''Chaunoides'' is an extinct genus of

screamer The screamers are three South American bird species placed in Family (biology), family Anhimidae. They were thought to be related to the Galliformes because of similar beak, bills, but are more closely related to the family Anatidae, i.e. ducks ...

. Only one species of this genus is known, ''Chaunoides antiquus'' from the upper

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

or lower

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Tremembé Formation of

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. It was smaller and more gracile than all living screamers.

Description

''Chaunoides'' is a small screamer, but still large when compared to most living ducks and geese. Its legs are similar in length to the other species of screamer, but thinner and less pneumatized, consistent with a more gracile body. The skeletal material is relatively fragmentary, including only a coracoid and fragmentary limb material. Like the femur, many of the skeletal elements of ''Chaunoides'' are less pneumatized than the living screamers. The coracoid is more slender than any living screamer, and smaller overall. Conclusive reconstructions or size estimates of the entire animal are difficult due to a lack of available fossil material.

Paleoecology

The Tremembe Formation is a small

lacustrine A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from t ...

deposit composed mainly of

Clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

and

Shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

. ''Chaunoides'' coexisted with a wide variety of other bird species, including the extinct flamingos Palaelodus and Agnopterus, as well as the Teratorn Taubatornis. Pyrotherian mammals are also known from the site. The preserved lake ecosystem was alkaline and shallow.

References

Anhimidae Miocene birds Prehistoric bird genera Fossil taxa described in 1999 {{Paleo-neornithine-stub