Esocoidei

Esocoidei is a small suborder of freshwater ray-finned fish.

This group is one of two suborders within the larger order Salmoniformes. It is highly significant for studying how fish species evolve and diverge over millions of years. The suborder is divided into two distinct families: Esocidae and Umbridae. The Esocidae family contains the pikes, which give the entire order their name.

These fish are typically found in freshwater habitats that are filled with weeds. Today, they live across North America and northern Eurasia.

The history of the esocoids is a long and complex journey. They first appeared during the late Cretaceous period. This was a time of great biological change known as the Euteleostei radiation. About 110 million years ago, they diverged from their sister group, the Salmonoidei. This divergence created two separate evolutionary paths. All living species in the suborder evolved from a common ancestor. This ancestor lived approximately 90 million years ago.

Taxonomy is the science of naming and classifying living things. The classification of Esocoidei has changed as scientists learned more. In the past, they were often placed as a suborder within Salmoniformes. During the early 21st century, researchers changed this. They treated them as their own separate order called Esociformes. This was because they looked morphologically different from salmon. However, modern phylogenetic studies have changed things again. These studies look at evolutionary relationships to build family trees. These studies affirmed the close link between Salmoniformes and Esociformes. Because of this, recent taxonomic authorities have revived the old classification. They now place the esocoids back into the Salmoniformes suborder.

The family Esocidae is quite diverse. It was established by Rafinesque in 1815. This family includes the subfamily Esocinae, which contains the pikes.

It also includes the subfamily Dalliinae. Recent genetic and paleontological research has clarified these relationships. Scientists used to think the family only included the genus Esox. Now, research shows that Novumbra and Dallia are also members of Esocidae. These two genera are more closely related to Esox than they are to Umbra.

The family Umbridae is much smaller in terms of living members. It was established by Bonaparte in 1845. Currently, the genus Umbra is the only living genus in this family.

These are known as mudminnows. They can be found in Europe and eastern North America. Genetic studies on Umbra have revealed a very old split. The North American and European species split during the late Cretaceous and early Paleogene. This means they have been separate for a very long time.

Fossils provide a window into the ancient world of these fish. In North America, several esocid genera are known from the Late Cretaceous. These include Estesesox, Oldmanesox, Archaeosiilik, and Nunikuluk.

These fossils are very important to scientists. They show that esocids were among the few North American freshwater teleost groups to diversify before the Cretaceous-Paleogene extinction event. In Europe, researchers have described three additional genera from Paleocene fossils. This tells us that these fish were successful across different continents and time periods.

Understanding Esocoidei helps us see the broader patterns of life on Earth. The three living genera, Esox, Novumbra, and Dallia, show a holarctic distribution. This means they are spread across the northern parts of the world. By studying the relationship between Esocidae and Umbridae, we learn about evolutionary splits. We see how a single ancestor can lead to many different types of fish. The study of these fish connects biology, geology, and history. It shows how life persists through massive changes in the planet's environment.