Agnatha
Foraicme na n-iasc éigiallach san bhfíleam Chordata, fofhíleam Vertebrata, is ea Agnatha (Sean-Ghréigis ἀ-yvάθος, ἀ-gnathos, "gan ghiall"), ina bhfuil na speicis seo a leanas; na cyclostomes (atá beo faoi láthair) agus na conodonts agus na n-ostracoderms (atá díofa). Is comhghrúpa é do gach veirteabrach le gialla, ar a dtugtar gnathostomes.[1]
 loimpre abhann  | |
| Tacsanomaíocht | |
|---|---|
| For-ríocht | Holozoa |
| Ríocht | Animalia |
| Fíleam | Chordata |
| Foraicme | Agnatha Cope, 1889 |
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Tacaíonn na sonraí móilíneacha is déanaí, ó rARN [2] agus ó mtADN [3] chomh maith le sonraí sutheolaíocha,[4] go láidir leis an hipitéis gur monaifíléiteach iad na héagabaigh bheo, na cyclostomes.[5]
Bhí na héagabaigh iontaise is sine le feiceáil sa Chaimbriach, agus tá dhá ghrúpa fós le maireachtáil inniu: na loimprí agus an cailleacha, ina bhfuil thart ar 120 speiceas san iomlán. Meastar gur baill den fhofhíleam Vertebrata iad éisc éisc, mar gur chaill siad veirteabraí ina dhiaidh sin; sular tuigeadh an t-imeacht seo ó shonraí móilíneacha [2][3][6] agus forbraíochta [7], chruthaigh Linnaeus an grúpa Craniata (agus úsáidtear uaireanta é mar thuairisceoir moirfeolaíoch) chun tagairt a dhéanamh do chailleacha móide veirteabraigh. Chomh maith le heaspa giall, an tréith is mó atá ag na héagabaigh ná easpa eití péireáilte; láithreacht nótacorda i larbhaí agus in aosaigh araon; agus seacht nó níos mó scoilteanna geolbhaigh phéireáilte sholasmhothálach (homalógach don fhaireog phinéalach i mamaigh). Níl goile inaitheanta nó aon géagán ag gach éagabach beo ná an chuid is mó dóibh ata díothaithate.
Tagairtí
cuir in eagar- ↑ Heimberg (2010-11-09). "microRNAs reveal the interrelationships of hagfish, lampreys, and gnathostomes and the nature of the ancestral vertebrate". Proceedings of the National Academy of Sciences 107 (45): 19379–19383. doi:. PMID 20959416.
- ↑ 2.0 2.1 "28S and 18S rDNA sequences support the monophyly of lampreys and hagfishes" (December 1998). Molecular Biology and Evolution 15 (12): 1706–18. doi:. PMID 9866205.
- ↑ 3.0 3.1 "Complete mitochondrial DNA of the hagfish, Eptatretus burgeri: the comparative analysis of mitochondrial DNA sequences strongly supports the cyclostome monophyly" (February 2002). Molecular Phylogenetics and Evolution 22 (2): 184–92. doi:. PMID 11820840.
- ↑ "Craniofacial development of hagfishes and the evolution of vertebrates" (January 2013). Nature 493 (7431): 175–80. doi:. PMID 23254938. Bibcode: 2013Natur.493..175O.
- ↑ "microRNAs revive old views about jawless vertebrate divergence and evolution" (November 2010). Proceedings of the National Academy of Sciences of the United States of America 107 (45): 19137–8. doi:. PMID 21041649. Bibcode: 2010PNAS..10719137J. “Although I was among the early supporters of vertebrate paraphyly, I am impressed by the evidence provided by Heimberg et al. and prepared to admit that cyclostomes are, in fact, monophyletic. The consequence is that they may tell us little, if anything, about the dawn of vertebrate evolution, except that the intuitions of 19th century zoologists were correct in assuming that these odd vertebrates (notably, hagfishes) are strongly degenerate and have lost many characters over time.”
- ↑ "Evidence from 18S ribosomal RNA sequences that lampreys and hagfishes form a natural group" (August 1992). Science 257 (5071): 787–9. doi:. PMID 1496398. Bibcode: 1992Sci...257..787S.
- ↑ "Identification of vertebra-like elements and their possible differentiation from sclerotomes in the hagfish" (June 2011). Nature Communications 2 (6): 373. doi:. PMID 21712821. Bibcode: 2011NatCo...2E.373O.