Batomorphi

Batomorphi is a major division of cartilaginous fishes, which are animals with skeletons made of tough, elastic cartilage instead of hard bone.

This group is commonly known as rays. They are part of a larger subclass called Elasmobranchii, which also includes sharks. Batomorphi is a very diverse group. It contains well over 600 species organized into 26 different families. These animals play vital roles in marine ecosystems across the globe.

The anatomy of a batomorph is quite different from a typical shark. Most species are dorsoventrally flattened, meaning they are pressed thin from top to bottom. This creates a mantle-like body shape. Their pectoral fins are often enlarged and fused to the head. Many species have turned these fins into broad appendages that look like wings.

They use these "wings" to flap through the water for locomotion. Unlike sharks, most batomorphs lack an anal fin.

Because many rays live on the sea floor, they have unique ways of breathing. They use spiracles, which are small openings on the top of their heads. Water enters through these spiracles rather than the mouth. The water then passes over the gills and exits through gill slits. These slits are located on the ventral surface, or the underside, of the animal.

Most species have five ventral gill slits, but the family Hexatrygonidae has six. Their mouths are also located on the underside of the body.

Feeding mechanisms vary depending on the specific type of ray. Many batomorphs have heavy, rounded teeth designed for crushing. They use these to eat snails, clams, oysters, and crustaceans. Their jaws use a specific type of support called euhyostylic suspension. This means the jaws rely entirely on the hyomandibular cartilages for support. In contrast, manta rays use dense gill rakers to capture tiny plankton from the water.

The history of Batomorphi reaches back into deep geological time. Fossil evidence shows tooth-like scales, called denticles, dating back to the Ordovician period. The oldest unambiguous fossils of cartilaginous fish are from the middle Devonian. A specific group called Neoselachii emerged by the Triassic period. The oldest confirmed ray fossil is named Antiquaobatis, found in the Pliensbachian of Germany.

Scientists use molecular evidence to understand how these lineages evolved.

Modern science classifies batomorphs into several major orders. These include Myliobatiformes, which contains stingrays and relatives. Rajiformes includes skates, while Torpediniformes contains electric rays.

The order Rhinopristiformes includes sawfishes and guitarfishes. Recent DNA studies have changed how we see these relationships. For example, researchers found that guitarfishes are actually two distinct groups. This study used nuclear and mitochondrial DNA from 37 different taxa to find these connections.

Reproduction in Batomorphi involves internal fertilization. This process is efficient because it conserves sperm and protects eggs from predators. There are two main ways these animals produce young. Skates and some rays are oviparous, meaning they lay eggs. These eggs are often found in leathery cases called "mermaid's purses."

Other rays are ovoviviparous. In these species, the young develop inside a womb without a placenta before being born.

Today, many batomorph species face serious conservation challenges. A 2021 study in the journal Nature reported a massive decline in these animals. The number of oceanic sharks and rays fell by 71% over the last 50 years. Overfishing is a primary cause of this trend. Currently, three-quarters of these species are threatened with extinction.

In the Mediterranean Sea, only 38 species of rays and skates remain. Protecting these animals is essential for the health of the entire ocean ecosystem.