Stingrays and manta rays are definitively related, sharing a deep common ancestry within the class of fish that possess skeletons made of cartilage instead of bone. Though they look and act vastly different today, both rays belong to a single, broad lineage. Their physical resemblance, characterized by flattened bodies and enlarged, wing-like pectoral fins, is a direct result of this shared evolutionary history. This foundational relationship links the small, bottom-dwelling stingray with the massive, open-ocean manta ray.
The Shared Evolutionary Tree
Manta rays and stingrays are members of the Class Chondrichthyes, the large group of cartilaginous fish that also includes sharks. Within this class, they fall under the subclass Elasmobranchii, which represents all sharks, skates, and rays. The shared presence of a skeleton made entirely of flexible cartilage, rather than true bone, is the defining physical characteristic of this ancient group.
More specifically, both rays are classified in the Order Myliobatiformes. This shared order confirms their close genetic relationship, even though they belong to separate families within it. Stingrays are a varied group spread across eight different families, while manta rays belong to the family Mobulidae, which includes all the large, filter-feeding rays. The common body plan of a flattened disc with gill slits located on the underside of the body is a hallmark inherited from this shared taxonomic order.
Defining Features of Stingrays
The distinguishing feature of a stingray is the presence of one or more serrated, venomous barbs located on its whip-like tail. This spine is a defensive mechanism, used only when the ray feels threatened, often by being accidentally stepped on. The venom is stored within specialized tissue cells that coat the barb, and it is released upon impact, causing intense pain.
Stingrays are characterized by their benthic lifestyle, meaning they primarily inhabit the sea floor in shallow, coastal waters. They often bury themselves in the sand to hide, using their flat body shape and coloration to camouflage effectively as ambush predators. They possess a mouth located on the underside of their body, equipped with powerful jaws capable of crushing the shells of prey like clams, oysters, and crustaceans.
Because their mouths are directed downward and often pressed against the substrate, stingrays rely on specialized openings called spiracles, located behind their eyes, to draw in water for respiration. This adaptation allows them to remain motionless and partially buried without sucking in sand through their ventral gill slits. Stingrays are typically much smaller than their manta cousins, with many species measuring only a few feet across, though some can reach six feet wide and weigh hundreds of pounds.
Defining Features of Manta Rays
Manta rays represent a distinct evolutionary path, having shed the defining feature of their relatives by completely lacking a venomous barb on their tails. Their massive size is a defining characteristic, as the giant oceanic manta ray can reach a wingspan of up to 23 feet, making it one of the largest fish in the ocean. This scale supports a pelagic existence, meaning they live in the open ocean and spend much of their lives swimming through the water column rather than resting on the bottom.
Their anatomy is specialized for filter feeding, a method that involves consuming vast quantities of plankton and small marine organisms. Manta rays possess a wide, terminal mouth located at the front of their head, unlike the ventral mouth of stingrays. Flanking this mouth are two specialized, paddle-like cephalic fins, which uncurl to funnel plankton-rich water into the mouth while the animal swims.
The water is then processed through gill rakers, which act like a sieve to trap the food particles before the filtered water exits through the gill slits. This continuous, active swimming is necessary because, like some sharks, manta rays must constantly move to push water over their gills to breathe. This combination of size, open-ocean habitat, and unique feeding structures differentiates the manta ray from its smaller, bottom-dwelling stingray kin.