Petrified Forest National Park

Petrified Forest National Park


Plant Megafossils

Late Triassic plant megafossils found in Petrified Forest National Park
Compiled by Dr. Sid Ash, September 2003

* species based on fossils collected in the park
** species and genotype based on fossils collected in the park

Chinlea campii**

Equisetites bradyi*
Equicalastrobus chinleana**
Neocalamites virginiensis

Ferns and Fernlike Foliage
Cladophlebis daughertyi*
C. yazzia*
Clathropteris walkeri*
Cynepteris lasiophora*
Itopsidema vancleaveii**
Phlebopteris smithii*
Sphenopteris arizonica*
Todites fragilis*
Wingatea plumosa**

Aricycas paulae**
Charmorgia dijolli**
Lyssoxylon grigsbyi**

Zamites powellii

Baiera arizonica*

Dadoxylon chaneyi*

Araucariorhiza joae**
Araucarioxylon arizonicum

Brachyphyllum hegewaldia*
Pagiophyllum simpsonii*
Podozamites arizonicus*
Samaropsis puerca*

Position Uncertain
Carpolithus chinleana*
Dinophyton spinosus**
Marcouia neuropteroides**
Pramelreuthia yazzi*
Schilderia adamanica**
Woodworthia arizonica**

Nonnative Species

The National Park Service places a high priority on encouraging, restoring, or maintaining plant and animal diversity in all of its sites across the country. One of the fronts in the battle to maintain healthy, balanced ecosystems is waged against invasive species.

Nonnative species (also referred to as invasives, exotics, introduced, or nonindigenous species) have been introduced intentionally or unintentionally into new ecosystems. An invasive species is a nonnative whose introduction causes or is likely to cause economic or environmental harm or harm to human health. Invasive species take over habitat, squeezing out the native flora and fauna. This reduces biodiversity, interferes with soil productivity, damages or replaces native populations, and changes land and water quality. Each year invasive plants cause billions of dollars in damage to public and private lands and the ecosystems upon which we all depend. In the National Park Service, 196 national park areas have serious problems posed by invasive plant species. The costs of managing weeds were estimated at $80 million from 1996-2000.

Of particular concern on the Colorado Plateau are plants which are invading rangelands and waterways. Control of infestations has been difficult and the ecological consequences have been serious. Invasive weeds which are of particular concern include camelthorn, Canadian thistle, Russian knapweed, cheatgrass, common purslane, and field bindweed. These plants grow where the earth has been disturbed and little competition for resources exists. They establish root systems and grow strong enough to expand aggressively. Some have seeds which can lie dormant for many years, even up to half a century. Others have extensive horizontal root systems which can spread rapidly over large areas. They may germinate in the fall and produce seeds in the early spring. The seedlings then have a considerable head start, stealing water from native seedlings which sprout later in the season.

Russian olives and tamarisk, or saltcedar, were introduced to the Southwest with the good intentions of providing ornamental plants and natural erosional controls. Unfortunately, these invasive species have taken over a lot of native habitat. They crowd out cottonwoods and willows at water sources, which in turn affects migrating and breeding bird species. The result has been a significant decrease in biodiversity and ecosystem health along much of the Colorado Plateau's waterways, including waterways within Petrified Forest National Park.

The consequences of introducing nonnative species are sometimes not recognized for generations, but rarely do the advantages outweigh the risks. Ongoing efforts are being made to take out invasive species throughout the parks. The National Park Service, in cooperation with a wide variety of local, state, and other federal agencies, is working to control invasive species through cooperative partnerships with communities and unifying management plans. Invasive species know no boundaries; the aliens are in everyone's neighborhood!

If you are a teacher or a student, you might be interested in an on-line program that will help you learn more about Invasive Plant Species. It's called Alien Invasions: Plants on the Move and is a K-12 curriculum-based program, developed by the Bureau of Land Management and scientists.

Kingdom Plantaea

Linnaean taxonomy of Late Triassic Plants of Petrified Forest National Park
Compiled by W.G. Parker and Sid Ash December 8, 2004

Kingdom Plantae
 Division Pteridophyta
Class Filicopsida
     Order Uncertain
       Family Guaireaceae
         Genus Itopsidema
           Species vancleaveii
       Family Cynepteridaceae
         Genus Cynepteris
           Species lasiophora
     Order Gleicheniales
       Family Gleicheniaceae (?)
         Genus Wingatea
           Species plumosa
     Order Matoniales
        Family Matoniaceae
      Genus Phlebopteris
            Species smithii
     Order Polypodiales
        Family Dipteridaceae
          Genus Clathropteris
            Species walkerii
     Order Osmundales
        Family Osmundaceae
          Genus Todites
            Species fragilis
     Order Hymenophyllales
         Family Hymenophyllacaea
           Genus Hopetedia
             Species n. sp.
   Class Uncertain
  Order Uncertain
     Family Uncertain
        Genus Cladophlebis 
          Species daughertyi
              Species yazzia
              Species sp.
           Genus Marcouia
              Species neuropteroides
Division Coniferophyta
Class Pinopsida
  Order Coniferales
     Family Uncertain
        Genus Araucarioxylon
              Species arizonicum
         Family Araucariaceae
            Genus Araucarites
               Species n. sp.
            Genus Araucariorhiza
               Species joae
         Family Uncertain
            Genus Brachyphyllum
               Species hegewaldia
            Genus Pagiophyllum
               Species simpsonii
            Genus Podozamites
               Species arizonica
               Species n. sp.
   Order Cordaitales
      Family Cordaitaceae
            Genus Samaropsis
               Species puerca
            Genus Dadoxylon
               Species chaneyi
   Class Uncertain
       Order Uncertain
          Family Uncertain
             Genus Schilderia
                Species adamanica
             Genus Woodworthia
                Species arizonica
             Genus Pelourdea
                Species sp.
             Genus Carpolithus
                Species chinleana
Division Pteridospermophyta
Class Uncertain
   Order Uncertain
      Family Uncertain
             Genus Sphenopteris
                 Species arizonicum
             Genus Dinophyton
                 Species spinosus
             Genus Pramelreuthia
                 Species yazzi
Division Sphenophyta
Class Equisetopsida
       Order Equisetales
          Family Equisetaceae
             Genus Equisetites
                 Species bradyi
                 Species sp.
             Genus Equicalastrobus
                 Species chinleana
             Genus Neocalamites
             Species virginiensis
                 Species sp.
 Division Lycophyta
Class Lycopsida
   Order Lycopodales
       Family Uncertain
           Genus Chinlea
              Species campii
               Species sp.
               Genus Lycopodites?
                   Species sp.
Division Cycadophyta 
Class Bennettitopsida
      Order Bennettitales
          Family Uncertain
              Genus Zamites
                   Species powellii
Class Cycadodsida
       Order Cycadales
           Family Uncertain
               Genus Aricycas
                   Species paulae
               Genus Cycadospadix
                   Species n. sp.
               Genus Lyssoxylon
                   Species grigsbyi
               Genus Charmorgia
               Species dijolli
 Division Ginkgophyta
Class Ginkgoopsida
   Order Ginkgoales
          Family Uncertain
               Genus Baiera
                   Species arizonica
               Genus Ginkgoites
                   Species n. sp.


Wildflowers have adapted to the arid climate at Petrified Forest National Park in many different ways. Thick, waxy coverings on leaves and stems reduce evaporation. Small leaves reduce the effects of solar radiation and water loss. Deep taproots reach far into the soil to find water while shallow, widespread roots catch and absorb surface water quickly. Despite these adaptations, wildflowers avoid drought and heat by hiding in the soil as seeds or bulbs, sometimes for decades. Germination only occurs after significant seasonal rainfall.

Not all wildflowers bloom during the day. Some take advantage of cooler night temperatures to open their flowers. These evening-blooming plants include evening primrose, sacred datura, sand verbena, and yucca. The yucca and the yucca moth have a fascinating dependency on one another which includes trysts in the night. After mating, the female moth gathers pollen from a yucca flower and packs it into a ball. She then flies into the night until locating another yucca flower. Here she lays eggs in the base of the flower's pistil and packs pollen from her pollen ball down into the pistil, providing food for her young when they hatch. She visits several flowers during the night, each time distributing the pollen from flower to flower. Thus she fertilizes the yucca flowers while ensuring that her young will have nutrients to live on. Yucca plants and moths have a symbiotic relationship: yucca flowers are only pollinated by yucca moths and yucca moth larvae only feed on yucca pollen.

April and May, following winter snow and rain, are generally the best months to see wildflowers throughout the Southwest. Beginning in late August, if the summer monsoon season (July-August) has brought significant rainfall, different species bloom and color the landscape once again.



Grasses are one of the most important plants within the grassland ecosystem found in the park. Large expanses of grasslands form where wind-blown sediment and erosion have created a layer of soil several feet thick. One of the most devastating causes of grassland destruction is grazing by cattle and horses. Because grazing is not allowed within the park, the area has returned to a more natural state and is one of the largest recovering grasslands in the Southwest.

Individual grasses sprout almost anywhere they can find soil, even in potholes filled with dirt. Most grasses fit into two basic groups, bunch grass and sod-forming grass. Bunch grass is classic arid adapted grass occurring in scattered clumps. Its spreading growth pattern reduces competition for limited soil nutrients and water. Examples of bunch grass include rice grass and needle-and-thread grass. The large rice grass seeds are rich in protein and were an important source of food for American Indians. Needle-and-thread grass has a sharp seed attached to a thin thread-like tail which develops in a spiral, wound fashion. As the thread unwinds, it drives the seed into the ground. Both of these grasses are perennial, becoming dormant during droughts. Rice grass plants have been known to live over 100 years, through wet and dry times.

Sod-forming grass is what most people have in their yards. Galleta and Blue Grama, sod-forming perennials native to Petrified Forest National Park, usually grow together. Cheat grass was accidentally brought to the United States in the 1800s and is now found throughout the park.

To visitors unaccustomed to the vast landscapes of the Southwest, Petrified Forest National Park can seem somewhat barren. On closer look, the land is teeming with interesting and clever life.


Not all plants at Petrified Forest National Park are fossils. Living plants are critical components within the grassland ecosystem found throughout the park. Plants capture particulate dust in the air, filter gaseous pollutants, convert carbon dioxide to oxygen, provide habitat for animals, and supply raw materials for humans.

Plants of arid climates have adaptations which enable them to survive the extremes of temperature and precipitation. These adaptations can be grouped in two basic categories, drought escapers and drought resistors. Drought escapers are plants which take advantage of favorable growing conditions when they exist, but go dormant when those conditions disappear. They are usually annuals, growing only when enough water is available. Seeds produced under good conditions can lie dormant for years if conditions are not favorable for germination. Most grasses and wildflowers are drought escapers.

Drought resistors are typically perennials. They have mechanisms for reducing the damage a drought can cause. For example, some will drop their leaves if water is unavailable. Many have small, hairy leaves which reduce exposure to air currents and solar radiation and thereby limit the amount of water lost to evaporation. Cacti, yuccas and mosses are examples of drought resistors. Yuccas have extensive taproots which can reach water beyond the ability of other plants. Mosses can tolerate complete dehydration. When rains return after extensive dry periods, mosses green up immediately.


In many areas of Petrified Forest National Park, large collections of exposed rock surfaces are covered by lichens, especially the shaded north side. A lichen is actually a simple community of at least two mutually-dependent organisms: fungi and green algae. When both organisms are dependent on the other, they are said to be symbiotic. Green algae uses the photosynthesis process to produce food for the fungus, while the fungus protects the algae from the elements and extracts nutrients from soil and rock. The lichen structure is more elaborate and durable than either fungus or algae alone.

Lichens are well adapted to arid climates. They can continue food production at any temperature above freezing. Lichens can absorb more than their own weight of water and can absorb emphemeral water, such as dew, almost directly into their cells. The water does not need to go through roots and stems as it does in vascular plants.

Many other plants benefit from the presence of lichens. The green algae component of lichens can transform nitrogen in the air, which is unusable to most organisms, into a form which is essential for life. This is especially important in arid climates where lack of nitrogen is known to limit productivity.

Because lichens take everything they need from the air, they are dependent on good air quality. Scientists turn to lichens as indicators of air quality. It is truly amazing how nature, over time, can establish symbiotic relationships for the benefit of the whole ecosystem.