Genevievella Explained

Genevievella is a genus of trilobites with a short inverted egg-shaped outline, a wide headshield, small eyes, and long genal spines. The backrim of the headshield is inflated and overhangs the first of the 9 thorax segments. The 8th thorax segment from the front bears a backward directed spine that reaches beyond the back end of the exoskeleton. It has an almost oval tailshield with 5 pairs of pleural furrows. It lived during the Upper Cambrian in what are today Canada and the United States.^[1]

Distribution

• G. caelata is known from the Upper Cambrian of Australia (Mindyallan, Upper beds Member, Mungerbar Formation, Glenormiston, Queensland, 22.9° S, 138.8° E).^[2]
• G. simon, G. cuniculaena, G. raggedi and G. campbellina have been found in the Upper Cambrian of Canada (Dresbachian, Rabbitkettle Formation, Yukon, 62.7° N, 128.4° W).^[3]
• G. campbellina occurs in the Upper Cambrian of the United States (Merioneth: Warriorsmark, Huntingdon, Huntingdon; Warrior Formation, near Waddle, Centre County, all Pennsylvania, 40.8° N, 77.9° W)^[4]
• G. spinox has been excavated from the Upper Cambrian of the United States (Dresbachian, Coosella zone, Riley Formation, Central Texas, 30.3° N, 97.7° W)^[5]
• G. bigranulosa is present in the Upper Cambrian of China (Guzhangian, Glyptagnostus stolidotus trilobite zone and Paibian, Glyptagnostus reticulatus trilobite zone, both Huaqiao Formation, Hunan, 28.4° N, 109.5° E).^[6]

Notes and References

1. Book: Moore, R.C.. 1959. Arthropoda I - Arthropoda General Features, Proarthropoda, Euarthropoda General Features, Trilobitomorpha. Geological Society of America/University of Kansas Press. Treatise on Invertebrate Paleontology. Part O.. O301. Boulder, Colorado/Lawrence, Kansas. 0-8137-3015-5.
2. J.. Pojeta. J. . Gilbert-Tomlinson. J.H.. Shergold. 1977. Cambrian and Ordovician rostroconch molluscs from Northern Australia. Australian Bureau of Mineral Resources, Geology and Geophysics Bulletin. 171. 1–54. cited in Web site: Pete Wagner. Locality 50. G127*. Glenormiston. Fossilworks. 17 December 2021.
3. B.R.. Pratt. 1992. Trilobites of the Marjuman and Steptoean stages (Upper Cambrian), Rabbitkettle Formation, southern Mackenzie Mountains, northwest Canada. Palaeontographica Canadiana. 9. 1–109. cited in Web site: Shanan Peters. Section N - collection N-33. Fossilworks. 17 December 2021.
4. P.. Tasch. 1951. Fauna and paleoecology of the Upper Cambrian Warrior Formation of central Pennsylvania. Journal of Paleontology. 25. 3. 275–306. cited in Web site: Uta Merkel. Highway No. 322 near Waddle, Bed 11.12. Fossilworks. 17 December 2021.
5. J.J.. Sepkoski Jr.. 1998. Rates of speciation in the fossil record. Philosophical Transactions of the Royal Society of London B: Biological Sciences. 353. 1366. 315–326. 10.1098/rstb.1998.0212. 1692211. 11541734. cited in Web site: Mike Sommers. Central Texas, Riley Fm., Texas. Fossilworks. 17 December 2021.
6. S.. Peng. R.A.. Robison. 2000. Agnostid biostratigraphy across the Middle-Upper Cambrian boundary in Hunan, China. Journal of Paleontology Memoir. 53. cited in Web site: Austin Hendy. Paibi section, bed 37a. Fossilworks. 17 December 2021.