|Spotted gar (Lepisosteus oculatus)|
Brian Gratwicke CC BY 2.5 (Wikimedia Commons)
|Alligator gar (Atractosteus spatula) Moon Lake, Mississippi. March 1910, Photographer D. Franklin, |
American Museum of Natural History (public domain)
What we now know is that teleosts are characterized by the Teleost Gene Duplication (TGD). This event was followed by rapid sequence evolution that may explain their success as a group. It can, however, make it difficult to identify orthologs to tetrapod genes and frustrate interpretation of data obtained in zebra fish (Danio rerio). To provide a bridge, Braasch et al. have sequenced and have just published the genome of the spotted gar (open access).
To my knowledge no living species of the gar family is viviparous.