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The egg case genera Palaeoxyris and Fayolia, which are thought to have been produced by hybodonts and xenacanths respectively, two groups of extinct shark-like cartilaginous fish more closely related to modern sharks and rays than to chimaeras, resemble those of bulldog sharks in having a spiral collarettes running around them.
One of the few sharks to exhibit parental care, female horn sharks in the wild pick up their eggs in their mouths and wedge them into crevices. [3] However, in captivity the eggs are simply dropped on the bottom and may later be cannibalized. [2] The eggs hatch in 6–10 months; at emergence the young measure 15–17 cm (5.9–6.7 in) long. [1]
Bullhead shark egg cases are shaped like an 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.
After an unknown gestation period, the female attaches an unknown number of spiral-shaped egg cases to rocks on the sea floor. The length of the incubation period of these egg cases is also unknown. Not much about the feeding habits of the Mexican hornshark is known, but it most likely feeds on shelled invertebrates.
The spiral valve is a coiled organ, it increases surface area so that nutrients can be absorbed. [11] ... Depiction of shark anatomy including eggs, pups, and the ...
The egg case of the crested bullhead shark has distinctive, long tendrils at one end. Crested bullhead sharks are oviparous with a possibly annual reproductive cycle. Females produce 10–16 eggs per year during late winter in July and August, though Michael (1993) noted that egg-laying may continue year-round. [1]
Early Jurassic estuarine ecosystem, with Palaeoxyris egg cases attached via tendril to Neocalamites, with hybodonts in the background. Palaeoxyris is a morphogenus of eggs cases, widely thought to have been produced by hybodonts, with a predominant occurrence in ancient freshwater environments. They comprise a beak, a body and a pedicle.
The smooth, cream-colored egg cases measure 12 cm (4.7 in) long, and have long, spiral tendrils at the corners that allow them to be fastened to underwater objects. [1] [9] Newly hatched sharks measure 16 cm (6.3 in) long; males and females mature sexually at 60 cm (24 in) and 80 cm (31 in) long respectively. [5]