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Conifer forests in Jurassic Morrison Formation



From: Ben Creisler
bcreisler@gmail.com

A new non-dino paper that may be of interest:

Carole T. Gee, Richard D. Dayvault, Ruth A. Stockey & William D. Tidwell (2014)
Greater palaeobiodiversity in conifer seed cones in the Upper Jurassic
Morrison Formation of Utah, USA.
Palaeobiodiversity and Palaeoenvironments (advance online publication)
DOI: 10.1007/s12549-014-0160-1
http://link.springer.com/article/10.1007/s12549-014-0160-1





Although fossil conifer wood, leaves, and pollen have been known from
the Upper Jurassic Morrison Formation of the Western Interior of North
America for many decades, only a few conifer seed cones have been
described as carbonaceous compressions and casts with little internal
structure. Recently, however, over 60 silicified seed cones with
preserved internal anatomy were amassed by collectors from 11
localities in northeastern and southern Utah and brought to the
attention of palaeobotanists. Here we describe the silicified cones
from Utah and compare them to one another in size, gross morphology
and internal construction. The fossil material is sorted into five new
morphotypes of seed cone. Morphotype 1 pertains to Araucariaceae,
Morphotype 2 is most likely Pinaceae, and Morphotype 5 is
Cheirolepidiaceae. The familial affinity of Morphotypes 3 and 4 cannot
be determined at this time. Comparative size analysis based on volume
calculations shows that Morphotypes 2, 3, 4 and 5 are extremely small,
smaller than any Mesozoic araucarian seed cone, and that Morphotype 1
falls within the range of small fossil araucarian cones. Most
cone-bearing localities are situated to the northwest, west, and south
of Hanksville in southcentral Utah. With regard to palaeobiodiversity,
if Araucaria delevoryasii Gee from Wyoming is included, there are now
six morphotypes of seed cones that represent at least three conifer
families in Utah and Wyoming. Because many conifers are arborescent
and form forests, the new fossil evidence suggests that
species-diverse conifer forests or woodlands were a major type of
vegetation in the Morrison Formation during the Late Jurassic.