Parilisthelyphonus bryantae, Knecht & Benner & Dunlop & Renczkowski, 2024

Knecht, Richard J., Benner, Jacob S., Dunlop, Jason A. & Renczkowski, Mark D., 2024, The largest Palaeozoic whip scorpion and the smallest (Arachnida: Uropygi: Thelyphonida); a new species and a new ichnospecies from the Carboniferous of New England, USA, Zoological Journal of the Linnean Society 200 (3), pp. 690-704 : 696-697

Parilisthelyphonus bryantae sp.nov.

( Fig.4A, B )

Material: Holotype (part and counterpart) and only known specimen, MCZ:IP:198710a (dorsal) and MCZ:IP:198710b (ventral) preserved as a compression fossil (body fossil) on grey shale.

Horizon and locality: Westphalian C ( Upper Carboniferous ); from Rhode Island Fm. of the Narragansett Basin (see Geologic setting and palaeobiological context).

Collector: This specimen was collected by the late Robert G. Sproule and generously donated to Harvard University’s Museum of Comparative Zoology posthumously by his widow, Joyce Sproule.

Etymology: This species is named in honour of the late American arachnologist Elizabeth Bangs Bryant (1875–1953). Known for her studies of New England and Caribbean spiders, Bryant had worked at the Museum of Comparative Zoology for over 50 years (1898–1950), and made significant contributions to the field of arachnology, authoring 38 publications at a time when women were often discouraged from participating in scientific pursuits. Known for her diligence to the collections and her scientific studies, as well as her mentorship of other women in science, Elizabeth Bryant’s legacy can still be seen and felt today in Harvard’s arachnological collection and beyond. For this, we name this new species in her honour.

Diagnosis: As for the genus.

Description: The holotype ( Fig. 4A, B ) comprises a part (MCZ:IP:198710a) and counterpart (MCZ:IP:198710b) representing the dorsal and ventral views respectively. Total body L 34.18 mm (excluding telson). Carapace elongate; L 15.91 mm, W 6.70 mm (L/W ratio 2.38) and nearly as long as the opisthosoma (carapace/opisthosoma ratio 0.85; Fig. 5 ). The carapace is entire, rectangular in shape, with a straight posterior margin, and straight posterolateral margins until nearing the coxa of the first set of legs where the anterolateral margins then turn inwards in a straight, nearly 45 angle, to the anterior tip of carapace. The carapace contains several folds suggestive of a more raised or domed position in life with a gentle slope towards the anterior margin. There is also a distinct fovea slightly anterior to mid-centre of the carapace. The coxosternal region is poorly preserved with coxa (left leg I, legs II–IV, and palpal coxae) and some trochanters (legs III, IV, and left pedipalp) identifiable but not in great detail. In dorsal view, both pedipalps appear fully intact although details of the morphology of the right pedipalp are not preserved. Pedipalps are subraptorial; fe L 2.24 mm, pa L 2.18 mm, ti L 1.60 mm, ta L 0.42 mm. Legs are poorly preserved with some proximal podomeres present in legs I–IV but none exceeding the femur. Femurs are distinguishably robust and inflated. Femur of leg IV is at least 9.20 mm; other podomeres are incomplete or immeasurable due to lack of preserved morphology showing segment boundaries. Opisthosoma is elongate and suboval, L 16.22 mm, minimum max W 6.53 mm (tergites TI–T9, L/W ratio 2.48), with 12 tergites and 12 sternites, the last three forming a squat pygidium (L 2.01 mm, max. W 1.76 mm, min. W 1.07 mm) that is preserved folded back on itself and orientated to the left. Left side of the opisthosoma is not visible and appears covered in matrix. No telson is preserved.

Discussion: The erection of the new genus Parilisthelyphonus is warranted as it differs significantly from the other four Palaeozoic genera (see above). The genus Geralinura was redefined by Tetlie and Dunlop (2008) as a whip scorpion with an elongate opisthosoma ending in an extended pygidium where the 12th opisthosomal segment is longer than the two previous segments combined. Parilisthelyphonus , in contrast, has a pygidium in which each pygidial segment is shorter in length as you move posteriorly. Parageralinura species are short- to medium-sized and have a broad opisthosoma with a rounded pygidum with each pygidial segment nearly equal in length, whereas Parilisthelyphonus is a genus of large whip scorpions with an elongate and ovate opisthosoma with pygidial segments of decreasing length. Proschizomus is unique as the only Carboniferous whip scorpion to have pedipalps that articulate in a non-horizontal plane, unlike the pedipalps of Parilisthelyphonus , which articulate more horizontally as in living species. The closest match in size and habitus is Prothelyphonus , which, like Parilisthelyphonus , includes large (30* mm) whip scorpions with a slender opisthosoma and large, robust pedipalps. Parilisthelyphonus differs from the Czech species in not having the well-developed spination on its pedipalps nor do its pedipalps exceed the length of its carapace as in Prothelyphonus . Parilisthelyphonus also has a more robust and somewhat inflated femora and, significantly, a greater carapace: opisthosoma length ratio. Given their overlapping geologic age ranges, the similarity in body length and opisthosomal shape, and differences seen in pedipalp length and structure and carapace morphology between Prothelyphonus and Parilisthelyphonus , it cannot be completely ruled out that they may be sexually dimorphic individuals of the same species; a feature seen in some extant thelyphonids ( Weygoldt 1971).

The high carapace: opisthosoma (C: O) ratio (0.85) is the best defining characteristic of Parilisthelyphonus bryantae . The range of all other Carboniferous whip scorpion species fall between 0.43 and 0.56 ( Fig. 5 ). The full-body impression Inmontibusichnus charleshenryturneri (this paper) is not included in these calculations since exact anatomical measurements are not possible given the nature of the trace fossil, but a rough estimate would place it as the species with the second highest C: O between Parilisthelyphonus bryantae (0.85) and Parageralinura marsiglioi (0.56). Despite being a significant outlier, there is no evidence to suggest that compression, distortion, or another taphonomic variable is responsible for the high C: O value of Parilisthelyphonus bryantae . While Parilisthelyphonus bryantae is nearly double the C: O of Geralinura brittanica , the Carboniferous species with the smallest ratio, it is not particularly unusual, nor the highest, C: O amongst extant species.

The precise age of Parilisthelyphonus bryantae cannot be determined beyond the known age of the Rhode Island Formation (Westphalian C–Stephanian B/C). This age range places Parilisthelyphonus bryantae as one of the youngest Palaeozoic thelyphonids along with Geralinura carbonaria and an unnamed carapace from Ukraine ( Selden et al. 2014). Parageralinura marsiglioi retains its place as possibly the youngest Palaeozoic thelyphonid. While its exact age is also unknown, as it was found associated with a landslide, the geographic range (Kasimovian– Gzhelian) extends younger than that of Parilisthelyphonus bryantae .

The Narragansett Basin, in which the RIFn is located and from where Parilisthelyphonus was recovered, represents only the second site in the western hemisphere, in what was western Laurasia, to have a Palaeozoic thelyphonid. This site is of significant biogeographical importance as it is located between the westernmost Palaeozoic thelyphonid site, the Mazon Creek Formation of Illinois, USA, and the eastern collection of Palaeozoic thelyphonid sites in Europe ( Fig. 6 ).

Systematic palaeoichnology

Data archiving statement This published work and the nomenclatural acts it contains have been registered with ZooBank: https://zoobank.org/References/ ABF4758F-1EC4-42C3-86E7-17EE826B7D41.

Figures

Figure 4. The holotype of Parilisthelyphonus bryantae gen. nov., sp. nov.. Part (A; MCZ:IP:198710a) and counterpart (B; MCZ:IP:198710b) representing the dorsal and ventral views respectively and their corresponding line drawings (A1,B1). Image in Figure 4B, 4B1 has been flipped horizontally to match the same image orientation seen in Figure 4A, 4A1. Keys to the anatomical abbreviations used can be found under the Material and methods section.

Figure 5. Carapace to opisthosoma ratios (C: O) of all eight Carboniferous thelyphonid species [body fossils; does not include full-body impression (trace fossil) Inmontibusichnus charleshenryturneri, see text]. Green boxes represent the opisthosoma (including pygidium but excluding telson) and purple boxes represent the carapace, relative to each other. Measurements only included complete specimens.Averages were taken when data for multiple specimens of a single species were available.

Figure 6. Palaeogeographic map of Carboniferous (c. 310 Mya) showing thelyphonid sites. Red star indicates new locality and new species described in this paper. A, Mazon creek, Illinois, USA; Geralinura carbonaria. B, North Attleboro, Massachusetts, USA; Parilisthelyphonus bryantae, Inmontibusichnus charleshenryturneri. C, Dudley, Staffordshire, England, UK; Proschizomus petrunkevitchi.D, Derbyshire, Lancashire, Staffordshire, England, UK; Geralinura brittanica.E, Domaniale Mine, Limburg, the Netherlands; Parageralinura neerlandica.F, Hagen- Vorhalle, Nordrhein-Westphalia, Germany; Parageralinura naufraga. G, RakovnÍk, Okres RakovnÍk, Czech Republic; Prothelyphonus bohemicus.H, Carnic Alps, Friuli, Italy; Parageralinura marsiglioi. Brown shading = land; blue shading = marine flooding of continents; white shading = ocean basin. Map modified after Kocsis and Scotese (2021).