The ocean is home to a diverse group of fish known as elasmobranchs, which includes all sharks, skates, and rays. These cartilaginous fishes share a skeletal structure made of cartilage instead of bone, but their outward appearance varies dramatically. The stingray, with its iconic flat, disc-like shape, is perhaps the most recognizable of the batoids. This distinct, flattened silhouette is shared by several other marine creatures, making it difficult to tell them apart. This article explores the species most frequently mistaken for the true stingray and outlines the specific biological details that allow for accurate identification.
Defining the Stingray
True stingrays belong to the order Myliobatiformes, a group of batoids characterized by their dorsoventrally flattened bodies. They possess a broad pectoral disc that can be oval, triangular, or kite-shaped. The eyes and spiracles, which draw in water for respiration, are located on the dorsal surface of the disc. Conversely, the mouth, nostrils, and gill slits are positioned on the ventral surface, reflecting their bottom-dwelling lifestyle.
The most defining characteristic of the stingray is its tail structure, which is typically long, thin, and whip-like. Positioned near the base of this tail is one or more serrated, saw-edged spines that contain venom-producing tissue. This stinging barb serves as a defensive weapon, used only when the animal feels threatened, which is the source of the ray’s common name. Most stingray species are viviparous, meaning they give birth to fully formed, live young.
Skates: Close Cousins of the Stingray
Skates, classified under the order Rajiformes, are the animals most commonly mistaken for stingrays, as they share the same flattened body plan and bottom-dwelling habits. Like stingrays, their pectoral fins are fused to their head, giving them a broad, wing-like appearance. Despite this shared morphology, the differences between skates and rays are substantial enough to place them in separate taxonomic orders.
A skate’s tail is generally shorter, thicker, and fleshier than the stingray’s whip-like appendage. Skates lack the venomous stinging barb found in stingrays, instead relying on rows of thorny projections, or denticles, along their backs and tails for protection. They also typically possess two small but distinct dorsal fins located near the tip of the tail.
Reproduction offers another clear distinction. Skates are oviparous, meaning they reproduce by laying eggs encased in a protective structure. These rectangular, leathery egg cases are often found washed up on beaches and are commonly referred to as “mermaid’s purses”. This egg-laying strategy contrasts with the live birth method used by the majority of true stingrays.
Ray-Like Sharks: The Guitarfish Family
Another group of animals frequently misidentified as rays are the guitarfish, which belong to the family Rhinobatidae and are often called shovelnose rays. This family represents a transitional form, possessing physical characteristics intermediate between those of true sharks and rays. Their body shape is the source of the confusion, as they have a flattened head and trunk that merges into a broader, ray-like disc.
The guitarfish body is more elongated and less disc-shaped than a true ray, often described as having a shovel or guitar-like outline. Unlike skates and rays, they possess a prominent, robust tail that is distinctly shark-like in its structure. This tail also features two well-developed dorsal fins and a pronounced caudal fin.
Guitarfish lack the venomous barb of a stingray, and their reproductive strategy is ovoviviparous. This means the embryos develop inside eggs within the mother’s body, hatching internally before the young are born live. Their overall morphology places them in the order Rhinopristiformes.
Key Differences for Identification
For quick identification, focus on three primary morphological features: tail structure, the presence of a venomous spine, and overall body shape. A true stingray (Myliobatiformes) is characterized by a long, slender, whip-like tail that harbors a venomous barb near its base. Their body forms a distinct, wide disc or kite shape.
In contrast, a skate (Rajiformes) has a noticeably shorter, thicker, and fleshy tail. The skate’s tail will often display small dorsal fins and sometimes have thorny spikes along its length.
The guitarfish (Rhinobatidae) is distinguishable by its elongated, shovel-like body that tapers gradually into a robust, shark-like tail complete with two prominent dorsal fins and a strong caudal fin.