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| Pygocephalus brymboensis Astrop, 2026 |
Abstract
The genus Pygocephalus was one of the first groups of eumalacostracan Crustacea to explore and adapt to the new and dynamic freshwater systems created by the Earth’s earliest established rainforest in the Carboniferous. Characterized by a flattened body with a distinct carapace covering the thorax and well-developed pleon, Pygocephalus is regularly recovered from what were the braided rivers of the Carbonifeorus forests of Europe and North America. In this paper a new species of Pygocephalus, Pygocephalus brymboensis sp. nov., is described from the Moscovian of North Wales, primarily distinguished by a carapace that is slightly broader than long, a rostrum equal in length to the carapace and a unique pleural morphology. This study explores the position of P. brymboensis within Pygocephalomorpha and investigates the use of non-carapace-based morphometry as a tool for exploring morphological relationships between related taxa. The description of this species and exploration of the taxonomic history of the genus highlights the need for close examination of historical collections for the identification of subtle morphological differences, particularly in collections primarily amalgamated from multiple geographically disparate ex situ localities.
Keywords: Carboniferous, Crustacea, fossil forest, Pygocephalus
Systematic palaeontology
Class Malacostraca Latreille, 1802
Subclass Eumalacostraca Grobben, 1892
Order Pygocephalomorpha Beurlen, 1930
Family Pygocephalidae Brooks, 1962
Genus Pygocephalus Huxley, 1857
Type species. Pygocephalus cooperi Huxley, 1857
Other included species. Pygocephalus aisenvergi (Birshteyn, 1967); Pygocephalus dubius (Prestwich, 1840); Pygocephalus brymboensis (this study)
Diagnosis (after Schram, 1979). Carapace without hepatic spines. Females with oostegites and seminal receptacle. Telson narrows posteriorly in two abrupt steps with furcal lobes at each narrowing.
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| Top: Pygocephalus brymboensis holotype BB0366 (NMW) from the Bashkirian (Brymbo, Denbighshire Coalfield) of North Wales (part and counterpart). Bottom: Inferred anatomy. Abbreviations: Ant1, remnants of first antenna; Ant2, distal flagelliform part of 2nd antenna; B, branchial region of carapace; Ba, basis; Bc, brancial chamber; Ca, carpus; Co, coxa; cvg, cervical groove; D, remains of the digestive tract; Gntbs, gnathobase; Gs, gastric spine; H, hepatic region of the carapace; Im, ischiomerus; Mxpd, remnants of maxipilleds; Pr, propodus; Prpd, pereopod; R, rostrum; S, scaphocerite, Tel, telson; TelL, telson lobe; TelS, telson spine; U, uropod; 1–5, antennal segments; VII–XII, thoracic sternites. Dashed line = inferred reconstruction of carapace margin. Scale bar = 10 mm. Original image reproduced with permission of Peter Appleton. |
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| Artistic reconstruction of Pygocephalus brymboensis (credit: William Norris). Scale bar = 5 mm. |
Pygocephalus brymboensis sp. nov.
Derivation of name. From Brymbo, the Welsh village in which the host deposit resides.
Tim Astrop. 2026. A New pygocephalomorph Crustacean from the Brymbo Fossil Forest (Moscovian), North Wales, UK and A Reassessment of the Genus Pygocephalus. Journal of Systematic Palaeontology. 24(2); 2699904. DOI: doi.org/10.1080/14772019.2026.2699904 [03 Aug 2026]
