Eosalmo
Encyclopedia
Eosalmo is a genus of extinct salmon
which lived during the Eocene
epoch. The genus was first described
in 1977 from fossils found in lacustrine
deposits near Smithers, British Columbia
, Canada. Fossils from this genus have also been found at sites in Princeton, British Columbia
and Republic, Washington
, USA. When first described the genus was thought to be intermediate in form to the living salmon subfamilies Salmoninae (trout and salmon) and Thymallinae (graylings). More recent review of the genus has placed Eosalmo as the most primitive
member of the Salmoninae subfamily.. Fossils found in at Driftwood Canyon Provincial Park
near Smithers
, British Columbia
display a full range of individuals from young juveniles through adults. This range indicates that the genus was completely freshwater dwelling and did not spend time in saltwater.
exhibits an anetrodorsal process which meets the edge of the subopercle at approximately a 60° angle. Also unique is the basihyal tooth plate, which is broad, flat, thin, and lacking any teeth along the edges. Modern salonids possess stout teeth along the edge of the basiyal. The morphology suggests Eosamo represents an intermediate between the modern Salmoninae and Thymallinae subfamilies and evolved from a grayling
like ancestor.
Salmonidae
Salmonidae is a family of ray-finned fish, the only living family currently placed in the order Salmoniformes. It includes salmon, trout, chars, freshwater whitefishes and graylings...
which lived during the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epoch. The genus was first described
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
in 1977 from fossils found in lacustrine
Lacustrine
Lacustrine means "of a lake" or "relating to a lake".Specifically, it may refer to:*Lacustrine plain*Lacustrine delta-Fish:*Lacustrine goby , a type of small fish found in Philippine waters belonging to the Gobiidae family, known in Tagalog as dulong-See also:*Fluvial - of or relating a...
deposits near Smithers, British Columbia
Smithers, British Columbia
Smithers is a town located in northwestern British Columbia, Canada, approximately halfway between Prince George and Prince Rupert. Smithers is located in the Regional District of Bulkley-Nechako....
, Canada. Fossils from this genus have also been found at sites in Princeton, British Columbia
Princeton, British Columbia
Princeton is a small town in the Similkameen region of southern British Columbia, Canada. It lies just east of the Cascade Mountains, which continue south into Washington, Oregon and California. The Tulameen and Similkameen Rivers converge here...
and Republic, Washington
Republic, Washington
Republic is a city in Ferry County, Washington, United States. The population was 1,073 at the 2010 census, a 12.5% increase over the 2000 Census. It is the county seat of Ferry County.-History:...
, USA. When first described the genus was thought to be intermediate in form to the living salmon subfamilies Salmoninae (trout and salmon) and Thymallinae (graylings). More recent review of the genus has placed Eosalmo as the most primitive
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
member of the Salmoninae subfamily.. Fossils found in at Driftwood Canyon Provincial Park
Driftwood Canyon Provincial Park
Driftwood Canyon Provincial Park is a provincial park in British Columbia, Canada. Driftwood Canyon Provincial Park covers 23 ha of the Bulkley River Valley, on the east side of Driftwood Creek, a tributary of the Bulkley River, 10 km northeast of the town of Smithers. The park is accessible from...
near Smithers
Smithers, British Columbia
Smithers is a town located in northwestern British Columbia, Canada, approximately halfway between Prince George and Prince Rupert. Smithers is located in the Regional District of Bulkley-Nechako....
, British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
display a full range of individuals from young juveniles through adults. This range indicates that the genus was completely freshwater dwelling and did not spend time in saltwater.
Physiology
Several unique characters found in Eosalmo separate the genus from extant salmonids. The subopercleOperculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
exhibits an anetrodorsal process which meets the edge of the subopercle at approximately a 60° angle. Also unique is the basihyal tooth plate, which is broad, flat, thin, and lacking any teeth along the edges. Modern salonids possess stout teeth along the edge of the basiyal. The morphology suggests Eosamo represents an intermediate between the modern Salmoninae and Thymallinae subfamilies and evolved from a grayling
Grayling (genus)
Thymallus is a genus of freshwater fish in the salmon family of order Salmoniformes; it is the only genus of subfamily Thymallinae. The type species is T. thymallus, the grayling. The genus's five distinct species are generically called graylings, but without qualification this also refers...
like ancestor.
See also
- Prehistoric fishPrehistoric fishPrehistoric fish refers to early fish that are known only from fossil records. They are the earliest known vertebrates, and include the first and extinct fish that lived through the Cambrian to the Tertiary. The study of prehistoric fish is called paleoichthyology...
- List of prehistoric bony fish