It's Tuesday, it's trilobites, it's #TrilobiteTuesday at #Fossilympics20, it must be time for the #Triarthlon!

Whether burrowing, crawling, or swimming is your strength, as long as you've got three lobes you're in the medal hunt.

Agnostus pisiformis, representing Baltica, is our first #Triarthlon challenger. As Mats Eriksson & Esben Horn explain, this is a Cambrian pea-shaped enigma: https://www.sciencedirect.com/science/article/abs/pii/S0012825217301903.

Will it win a #Fossilympics20 medal? Can we say we're agnostic?

The reconstruction of Agnostus pisiformis, shown above, was made by Esben Horn and the @10tonsDK team in 2016:

https://twitter.com/10tonsdk/status/793369925490466816?lang=en

#TrilobiteTuesday #Triarthlon #Fossilympics20

Our second #Triarthlon entrant at #Fossilympics20 is the pride of the Black Country, and Avalonia. It's the Dudley Bug, Calymene blumenbachii!

You can see it in its natural habitat at the Black Country UNESCO Geopark, or admire it in the Lapworth Museum: https://www.expressandstar.com/entertainment/2016/06/22/dudley-bug-in-pride-of-place-at-museum/.

But as Black Country lad Derek Siveter (then of @GeologyHull, now of @morethanadodo) explains in this #Palaeontology article, the Dudley Bug typically resides in Paris: https://www.palass.org/sites/default/files/media/publications/palaeontology/volume_28/vol28_part4_pp783-792.pdf!

#Triarthlon #Fossilympics20 #TrilobiteTuesday

Our third triarthlete is Olenellus thompsoni, from the Cambrian of Laurentia: https://www.si.edu/object/nmnhpaleobiology_3586539.

The specimen figured below is from Pennsylvania, and resides in the Smithsonian.

#Triarthlon #Fossilympics20

New research on specimens in the Smithsonian (Bicknell & Pates 2020: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7003707/) indicates that Olenellus thompsoni recovered well from injury, which bodes well for its chances in the #Fossilympics20 #Triarthlon.

#TrilobiteTuesday

Our fourth and final competitor in the #Fossilympics20 #Triarthlon is Paradoxides davidis, from the Cambrian of south-west Wales (and south-east Newfoundland).

If you've not read John Salter's (1863) paper on its discovery, you really must: https://jgs.lyellcollection.org/content/jgsleg/19/1-2/274.full.pdf!

Paradoxides was crucial to the recognition that the present-day Atlantic Ocean had a precursor, and of the microcontinent #Avalonia: https://www.amnh.org/research/paleontology/collections/fossil-invertebrate-collection/trilobite-website/the-trilobite-files/the-paradoxides-paradox-plate-tectonics-and-continental-drift2.

It is also Wales' national fossil: https://museum.wales/articles/2007-07-26/International-fame-for-Waless-National-Fossil/!

How anyone's going to choose between these four fabulous fossils, we couldn't say, but throw your fossil facts our way on #TrilobiteTuesday and see if you can swing the #Triarthlon vote!

#Fossilympics20

As @FossilRod illustrates, Paradoxides davidis occurs splendidly in Newfoundland as well as Wales: https://twitter.com/FossilRod/status/1293175432720809984.

But which way will you vote in the #Fossilympics20 #Triarthlon this #TrilobiteTuesday?

And rather neatly, you can find one of our other #Triarthlon competitors on the other side of Newfoundland, indicating that western edge of the province is Laurentian whilst the eastern side is Avalonian: https://twitter.com/geoillogicalguy/status/902598494191570945