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Marmarthia pearsonii
Marmarthia pearsonii K.R. Johnson Proc. Denver Mus. Nat. Hist., Series 3, (12): 5. 1 Apr 1996
- Name
- Marmarthia pearsonii
- Rank
- Species
- Generic Name
- [Genus] Marmarthia
- Authors (Pub.)
- Johnson K. R.
- Publication
- Description of seven common fossil leaf species from the Hell Creek Formation (Upper Cretaceous: Upper Maastrichtian) North Dakota, South Dakota, Montana [1996/4]
- Journal
- Proceedings of the Denver Museum of Natural History
- Annee/Jahrgang
- Series 3
- Issue
- 12
- Page number
- 5
- Year
- 1996
- Fossil Status
- leaves
- Stratigraphy
- Maastrichtian
- Strat. comment
- Hell Creek Formation
- Location
- Slope County, North Dakota, USA
- Paleoregion
- America (North)
Data for Holotypus
- Repository
- Denver Museum of Nature and Science, DMNH, Denver, USA
- Repository Number
- DMNH 7713
- Diagnosis
- Lamina elliptic; length: 5.5—13.3 cm, average
length: 9 cm; width: 2—5.2 cm, average width: 3.2 cm;
average l:w ratio: 2.9 (n=32); apex acute to acuminate; base
acute to decurrent with lateral primaries forming the margin
of the leaf; margin entire; petiole normal. Venation
basal acrodromous with naked basal lateral primaries; two
lateral primaries that in some cases extend nearly to the
apex of the lamina and in other cases thin rapidly and are
barely visible at the midpoint where they merge with looping
brochidodromous secondaries. Lateral primaries
generally have 7—10 lateral secondaries that diverge at
angles of 40—70°. Secondaries and lateral secondaries primarily
brochidodromous but occasionally eucamptodromous.
Secondaries rarely present below the midpoint of
the lamina. The brochidodromous loops may merge to
form a knitted intramarginal vein that follows the course of
the acrodromous primary. Some specimens have a secondary
vein that begins at the base of the leaf and forms a
marginal or intramarginal vein. Weak intersecondary veins
occasionally present above the midpoint of the lamina. Tertiary veins weakly to strongly percurrent in the area
between the lateral primaries and the midrib, running perpendicular
to the midrib and slightly apically arched.
Quaternaries weakly perpendicular to tertiaries. Highest
order venation: 6th.
