Anabernicula: small waterfowl from ancient North America

Anabernicula is a genus of small extinct waterfowl known from Pliocene and Pleistocene deposits in North America. Named species were founded on isolated limb bones from Arizona, California, Oregon and elsewhere; they are not all represented by complete skeletons. Some authors place the genus among shelducks and sheldgeese, while its exact position within Anatidae remains open to revision. The extinct bird catalogue lists the named forms with geographic and chronological context instead of treating every “pygmy goose” as one population.

Quick facts

From asphalt bones to a genus name

Hildegarde Howard named Anabernicula in 1935 for small fossil waterfowl from the McKittrick asphalt deposits of California. The material included tarsometatarsi, the lower leg bones fused to parts of the foot in birds. Small size and a combination of skeletal features distinguished the fossils from larger waterfowl. The first material did not include an associated skull and skeleton, so the genus began with a narrow anatomical basis.

The name’s history also involves older fossils. Alexander Wetmore described a small goose from Pliocene deposits in Arizona as Branta minuscula in 1924. Howard combined that species with the Californian form in 1936. Later, she separated the Arizona material again from the younger California fossils and restored A. gracilenta for the California birds. Other authors named forms such as A. oregonensis and A. robusta from additional isolated limb bones.

Authors have differed over whether specimens belong to the same species, whether some names are synonyms, and how the genus fits within waterfowl. A list of names should therefore not be treated as a complete census of one uniform population. The specimens and measurements remain useful even when classification changes.

What the bones reveal

Most described material consists of limb elements, especially the tarsometatarsus and other leg bones. Their length, breadth, muscle scars and joint surfaces can be compared with living and fossil Anatidae. Some features have been read as goose-like; others have been discussed as closer to ducks or the sheldduck-and-sheldgoose tribe Tadornini. This mixture is one reason the genus has not occupied a completely stable branch of the family tree.

The fossils support a relatively small waterfowl, but estimates of standing height or mass depend on how a missing torso and neck are scaled. “Pygmy goose” is a historical descriptive label, not a claim that each species had the proportions of a modern goose. The named species may also have differed in size. Isolated limb bones cannot tell us whether one specimen was male, female, young or from a distinct species without other evidence.

No complete skull is known to establish bill shape in detail. The fossils do not preserve gut contents, an associated nest, securely assigned eggs or a diagnostic feeding trace. Anatidae anatomy makes a waterfowl lifestyle a reasonable inference, but a particular menu of aquatic plants, seeds or invertebrates is not directly demonstrated for Anabernicula.

Where and when it lived

Named fossils come from several North American localities. The Pliocene Arizona form is older than late Pleistocene occurrences in California and Oregon; other material has been reported from Nebraska. Together the records indicate that small anatids occurred across a broad region through a long interval. They do not document a continuous population, and each specimen needs its own geological and anatomical assessment.

McKittrick and Rancho La Brea are famous asphalt deposits that preserve diverse Ice Age animals. Their bone accumulations formed through complicated taphonomic processes and represent repeated events. A fossil in asphalt was not necessarily trapped in the same episode as every other animal, and a species list from a deposit does not prove that each named bird lived at the site at exactly the same time.

Other fossil waterfowl, including the much older Presbyornis, help show that similar wading and swimming habits evolved in different branches. They are not evidence that Anabernicula descended directly from that genus.

Classification without false certainty

Most references place Anabernicula in Anatidae, the family containing ducks, geese and swans. Some treatments associate it with Tadornini based on aspects of its skeleton. Yet the genus is known chiefly from incomplete postcranial bones, and its exact relationships need more complete comparative material. Similar body proportions alone do not establish close ancestry.

The Latin name connects published specimens and diagnostic descriptions. “Pygmy goose” gives a reader a rough size-and-shape analogy, but does not settle phylogeny or diet. As researchers compare more material, species boundaries may change without invalidating the measured fossils.

What can be reconstructed?

A cautious illustration can show a small waterfowl with the general outline expected for an anatine bird. Exact bill profile, feather pattern, colour, sex differences, courtship and feeding behaviour remain poorly constrained by the named fossils. A living duck or goose is a useful visual comparison, not a direct portrait of the extinct genus.

Anabernicula matters because it records small waterfowl in the North American Neogene and Quaternary fossil record. The bones establish presence, lower-limb proportions and a set of taxonomic questions. They leave details of ecology and the boundaries among named species open.