The gymnosperms generally have a softer, lighter wood than the angiosperms.  The term “softwoods” generally refers gymnosperms and  ”hardwoods” is a term usually associated with angiosperms.

Rudolf Florin - famous 20th century paleobotanist

It is generally accepted that the earliest gymnosperms, or their predecessors, arose in the Devonian era (395-345 million years ago).  Progymnosperms gave rise to the first well known large gymnosperm order, the Chordaitales which thrived in the Carboniferous era (345-290 million years ago).  The other major group, the angiosperms, arose much later approximately 130 million years ago in the Cretaceous era.  It is still unsettled as to whether the gymnosperms form a single monophyletic clade originating from the Chordaitales and possibly later through the Voltziales (a view proposed by the 20th century’s greatest gymnosperm paleobotanist Carl Rudolf Florin) or whether they are polyphyletic with different evolutionary origins not all included in a single clade originating from a single Carboniferous order.  In fact, a gymnosperm precursor of the angiosperms has not been completely disproven.

There are 4 major groups of gymnosperms.   Whether these are considered to be different divisions, subdivisions, classes or orders varies with the different classification schemes.  For the purpose of clarity here we will consider the 4 major groups of gymnosperms to be order level designations:  the Pinales (conifers), the Cycadales (cycads), the Gnetales (ephedras etc.), and the Ginkgoales (ginkgos).  This is the old Linnaean classification but since the newer schemes vary so much, we’ll use it for clarity.

Podocarpus henkelii-Podocarpaceae family

1.  Pinales (a.k.a. Coniferales):  There are nine families: Pinaceae, Taxaceae, Cephalotaxaceae, Cupressaceae, Sciadopityaceae (only one species), Podocarpaceae, Phylocladaceae, Araucariaceae,  and Amentotaxaceae.  This is the largest order of gymnosperms—approximately 630 species.

Cycas revoluta-Cycadaceae Family

2.  Cycadales.  There are three families:  Cycadaceae, Stangeriaceae and Zamiaceae.  The number of species is rather fluid right now,  probably in the range of 160-280 species.

Zamia pumila-Zamiaceae Family

3. Gnetales:  there are three families (approximately 100 species):  Ephedraceae, Gnetaceae and Welwitschiaceae (only one species of Welwitschiaceae).

Ephedra major-Ephedraceae Family

 4.  Ginkgoales, only one species, Ginkgo biloba

There are several predominantly dioecious (separate female and male plants) gymnosperm taxa such as: Junipers, Yews, Plum Yews, Podocarps, Araucaria and Cycads.

There are many extinct taxa of gymnosperms, the largest group being the seed producing ferns, known collectively as the Pteridosperms.  Since we are considering gymnosperms to include all vascular seed-bearing taxa not includable under angiosperms, we mention Pteridosperms here.  They were a very important group of plants in the Carboniferous Period and constitute the bulk of the mass of coal.  The last of these probably disappeared from the geologic record in the Eocene (3.5-5 million years ago, in Tasmania) or perhaps much sooner.

Much of the pioneering work in the Carboniferous-Permian Pteridosperm Glossopteris was done by Marie Stopes (1880-1958).  This work contributed support for the idea of the Permian break up of Gondwana, originated by the Austrian geologist Edward Suess.  This was suggested by the wide distribution of Glossopteris fossils throughout all of the southern hemisphere landmasses including India.  Marie Stopes also investigated carbonate concretions (”coal balls”) in England and North America (none in Japan).

Marie Stopes

A question which remains unanswered: did all of this large rather heterogenous group become extinct without leaving modern successors (i.e., were paraphyletic) or are some (or one) of them in the evolutionary pathway to modern gymnosperms (i.e., monophyletic with gymnosperms)?  It is possible that the modern order of Cycadales arose from a Pteridosperm and also that an extinct cycad-like order, the Cycadeoidales (aka Bennettitales) (extinct in the Cretaceous) had a Pteridosperm origin.  Almost all Pteridosperms became exticnt during the Mesozoic Era (245-65 m.y.a.) although there are some Eocene fossils which appear to belong in this group.

An Example of the Taxonomic Classification: