Plutonides Explained

Plutonides is a genus of Middle Cambrian trilobite in the family Paradoxididae with species Plutonides sedgwickii and possibly Plutonides? illingi. Several other species and subspecies were at times placed in Plutonides but have subsequently been moved to other genera.

In terms of the Scandinavian Middle Cambrian sequence the genus ranges from the Baltoparadoxides oelandicus Biosuperzone (B. pinus Biosubzone) at the type locality for P. sedwickii on Trwyncynddeiriog headland located 1.3km (00.8miles) south-southwest of St David’s Cathedral and 500m (1,600feet) east of Porth Clais Harbour - Pen-y-Cyfrwy Member, Newgale Formation,^[1] and possibly to middle part of the Mawddachites hicksii Biozone on the Penpleidiau (eastern) Headland of Caerfai Bay south of St David’s in southwest Wales, where P? illingi occurs [Locs. TC-1 & CF-1 of Rees ''et al.'']^[1]

Type

Plutonia sedgwickii is the type species for the genus^[2] and was first described in 1871 as "Plutonia" sedgwickii. However the genus name "Plutonia" had already been used for the Vitrinidae snail genus Plutonia by Morelet in Stabile (1864),^[3] and so the new genus Plutonides was coined by Hicks (1895).^[4] The species Lectotype is SM A1086, an internal mould of cranidium,.^{[5] [6] [1] [7]}

Species

Paradoxides cf. sedgwickii, described by Smith and White (1963) from the Baltoparadoxides pinus Biosubzone in the upper part of the Purley Shale Formation of Warwickshire, central England^[7] was redescribed by Rushton (1966, p. 42, pl. 6, figs. 1-10) ^[8] as ‘Paradoxides’ sedgwickii porphyrus. The subspecies has broader palpebral lobes and finer surface granulation than observed in P. sedgwickii sedgwickii.

Vanĕk et al. (1999) ^[9] described cranidia from the Middle Cambrian of Skrije - Týřovice area in the Czech Republic as Plutonides hicksi, although the specimens illustrated are of a different species to that from Wales. Fletcher (2007) however, has also since established the new subgenus, Paradoxides (Mawddachites), to include P. hicksii as type species.^[10] Alvarez et al. (2010) raised Mawddachites to a full genus.^{[11] [12]}

Notes and References

1. Rees . A. J. . Thomas . A. T. . Lewis . M. . Hughes . H. E. . Turner . P . 2014 . The Cambrian of SW Wales: Towards a United Avalonian Stratigraphy . Geological Society, London, Memoirs . 42 . 1–31. 10.1144/M42.1 . 130386389 .
2. Harkness . R. . Hicks . H . 1871 . On the ancient rocks of the St David's Promontory, South Wales, and their fossil contents: with descriptions of the new species, by H. Hicks, Esq. . Quarterly Journal of the Geological Society of London . 27 . 1–2 . 384–404. 10.1144/GSL.JGS.1871.027.01-02.46 . 128467392 .
3. Stabile, J., 1864. Mollusques terrestres vivants du Piemont. Atti della Societd italiana di Scienze naturali di Milano, 7: 1-141.
4. Hicks . H. . 1895 . On the genus Plutonides (non Plutonia) from the Cambrian rocks of St. David's. . Geological Magazine . Decade 4 . 2 . 230–231. 10.1017/S0016756800121193 . 1895GeoM....2..230H . 130849465 .
5. Morris . S. F. . 1988 . A Review of British Trilobites, Including a Synoptic Revision of Salter's Monograph . Monograph of the Palaeontographical Society, London . 140 . 374 . 1–316.
6. Lake . P. . 1935 . A Monograph of the British Cambrian Trilobites . Monograph of the Palaeontographical Society, London . 197–224, pls. 26–31, pl. 31, fig. 9. 88. 10.1080/02693445.1935.12035634 .
7. Smith . J.D.D. . White . D.E. . 1963 . Cambrian trilobites from the Purley Shales of Warwickshire . Palaeontology . 6 . 397–407, pl. 58, fig. 9.
8. Rushton1966 . A. W. A. . 1966 . The Cambrian Trilobites from the Purley Shales of Warwickshire. . Monograph of the Palaeontographical Society, London . 120 . 511. 1 . 10.1080/25761900.2022.12131699 . 1966MPalS.120....1R . 251144643 .
9. Vanĕk . J . Valiček . J. . Vocáč . V. . 1999 . Plutonides hicksi (Salter) from the Middle Cambrian of Skrije - Týřovice Area (Czech Republic) . Palaeontologica Bohemiae . 6 . 36–38 . 2015-01-04.
10. Fletcher . T. P. . 2007 . Correlating the zones of "Paradoxides hicksii" and "Paradoxides davidis" in Cambrian Series 3 . Memoirs of the Association of Australasian Palaeontologists . 33 . 35–56.
11. Dies Alvares . M. E. . Rushton . A. W. A. . Gozalao . R.. Pillola . G. L. . Liñan . E. . Ahlberg . P. . 2010 . Paradoxides brachyrhachis Linnarsson, 1883 versus Paradoxides mediterraneus Pompeckj, 1901: a problematic determination. . GFF . 132 . 2, June . 95–104 . 10.1080/11035897.2010.481363 . 2010GFF...132...95D . 129620469 . 1103-5897.
12. Web site: Trilobiti - Barrandien. Plutonides hicksi (Salter, 1864). 2015-01-04.