They differ from the cryptobranchids by having fused prearticular bones in the lower jaw, and by using internal fertilisation.
ðeɪ dˈɪfɚ fɹʌmðə kɹˈɪptəbɹˌæntʃɪdz baɪ hˌævɪŋ fjˈuːzd pɹɪɹtˈɪkjʊlɚ bˈoʊnz ɪnðə lˈoʊɚ dʒˈɔː, ænd baɪ jˈuːzɪŋ ɪntˈɜːnəl fˌɜːɾɪləzˈeɪʃən.