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Carboniferous Fossil Plant Identification for Western PA

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Recommended Fossil Plant Identification Books:



A Guide to Pennsylvanian (Carboniferous) Age Plant Fossils of Southwest Virginia

By Thomas F. McLoughlin, 2013
280 Fossil Plant Illustrations





Plant Fossil Identification - Carboniferous of Western PA - Conemaugh Group


Location:
Fossil Plant Material in Road Cuts near Pittsburgh and Ambridge, Pennsylvania
Pennsylvanian Coal Forest
~ 299 - 300 Million Years Old
Upper Pennsylvanian, Westphalian D to Stephanian A
Conemaugh Group: Glenshaw Formation: Mahoning Shale

Back to Main Ambridge Fossils Page


Fossil Ferns from the Mahoning Layer in Ambridge, PA

Fossil Ferns from the Mahoning Layer in Ambridge, PA





Carboniferous Plant Identification - Western PA sites
Illustration of a Carboniferous Coal Forest

Illustration of a Carboniferous Coal Forest

The Ambridge site and many nearby sites expose the remains of a Carboniferous Coal Forest. These remains are now fossilized in layers of shale from the Glenshaw Formation.

By far the most common plants are frond sections of the Pecopteris seed ferns, branch and trunk sections of the Calamites horse tails, and the needle like leaves from giant Lycopod scale trees. Other, less common plants include various Neuropteris seed ferns and a small plant called Sphenophyllum. One notable plant that is not found here, or very rare, is the Alethopteris seed ferns. They are very common to abundant in other formations, but not present here.

Below you can find a sample of fossils found at this location. Click on a thumbnail to go to the section about that plant. Each section includes reconstructions, descriptions, and fossil examples.






Calamites: Horse Tail
calamites plant fossils - carboniferous
Calamites - Stem and Trunk Fragments


calamites diagram from Dunbar 1963

From Dunbar, 1963

Description

Calamites was a common Carboniferous tree-like plant that populated the swampy coal forests of the Carboniferous Period. The trunks of Calamites were thick, hollow, and segmented, sort of like bamboo today. They also had ribbed surfaces. A whorl of leaves, called Annularia radiated from each segment of the plant. Calamites could grow quite tall, possibly around 50 feet in height. Extinct Calamites are closely related to the small modern horsetail plants, Equisetum. An illustration of a reconstructed Calamites plant by Dunbar, 1963, can be seen to the right.

As fossils, Calamites are found as carbon films and as casts when sediments filled in the hollow stems.



Similar Fossils

Calamites trunk and branch sections are easy to identify due to thier segmented nature and the ribbed nature of the wood.

The leaves, called Annularia, are also easy to identify, as each leaf cluster is arranged in a distinct starburst pattern, with 8 or more leaves. However, the leaves of a shrub or vine like plant, Sphenophyllum, has similar looking leaves. In general, Sphenophyllum leaves are wider and more triangular. Also, sphenophyllum leaf clusters usually have less than 8 leaves.




Sample Fossils from Ambridge Shown Below: Calamates and Annularia

Stem and Trunk Sections:

Fossil Calamites Plant Stem from near Pittsburgh.

Calamites stem section. Notice the ribbing and the segments.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA

Carbon Film Fossil Calamites Plant Stem from near Pittsburgh.

This Calamites stem section is preserved as a carbon film. Both the positive and negative are shown, they are to the left of the image.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA


Calamites Leaves (Annularia):

Hash plate showing one Calamites leaf cluster (annularia); toward the lower left.

Fossil hash plate showing one Calamites leaf cluster (annularia); toward the lower left
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA

Closeup of the Calamites leaf cluster (annularia).

Closeup of the Calamites leaf cluster (annularia).
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA





Cordaites:
Cordaites: Early Conifer


Cordaites Illustration

Cordaites Illustration
From: Cridland, 1964

Description

Cordaites is an extinct gymnosperm tree that grew in the swampy coal forests of the Carboniferous. These trees grew up to 100 feet in height and may have had root systems similar to that of mangrove trees. The leaves of Cordaites are strap like, meaning they are very long and narrow, growing up to lengths of 27 inches. The leaves are also very thick and leathery. A close inspection shows parallel leaf veins, making numerous parallel lines running down the leaf.

The term Cordaites technically only refers to the name of the leaves of this tree. The bark is called Mesoxylon, and the roots are called Amyelon.



Similar Fossils

Cordaites leaves are often found as fragmented carbon films. These can sometimes be confused with the long leaves of Lepidophylliodes. However, Lepidophylliodes do not have the numerous parallel veins running down the leaf.




Sample Fossils from Ambridge Shown Below: Cordaites leaf fragments

Fossil Sphenophyllum leaf clusters from near Pittsburgh.

Cordaites leaf fragments. Notice the numerous "grooves" in the leaves, these are the many parallel veins.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA





Lepidodendron: Scale Tree
Lycopod


Lepidodendron Illustration

Lepidodendron Illustration
From Dunbar, 1963

Description


Lepidodendron is a common tree like plant that grew in the Carboniferous forests. This tree could exceed a height of 120 feet. It's closely related to club mosses of today. Lepidodendron is often called a "scale tree" due to the scale like imprints found on its trunk and limbs. These scale imprints are actually leaf scars from were leaves would exit the trunk and branches. The tree looked nothing like real trees , but instead had long, needle like leaves covering the entire trunk. This would give the entire tree a hairy looking appearance, as shown in accompanying the diagrams. The roots of scale trees are called "Stigmaria" fossils.

Lepidodendron Illustration

Closeup of a branch section of Lepidodendron, showing the leaf scars and the leaves as it would have looked in life. It also shows the bark pattern, as this pattern can be confused with other scale trees.
From The American Cyclopedia, v. 4, 1879. (Public Domain)



Similar Fossils

Lepidodendron branches and trunks look similar to other club moss type trees, such as Sigillaria. The difference is in the texture of the trunk sections. Lepidodendron has diamond shaped leaf scars, while Sigillaria has rows of parallel leaf scars.




Sample Fossils from Ambridge Shown Below: Lepidodendron Scale Trees
Trunk and Limb Sections

Fossil Sphenophyllum leaf clusters from near Pittsburgh.

Branch section of a Lepidodendron. The preservation is poor, but one can still see the diamond "scale" pattern in the closeup. Each scale is a leaf scar, where a long leaf would grow from.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA


Fossil Sphenophyllum leaf clusters from near Pittsburgh.

Closeup of the diamond scale pattern. If better preserved, there would be more detail in the leaf scars.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA

Lepidodendron Scale Trees
Leaves
Fossil Sphenophyllum leaf clusters from near Pittsburgh.

These are leaves from the Lepidodendron scale tree. They are usually found as isolated pieces, this one shows a cluster still intact. The leaves would sprout all over the trunk and branches, making the tree look hairy.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA





Tree Ferns / Seed Ferns:
Neuropteris - Macroneuropteris - Pecopteris - Sphenopteris


Psaronius Pecopteris Illustration

Pecopteris - Tree Fern
La terre avant le deluge, 1874, 7th edition.
(Public Domain)

Description

Seed Ferns, which are technically called (Peridospermatophyta), are some of the most common plants in the Carboniferous coal forests. They are often preserved as intricate carbon films and are prized by fossil plant collectors. The name comes from the fact that they had fern like foliage, but reproduced with seeds. Many seed ferns of the Carboniferous were tree like, while others were vine like. The tree forms did not have true trunks, but instead had a large trunk that was made from hundreds of tiny roots.

Two common seed ferns from the Pittsburgh area are Psaronius (Pecopteris) and Medullosa (Macroneuropteris).

Psaronius (Pecopteris)
Psaronius was a tree fern that grew up to 30 feet in height. The fern like fronds of Psaronius are composed of many small leaflets. The leaf fossils are called Pecopteris. Fossilized leaf sections are very common in the shale layers around Pittsburgh.

Medullosa (Macroneuropteris)
Medullosa was another tree fern that grew around 25 to 30 feet in height. The leaf fossils are called Macroneuropteris. Macroneuropteris is often called Neuropteris, which is a closely related tree fern. These fern trees often had larger leaves making up the fronds. Many different types of Macroneuropteris and Neuropteris fossils can be found throughout the Pittsburgh region.



Similar Fossils

Many Tree Ferns and other Seed Ferns look very similar to each other, and there are MANY types of fossil ferns. This often makes identification, even to the genera level, very difficult.

A good identification book is recommended.

Macroneuropteris Illustration

Illustration of a Macroneuropteris Tree Fern
This illustration is by Leo Lesquereux, 1879 (Public Domain)




Sample of Tree Fern Fossils from Ambridge Shown Below

Macroneuropteris scheuchzeri

Fossil Macroneuropteris scheuchzeri from near Pittsburgh.

This is a leaf from a frond of Macroneuropteris scheuchzeri. These are large and easy to identify when found.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA



Fossil Macroneuropteris from near Pittsburgh.

Another leaf from a frond of Macroneuropteris scheuchzeri. This one was shattered, but glued back together ok.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA



Fossil Macroneuropteris from near Pittsburgh.

This is a leaf from a frond of Macroneuropteris scheuchzeri. These are large and easy to identify when found.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA






Neuropteris ovata

Fossil neuropteris ovata from near Pittsburgh.

This is a frond section from N. ovata. The individual leaves are small and oval shaped.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA



Fossil neuropteris ovata from near Pittsburgh.

These are two small sections of N. ovata leaves.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA






Pecopteris sp. (Psaronius)

Pecopteris are by far the most common fossils found at the Ambridge site, and fossil fern sites around the Pittsbugh area.


A mangled fossil fern frond from the mahoning shale near Pittsburgh

This is a mangled pecopteris fossil fern frond. It was too mangled to save.



Fossil pecopteris frond pieces from near Pittsburgh.

These are pieces of Pecopteris fronds of Psaronius fern trees. There are two species present on this foot long fern plate.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA



Fossil pecopteris frond pieces from near Pittsburgh.

This is a section of Pecopteris frond of a Psaronius fern tree. A Neuropteris ovata stem is also present. It's labeled "2".
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA




Sphenopteris

Fossil fern from near Pittsburgh.

Sphenopteris leaves are a little more ornate than Neuropteris and Pecopteris leaves. This specimen is 2" across
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA







Sphenophylum: Shrub / Vining Plant
Sphenophylum: Leaf Clusters


Sphenophyllum Illustration

Sphenophyllum Illustration

Description



Sphenophyllum is a small plant from the Carboniferous coal forests. It's not a tree, but designated as a sprawling or scrambling plant, this is kind of like how a tomato plant would naturally grow if it was not staked up. They are usually less than 3 feet tall with many stems that would vine out. The stems contain whorls of leaf clusters. The individual leaves are fan shaped. There are less than 8 leaves per cluster. The leaf clusters are each around an inch or so in size.



Similar Fossils

Sphenophyllum fossils are easily confused with the leaves of calamites trees. The calamites leaves are called Annularia. Annularia leaves come in clusters of more than 8 leaves. The individual leaves are also much narrower than Sphenophyllum




Sample Fossils from Ambridge Shown Below: Sphenophyllum Leaf Clusters

Fossil Sphenophyllum leaf clusters from near Pittsburgh.

Sphenophyllum leaf clusters with a stem fragment connecting them. The clusters are about an inch and a half in diameter.
Carboniferous: Pennsylvanian: Glenshaw Formation: Mahoning Shale
Butler Co., PA





References and Works Cited:


Dunbar, Carl O. (1963) Historical Geology. John Wiley & Sons, Inc.