Systematics and evolution of cladoxylopsids: a consequential yet underappreciated tracheophyte group with a deep fossil history
Abstract
The cladoxylopsids are the first of the major euphyllophyte groups recognized in Middle Devonian and younger floras to acquire individuality from among a plexus of simple Early Devonian euphyllophytes. The first plants to evolve arboreous growth habits were members of this group, which has also been hypothesized to lie at the origin of ferns and equisetophytes. However, despite such multifaceted importance, and despite having been first recognized more than one-and-a-half centuries ago and subsequently documented from Early Devonian to Mississippian localities worldwide, our understanding of the cladoxylopsid clade is still quite incomplete. Nevertheless, the last 30 yr have seen consequential discoveries that provided key insights on their development, architecture, and evolution. Our review of the cladoxylopsids, aimed at providing an entry point to the study of this particularly challenging group, addresses their taxonomic history and the current status and diversity of the different subgroups (iridopterids, and pseudosporochnalean and cladoxylalean cladoxylopsids); their geographic distribution across their stratigraphic range; and evolutionary trends in their stelar architecture and ultimate appendage morphology, position in the body plan and taxis, and their ontogeny and growth habits as formalized in architectural models. Reviewing all of these aspects led us to identify the main gaps in our understanding of cladoxylopsids and to formulate questions about the developmental and functional significance of their unique vascular system in relation to their morphologies, the evolutionary patterns of their reproductive organs, and the still unresolved phylogenetic relationships of the group with other major lineages of pteridophytes and lignophytes within the euphyllophytes.
Non-technical SummaryThe cladoxylopsids are a group of Early Devonian to early Carboniferous plants known primarily for including the first species that grew as trees. They are also hypothesized to have given rise to the living horsetails and ferns and, thus, hold the key to understanding the deep evolutionary history and relationships of these groups. Despite these aspects of evolutionary importance and the fact that the group was recognized more than one-and-a-half centuries ago, the study of cladoxylopsids poses challenges due to their complexity and (in some cases) size, and the group has consequently remained relatively understudied. Fossil discoveries and substantial progress in our understanding of the group over the last 30 years have nevertheless increased our knowledge of these plants in areas such as the diversity and evolution of their vascular tissue organization, lateral appendages, growth patterns and architecture; their geographic distribution over time; and the pattern of evolutionary relationships within the group. This review, aimed at providing an entry point to the study of this particularly challenging group, addresses their taxonomic history and the current status and diversity of the different subgroups (iridopterids, and pseudosporochnalean and cladoxylalean cladoxylopsids); their distribution across time and space; and evolutionary trends in their anatomy, morphology, and developmental patterns. Reviewing these aspects led us to identify the main gaps in our understanding of cladoxylopsids and to formulate a series of outstanding questions.
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BibTeX
@article{durieux2026systematics,
title = {{Systematics and evolution of cladoxylopsids: a consequential yet underappreciated tracheophyte group with a deep fossil history}},
author = {Thibault Durieux and Brigitte Meyer-Berthaud and Alexandru M F Tomescu},
journal = {Journal of Paleontology},
year = {2026},
month = sep,
doi = {10.1017/jpa.2026.10278},
url = {https://hal.inrae.fr/hal-05802480v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Systematics and evolution of cladoxylopsids: a consequential yet underappreciated tracheophyte group with a deep fossil history
AU - Thibault Durieux
AU - Brigitte Meyer-Berthaud
AU - Alexandru M F Tomescu
PY - 2026
DA - 2026/09/24
JO - Journal of Paleontology
DO - 10.1017/jpa.2026.10278
UR - https://hal.inrae.fr/hal-05802480v1
AB - The cladoxylopsids are the first of the major euphyllophyte groups recognized in Middle Devonian and younger floras to acquire individuality from among a plexus of simple Early Devonian euphyllophytes. The first plants to evolve arboreous growth habits were members of this group, which has also been hypothesized to lie at the origin of ferns and equisetophytes. However, despite such multifaceted importance, and despite having been first recognized more than one-and-a-half centuries ago and subsequently documented from Early Devonian to Mississippian localities worldwide, our understanding of the cladoxylopsid clade is still quite incomplete. Nevertheless, the last 30 yr have seen consequential discoveries that provided key insights on their development, architecture, and evolution. Our review of the cladoxylopsids, aimed at providing an entry point to the study of this particularly challenging group, addresses their taxonomic history and the current status and diversity of the different subgroups (iridopterids, and pseudosporochnalean and cladoxylalean cladoxylopsids); their geographic distribution across their stratigraphic range; and evolutionary trends in their stelar architecture and ultimate appendage morphology, position in the body plan and taxis, and their ontogeny and growth habits as formalized in architectural models. Reviewing all of these aspects led us to identify the main gaps in our understanding of cladoxylopsids and to formulate questions about the developmental and functional significance of their unique vascular system in relation to their morphologies, the evolutionary patterns of their reproductive organs, and the still unresolved phylogenetic relationships of the group with other major lineages of pteridophytes and lignophytes within the euphyllophytes. Non-technical SummaryThe cladoxylopsids are a group of Early Devonian to early Carboniferous plants known primarily for including the first species that grew as trees. They are also hypothesized to have given rise to the living horsetails and ferns and, thus, hold the key to understanding the deep evolutionary history and relationships of these groups. Despite these aspects of evolutionary importance and the fact that the group was recognized more than one-and-a-half centuries ago, the study of cladoxylopsids poses challenges due to their complexity and (in some cases) size, and the group has consequently remained relatively understudied. Fossil discoveries and substantial progress in our understanding of the group over the last 30 years have nevertheless increased our knowledge of these plants in areas such as the diversity and evolution of their vascular tissue organization, lateral appendages, growth patterns and architecture; their geographic distribution over time; and the pattern of evolutionary relationships within the group. This review, aimed at providing an entry point to the study of this particularly challenging group, addresses their taxonomic history and the current status and diversity of the different subgroups (iridopterids, and pseudosporochnalean and cladoxylalean cladoxylopsids); their distribution across time and space; and evolutionary trends in their anatomy, morphology, and developmental patterns. Reviewing these aspects led us to identify the main gaps in our understanding of cladoxylopsids and to formulate a series of outstanding questions.
SN - 0022-3360
ER -