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Palmoxylon

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Petrified palmwood
Temporal range: 83–34 Ma Late Cretaceous to Oligocene
Palmoxylon sp. wood round
Scientific classification
Kingdom:
Plantae
(unranked):
Angiosperms
(unranked):
Monocots
(unranked):
Commelinids
Order:
Arecales
Family:
Arecaceae
Subfamily:
Coryphoideae
Genus:
†Palmoxylon
Species

See text

Palmoxylon (Petrified palmwood), is an extinct genus of palm named from petrified wood found around the world. A number of species from the Cretaceous and Tertiary have been described from the Patagonia region of South America.[1] There have been a number of species reported from Egypt which are dated to the Late Eocene and Early Miocene.[2]

Specimens from the Oligocene epoch (34 - 23 mya) can be collected from many scattered sites in east Texas and western Louisiana. Fossils found near fossil palmwood include corals, sponges, and mollusks, indicating that the palms grew along prehistoric beaches. For millions of years, the Gulf Coast shoreline has been moving farther south.

Petrified palmwood includes a group of fossil woods that contain prominent rod-like structures within the regular grain of the silicified wood. Depending upon the angle at which they are cut by fracture, these rod-like structures show up as spots, tapering rods, or continuous lines. The rod-like structures are sclerenchyma bundles that comprise part of the woody tissues that gave the wood its vertical strength.

Petrified palmwood is a favorite of rock collectors because it is replaced by silica and exhibits well-defined rod-like structures and variety of colors. As a result, it exhibits a wide range of colors and designs when cut that can be incorporated into jewelry and other ornamental items. Because it is composed of silica, it is hard enough to polish and withstand the wear and tear of normal use.

In Texas and Louisiana, petrified palmwood is most common in the Toledo Bend area, which is shared by both states. It was left by trees that grew when the Gulf of Mexico's shoreline was much farther north from its present day position. In Louisiana, petrified palmwood is found in the parishes of Rapides, Natchitoches, and Sabine. It is the state stone of Texas and the official state fossil of Louisiana.[3]

Species

There are more then 200 species assigned to the genus Palmoxylon at this time.[4]

  • Palmoxylon arcotense
  • Palmoxylon blandfordi
  • Palmoxylon bororense
  • Palmoxylon chhindwarense
  • Palmoxylon compactum
  • Palmoxylon concordiense
  • Palmoxylon eocenum
  • Palmoxylon geometricum
  • Palmoxylon indicum
  • Palmoxylon livistoniforme
  • Palmoxylon pichaihuensis
  • Palmoxylon pondicherriense
  • Palmoxylon pyriforme
  • Palmoxylon queenslandicum
  • Palmoxylon rewahense
  • Palmoxylon riograndense
  • Palmoxylon sagari
  • Palmoxylon santarosense
  • Palmoxylon valchetense
  • Palmoxylon vaterum
  • Palmoxylon wadiai
  • Palmoxylon yuqueriense

See also

References

  1. ^ Ottone E. G. 2007 "A new palm trunk from the Upper Cretaceous of Argentina" Ameghiniana v.44 n.4
  2. ^ EL-Saadawi, W., Youssef, S. G. & Kamal-EL-Din, M. M. 2004 "Fossil palm woods of Egypt: II. Seven Tertiary Palmoxylon species new to the country" Review of Palaeobotany and Palynology 129(4):199-211
  3. ^ http://www.statefossils.com/la/la.html
  4. ^ Raizada P., Sharma G.P., Raghubanshi A.S., 2008 "A dichotomously branched fossil palm stem from the Deccan Intertrappean beds of India" Current Science 94(2):182-183
  • McMackin, C. E., 1984, "Petrified wood from east to west; some we've liked best." Lapidary-Journal. vol. 37, no. 11, p. 1582-1588.
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