Blastoids or fossil extinct echinoderms: Pentremites pyriformis 1, Orophocrinus orbignyanus 2, Pentremites species 3, Astrocrinus cruciatus 4, Orophocrinus stelliformis 5, Phaenoschisma acutum 6, Nucleocrinus species 7, Nucleocrinus verneuili 8, Codaster

Blastoids or fossil extinct echinoderms: Pentremites pyriformis 1, Orophocrinus orbignyanus 2, Pentremites species 3, Astrocrinus cruciatus 4, Orophocrinus stelliformis 5, Phaenoschisma acutum 6, Nucleocrinus species 7, Nucleocrinus verneuili 8, Codaster acutus 9, Eleutherocrinus cassedayi 10, Asteroblastus stellatus 11, and Asteroblastus volborthi 12. Chromolithograph by Adolf Glitsch from an illustration by Ernst Haeckel from Art Forms in Nature, Kunstformen der Natur, Liepzig, Germany, 1904. . (Photo by: Florilegius/Universal Images Group via Getty Images)