Cyathea cranhamii is an extinct

Extinction

In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

 species of tree fern

Cyatheales

The order Cyatheales is a taxonomic division of the fern subclass, Cyatheatae, which includes the tree ferns. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicates that the order is monophyletic. Some species in the Cyatheales have tree-like growth...

. It was described based on permineralised sori

Sorus

A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....

 from the Early Cretaceous

Early Cretaceous

The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...

 deposits of Apple Bay in Vancouver Island

Vancouver Island

Vancouver Island is a large island in British Columbia, Canada. It is one of several North American locations named after George Vancouver, the British Royal Navy officer who explored the Pacific Northwest coast of North America between 1791 and 1794...

, 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...

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C. cranhamii has sori arranged in two rows on narrow pinnules. They are covered by globose indusia which resemble those of Sphaeropteris

Cyathea sect. Sphaeropteris

Sphaeropteris is a section in the monotypic subgenus Sphaeropteris. The name was originally applied to a genus of tree ferns which is now considered to be synonymous with Cyathea.-Classification:*Subgenus Sphaeropteris...

species in morphology. Sporangia

Sporangium

A sporangium is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. All plants, fungi, and many other lineages form sporangia at some point in their life cycle...

 are circinate (ring-shaped) and bear multicellular stalks. They diverge from a basal, vascular receptacle. The sporangia contain 64 trilete spore

Spore

In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s which bear sculpturing on their outer covering (perispore) ranging from irregular granulate or echinate to prominent rodlets. The annulus is nearly vertical and arranged in a single series. It is not interrupted by the stalk.

The specimens used to describe C. cranhamii are the first anatomically preserved tree fern sori known from the fossil record. Smith, Rothwell and Stockey (2003) state that "they represent the most ancient evidence for fertile structures of the Cyatheaceae

Cyatheaceae

The Cyatheaceae is the scaly tree fern family and includes the world's tallest tree ferns, which reach heights up to 20 m. They are also very ancient plants, appearing in the fossil record in the late Jurassic, though the modern genera likely appeared in the Tertiary. Cyatheaceae is the largest...

 and demonstrate that essentially modern species of cyatheaceous tree ferns had evolved by the Early Cretaceous".

Numerous Cyathea

Cyathea

Cyathea is a genus of tree ferns, the type genus of the fern order Cyatheales. They are mostly terrestrial ferns, usually with a single tall stem. Rarely, the trunk may be branched or creeping. Many species also develop a fibrous mass of roots at the base of the trunk. The genus has a pantropical...

species are present today in the Americas

Americas

The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

, especially the Greater Antilles

Greater Antilles

The Greater Antilles are one of three island groups in the Caribbean. Comprising Cuba, Jamaica, Hispaniola , and Puerto Rico, the Greater Antilles constitute almost 90% of the land mass of the entire West Indies.-Greater Antilles in context :The islands of the Caribbean Sea, collectively known as...

, the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

, and Central

Central America

Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...

 and South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

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C. cranhamii is named after Gerald Cranham of Parksville

Parksville, British Columbia

-Demographics:Parksville had a population of 10,993 people in 2006, which was an increase of 6.5% from the 2001 census count. The median household income in 2006 for Parksville was $55,524, which is below the British Columbia provincial average of $62,346....

, British Columbia, who provided plant specimens for study at the University of Alberta

University of Alberta

The University of Alberta is a public research university located in Edmonton, Alberta, Canada. Founded in 1908 by Alexander Cameron Rutherford, the first premier of Alberta and Henry Marshall Tory, its first president, it is widely recognized as one of the best universities in Canada...

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