Adult and juvenile fangtooths are so morphologically dissimilar that they were believed to be separate species in the 1800s. In addition to differences in their physical appearance, they also consume different prey. Juveniles begin to look like adults after reaching approximately 8 cm in length, and they typically grow to 17 cm in length, with a maximum recorded length of 18 cm, although other sources report a maximum length of 16 cm. Length at reproductive maturity has been reported to be approximately 13 cm. Individuals are found at different depths during different stages of their life cycle, with larvae occuring closer to the surface and adults occuring at depths of up to 5000 m. However, overlap of habitats with respect to depth does occur at various stages of maturity.
Anoplogaster cornuta is found at different depths during various stages of its life cycle and occupies a wide range of temperatures throughout its life. Juveniles may be captured at relatively shallow depths of 45 m in the tropics, where temperatures can rise above 15ºC. This suggests that while they are a stenothermal species with adults often captured at depths with temperatures between 4ºC and 6ºC, adults may be able for survival across a much broader thermal range.