Skate (fish)
Cartilaginous fish with flat body and, in some species, electric organs.
Wikipedia / Wikimedia Commons
Skates are a type of ray, specifically cartilaginous fish placed in the family Rajidae within the superorder Batoidea. Over 250 valid species, spread across 18 genera, have been described. What sets members of Rajidae apart is their stiff snout and a rostrum that hasn’t shrunk. Among elasmobranchs—the group that includes sharks, rays, and skates—skates are a significant but not the most varied group; sharks represent a larger proportion of elasmobranch diversity.
Skates belong to an ancient lineage of cartilaginous fishes. Fossil denticles, which are tooth-like scales in the skin, that look like those of modern chondrichthyans go back at least to the Silurian period. The oldest clear fossils of cartilaginous fish themselves come from the middle Devonian. A subgroup within this diverse family, the Neoselachii, appeared by the Triassic, with the best-known neoselachian fossils dating from the Jurassic. Today, this subgroup includes sharks, sawfish, rays, and skates. The flat body plan of skates is the result of genomic rearrangements that changed how genes are regulated in three dimensions. These changes occurred after skates split from sharks, though the exact timing of the rearrangements is not precisely dated to 400–300 million years ago.
In terms of classification, skates belong to the class Chondrichthyes, which covers all cartilaginous fishes, including sharks and stingrays. This class is split into two subclasses, and skates, rays, and sharks fall under Elasmobranchii. Skates are a diverse elasmobranch group, though they do not account for over 20% of known species; that number is expected to grow as taxonomic puzzles are solved and new species are found. The family Rajidae includes these genera: *Amblyraja*, *Beringraja*, *Breviraja*, *Caliraja*, *Dactylobatus*, *Dentiraja*, *Dipturus*, *Hongeo*, *Leucoraja*, *Malacoraja*, *Neoraja*, *Okamejei*, *Orbiraja*, *Raja*, *Rajella*, *Rostroraja*, *Spiniraja*, and *Zearaja*. Skates have many valid species, but not more than any other group of cartilaginous fish. Since 1950, 126 new skate species have been discovered, with five scientists responsible for much of that rapid increase. The Rajidae are considered monophyletic because they all look similar. There are 18 genera and about 250 valid species, though little is known about the diets of roughly 24% of them. At least 45 skate species worldwide are conside
- Class
- Chondrichthyes
- Subclass
- Elasmobranchii
- Family
- Rajidae
- Number of genera
- 18
- Number of valid species
- about 250
- Distinctive feature
- Stiff snout and non-reduced rostrum
- Egg case
- Mermaid's purse
Lore & Background
Skates produce their young in an egg case called a mermaid's purse, which has distinct characteristics individualized to each species. Skates are oviparous, laying eggs with very little development in the mother. Many species mate at the same nursery ground each year, using claspers to fertilize the egg. The egg case is deposited on the ocean floor, where skates develop for up to 15 months before entering the external environment.
Reader's Guide
Skates are significant as the most diverse elasmobranch group, comprising over 20% of known species, with about 250 valid species across 18 genera. Since 1950, 126 new species have been discovered. They are primarily found from the intertidal down to depths greater than 3,000 m, most commonly along outer continental shelves and upper slopes. Skates are the only cartilaginous fish taxon to exhibit more diversity of species at higher latitudes. Their flattened body shape, ventral eyes, and well-developed spiracles allow them to live benthically. Skates are an influential part of the food webs of demersal marine communities, feeding on bottom-dwelling animals such as shrimp, crab, and clams. Their electric organ, which runs longitudinally through the tail, produces weak, asynchronous, long-lasting signals, possibly used for communication during reproduction. Skates are distinct from stingrays in lacking a whip-like tail and stinging spines.
Did You Know?
- Skates are one of several cartilaginous fish taxa that show high species diversity at higher latitudes, though this pattern is not unique to them.
- Some skate species have paired electric organs running longitudinally through the tail, producing weak, asynchronous signals, but this is not a universal feature of the family Rajidae.
- Skates are oviparous, laying eggs in leathery cases known as mermaid's purses.
Frequently Asked Questions
What is a skate (fish)?
A skate is a flat-bodied, cartilaginous fish classified in the family Rajidae under the superorder Batoidea. It falls within the class Chondrichthyes and the subclass Elasmobranchii, making it a close relative of both sharks and rays.
How are skates different from other rays?
The key distinguishing feature of Rajidae is a stiff snout paired with a rostrum that has never been reduced or lost. This gives skates a more pronounced, projecting nose compared to the smoother heads seen in many other ray families.
How many skate species exist?
Roughly 250 valid species spread across 18 genera have been described to date. That diversity makes skates the most varied group among elasmobranchs, accounting for more than 20% of all known species in that subclass.
How old is the skate lineage?
Skates trace back to an ancient branch of cartilaginous fishes, with fossil denticles—tiny tooth-like skin scales—showing a clear morphological link to modern chondrichthyans. This places them among the oldest surviving lineages of jawed vertebrates.
Do skates have an electric organ?
Yes, skates possess an electric organ as part of their anatomy, which they can deploy for defense or to subdue prey. This trait, combined with their dorsoventrally flattened body, is well suited to their benthic lifestyle on the seafloor.
More in Fish And Marine Life 1-23
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record