Nathorstiana

Nathorstiana Temporal range: Early Cretaceous PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Lycophytes
Class:	Lycopodiopsida
Order:	Isoetales
Family:	† Nathorstianaceae Němejc (1963)
Genus:	† Nathorstiana P.B.Richt. (1909)
Species:	†N. arborea
Binomial name
†Nathorstiana arborea P.B.Richt. (1909)

Nathorstiana is an extinct genus of lycopsid from the Early Cretaceous; it contains the single species Nathorstiana arborea. The genus is important in lycopod evolution for being a potential bridge between the Triassic Pleuromeia and extant Isoetes . It is known from one collection of nearly 270 specimens that include many different ontogenetic stages, including nearly every part of the plant. The root-bearing base grew downwards, shedding older root growth as it produced newer roots on its lower end, which varied in shape depending on the plant's age. Younger Nathorstiana exhibited a radially symmetrical, dome-shaped root structure with no lobes. As they grew, the dome grew into a cylindrical shape before splitting into two and then four lobes distally. ^[1]

Nathorstianaceae

Nathorstianaceae is a family of extinct represented only by the genus Nathorstiana. Representing a bridge between older and extant families of Isoetales, they persisted until the Early Cretaceous and are the most recent in the order to possess elongated stems. ^{[2] [1]}

References

1. Karrfalt, Eric (1984). "Further Observations on Nathorstiana (Isoetaceae)". American Journal of Botany. 71 (8): 1023–1030. doi:10.1002/j.1537-2197.1984.tb11953.x. ISSN   0002-9122. JSTOR   2443376.
2. Doweld, Alexander (28 December 2001). Prosyllabus Tracheophytorum: Tentamen systematis plantarum vascularium (Tracheophyta). Опыт системы сосудистых растений (Tracheophyta). Moscow: Geos. ISBN   5-89118-283-1.