The Triassic Period (245-190 Ma) witnessed the mass radiation of the conifers (Coniferales) across the planet.
The oldest conifer fossil so far discovered is Swillingtonia denticulata, which dates from the Carboniferous of c.310 Ma.
While the conifers were present from this time onwards, it was not until the Triassic (245-208 Ma) that they radiated out and probably occupied the drier parts of the planet. The eight conifer families which still exist today (Pinaceae, Podocarpaceae, Taxaceae, Cupressaceae, Taxodiaceae, Araucariaceae and Cephalotaxaceae) appear in the fossil record from this time.
Conifers are typified by a pyramidal growing form in many species, as well as needle-like or scale-like and often waxy leaves and tracheids which are often arranged into rings with resin-canals.
The pollen of conifers has a pollen tube which delivers sperm cells directly to the eggs and this makes the Coniferales more advanced that the Cycadales and Ginkgoales.
A common fossilised conifer is Utrechia which grew to about 5 metres in height. It had a resemblance to the modern-day Araucaria heterophylla or the Norfolk Island Pine which is a native of Australia. The leaves of this species were needle-shaped and microphyllous. This species, like many conifers, produced separate male and female cones on the one plant meaning that the species was monoecious. The evolutionary origins of the Coniferales is uncertain at present.
The Triassic also saw the development of the forked-frond seed ferns. The first to be found in the fossil record was Dicroidium callipteroides of New South Wales, Australia, which emerged approximately 200 Ma. This species had repeated forking in its fronds unlike later fork-fronded Triassic seed ferns which only had a single fork. The fork-fronded seed ferns were more advanced than the earlier seed ferns that grew alongside the Glossopterids.
There was significant diversity in the Dicroidium flora, and as is the case for the Glossopterids, there is considerable difficulty in naming some species. The reproductive organs of Dicroidium bear resemblance to those of the Glossopterids, and some scientists believe they could be descended from them.