''Furcacauda'' is a genus of thelodontid

agnathan Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both living ( cyclostomes such as hagfishes and lampreys) and ext ...

from the Lower Devonian of

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, and is the type genus of the order

Furcacaudiformes Furcacaudiformes is an extinct order of jawless fish in the class Thelodonti. Because the paucity of intact fossils, especially since some families are known entirely from scale fossils, taxonomy of thelodonts is based primarily on scale morphol ...

. Furcacaudiform thelodontids were deep water jawless vertebrates with symmetrical fork and lobed-finned tails and scales smaller than typical loganellid and nikoliviid thelodonti scales. Furcacaudiform thelodonts are noted as having a laterally compressed body, large anterior eyes, slightly posterior, lateral, and vertical to a small mouth, and a condensed curved row of branchial openings (gills) directly posterior to the eyes. Many but not all had laterally paired fins. Wilson and Caldwell also note the presence of a caudal peduncle and a long caudal fin made of two large lobes, one dorsal and one ventral separated by 8 to 14 smaller intermediate lobes, giving the appearance of a striated half-moon shaped tail resembling the tail of a heterostracan. A large square cavity within the gut connecting a small intestine to an anal opening lead many to believe that it is this genus that exhibits the first vertebrate stomach. According to Wilson and Caldwell their discovery, based on sediment infillings of fossils of the ''Furcacauda heintze'', gives credence to the evolutionary development of stomach before jaws.

Gallery of species

Image:Furcacauda_heintzae.png, ''Furcacauda heintzae'' Image:Furcacauda_fredholmae.png, ''Furcacauda fredholmae''

References

External links

*
The Taxonomicon. (2004–2009)
Retrieved November 6, 2009. {{Taxonbar, from=Q5509484 Devonian jawless fish Thelodonti genera Devonian fish of North America