Betula leopoldae

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Betula leopoldae
Temporal range: Ypresian
leaf fossil
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Fagales
Family: Betulaceae
Genus: Betula
Subgenus:
Betula subg. Neurobetula
Species:
†B. leopoldae
Binomial name
†Betula leopoldae

Betula leopoldae is an

extinct species of birch in the family Betulaceae. The species is known from fossil leaves, catkins, and inflorescences found in the early Eocene deposits of northern Washington state, United States, and similar aged formations in British Columbia
, Canada. The species is placed as basal in Betula, either as a stem group species, or an early divergent species.

History

Betula leopoldae fossils have been identified from a number of locations in Western North America, the 49

Quilchena, British Columbia.[7]

In general, the geologic ages for the Okanagan Highland locations are of

uranium-lead or argon–argon radiometric dates indicating Ypresian ages, while the undated sites or those given older dates being possibly slightly younger and Lutetian in age.[8]

Betula leopoldae was described from a series of

matronym recognizing paleobotanist and conservationist Estella Leopold, though this was not noted in the type description.[9] In a paper which appeared that same year, Peter Crane and Ruth Stockey described a series of B. leopoldae leaves along with catkins, flowering bodies, and pollen from the Allenby Formation. Crane and Stockey noted B. leopoldae to be the oldest reproductive plus vegetative record for a Betula species at that time.[2] A B. leopoldae leaf from the Klondike mountain formation was figured by Conrad Labandeira in 2002 which displayed distinct interior foliage feeding damage from insect feeding, in which a series of four leaf blade sections had been removed between successive secondary veins.[10]

Classification

Living Betula alleghaniensis, which is similar to B. leopoldae

While Wolfe and Wehr did not detail any subgenus placement in the original type description from Republic, the complete nature of the fossil suite in the Allenby Formation allowed for more detailed examination of the relationships. Based on the details from the associated fossils Crane and Stockey placed B. leopoldae within Betula section Eubetula, subsection Costatae, near the living species Betula alleghaniensis. They noted that the last revision of Betula was undertaken by Winkler in 1904 and there were no reasons to conclude subsection Costatae was paraphyletic.[2] Further revision of the genus was done by Forest et al in 2005, who found that subsection Costatae was paraphyletic based on molecular comparisons and the species in the subsection were grouped in the basal nodes of the genus phylogeny. B. leopoldae was interpreted as positioned either in the stem lineage of the genus, or as one of the grade of species which diverged early in Betula diversification.[11] Crane and Stockey noted that the pollen preserved in the flowers is a close match for pollen morphotype Betula claripites that has been reported from the Princeton Basin and François Lake.[2]

Description

Overall the leaves of B. leopoldae are elliptical to circular in outline ranging up to 145 mm (5.7 in) long, though averaging between 60–90 mm (2.4–3.5 in). The leaf width is typically 30–50 mm (1.2–2.0 in) but ranges up to 65 mm (2.6 in). The 7–18 mm (0.28–0.71 in) long petioles narrow from base to leaf blade and meet the blade at a symmetrical to asymmetrical base which may be cordate to obtuse. The margin is serrated with larger primary teeth that are separated by 7 or less smaller subsidiary teeth, all of which have a variable morphology from pointing apically to pointing basally. The teeth are non-glandular and each primary tooth is supplied by a secondary vein and each subsidiary tooth by a secondary vein branchlet. The leaves are pinnately veined with a thin midvein from which the secondary veins alternately or oppositely branch off between 40 – 80°. There are between 7 and 13 secondary veins that run parallel to each other and curve upwards near the tips before terminating in the teeth. As the secondaries approach the margin they produce up to 7 branches from the abaxial side, each of which supply subsidiary teeth. The tertiary veins are usually branching near the margin and less so not branching near the midvein. The quaternary veins fully extend between the tertiary veins with both branched and unbranched veins forming polygonal shaped areolae with veinlets terminating in them. The undersides of the leaves, the leaf margins, and the petioles sport numerous 0.1–0.35 mm (0.0039–0.0138 in) long simple hairs. On the smaller leaves the hairs are notably dense in covering.[2]

The

exine. The surface also has spines and granular nodes that are grouped into rows on ridges of the exine.[2]

References

  1. ^ a b Wolfe, J.A.; Wehr, W.C. (1987). "Middle Eocene dicotyledonous plants from Republic, northeastern Washington". United States Geological Survey Bulletin. 1597: 1–25.
  2. ^
    doi:10.1139/b87-338
    .
  3. S2CID 129448108
    .
  4. doi:10.1139/e04-084
    .
  5. S2CID 134962126
    .
  6. hdl:1807/71979
    .
  7. ISBN 978-0774841511
    .
  8. doi:10.1139/e04-100
    .
  9. ^ Pigg, K. B.; DeVore, M. L. (2007). "East meets West: the contrasting contributions of David L. Dilcher and Jack A. Wolfe to Eocene systematic paleobotany in North America". Courier Forschungsinstitut Senckenberg. 258: 89.
  10. doi:10.2113/gsrocky.37.1.31
    .
  11. S2CID 86080433
    .

External links

Media related to Betula leopoldae at Wikimedia Commons

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