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A Chasmataspidid Affinity for the Putative Xiphosuran Kiaeria Størmer, 1934

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A Chasmataspidid Affinity for the Putative Xiphosuran Kiaeria Størmer, 1934 PalZ (2020) 94:449–453 https://doi.org/10.1007/s12542-019-00493-8 SHORT COMMUNICATION A chasmataspidid afnity for the putative xiphosuran Kiaeria Størmer, 1934 James C. Lamsdell1 Received: 3 April 2019 / Accepted: 20 August 2019 / Published online: 4 November 2019 © Paläontologische Gesellschaft 2019 Abstract The putative xiphosuran Kiaeria Størmer, 1934, from the Late Silurian (Ludlow) of Ringerike, Norway, is redescribed from the holotype and only known specimen as a chasmataspidid chelicerate arthropod. Morphological features such as the presence of a fused buckler of three opisthosomal segments clearly indicate a chasmataspidid afnity, while the size of Kiaeria, along with the occurrence of a raised axial region and expanded anterior articulation, suggest a close phylogenetic relationship to the Ordovician Chasmataspis. As such, Kiaeria represents the frst indication that the Chasmataspis-type chasmataspidid morphology persisted alongside the radiation of diploaspidids. This is also only the third chasmataspidid species recorded from the Silurian. Keywords Chasmataspidida · Chelicerata · Kiaeria · Kiaeritia · Ringerike Introduction is potentially a crustacean or other arthropod of unknown afnity, as is Marsupipterus sculpturatus Caster and Kjelles- The Paleozoic record of Chelicerata includes numerous vig-Waering, 1955, which strongly resembles a phyllocarid aquatic representatives divided between the bizarre Pyc- telson. Finally, Willwerathia laticeps (Størmer, 1936), from nogonida Latreille, 1810, morphologically distinctive the Lower Devonian of Germany, has been interpreted as a Xiphosura Latreille, 1802, taxonomically diverse Euryp- ‘synziphosurine’ chelicerate (Anderson et al. 1998), how- terida Burmeister, 1843, enigmatic Chasmataspidida ever the prosomal carapace does not bear any resemblance Caster and Brooks, 1956, and synziphosurines, which are to other aquatic chelicerates; instead, Willwerathia bears a now recognized to be a polyphyletic grouping of taxa dis- strong resemblance to the Cambrian artiopod Falcatama- tinct from Xiphosura (Lamsdell 2013a, 2016; Selden et al. caris Ortega-Hernández et al. 2015. 2015; Lamsdell et al. 2015). However, there remain a few Here, I review the afnities of another chelicerate of described chelicerate species that are of uncertain afn- unclear afnities, Kiaeria limuloides Størmer, 1934, from ity, often retained within Xiphosura as a legacy of when the Late Silurian (Ludlow) of Ringerike, Norway. Origi- it included synziphosurines. For example, Archaeolimu- nally described as a xiphosurid, Kiaeria instead exhibits a lus hanusi Chlupáč, 1965, a supposed xiphosurid from the number of characteristics of chasmataspidids, particularly Middle Ordovician of the Czech Republic, most likely rep- Chasmataspis Caster and Brooks, 1956. resents a bradoriid arthropod. Probable misidentifcations occur in other aquatic chelicerate groups, too; Mycterops whitei Schram 1984, from the Carboniferous of Iowa, USA, Geological setting Kiaeria is part of the diverse fauna described from the Handling Editor: Mike Reich. Silurian (Ludlow) Sundvollen Formation of the Ringerike Group exposed at Rudstangen, Norway, discovered by Johan * James C. Lamsdell [email protected] Kiær (1911, 1924). The fauna is derived from a greyish- green to brownish-red schistose sandstone with occasional 1 Department of Geology and Geography, West Virginia interbedded shales representing marine conditions within a University, 98 Beechurst Avenue, 330 Brooks Hall, broad coastal plain (Davies et al. 2003). The fauna includes Morgantown, WV 26506, USA Vol.:(0123456789)1 3 450 J. C. Lamsdell numerous fsh and arthropods preserved alongside Dictyo- Kiaeria limuloides Størmer, 1934 caris (Kiær 1911, 1924), which is now known to be a ben- Figure 1a, b thic marine alga (Botting 2007). Størmer (1934) described the arthropods, most of which represented eurypterids, in Material. PMO H 2038 (holotype), preabdominal buckler. detail. Kiaeria, from the same horizon as the eurypterids and fsh, represents the only supposed xiphosuran from the Description. PMO H 2038 preserves a largely complete pre- locality. abdominal buckler comprising opisthosomal segments 2–4. The specimen of Kiaeria is stored in the Geologisk The specimen is preserved as a fattened compression of Museum, Universitetet i Oslo, Norway (PMO). Specimens grey-brown cuticle which has faked of in places, particu- of Chasmataspis fgured for comparative purposes are stored larly on the right of the buckler (Fig. 1a), although compari- at the National Museum of National History, Washington, son with the fgure of the specimen presented by Størmer DC, USA (NMNH). (1934) (his pl. 12, fg. 1) shows that this damage had already occurred to the specimen prior to its initial description and has not advanced since. To the left, the specimen is trun- Systematic palaeontology cated by the rock that hosts the specimen having broken away. Anteriorly, the expanded articulation of the buckler is damaged and absent on the right due to a small escarp- Arthropoda von Siebold, 1848 ment in the matrix of the specimen. The buckler is 60 mm Chelicerata Heymons, 1901 long, from the anterior margin of the articulation to the tip Euchelicerata Weygoldt and Paulus, 1979 of the posterior projections; along the axis, the buckler is Chasmataspidida Caster and Brooks, 1956 40 mm long. The axis is defned by narrow furrows that Incertae sedis are likely the result of compression of an originally infated axial region. The axis is 32 mm wide at the buckler ante- Genus Kiaeria Størmer, 1934 rior and narrows evenly posteriorly to a width of 19 mm at the posterior margin. The anterior margin of the buckler Type species. Kiaeria limuloides Størmer, 1934, by is dominated by a broad articulation that likely represents monotypy. the expanded articulation facet of the frst buckler tergite. The anterior margins of the articulation are rounded; it is Revised diagnosis. Chasmataspidid arthropod with buck- 5 mm long at the centre of the axis (which extends on to ler displaying clear axial furrows; buckler anterior with the articulation) and narrows laterally to 3 mm in length expanded articulation surface; postero-lateral margins of before expanding again to a maximum preserved width of buckler drawn out into broad projections (emended from 8 mm towards the pleural margin. Posterior to the buckler Størmer, 1934). articulation, the frst buckler tergite (representing the sec- ond opisthosomal segment) is 9 mm long at the centre of Remarks. The genus name Kiaeria has previously been the axis, exhibits moderate posterior curvature laterally and assigned to two arthropods: the chelicerate Kiaeria Størmer, expands in length to 12 mm. The tergite is laterally incom- 1934, and the bivalved leperditicopid Kiaeria Glebowskaja, plete on both sides, but has a maximum preserved width of 1949, with the leperditicopid clearly representing the junior 86 mm. The second tergite (third opisthosomal segment) has homonym. The replacement name Kiaeritia Schallreuter and a preserved width of 80 mm, is 10 mm long at the centre of Hinz-Schallreuter, 1999 has been introduced as a replace- the axis, and exhibits extreme posterior curvature laterally, ment name for Kiaeria Glebowskaja, 1949; however, the expanding to a maximum preserved width of 17 mm. The original homonym Kiaeria Glebowskaja, 1949 was still in fnal buckler tergite (fourth opisthosomal segment) exhibits use as recently as 2016 (e.g., Johnson and Baarli 2012; Abu- extreme lateral curvature, has a preserved width of 64 mm, shik et al. 2016). The history of the taxonomic revision is is 16 mm long at the axis, and 11 mm long at the lateral mar- therefore repeated here in the hope of spreading awareness gin. Due to the extreme curvature of the segment, the pleural of the replacement name. margins extend some 18 mm beyond the posterior margin of Kiaeria shows close afnities to the genus Chasmataspis the axis. Despite preserving the cuticle, no ornamentation Caster and Brooks, 1956, and arguably could be assigned beyond very fne granulations are present anywhere on the to the family Chasmataspididae Caster and Brooks, 1956. buckler. However, as the only known specimen is represented solely by a partially complete buckler, the genus is considered Remarks. Siveter and Selden (1987) considered Kiaeria to incertae sedis within Chasmataspidida pending the discov- be only questionably assigned to Xiphosura. The style of ery of further, more complete, material. preservation (a fattened compression preserving the original 1 3 A chasmataspidid afnity for the putative xiphosuran Kiaeria Størmer, 1934 451 Fig. 1 a PMO H 2038, Kiaeria limuloides (holotype), buckler. b ▸ Interpretive diagram of PMO H 2038. Cuticle is shown in brown, pyrite growth in grey. Natural boundaries indicated by solid lines, while dashed lines represent boundaries due to breakage. c USNM 125117, Chasmataspis laurencii (paratype), buckler. d USNM 125103, Chasmataspis laurencii (paratype), buckler. Abbreviations: Ar articulation, Ax axis, T2–T4 tergites 2–4. Scale bars = 10 mm cuticle) does not match that of other xiphosurids, which are generally resistant to complete compression and do not pre- serve the cuticle (Babcock et al. 2000; Feldmann et al. 2011; Lamsdell and McKenzie 2015). The preservation of Kiaeria does, however, match that typical of eurypterids and chas- mataspidids (see Dunlop et al. 2001; Lomax et al. 2011; Lamsdell 2013b; Marshall et al. 2014), suggesting that the afnity of Kiaeria lies with one of
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