Astraspis ('star shield') is an extinct genus of primitive jawless fish. It has a small cameo in the 2003 BBC series Sea Monsters, a spin-off to the famed Walking With Dinosaurs, where Nigel Marven uses a dead Astraspis as bait to attract a sea scorpion. The creature is identified in the series' novelisation. The conservation status of a species is an indicator of the likelihood of that species continuing to survive. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... Scientific classification or biological classification is how biologists group and categorize extinct and living species of organisms (as opposed to folk taxonomy). ... Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Typical Classes Subphylum Urochordata - Tunicates Ascidiacea Thaliacea Larvacea Subphylum Cephalochordata - Lancelets Subphylum Myxini - Hagfishes Subphylum Vertebrata - Vertebrates Petromyzontida - Lampreys Placodermi (extinct) Chondrichthyes - Cartilaginous fishes Acanthodii (extinct) Actinopterygii - Ray-finned fishes Actinistia - Coelacanths Dipnoi - Lungfishes Amphibia - Amphibians Reptilia - Reptiles Aves - Birds Mammalia - Mammals Chordates (phylum Chordata) include the vertebrates, together with... Pteraspidomorphi is an extinct taxon of early jawless fish. ... The Guppy, also known as guppie (Poecilia reticulata) is one of the most popular freshwater aquarium fish species in the world. ... 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... The British Broadcasting Corporation (BBC, sometimes also known as the Beeb or Auntie) is the largest broadcasting corporation in the world, founded in 1922. ... Sea Monsters was a BBC television program which used computer-generated imagery to show past life in Earths seas. ... Walking with Dinosaurs is a 1999 six-part television series produced by the BBC, narrated by Kenneth Branagh. ... Orders many, all extinct The eurypterids were the largest known arthropods that ever lived. ...