Reconstruction of Astraspis desiderata 。圖片來源：Philippe Janvier，採用  CC BY 3.0   授權。 Age Ordovician（Darriwilian-Hirnantian） 467-443 Ma Taxonomy Kingdom: Animalia Phylum: Chordata Class: Pteraspidomorphi Order: Astraspidiformes Family: Astraspididae Genus: Astraspis Species: Astraspis desiderata Morphological description Astraspis desiderata  is an Ordovician vertebrate whose head shield is composed of numerous small tesserae. These elements are tightly packed, forming a continuo

Reconstruction of Nuucichthys rhynchocephalus （圖片來源：Lerosey-Aubril R and Ortega-Hernández J，採用  CC BY 4.0  授權） Age Cambrian（Drumian） 504.5-500.5 Ma Taxonomy Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Genus: Nuucichthys Species: Nuucichthys rhynchocephalus Morphological description Nuucichthys rhynchocephalus  is a soft-bodied vertebrate with a torpedo-shaped body approximately four times longer than its maximum height, and bearing a ventral notch at mid-length.

Reconstruction of Haikouichthys ercaicunensis （圖片來源：Makergreen，採用  CC BY-SA 4.0  授權） Age Cambrian（"Stage 3"） 525-520 Ma Taxonomy Kingdom: Animalia Phylum: Chordata Superclass: Agnatha Order: Myllokunmingiida Family: Myllokunmingiidae Genus: Haikouichthys Species: Haikouichthys ercaicunensis Morphological description Haikouichthys ercaicunensis  is an early Cambrian jawless fish from the Chengjiang biota of Yunnan, China, dating to approximately 525 million years ago. It exhib