the species formerly described as ‘Paleolimulus’ jakovlevi and refer Paleolimulus juresanensis to Paleolimulidae incertae sedis. Phylogenetic analysis places S. jakovlevi at the base of Limulina. This position, coupled with a prosomal shield that is notably larger than the thoracetron, and lack of hypertrophied genal spines, suggests that this morphology may represent the ancestral austrolimulid shape. As an extension of this revision, we assessed the general austrolimulid morphological characters and uncovered two possible groups of these bizarre xiphosurids. Keywords Xiphosurida . Bellinuroopsis . Shpineviolimulus . Paleolimulidae . Austrolimulidae
Introduction The evolutionary history and diversity of Russian xiphosurid fossils have recently been subject to renewed interest (Marshall et al. 2014; Naugolnykh 2017, 2018a; Shpinev and Vasilenko 2018; Shpinev 2018; Naugolnykh and Areshin 2019), a transition fuelled by an overall interest in Russian marine chelicerates
Communicated by: Julien Denayer Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00114-020-01701-1) contains supplementary material, which is available to authorized users. * Russell D. C. Bicknell [email protected] 1
Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, New South Wales 2351, Australia
2
Geological Institute, Russian Academy of Sciences, Moscow, Russia 119117
(Naugolnykh and Shpinev 2018; Shpinev and Filimonov 2018) and xiphosurids and stem-xiphosurids globally (Dunlop 2010; Lamsdell 2016; Bicknell 2019; Bicknell et al. 2019a, c; Bicknell and Pates 2019; Selden et al. 2019; Lamsdell 2020). A significant proportion of the recent xiphosurid research has come from re-examining specimens in museum coll
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