Rhyacotriton is more closely related to Plethodontidae and Amphiumidae.
Dicamptodon is closer to
Ambystoma. Those who look only at living species tend to combine them in a single family. However, there are fossil species of
Dicamptodon, and genera related to
Dicamptodon, leading others to maintain separate but related families.
Rhyacosiredon,
Siredon, and
Bathysiredon are synonyms of
Ambystoma, and more specifically
Heterotriton. That is, they are neotenic members of the tiger salamander group, with
Siredon and
Bathysiredon being applied to lake-dwelling neotenes and
Rhyacosiredon being applied to the stream-dwelling neotenes.
The most up to date source for Amphibian taxonomy, including synonym lists for every species and higher group, is Amphibian Species of the World [online edition]. It has errors, omissions, and items which are not universally agreed upon, but it is nonetheless the most current, correct, and useful source on the subject:
Amphibian Species of the World
Under "Caudata" you will find a long discussion with all the significant references you need. Most or all can be found online at no charge. If you start with the most recent paper, generally it will list all the other recent useful papers in the references.
Edit - yes, the symbol that resembles a cross or "dagger" usually is used for an extinct taxon, but you should always check the source to be sure of what THEY intend the symbols to mean.