One of the oldest fossil horseshoe crabs figured in the literature is Entomolithus lunatus Martin, 1809, a Carboniferous species included in his Petrificata Derbiensia. While the species has generally been included within the genus Belinurus Bronn, 1839, it was recently used as the type species of the new genus Parabelinurus Lamsdell, 2020. However, recent investigation as to the appropriate authority for Belinurus (see Lamsdell and Clapham, 2021) revealed that all the names in Petrificata Derbiensia were suppressed in Opinion 231 of the International Commission on Zoological Nomenclature (1954) for being consistently nonbinomial under Article 11.4 of the International Code of Zoological Nomenclature (ICZN) (International Commission on Zoological Nomenclature, 1999). Despite the validation of several species names for anthozoans, brachiopods, and cephalopods described in Petrificata Derbiensia in subsequent rulings (International Commission on Zoological Nomenclature, 1956a, b), Belinurus lunatus has not been the subject of any subsequent Commission ruling or opinion, and so its use in Petrificata Derbiensia remains suppressed. The Belinurus lunatus species name was used in several subsequent publications during the 1800s, none of which made the name available under ICZN article 11.5; Parkinson (1811) is also suppressed for being nonbinomial, while Woodward (1830), Buckland (1837), Bronn (1839), and Baily (1859) refer to the species only as a synonym of Belinurus trilobitoides (Buckland, 1837) through citation to the suppressed Pretificata Derbiensia. The first author to make Belinurus lunatus an available name was Baldwin (1905), who used the name in reference to a new figured specimen from Sparth Bottoms, Rochdale, UK, but again as an explicit junior synonym of Belinurus trilobitoides (Buckland, 1837). Therefore, it was not until Eller (1938) treated B. lunatus as a distinct species from B. trilobitoides that B. lunatus became an available name as per ICZN Article 11.6.1 under the authorship of Baldwin (1905) following ICZN Article 50.7.
When Eller (1938) made B. lunatus available, he did so seemingly unwittingly, with no reference to distinguishing characteristics. Belinurus lunatus is furthermore noticeably absent from otherwise comprehensive species lists (e.g., Raymond, 1944; Morris, 1980). Prantl and Přibyl (1955) correctly listed B. lunatus as a synonym of B. bellulus (itself a junior synonym of B. trilobitoides); Filipiak and Krawczyński (1996) deferred to (but did not reiterate) Prantl and Přibyl's (1955) synonymy, but incorrectly retained B. lunatus under Martin (1809) as the senior species. Belinurus lunatus, therefore, is and always has been a junior synonym of B. trilobitoides.
Lamsdell (2020) and Bicknell and Pates (2020) both erroneously included B. lunatus as a valid species, referring particularly to Filipiak and Krawczyński's (1996) treatment of the species. In coding the species for phylogenetic analysis, Lamsdell (2016, 2020) referred extensively to Filipiak and Krawczyński's (1996) material, which incidentally comprises predominantly large individuals. On the basis of the resulting tree topology, Lamsdell proposed the new genus Parabelinurus, with P. lunatus (Martin) as the type species. As P. lunatus and B. trilobitoides are synonyms, Parabelinurus Lamsdell, 2020 and Belinurus Bronn, 1839 are objective synonyms. Thirteen other Belinurus species have also been proposed as synonyms with B. trilobitoides, with their constituent specimens representing taphonomic or ontogenetic variants (Fisher, 1975; Anderson, 1996; Haug and Haug, 2020), including the type species of further genera considered valid by Lamsdell (2020), Koenigiella Raymond, 1944 and Macrobelinurus Lamsdell, 2020. To clarify this issue for future researchers, a full taxonomic history of Belinurus trilobitoides (Buckland, 1837), including all synonymies, is presented here.
Systematic paleontology
Belinurus Bronn, 1839
(= Bellinurus Pictet, 1846; = Steropis Baily, 1859; = Koenigiella Raymond, 1944
; = Macrobelinurus Lamsdell, 2020; =
Parabelinurus Lamsdell, 2020)
Type species.—Limulus trilobitoides (Buckland, 1837), by subsequent designation (= Belinurus bellulus König, c.1851/ Pictet, 1854; = Steropis arcuatus Baily, 1859; = Belinurus reginae Baily, 1863; = Belinurus koenigianus Woodward, 1872; = Bellinurus grandaevus Jones and Woodward, 1899; = Parabelinurus lunatus (Baldwin, 1905); = Bellinurus baldwini Woodward, 1907; = Bellinurus longicaudatus Woodward, 1907; = Bellinurus trechmanni Woodward, 1918; = Belinurus concinnus Dix and Pringle, 1929; = Belinurus carwayensis Dix and Pringle, 1929; = Belinurus truemani Dix and Pringle, 1929; = Belinurus pustulosus Dix and Pringle, 1929; = Belinurus morgani Dix and Pringle, 1930).
Other species.—?Belinurus iswariensis (Chernyshev, 1928); ?Belinurus kiltorcanensis Baily, 1869; Belinurus lacoei (Packard, 1885); ?Belinurus metschensis (Chernyshev, 1928); Belinurus silesiacus (Roemer, 1883); ?Belinurus stepanovi (Chernyshev, 1928); Belinurus sustai (Prantl and Přibyl, 1955).
Diagnosis.—Belinurid with ophthalmic spines positioned at posterior of ophthalmic ridges; axis of first thoracetron tergite medially inflated; thoracetron ovoid to semicircular in outline; thoracetron fixed tergopleural spines elongate, needle-like; conical opisthosomal boss present (after Lamsdell, 2020).
Remarks.—The correct authorship and spelling of Belinurus was recently clarified by Lamsdell and Clapham (2021), who demonstrated that Belinurus Bronn, 1839 was the correct spelling and attribution as opposed to Bellinurus Pictet, 1846.
Belinurus kiltorcanensis is known only from an isolated carapace that exhibits ophthalmic ridges similar to those in Bellinuroopsis and may not be a Belinurus. The Belinurus species described by Chernyshev (1928) need restudy to ascertain their placement within the genus.
Belinurus trilobitoides (Buckland, 1837)
Figure 1
1809 ‘Entomolithus Monoculites? (lunatus)’; Martin, p. 191, pl. 45, fig. 4.
1811 ‘Monoculites lunatus’; Parkinson, p. 275, pl. 18, fig. 18.
1830 ‘Entomolithus Derbyensis lunatus’; Woodward, p. 8.
1837 Limulus trilobitoides Buckland, p. 77, pl. 46″, fig. 3.
1839 ‘Belinurus monoculites’; Bronn, p. 489.
1839 Belinurus trilobitoides; Bronn, p. 489.
1840 Limulus trilobitoides; Prestwich, p. 491, pl. 41, fig. 8.
1843 Limulus trilobitoides; Morris, p. 75.
1850 Limulus trilobitoides; Mantell, p. 156, pl. 68, fig. 15.
c.1851 Belinurus bellulus König, pl. 28, fig. 230.
1854 Bellinurus bellulus; Pictet, p. 538, pl. 46, fig. 23.
1859 Steropis arcuatus Baily, p. 90.
1859 Steropis trilobitoides; Baily, p. 91.
1859 ‘Steropis monoculus’; Baily, p. 91.
1859 Steropis bellulus; Baily, p. 91.
1863 Belinurus reginae Baily, p. 110, pl. 5, fig. 1A–D.
1863 Belinurus arcuatus; Baily, p. 111, pl. 5, fig. 2A–C.
1867 Belinurus trilobitoides; Woodward, p. 32.
1867 Belinurus reginae; Woodward, p. 32, pl. 1, fig. 1.
1867 Belinurus arcuatus; Woodward, p. 32.
1872 Limulus trilobitoides; Woodward, p. 439.
1872 Bellinurus bellulus; Woodward, p. 439.
1872 Bellinurus reginae; Woodward, p. 439.
1872 Bellinurus arcuatus; Woodward, p. 439.
1872 Bellinurus koenigianus Woodward, p. 439, pl. 10, fig. 8.
1878 Bellinurus bellulus; Woodward, p. 239, pl. 31, fig. 3a–c.
1878 Bellinurus reginae; Woodward, p. 240, pl. 31, fig. 1a–d.
1878 Bellinurus arcuatus; Woodward, p. 241, pl. 31, fig. 2a, b.
1878 Bellinurus koenigianus; Woodward, p. 243, pl. 31, figs. 3c, 4.
1899 Bellinurus grandaevus Jones and Woodward, p. 388, pl. 15, figs. 2, 3.
1903 Belinurus bellulus; Baldwin, p. 198.
1905 Belinurus lunatus Baldwin, p. 136, fig. 2.
1907 Belinurus lunatus; Parker, p. 44.
1907 Bellinurus baldwini Woodward, p. 540, fig. 1.
1907 Bellinurus longicaudatus Woodward, p. 451, fig. 2.
1908 Belinurus baldwini; Parker, p. 71.
1908 Belinurus longicaudatus; Parker, p. 72.
1909 Belinurus baldwini; Parker, p. 6.
1909 Belinurus longicaudatus; Parker, p. 6.
1911 Belinurus reginae; Pruvost, p. 299, pl. 7, fig. 4, 4a.
1918 Bellinurus trechmanni Woodward, p. 462, fig. 5.
1929 Belinurus concinnus Dix and Pringle, p. 92, fig. 1.
1929 Belinurus carwayensis Dix and Pringle, p. 93, fig. 2.
1929 Belinurus truemani Dix and Pringle, p. 94, fig. 3.
1929 Belinurus pustulosus Dix and Pringle, p. 95, fig. 4.
1929 Belinurus bellulus; Dix and Pringle, p. 97, fig. 5.
1929 Belinurus arcuatus; Dix and Pringle, p. 98, fig. 6.
1929 Belinurus cf. B. arcuatus; Dix and Pringle, p. 99, fig. 7.
1929 Belinurus cf. B. koenigianus; Dix and Pringle, p. 100, fig. 8.
1930 Belinurus reginae; Pruvost, p. 197, pl. 12, fig. 5.
1930 Belinurus lunatus; Pruvost, p. 198, pl. 12, figs. 7, 8.
1930 Belinurus koenigi; Pruvost, p. 199, pl. 12, fig. 6.
1930 Belinurus morgani Dix and Pringle, p. 137, fig. 1.
1930 Belinurus cf. B. truemani; Dix and Pringle, p. 138, fig. 2.
1930 Belinurus bellulus; Dix and Pringle, p. 139, fig. 3.
1930 Belinurus konigianus; Dix and Pringle, p. 141.
1930 Belinurus reginae; Dix and Pringle, p. 141.
1938 Belinurus bellulus; Eller, p. 132, p. 10, figs. 3–10.
1938 Belinurus koenigianus; Eller, p. 132, pl. 9, fig. 3, pl 11., figs. 1, 2, 8.
1938 Belinurus grandaevus; Eller, p. 132, pl.12, figs. 7, 8.
1938 Belinurus pustulosus; Eller, p. 133, pl. 12, fig. 9.
1938 Belinurus reginae; Eller, p. 133, pl. 10, figs. 1, 2.
1938 Belinurus arcuatus; Eller, p. 133, pl. 11, figs. 3–6.
1938 Belinurus lunatus; Eller, p. 133, pl. 14, fig. 3.
1938 Belinurus baldwini; Eller, p. 133, pl. 14, fig. 1.
1938 Belinurus longicaudatus; Eller, p. 133, pl. 14, fig. 2.
1938 Belinurus truemanni; Eller, p. 134, pl. 11, fig. 7.
1938 Belinurus concinnus; Eller, p. 134, pl. 12, fig. 5.
1938 Belinurus carwayensis; Eller, p. 134, pl. 12, fig. 6.
1938 Belinurus morgani; Eller, p. 134, pl. 12, fig. 2.
1938 Belinurus trechmanni; Eller, pl. 12, fig. 1.
1944 Belinurus concinnus; Raymond, p. 480.
1944 Belinurus grandaevus; Raymond, p. 480.
1944 Belinurus bellulus; Raymond, p. 480.
1944 Belinurus truemani; Raymond, p. 480.
1944 Belinurus morgani; Raymond, p. 480.
1944 Belinurus pustulosus; Raymond, p. 480.
1944 Koenigiella reginae; Raymond, p. 480.
1944 Koenigiella arcuata; Raymond, p. 480.
1944 Koenigiella koenigiana; Raymond, p. 480.
1951 Belinurus reginae; van der Heide, pl. 7, figs. 2, 5.
1952 Belinurus reginae; Størmer, p. 635.
1952 Belinurus bellulus; Størmer, p. 635.
1955 Belinurus regina; Størmer, p. 20, fig. 13.1a.
1955 Belinurus arcuatus; Størmer, p. 20, fig. 13.1b.
1955 Belinurus baldwini; Størmer, p. 20, fig. 13.1c.
1955 Belinurus bellulus; Prantl and Přibyl, p. 385, pl. 1, figs. 1, 2.
1957 Belinurus reginae; Copeland, p. 48, pl. 16, figs. 2, 9, 10.
1957 Belinurus grandaevus; Copeland, p. 48, pl. 16, figs. 1, 3–8.
1975 Belinurus koenigianus; Bergström, p. 294, pl. 1, fig. 5.
1980 Belinurus bellulus; Morris, p. 31.
1980 Bellinurus baldwini; Morris, p. 31.
1980 Bellinurus koenigianus; Morris, p. 31.
1980 Bellinurus longicaudatus; Morris, p. 31.
1980 Bellinurus trilobitoides; Morris, p. 31.
1981 Belinurus koenigianus; Fisher, p. 51, fig. 3A.
1984 Belinurus reginae; Fisher, p. 199.
1984 Belinurus bellulus; Fisher, p. 199.
1984 Belinurus koenigianus; Fisher, p. 199.
1987 Bellinurus koenigianus; Selden and Siveter, p. 384.
1994 Bellinurus grandaevus; Schultka, p. 347.
1994 Bellinurus arcutus; Schultka, p. 347.
1994 Bellinurus reginae; Schultka, p. 347.
1994 Bellinurus lunatus; Schultka, p. 347.
1994 Bellinurus concinnus; Schultka, p. 347.
1994 Bellinurus longicaudatus; Schultka, p. 347.
1994 Bellinurus koenigianus; Schultka, p. 347.
1994 Bellinurus baldwinii; Schultka, p. 347.
1994 Bellinurus bellulus; Schultka, p. 347.
1994 Bellinurus carwayensis; Schultka, p. 347.
1994 Bellinurus morganii; Schultka, p. 347.
1994 Bellinurus truemanii; Schultka, p. 347.
1994 Bellinurus trechmannii; Schultka, p. 347.
1996 Bellinurus lunatus; Filipiak and Krawczyński, p. 420, fig. 4C–H.
1997 Bellinurus truemani; Anderson and Selden, p. 20.
1997 Bellinurus morgani; Anderson and Selden, p. 20.
1997 Bellinurus koenigianus; Anderson and Selden, p. 20.
1997 Bellinurus trilobitoides; Anderson and Selden, p. 20, fig. 1.
1997 Bellinurus arcuatus; Anderson and Selden, p. 20.
1997 Bellinurus trilobitoides; Anderson et al., p. 203, fig. 4a, b.
2016 Bellinurus arcuatus; Lamsdell, p. 182.
2016 Bellinurus bellulus; Lamsdell, p. 182.
2016 Bellinurus lunatus; Lamsdell, p. 182.
2016 Bellinurus reginae; Lamsdell, p. 182.
2016 Bellinurus trilobitoides; Lamsdell, p. 182.
2016 Bellinurus truemanii; Lamsdell, p. 182.
2020 Bellinurus arcuatus; Bicknell and Pates, p. 18, fig. 13C.
2020 Bellinurus baldwini; Bicknell and Pates, p. 18, fig. 13E.
2020 Bellinurus bellulus; Bicknell and Pates, p. 18, fig. 13D.
2020 Bellinurus carwayensis; Bicknell and Pates, p. 18, fig. 13F.
2020 Bellinurus concinnus; Bicknell and Pates, p. 18, fig. 14B.
2020 Bellinurus koenigianus; Bicknell and Pates, p. 18, fig. 14E.
2020 Bellinurus longicaudatus; Bicknell and Pates, p. 18, fig. 15C.
2020 Bellinurus lunatus; Bicknell and Pates, p. 18, fig. 15A, B.
2020 Bellinurus pustulosus; Bicknell and Pates, p. 18, fig. 16D.
2020 Bellinurus reginae; Bicknell and Pates, p. 19, fig. 16C, E.
2020 Bellinurus trechmanni; Bicknell and Pates, p. 19, fig. 17B.
2020 Bellinurus trilobitoides; Bicknell and Pates, p. 19, fig. 17D.
2020 Bellinurus truemani; Bicknell and Pates, p. 19, fig. 17C.
2020 ‘Belinurus sp.’; Haug and Haug, figs. 1I–VI, 3, 4, 5, 8a–f, 10a–c.
2020 Belinurus bellulus; Lamsdell, p. 13.
2020 Belinurus carwayensis; Lamsdell, p. 13, fig. 1G.
2020 Belinurus concinnus; Lamsdell, p. 13.
2020 Belinurus grandaevus; Lamsdell, p. 13.
2020 Belinurus morgani; Lamsdell, p. 13, fig. 1J.
2020 Belinurus pustulosus; Lamsdell, p. 13.
2020 Belinurus trechmanni; Lamsdell, p. 14.
2020 Belinurus trilobitoides; Lamsdell, p. 14.
2020 Koenigiella reginae; Lamsdell, p. 14.
2020 Koenigiella baldwini; Lamsdell, p. 15.
2020 Koenigiella koenigianus; Lamsdell, p. 15.
2020 Koenigiella longicaudatus; Lamsdell, p. 15.
2020 Koenigiella truemani; Lamsdell, p. 15.
2020 Macrobelinurus arcuatus; Lamsdell, p. 15.
2020 Parabelinurus lunatus; Lamsdell, p. 15.
Lectotype.—Complete individual preserving dorsal exoskeleton, comprising prosomal carapace, thoracetron, and telson (BNMH 34889) from the Carboniferous clay ironstone of the Coalbrookdale Coal Measures, Telford, Shropshire (Buckland, 1837, pl. 46″, fig. 3).
Remarks.—Fifteen of the 22 species historically included within Belinurus have been considered synonyms after critical evaluation by a number of researchers (Fisher, 1975; Anderson, 1996), with many regularly co-occurring (e.g., B. reginae and B. grandaevus in Nova Scotia, Canada (Copeland, 1957); B. arcuatus and B. reginae in Leinster, Ireland (Baily, 1863); B. trilobitoides, B. lunatus, B. longicaudatus, and B. baldwini in Rochdale, UK (Eller, 1938); B. morgani, B. trilobitoides, and B. reginae in Neath, Wales (Dix and Pringle, 1930)). Haug and Haug (2020), in reconstructing an ontogenetic series of Belinurus specimens based on material held in the Natural History Museum, London (BMNH), did not refer to the previous species assignments of individual specimens but included numerous specimens referred to B. trilobitoides (BMNH 18357, 18565, 18571, 36188, 13897, 13898, 13958, In41494, 46421) along with the holotypes of B. baldwini (BMNH In18572), B. koenigianus (BMNH In59227), and B. trechmanni (BMNH In18487) as different ontogenetic stages of the same species.
Most of the 14 junior synonyms of B. trilobitoides were diagnosed on the basis of dubious morphological criteria that are now known to be the result of taphonomic or ontogenetic processes, a conclusion supported by recent increases in our understanding of horseshoe crab decay (Babcock and Chang, 1997) and development (Haug et al., 2012; Haug and Rötzer, 2018; Tashman et al., 2019; Haug and Haug, 2020; Lamsdell, 2021). Belinurus arcuatus (the type species of Macrobelinurus Lamsdell, 2020), known from an isolated carapace, was diagnosed on the basis of the presence of a “facial suture” that is actually a crease in a taphonomically deformed specimen that otherwise exhibits no clear differences from specimens of B. trilobitoides. Belinurus reginae (type species of Koenigiella Raymond, 1944) was diagnosed solely on the occurrence of long thoracetron epimera, a trait known to vary throughout ontogeny. Belinurus koenigianus was diagnosed on the basis of the lack of carapace spines (which are actually broken away from the specimen rather than absent) and the proportions of the thoracetron, which is laterally compressed. No diagnosis was presented for B. grandaevus, which appears to have been named solely due to its geographic occurrence, and the available material shows no obvious differences from B. trilobitoides. Baldwin (1905) explicitly named B. lunatus as a junior synonym of B. trilobitoides and as such provided no diagnostic differences. Belinurus baldwini was defined as a species on the basis of carapace dimensions; however, the type specimen is taphonomically distorted and no other characters separate it from B. trilobitoides. Belinurus longicaudatus was diagnosed solely on its possession of a long telson although telson length is known to vary between individuals and through ontogeny. Belinurus trechmanni is known from a small specimen and diagnosed on the basis of genal spine length and thoracetron shape, both of which change through ontogeny. Finally, Dix and Pringle (1929, 1930) named B. concinnus, B. carwayensis, B. truemanni, and B. morgani on the basis of their possession of different numbers of free segments in the thoracetron, an interpretation of segment articulation now recognized as erroneous (Anderson and Selden, 1997). Belinurus truemanni was further diagnosed by the possession of curved genal spines (the form of which is due to compression), B. concinnus by a long headshield (when the specimen is tectonically distorted), and B. morgani by granulation on the prosoma (which is also known from B. trilobitoides). The final synonymous species, B. pustulosus, was diagnosed on the basis of a pustulose cuticular ornament, which again does not serve to distinguish the specimens from B. trilobitoides. With none of these species having valid diagnostic traits to separate them from B. trilobitoides, the weight of evidence suggests that all are considered synonyms, in keeping with the conclusions of Fisher (1975), Anderson (1996), and Haug and Haug (2020).
Figure 1.
Specimens of Belinurus trilobitoides previously considered to represent distinct species and genera. (1) MM LL.111267a, assigned to Belinurus trilobitoides. (2) NHMUK PI. I. 2754, previously assigned to Belinurus lunatus. (3) GSC 12803, previously assigned to Belinurus reginae. (4) NHMUK PI. In. 18572, holotype of Belinurus baldwini. (5) AM F29886, previously assigned to Belinurus arcuatus. Scale bars = 5 mm. Institutional abbreviations: AM = Australian Museum, Sydney, Australia; GSC = Geological Survey of Canada, Ottawa, Canada; MMUP = Manchester Museum, Manchester, UK; NHMUK = Natural History Museum, London, UK. (1, 2, 4, 5) Images reproduced from Bicknell and Pates (2020) under a CC BY 4.0 license.
Acknowledgments
I am grateful to L. Babcock and C. Schweitzer for their reviews of the manuscript. I thank R. Bicknell for providing a copy of Prantl and Přibyl (1955).
