Hvirveldyr

Hvirveldyr
	Skelet af benfisk; Beryx decadactylus
Videnskabelig klassifikation
Rige	Animalia (Dyr)
Underrige	Deuterostomia
Række	Chordata (Chordater)
Underrække	Vertebrata (Hvirveldyr)
Klasser
	Agnatha; Chondrichthyes; Osteichthyes; Amphibia; Reptilia; Aves; Mammalia;
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Hvirveldyr (latin: vertebrata) tilhører Chordaterne. Hvirveldyrene har en rygsøjle, et akseskelet af brusk, ben eller forbenet brusk.

De fleste hvirveldyr har udviklet to par lemmer samt en hjernekasse.

Nogle hvirveldyr deler neurale kredsløb for mange forskellige typer af social adfærd. Det er undersøgt for frøer (krybdyr), fisk og mennesker. ^[1]

Ifølge Tree of Life web projekt ser en delmængde af hvirveldyrs hierarki sådan ud (2003)^[2]:

Vertebrata (Hvirveldyr)
- Agnatha (Kæbeløse hvirveldyr)
  - Cyclostomata (Rundmundede fisk:,slimål, lampret.(Se evt. fisk)
  - Ostracoderms (uddød)
- Gnathostomata (Kæbebærende hvirveldyr)
  - Placodermi (Panserhajer, uddød)
  - Chondrichthyes (Bruskfisk, se evt. også fisk)
    - Elasmobranchii (tværmunde) (haj, rødhaj, sildehaj, den hvide haj, sømrokke, rokke, elrokke...)
    - Subterbranchialia (havmus m.fl.)
  - Teleostomi
    - Acanthodii (uddød)
    - Osteichthyes (Benfisk)
      - Actinopterygii (Strålefinnede fisk (se evt. også fisk): (torsk, søhest, hvilling, ål, søheste...)
      - Sarcopterygii (Kødfinnefisk (Se evt. også fisk))
        Crossopterygii (Kvastfinnefisk, f.eks. Coelacanth
        
        Dipnoi (Lungefisk)
        
        Tetrapoder (Krybdyr, Dinosaurer, Pattedyr, Fugle, Padder...)

Kilder/referencer

^ University of Texas at Austin (2012, May 31). Vertebrates share ancient neural circuitry for complex social behaviors, biologists find. ScienceDaily Citat: "...Humans, fish and frogs share neural circuits responsible for a diversity of social behavior, from flashy mating displays to aggression and monogamy, that have existed for more than 450 million years, biologists at The University of Texas at Austin found..."In these key brain regions, we found remarkable conservation of gene activity across species," said Hofmann..."
^ Tree of Life Web Project: Vertebrata, Animals with backbones

2004-05-07, Sciencedaily: Surprising 'Ultra-conserved' Regions Discovered In Human Genome Citat: "..."As far as we can tell, most of these ultra-conserved elements showed up during the evolution of vertebrates, perhaps during the period when land animals emerged, or a bit earlier. But their early evolutionary history is still mysterious," Haussler said..."
2004-05-06, Sciencedaily: Scripps Scientists Look Deep Inside Sharks And Their High-performance Swimming System Citat: "..."Sharks and bony fishes have been separated for over 400 million years and yet we see one group of sharks and one group of bony fish that share a remarkable host of similarities in body form and function," said Donley..."
BBCNews, 9 May, 2003, Animals 'are moral beings' Citat: "..."But the weight of scientific opinion is that it's certainly right to give the benefit of the doubt to all vertebrates."..."
Markku Savela: Life (Omfattende).
Fishbase search ( 27,315 Species, 76,410 Synonyms, 137,515 Common names, 34,720 Pictures, 29,525 References, 930 Collaborators, 6.2 million Hits/month) (3/2003).

Nielsen, Claus: "Nyt om hvirveldyrenes oprindelse – Vender vi ryggen fremad?", Naturens Verden, nr. 6/1999, vol. 82, side 33-40.