Squamates are represented by viviparous, ovoviviparous, and oviparous species. He made ovoviviparous fire salamanders become viviparous, and viviparous alpine salamanders become ovoviviparous. Aquarists commonly refer to ovoviviparous and viviparous fish as livebearers. Aquarists commonly refer to ovoviviparous and viviparous fish as "livebearers". Development is usually oviparous (egg-laying) but can be ovoviviparous, or viviparous. Chameleons are mostly oviparous, with some being ovoviviparous. Scorpions, however, are either ovoviviparous or viviparous, depending on species, and bear live young. Velvet worms are found in egg-laying (oviparous), egg-live-bearing (ovoviviparous) and live-bearing (viviparous) forms. Development is usually live birth (ovoviviparous species) but can be through eggs (oviparous). Familiar examples of ovoviviparous fish include guppies, angel sharks, and coelacanths. Other amphibians, but not caecilians, are ovoviviparous. "Potamopyrgus antipodarum" is ovoviviparous and parthenogenic. Saw sharks are ovoviviparous meaning eggs hatch inside the mother. He gave accurate descriptions of the ovoviviparous embryological development of the hound shark "Mustelus mustelus". The shortfin mako shark is a yolk-sac ovoviviparous shark, giving birth to live young.