Egg case (Chondrichthyes): Difference between revisions

Bullhead shark egg cases are shaped like an [[Auger (drill)|auger]], with two spiral flanges. This allows the egg cases to become wedged in the crevices of rocky sea floors, where the eggs are protected from predators; however, some bullhead sharks deposit their eggs on sponges or seaweed.<ref>{{Cite web|url=https://www.floridamuseum.ufl.edu/fish/discover/species-profiles/heterodontus-francisci/|title=Heterodontus francisci|last=Buch|first=Robert|website=Florida Museum}}</ref><ref name=":2">{{Cite journal|last=Compagno|first=Leonard|date=2002|title=Sharks of the World|journal=FAO Species Catalogue for Fishery Purposes|volume= 2|pages=31–50}}</ref> Hatchlings are considered large for sharks, reaching over 14&nbsp;cm in length by the time they leave the egg case.<ref name=":2" /> Bullhead shark eggs typically hatch after 7 to 12 months, depending on the species.<ref name=":2" /> The Femalefemale [[Japanese bullhead shark]] has been known to deposit their eggs in one location along with other females, called a "nest".<ref name=":2" /> The egg case of the [[Mexican hornshark]] features a tendril and more rigid flanges, suggesting that egg case design of this species is evolving towards anchoring with tendrils and away from wedging into crevices.<ref name=":2" /> As a member of the order Heterodontiformes, the [[whitespotted bullhead shark]]s<nowiki/> is thought to be oviparous, but egg cases have never been observed.<ref name=":2" />

Big skate egg cases are larger than most other skate egg cases; typically ranging from 210 to 280&nbsp;mm in length and 110 to 180&nbsp;mm in width.<ref name="Ebert2"/><ref name="Zipcodezoo2Zipcodezoo">{{cite web|url=http://zipcodezoo.com/Animals/R/Raja_binoculata/|title=''Raja binoculata'' (Big Skate, Big Skate)|website=Zipcodezoo.com|archive-url=https://web.archive.org/web/20080908085320/http://zipcodezoo.com/Animals/R/Raja_binoculata|archive-date=8 September 2008|url-status=dead}}</ref> Big skates egg cases are approximately 15% of the overall length of the female skate.<ref name="Ebert2" /> The egg case is very smooth and lacks external fibrous material.<ref name="Ebert2" /> This egg case can be easily identified from all others in that it is the only one to have a steep ridge; giving the case a convex shape.<ref name="Ebert2" /> The keel on the egg case is considered very broad; representing 30–33% of the width of the egg case.<ref name="Ebert2" />