Lampriformes

Lampriformes is a diverse order of ray-finned fishes found in the open ocean.

These pelagic feeders live well above the sea floor. They are typically found in waters ranging from 100 to 1,000 meters deep. The group includes several distinct families, such as the opahs and the oarfishes. While they look very different, they are united by specific anatomical features. The name Lampriformes comes from the Ancient Greek word *lamprós*, meaning bright, and the Latin *forma*, meaning external form. This name refers to the brilliant coloration seen in the opah, which is the type genus for this order.

The body shapes of lampriforms vary significantly between different types. Scientists categorize these shapes into two main groups. The first group is known as bathysomes, which means "deep-bodies" in Greek. These fish have rounded, laterally compressed bodies. The second group is called taeniosomes, meaning "ribbon-bodies." These fish have very elongated, ribbon-like shapes. Most adult lampriforms are brightly colored. Many species feature brilliant crimson fins. They may also have tiny scales or even naked skin.

The anatomy of these fishes includes several unique mechanical features. Lampriforms have between 84 and 96 total vertebrae. Their jaws are highly protrusible, meaning they can move forward to catch prey. This movement happens through a unique process involving the maxilla. Instead of being attached to the ethmoid and palatine bones by ligaments, the maxilla slides in and out with the premaxilla. Their dorsal fins are often long and extend along most of the body length. However, they lack fin spines entirely. Some members possess a physoclistous gas bladder, while others do not.

The history of the Lampriformes spans millions of years. They likely diverged from other teleosts during the Cretaceous period, perhaps over 80 million years ago. The oldest known fossil in this order is *Nardovelifer*, which dates to the late Campanian epoch. Early lampriforms were mostly bathysomes with rounded bodies. The elongated taeniosome shape is an apomorphic trait, meaning it evolved later. This ribbon-like shape appears to have evolved only once in their history. The order underwent a major radiation during the Paleocene period.

Fossil records show that different families lived and died out at different times. For example, the Turkmenidae were a family of opah-shaped fish. They thrived during the Paleocene but went extinct around the start of the Neogene, about 23 million years ago. Today, the order is much smaller. There are only 12 recognized genera and about 20 species remaining. These living species are divided into seven extant families. These families include the Veliferidae, Lampridae, Lophotidae, Radiicephalidae, Trachipteridae, and Regalecidae. Some researchers also divide the order into two suborders: Lamproidei and Trachipteroidei.

Some species in this order are much larger than others. The sailfin moonfishes of the Veliferidae family are quite small. In contrast, the oarfish, or *Regalecus glesne*, is a true giant. It is the longest of all living bony fishes. These massive creatures can reach incredible lengths in the deep ocean. This extreme difference in size shows how much the order has changed. From tiny moonfishes to massive oarfishes, the group represents a huge range of biological forms.

The scientific classification of lampriforms is still a subject of active study. They are considered part of the advanced Teleostei clade. Some scientists place them in a monotypic superorder called Lampridiomorpha. Others suggest they sit just outside the Acanthomorpha clade. Molecular data shows they are close to advanced teleosts, but the exact relationships remain uncertain. They may be the sister taxon to the Myctophiformes. Because modern taxonomy is always changing, researchers continue to investigate how these fishes fit into the larger tree of life.