Deep Springs Road Phacopid

This looks similar to a large female cephalon I found at Montour Fossil Pit (only this one's probably a male).

19 minutes ago, Bringing Fossils to Life said:

This looks similar to a large female cephalon I found at Montour Fossil Pit (only this one's probably a male).

We do not have any evidence of sexual dimorphism in trilobites.

Why do you say it's a male?

Tim, that's a really nice one.

It's definitely a male, as I named him Ozzymandius. 

Over the years there have been many papers on this subject by numerous noteworthy authors. There is a smattering of 'evidence' that points to the possibility of dimorphism in trilobites.....unfortunately there has been nothing definitive published yet to substantiate any of those claims.

Alberti, G.K.B. 1971. Sexual-Dimorphismus (?) bei Cheirurus (Crotalocephalus) cf. pauper Barrande 1852 (Trilobita, Devon). [Sexual Dimorphism (?) of Cheirurus (Crotalocephalus) cf. pauper Barrande 1852 (Trilobita, Devonian).] Paläontologische Zeitschrift, 45(3/4):167-172

Cederström, P., Ahlberg, P., Nilsson, C.H., Ahlgren, J., Eriksson, M.E. 2011. Moulting, Ontogeny and Sexual Dimorphism in the Cambrian Ptychopariid Trilobite Strenuaeva inflata from the Northern Swedish Caledonides. Palaeontology, 54(3):685-703

Clarkson, E.N.K. 1968. Dimorphism of the eye in Weberides shunnerensis. pp.185-195, In: Westermann, G.E.G. (ed.) Sexual Dimorphism in Fossil Metazoa and Taxonomic Implications. E. Schweizerbart'sche Verlagsbuchhandlung. 215 pp.

Corbacho, J., Calzada, S. 2014. Posible dimorfismo sexual en Trilobites del Ordovícico inferior. [Possible sexual dimorphism in Trilobites of the Lower Ordovician.] Batalleria, 21:22-26

Goo, C.E. 2021. Trilobites Sexual Dimorphism - The Discover of the Oldest Known Morphological Difference between Male and Female Dating Back to Cambrian. Smash Words Edition

Gozalo, R.R., Liñán, E. 1998. Two cases of dimorphism in Paradoxides species (Trilobita) from Spain. Lund Publications in Geology, 142:8-9

Gozalo, R., Liñán, E. 1998. El problema del dimorfismo en trilobites. Nuevos datos del Cámbrico medio de España. [The problem of dimorphism in trilobites. New data on the middle Cambrian of Spain.] pp. 93-94 In: XIV Jornadas de Paleontología, Tenerife 9-11 de Octubre de 1998

Gozalo, R., Liñán, E., Dies, M.E. 2001. Poster: Dimorphism in the evolutionary trends of paradoxidids from Murero (Spain). in: International Trilobite Conference 3 (Oxford, U.K., 2001) Abstracts

Gozalo, R., Liñán, E., Dies, M.E. 2003. Intraspecific Dimorphism in an Evolutionary Series of Paradoxidids from the Middle Cambrian of Murero, Spain. Special Papers in Palaeontology, 70:141-156

Hu, C.H. 1963. The dimorphism and ontogeny of Norwoodella halli Resser. Transactions and Proceedings of the Palaeontological Society of Japan, new series, 52:129-132

Hu, C.H. 1964. Ontogeny and Dimorphism of the Trilobite Peltura scarabaeoides (Wahlenberg) from the Upper Cambrian of Norway. Journal of the Palaeontological Society of India, 5-9:39-44

Hu, C.H. 1964. The Ontogeny and Dimorphism of Welleraspis lata Howell (Trilobita). Journal of Paleontology, 38(1):95-97

Hu, C.H. 1968. Ontogeny and sexual dimorphism of Lower Paleozoic Trilobita. PhD Thesis, University of Cincinnati, 446 pp.

Hu, C.H. 1968. Notes on the ontogeny and sexual dimorphism of Upper Cambrian trilobites of the Welleraspis Faunule from Pennsylvania. Journal of Nanyang University, 2:321-357

Hu, C.H. 1969. Ontogeny and sexual dimorphism of three Upper Cambrian trilobites. Journal of Nanyang University, 3:438-462

Hu, C.H. 1970. Ontogenies and sexual dimorphisms of two upper Cambrian trilobites. Proceedings of the Geological Society of China, 13:143-155

Hu, C.H. 1971. Ontogeny and Sexual Dimorphism of Lower Paleozoic Trilobita. Palaeontographica Americana, 7(44):1-155

Hughes, N.C., Fortey, R.A. 1995. Sexual Dimorphism in Trilobites, with an Ordovician Case Study. pp. 419-421. In: Cooper, J.D.; Droser, M.L.; Finney, S.C. (eds.) Ordovician Odyssey: Short Papers for the Seventh International Symposium on the Ordovician System. The Pacific Section Society for Sedimentary Geology (SEPM) Pacific Section, Book 77

Lei, Q. 2015. New ontogenetic information on Duyunaspis duyunensis Zhang & Qian in Zhou et al., 1977 (Trilobita, Corynexochida) from the Cambrian and its possible sexual dimorphism. Alcheringa, 40(1):12-23

Liñán, E., Gámez-Vintaned, J.A., Gozalo, R., Dies Álvarez, M.E., Chirivella Martorell, J.B., Esteve, J. 2009. Las especies de "Paradoxides" del yacimiento cámbrico de Murero y el hallazgo de dimorfismo sexual en los trilobites. [The species of "Paradoxides" of the Cambrian Murero site and the finding of sexual dimorphism in the trilobites.] Naturaleza Aragonesa 23:4-11

Pillet, J. 1992. Variabilité intraspécifique et dimorphisme sexuel chez quelques trilobites. [Intraspecific variability and sexual dimorphism in some trilobites.] Bulletin de la Société des Sciences Naturelles de l'Ouest de la France, 14(2):53-64

Sellwood, E.B., Burton, C.J. 1969. Possible dimorphism in certain Devonian phacopids (Trilobita). In: G.E.G. Westermann [ed.], Sexual dimorphism in fossil Metazoa and taxonomic implications. International Union Geological Science. A, 1:196-200

Sinclair, C.R., Gibb, S., Sperling, F. 2017. Sexual dimorphism in Moroccan trilobites: evidence from morphological clustering and phylogenetic bracketing. p. 36 In: Pärnaste, H. 2017. Abstracts: 6th International Conference on Trilobites and their Relatives, Tallinn, Estonia, 7-10 July 2017.

Tuckey, M.E. 1975. Sexual Dimorphism in the Devonian Trilobite Phacops rana. MSc Thesis, Michigan State University. Dept. of Geology. 90 pp.

Vaccari, N.E., Waisfeld, B.G., LeGrand, S. 2003. Una nueva especie de Parabolinella Bröger en el Tremadociano inferior de Bolivia y Argentina; un posible ejemplo de dimorfismo sexual en trilobites. [New specimen of Parabolinella Bröger from the lower Tremadocian of Bolivia and Argentina; a possible example of sexual dimorphism in trilobites.] Ameghiniana, 40(4,Suppl.):96

Thanks Scott!  What a reference list!

Don

I interpreted this wrong; trilobite eggs were held in front of the glabella or inside the cheeks, not inside the glabella. This article can help: https://www.amnh.org/research/paleontology/collections/fossil-invertebrate-collection/trilobite-website/the-trilobite-files/sexual-dimorphism-trilobite-eggs