Early Devonian in the context of "Rhyniognatha hirsti"

Myriapods (from Ancient Greek μυρίος (muríos) 'countless' and πούς (poús) 'foot') are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial.

Although molecular evidence and similar fossils suggests a diversification in the Cambrian Period, the oldest known fossil record of myriapods dates between the Late Silurian and Early Devonian, with Pneumodesmus preserving the earliest known evidence of air-breathing on land. Other early myriapod fossil species around the similar time period include Kampecaris obanensis and Archidesmus sp. The phylogenetic classification of myriapods is still debated.

The rhyniophytes are a group of extinct early vascular plants that are considered to be similar to the genus Rhynia, found in the Early Devonian (around 420 to 393 million years ago). Sources vary in the name and rank used for this group, some treating it as the class Rhyniopsida, others as the subdivision Rhyniophytina or the division Rhyniophyta. The first definition of the group, under the name Rhyniophytina, was by Banks, since when there have been many redefinitions, including by Banks himself. "As a result, the Rhyniophytina have slowly dissolved into a heterogeneous collection of plants ... the group contains only one species on which all authors agree: the type species Rhynia gwynne-vaughanii". When defined very broadly, the group consists of plants with dichotomously branched, naked aerial axes ("stems") with terminal spore-bearing structures (sporangia). The rhyniophytes are considered to be stem group tracheophytes (vascular plants).

Doliodus is a genus of cartilaginous fish known from the Early Devonian period of what is now New Brunswick, Canada. It includes a single named species, either D. problematicus or D. latispinosus, which was originally described based on isolated teeth and potentially fin spines, but has since had a well-preserved body fossil assigned. The classification of the genus is uncertain, but it has been considered a member of the order Omalodontiformes. A more complete specimen that some authors assign to the genus shows features that are transitional between the extinct acanthodians and cartilaginous fish.

Holocephali (sometimes spelled Holocephala; Greek for "complete head" in reference to the fusion of upper jaw with the skull) is a subclass of cartilaginous fish. The only living holocephalans are the three families of chimaeras, but the group also includes many extinct members and was more diverse during the Paleozoic and Mesozoic eras. The earliest known fossils of holocephalans date to the Middle Devonian, and the subclass likely reached its peak diversity during the following Carboniferous Period. Molecular clock studies suggest that holocephalans diverged from their closest relatives, elasmobranchs such as sharks and rays, during the Early Devonian or the Silurian Period.

Extinct holocephalans are typically divided into a number of orders, although the interrelationships of these groups are poorly understood. Several different definitions of Holocephali exist, with the group sometimes considered a less inclusive clade within the larger subclasses Euchondrocephali or Subterbranchialia and with its members spread into the now obsolete groups Paraselachimorpha or Bradyodonti. Per these classification schemes, the name Holocephali is used only for chimaeras and their closest relatives. Recent research has suggested that the orders Cladoselachiformes and Symmoriiformes, which were historically considered relatives or ancestors of sharks, should instead be considered holocephalans. Information on the evolution and relationships of extinct holocephalans is limited, however, because most are known only from isolated teeth or dorsal fin spines, which form much of the basis of their classification.