Notes on Fossil Nomenclature Species Living Today, the Forests
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Psilophyton is an extinct Sigillaria belongs to a primitive non-seedbearing group of extinct, spore- vascular plant. It is categorized as bearing, arborescent an herbaceous lycopod—in the plants called tree plant division Lycopodiophyta. lycopods, which were This is one of the earliest plant prominent in the Late divisions that has descendent Carboniferous Coal Swamp Notes on Fossil Nomenclature species living today, the Forests. They had long, clubmosses (although they are unbranched main trunks, It is difficult for paleobotanists to identify and categorize plant fossils. not mosses, but more closely branching only once or Usually they only see fragments. As a result, a somewhat artificial related to ferns). First described twice at the top, unlike classification system was developed, grouping together fossils on the in 1859, Psilophyton was one of Lepidodendron, which basis of morphological resemblance of the separate parts of fossil plants. the first fossil plants from the branched profusely at the Each part may be given a separate name. This name is called a Devonian period to be found. It top. Sigillaria was also shorter, reaching heights of about 60 feet. Seen morphotaxon or form genus. This can at times be confusing, since it is a has true roots, stems, and true here is a bark fossil. very different kind of system from the botanical identification and classification of living plants. leaves, although the leaves were extremely small, Seen on Panel 5 of the Plant Evolution Mural known as microphylls. First appearing in the late Alethopteris is an extinct genus of Early Devonian, Psilophyton became extinct by the seed ferns or pteridosperms. Part end of the Middle Devonian. Williamsonia was part of an extinct and counterpart fossils here display Seen on Panel 3 of the Plant Evolution Mural group of gymnosperms called a part of an Alethopteris frond. The Cycadeoids, because they exhibited fossils create planes of weakness much resemblance in growth form to within the nodules, which tend to the cycads. Cycadeoids first appeared split open so that one half reveals Sphenopteris is the form genus in the Triassic Period and had died the upper surface of the plant name given to particular forms out by the end of the Cretaceous (part), while the other half contains an impression of the upper surface of fern-like foliage. The term was Period. Williamsonia had slender, (counterpart). Althopteris is not depicted in the Plant Evolution Mural, applied to predominantly late branching trunks and cones (strobili) although another pteridosperm, Medullosa, is seen on Panel 5. Paleozoic foliage types, generally that were either unisexual or bisexual characterized by pinnules (with both seed and pollen-producing Calamites is a genus of extinct giant constricted at the base. structures). horsetails. They were arborescent with However, this name has been secondary growth and woody tissue, applied to a variety of disparate Seen on Panel 6 of the Plant Evolution enabling them to reach heights of 60 feet or plants, which have now been Mural more. The stems were conspicuously jointed identified as including seed ferns and ribbed and, as well as true ferns. Attempts unlike today’s have been made to define horsetails, which clusters or subgroups, but the have leaves individual species are not well Many thanks to the Beneski Museum of Natural History for the loan of reduced to small understood and often the fossils are only fragments most of the plant fossils on display here and to John Nicholson for the scales, Calamites had well-developed leaves. and not whole fronds. Natural variation inherent in loan of the Pagiophyllum fossil that he collected locally at the dam in foliage from different parts of the frond, or in South Hadley Falls. Seen on Panel 5 of the Plant Evolution Mural. different stages of development also confuse the Special thanks are due to Kate Wellspring, Beneski Museum Collections issue. Sphenopteris foliage was very common in the Curator, for her sharing of knowledge and expertise and the willingness Carboniferous, surviving into the Mesozoic Era. to work with us and lend us materials to create this wonderful Annularia is the name given to one of Although not depicted on the Plant Evolution Mural, paleobotanical showcase. the forms of Calamites leaves. Seen on Sphenopteris would be seen on Panel 5. Panel 5 of the Plant Evolution Mural. Callipteridium is an extinct genus of seed ferns Ginkgophytes are an ancient Pagiophyllum is an extinct or pteridosperms. They were vascular plants group of gymnosperms, member of the Araucariaceae that bore seeds on fern-like leaves, but they thought to have originated in family, which today is restricted were not ferns, but rather gymnosperms. It the late Paleozoic Era. Large to the Southern Hemisphere. was not until the early 1900s that much of the fan-like leaves reminiscent of This family includes the common fern-like foliage found in Paleozoic rocks was Ginkgo leaves can be found in houseplant, the Norfolk Island recognized to belong to plants that bore Carboniferous fossils and pine. The genus Pagiophyllum seeds. Pteridosperms were particularly have been called was extant between 290 and 85 characteristic of the Carboniferous Period. Ginkgophytopsis, but fossils million years ago, with a world- Mature fronds are speculated to have been from that era can be very wide distribution. This fossil is over 10 feet long. difficult to interpret. During the Jurassic Period, many species of Ginkgo were approximately 190-200 million common, but today they are represented by only a single extant species—Ginkgo Callipteridium is not depicted in the Plant Evolution Mural, although years old. biloba, the maidenhair tree, so named because its leaves resemble those of the another pteridosperm, Medullosa, is seen on Panel 5. maidenhair fern. Ginkgo has distinctive broad leaves that have dichotomous Cordaites were an extinct group of venation. gymnosperms that gave rise to the conifers, Although another ginkgophyte, Sphenobaiera, is seen on Panel 4 of the Plant e.g., pine, spruce, hemlock, fir, and their Evolution Mural, Ginkgo is on Panel 5. Pecopteris is the form relatives. These tall trees are estimated to genus name for the have grown up to 100 feet tall and had large Glossopteris comes from the Greek: γλώσσα leaves of the strap-shaped leaves. They first appeared in glossa, meaning tongue, because of the large, marattialean fern the latest part of the Late Devonian and the tongue-shaped leaves on these 20 foot tall trees. Psaronius. The name earliest part of the Early Carboniferous and Now extinct, Glossopteris is famous as the fossil is applied to tongue- became common in the Late Carboniferous, that led Austrian geologist Eduard Suess to shaped pinnules dying out by the end of the Permian Period. conclude, based on its distribution, that there had (lobes) of the fern The name Cordaites was originally applied once been a large southern continent, which he frond, which are only to the foliage, but is now also used for named Gondwanaland. The past distribution of broadly attached to the rachis (the main axis of the leaf). This is one of the stems and the entire plant. Glossopteris fossils constituted one of the most the best known Paleozoic tree ferns. Seen on Panel 5 of the Plant Seen on Panel 5 of the Plant Evolution Mural. important pieces of supporting evidence for the Evolution Mural. theory of Continental Drift, the precursor to the Cryptozoon is the name given to a form modern theory of plate tectonics. Petrified wood is a permineralization fossil. This kind of fossil of Cambrian and Precambrian reef- forms when a plant part becomes immersed in water containing a Seen on Panel 6 of the Plant Evolution Mural. forming rocks. They are composed of high concentration of dissolved minerals (most commonly silica), alternating light and dark layers of which then permeate all the sediment, thought to represent fossilized Lepidodendron is among the extinct arborescent cells and tissues of the plant. remains of ancient microbial mat lycopods. With their secondary growth (woody Something triggers the communities growing in the sea. These tissue) they grew to heights of 130 to 150 feet. The precipitation of the dissolved are examples of trace fossils, which are massive, erect trunks of some Lepidodendron minerals so that they harden indicative of activities of living organisms species branched profusely to produce large crowns around and within the plant but which do not preserve any remains of of leafy twigs. Some leaves reached three feet long, fragment. When the mineral is the organisms themselves. Also known as leaving conspicuous leaf bases on the stem surface completely solidified, the plant Stromatolites, these laminated rocks were when they dropped off. It was in fact the distinctive fragment is essentially widespread during Precambrian times, when the world was dominated pattern of these leaf base scars that gave it its entombed within solid rock. In by microbial life. Some stromatolites have been found that date back 3.5 name— Lepidodendron or scale-tree. The bark these kinds of fossils, scientists billion years ago, thus they are evidence of some of the earliest life on fossil on display here shows that pattern. Also can study the internal anatomy Earth. Today one can see living examples of stromatolite beds in Shark shown is a fossil featuring smaller stems. of ancient plants. Often this is Bay on the west coast of Australia. done by making very thin Seen on Panel 5 of the Plant Evolution Mural. Seen on Panel 1 of the Plant Evolution Mural sections of the fossil. .