#engrailed

293 Knee-Monix

Trilobite - Calymene This trilobite staring right at you with a cheeky smile on its face is around 425 million years old, from the Silurian Period. Trilobites of this species (Calymene) are frequently found inrolled (curled up), much the same as many modern arthropods such as woodlice. It has been touted as a possible defence mechanism. The ability to curl up is linked to a particular shape of segment (which the main body of the middle of the trilobite is made of) and is not present in all trilobites. This has led to research on modern arthropods, and the identification of the ‘engrailed’ gene, linked to the ability of arthropods to curl up. Did trilobites who could curl up have this gene? We will never know for sure, but it is a distinct possibility. Sedg Image Credit (non-commercial): Black Country Museum (https://flic.kr/p/7FUVj3) References, further reading: http://www.plosone.org/article/info%3Adoi/10.1371/journal.pone.0052623#pone-0052623-g012 http://en.wikipedia.org/wiki/Calymene http://en.wikipedia.org/wiki/Phacopida

292 Engrailed

Ectropis bistortata.