What order is the common loon in?

The common loon, also known as the great northern diver in Eurasia, is a large member of the loon or diver family of birds. Loons are found primarily in North America and northern Eurasia. There are 5 living species of loons, and they are all placed within the genus Gavia. The common loon specifically is scientifically known as Gavia immer and belongs to the order Gaviiformes.

Quick Facts About the Common Loon’s Classification

Here are some key facts about the taxonomic classification and order of the common loon:

• Kingdom: Animalia
• Phylum: Chordata
• Class: Aves
• Order: Gaviiformes
• Family: Gaviidae
• Genus: Gavia
• Species: Gavia immer

So in summary, the common loon belongs to the order Gaviiformes. All loons are placed within this order. There are 5 species in the genus Gavia, with Gavia immer specifically referring to the common loon.

Overview of the Order Gaviiformes

The order Gaviiformes contains just one family – Gaviidae. There are 5 living species divided between 4 genera within Gaviidae:

• Gavia (4 species including the common loon)
• Gavia (arctic loon)
• Gavia (Pacific loon)
• Gavia (yellow-billed loon)

Some key features of loons in the order Gaviiformes include:

• Streamlined bodies ideal for swimming and diving
• Dense bones to help with diving
• Large feet located far back on the body
• Sharp, pointed bills

Loons in this order are highly adapted for an aquatic lifestyle. Their legs are set far back on their bodies, which makes them awkward on land but provides excellent propulsion in water. Loons have solid bones rather than air pockets, which allows them to dive deep underwater. They use their pointed bills to catch slippery fish.

History and Relationships of the Order Gaviiformes

The order Gaviiformes split from other modern bird orders around 80-90 million years ago during the Late Cretaceous period. Loons were once believed to be related to grebes and divers, which are also waterbirds. However, anatomical and genetic studies have shown loons are more closely related to penguins, tubenoses, storks, and pelicans.

Prehistoric loon relatives from the Paleogene and Neogene periods have been discovered across Europe and North America. The earliest fossil loon is Colymboides minutus from early Eocene deposits. Prehistoric loons resemble modern species but were generally smaller in size. Loons were common among aquatic bird faunas throughout the Cenozoic era.

Today the Gaviiformes contain just the single family Gaviidae. But the order historically contained two other extinct families from the Cretaceous and Paleogene:

• Hesperornithidae – toothed diving birds
• Baptornithidae – close relatives of Hesperornis

So while the only living family left is the Gaviidae loons, the order Gaviiformes once contained much greater diversity.

Characteristics of the Family Gaviidae

The Gaviidae family includes all living loon species. Some distinctive traits of this family include:

• Streamlined bodies shaped like a spear or torpedo
• Short tails and long necks
• Legs set far back on the body
• Webbed feet used for propelling through water
• Pointed bills with slight hook at the end
• Dense bones that aid in diving
• Primarily piscivorous – feed mainly on fish

In addition to their anatomical adaptations for aquatic living, loons in the Gaviidae family also have a distinctive behavior and appearance:

• Distinctive black and white plumage patterns
• Red eyes
• Distinctive wailing cries
• Territorial behavior and elaborate mating dances

The loon family has existed for at least 30 million years since the Oligocene. Five extant species all share these common loon traits and adaptations for pursuing fish beneath the water’s surface.

Species in the Gaviidae Family

Here are the 5 living loon species in the Gaviidae family:

Fossil Record of the Gaviiformes

The fossil record provides evidence of primitive loons and loon-like species going back to the Late Cretaceous. Some major evolutionary stages and fossil representatives of Gaviiformes include:

• Polarornis gregorii – Large loon-like species from Late Cretaceous Antarctica 70 million years ago
• Neogaeornis wetzeli – Earliest known Gaviiform from Late Cretaceous Chile
• Colymboides minutus – Small loon from Early Eocene England 54-37 million years ago
• Gaviella pusilla – One of the earliest fossils in the Gaviidae family from the Oligocene period 34-23 million years ago
• Gavia moldavica – Nearly modern Gavia loon from the Miocene epoch 23-5 million years ago

By charting fossils like these across time, paleontologists can trace the evolution of loons from more ancient bird groups into the specialized diving birds we see today.

Related Extinct Families

As previously mentioned, two extinct families called the Hesperornithidae and Baptornithidae were once also part of the order Gaviiformes. These represent early evolutionary experiments in toothed, diving birds:

• Hesperornithidae – Known as the “western birds” they were toothed, foot-propelled diving birds from the Late Cretaceous that became extinct at the end of the Mesozoic along with the dinosaurs 66 million years ago.
• Baptornithidae – A Cretaceous family closely related to Hesperornis but retaining teeth and the ability to fly. Went extinct around 80 million years ago.

So while all living members of Gaviiformes are now toothless loons in the Gaviidae, distant extinct relatives retained teeth and other primitive features on the path towards the modern loon body plan.

Conclusion

In summary, the common loon belongs to the order Gaviiformes, which includes one extant family – the Gaviidae. This order split from other modern birds over 80 million years ago and its members are highly adapted for foot-propelled diving and catching fish. Prehistoric loon relatives date back to the Late Cretaceous, and related extinct families like the Hesperornithidae retained teeth unlike modern loons. So while the Gaviiformes today are relatively small with just 5 species, they have a long and fascinating evolutionary history connecting them to ancient toothed diving birds.