This orifice is the spiraculum, which is lateral, on the left side of the body, in most tadpoles, but median, on the breast or belly, in those of the Discoglossidae and of some of the Engystomatidae.
Although toad-like it is not really related to the toads proper, but belongs to the family Discoglossidae, characterized by a circular, adherent tongue, teeth in the upper jaw and on the palate, short but distinct ribs on the anterior vertebrae, and convex-concave vertebrae.
The Discoglossidae are noteworthy for the presence of short ribs to some of the vertebrae, and in some other points also they approach the tailed batrachians; they may be safely regarded as, on the whole, the most generalized of known Ecaudata.
In the lower jaw of most of the Ecaudata the symphysial cartilages ossify separately from the dentary bones, forming the so-called mento-meckelian bones; but these symphysial bones, so distinct in the frog, are less so in the Hylidae and Bufonidae, almost indistinguishable in the Pelobatidae and Discoglossidae, whilst in the Aglossa they do not exist any more than in the other orders of batrachians.
The first would be characterized by the Caudata, which are almost confined to it (although a few species penetrate into the Indian and neotropical regions), the Discoglossidae, mostly Europaeo-Asiatic, but one genus in California, and the numerous Pelobatidae; the second by the presence of Apoda, the prevalence of firmisternal Ecaudata and the absence of Hylidae; the third by the presence of Apoda, the prevalence of arciferous Ecaudata and the scarcity of Ranidae, the fourth by the prevalence of arciferous Ecaudata and the absence of Ranidae, as well as b y the absence of either Caudata or Apoda.