Irolita is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of softnose skates, family Rajidae, commonly known as the round skates. There are two species, both endemic to Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

, found over soft bottoms on the outer continental shelves and upper continental slopes, at depths of 50-200 m for the southern round skate and 142-209 m for the western round skate. The distributions of the two species do not overlap.

Both species are unique amongst Australian skates in having a smooth, almost circular heart-shaped pectoral fin disc. The head is short, with a small fleshy process at the tip of the snout

Snout

The snout, or muzzle, is the protruding portion of an animal's face, consisting of its nose, mouth, and jaw.-Terminology:The term "muzzle", used as a noun, can be ambiguous...

 and large spiracle

Spiracle

Spiracles are openings on the surface of some animals that usually lead to respiratory systems.-Vertebrates:The spiracle is a small hole behind each eye that opens to the mouth in some fishes. In the primitive jawless fish the first gill opening immediately behind the mouth is essentially similar...

s behind the eye

Eye

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

s. The nasal flaps are merged into a well-developed, bilobed nasal curtain forward of the mouth

Mouth

The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

. The jaw

Jaw

The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term jaws is also broadly applied to the whole of the structures constituting the vault of the mouth and serving to open and close it and is part of the body plan of...

s are slightly arched with the upper teeth exposed. The teeth are sexually dimorphic; those of adult males are spear-shaped with long, sharp cusps, while those of females and juveniles are plate-like with short posterior cusps. The pelvic fins are deeply incised, with the anterior lobe moderately long and slender and the posterior lobe broadly rounded. The tail is narrow, tapering gradually to a very slender tip and bearing two small dorsal fin

Dorsal fin

A dorsal fin is a fin located on the backs of various unrelated marine and freshwater vertebrates, including most fishes, marine mammals , and the ichthyosaurs...

s near the end. The caudal fin is reduced to minute lobes. Males have alar thorns near the pectoral fin tips and the tail is covered with irregular rows of small recurved thorns.

Species

• Southern round skate, Irolita waitii (McCulloch
  Alan Riverstone McCulloch
  Alan Riverstone McCulloch was a prominent Australian ichthyologist.McCulloch was born in Sydney, and began his scientific career at the age of 13 as an unpaid assistant to Edgar Ravenswood Waite in the Australian Museum there; Waite encouraged McCulloch to study zoology...
  
  , 1911) This species occurs along the southern coast of Australia, from Port Lincoln, South Australia
  Port Lincoln, South Australia
  - Transport :Port Lincoln is the port for the isolated narrow gauge Eyre Peninsular Railway.There is also a subsidiary port at Proper Bay which may be restored to use for iron ore traffic. The export of iron ore through Port Lincoln has been approved by the South Australian Government. Port...
  
   to Perth, Western Australia
  Perth, Western Australia
  Perth is the capital and largest city of the Australian state of Western Australia and the fourth most populous city in Australia. The Perth metropolitan area has an estimated population of almost 1,700,000....
  
  . It reaches a maximum length of 52 cm. Reproduction is oviparous; the egg
  Egg (biology)
  An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
  
   cases are oblong with stiff pointed horns at the corners, measuring 5.1-7.6 cm long and 3.2-3.8 cm wide.

• Western round skate, Irolita westraliensis Last & Gledhill, 2008 This species occurs along the northwestern coast of Australia from Imperieuse Reef to Exmouth Gulf
  Exmouth Gulf
  Exmouth Gulf is a gulf in the north west of Western Australia. It lies between North West Cape and the main coastline of Western Australia. It is considered to be part of the region of the North West Shelf and in the Canning Basin area.-Environment:...
  
  . It is smaller than the southern round skate, with the largest known specimen measuring 43 cm long. Its coloration is yellowish brown above, with irregular bluish spots, scattered larger dark brown blotches, and sometimes a dark bar between the pectoral fin insertions. The tail is brownish with five blackish bands. The underside is dark greyish pink with variable, irregular darker markings. It is distinguished from the southern round skate by having a less densely spotted color pattern, a more slender tail, a shorter disc and head, no thorns near the orbit, a more forwardly placed second dorsal fin, and other details.