SOME LATE CRETACEOUS NATIVE 
CONI FERS OF WYOMI NG 
Text, photos, and pen & ink illustrations 
by Gretchen L Hurley 
356 Nostrum Road, Thermopolis, Wyoming 
Wyoming is populated with many different types of 
conifers today - pines, spruces, firs, and junipers. So it 
was many millions of years ago as well. In fact, 
conifers, along with ferns, have been present in the 
North American flora since about the Pennsylvanian 
Period of the Paleozoic Era - some 310 million years 
ago. This article will present information about some of 
the conifer fossils found in late Cretaceous rocks of 
Wyoming, in other words, in rocks ranging in age from 
65-75 million years ago (mya). 
According to Arnold (1947), conifers or evergreens 
are defined as woody, naked-seeded plants with leaves 
generally like needles or scales. “Most of their 
fructifications are unisexual cone-like inflorescences in 
which the seeds are born on spirally arranged hard and 
woody cone scales”. The pollen is produced in pollen 
sacs attached to the lower surface of stamens, and in 
spiral sequences on the axis of the staminate cone. 
The first conifers are seen in the fossil record about 
Pennsylvanian time, with species diversity peaking in 
early Cretaceous time (~ 130 mya) (Arnold, 1947). Since 
then, conifers have held their own as a dominant part of 
the flora, although some types are in a decline, namely 
the sequoias and some of the cypress. 
Try to imagine a scene in northwestern Wyoming 
about 72 mya - late Cretaceous time. You are standing 
in what is to become the southeastern Bighorn Basin, 
southwest of Tensleep. If you look towards the east, 
you will see, instead of the Bighorn mountains of today, 
a coastal upland and a shimmering seaway - the famous 
inland seaway of middle to late Cretaceous time. You 
are, therefore, just a few feet higher than sea level. 
Fern meadows dominate the ancient landscape, with 
occasional palms, subtropical conifers and flowering 
plants seen as well. Marshes and swamps dot the 
terrain in scattered small basins. Meandering rivers carry 
water sluggishly east towards the seaway, and duck bill 
dinosaurs drink languidly in the afternoon air. A warm 
gentle breeze moves through the ferns, and the sun 
filters down through hot, hazy skies. 
Rather suddenly, the wind picks up. A moderate 
seismic shock rattles through the fern meadow, and the 
duckbills scatter in panic. The river nearby starts to turn 
color with a grayish silt, and a small hill nearby collapses 
into the river during the temblor. This landslide causes 
the river to back up behind it, while the inflow increases 
from some distant storm’s rainfall. More and more ash 
is blown over the meadow and washed in by the river, 
which continues to pond behind the temporary dam. In 
a matter of two hours, the fern meadow with its palms 
and conifers is halfway submerged beneath this ashy 
deluge. After the first two hours, the river begins to 
bring in a thick, ashy sludge, more full of sediment than 
water. This gray slurry also backs up behind the 
temporary dam, further trapping the flora in mud to a 
depth of 12-15 feet. A volcano has erupted somewhere 
in Montana or Idaho, and its ash has been washed and 
blown east by the winds and waters of the storm. The 
sediments trapped behind the dam are preserved by 
later layers of river and marsh sediment. They are 
buried and pressurized, hardened into a mudstone, and 
later uplifted gently as the Bighorn mountains formed 
about 60 mya during the Laramide Orogeny. With uplift, 
erosion begins to remove the layers above the fern 
meadow, eventually revealing a strip of it in outcrop - 
an area known today as Big Cedar Ridge. Entombed 
within the ashy mudstone, are museum quality fossils of 
palms, ferns, conifers and angiosperms. 
This site was discovered in 1990 by Dr. Scott Wing of 
the Smithsonian Institution. Dr. Wing and his team of 
paleobotanists have discovered dozens of new species in 
the ancient fossils of the fern meadow, 9% of which 
were conifers (Wing et al, 1993). Fossil remains found 
here include twigs, foliage, seeds, cones, cone scales 
and petrified wood. This site is located on land 
administered by the Bureau of Land Management, and is 
used today by the public for research and educational 
purposes. 
FIGURE 1 . Parataxodium sp. - Big Cedar Ridge, 
Wyoming; Meeteetse Formation, Late Cretaceous 
Some of the 72 million year old conifers found at this 
site, as well as in other parts of Wyoming include the 
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