Arthrocormus

Arthrocormus refers to a hypothetical or extinct group of early vascular plants that are inferred from fossil evidence but lack direct morphological preservation. The term was introduced by botanist William Henry Lang to describe a plant body type characterized by a segmented, jointed structure, resembling modern horsetails (Equisetum) but distinct in evolutionary context. These plants are believed to have existed during the early Devonian period, approximately 400 million years ago, marking a transitional phase in the evolution of land plants.

The defining feature of arthrocormous plants is their segmented stems, which appear to have been composed of repeating units or nodes, allowing for potential flexibility and growth. Unlike later vascular plants, such as rhizomes or true roots, their root systems are poorly understood, often inferred from associated fossils or comparative anatomy. Some researchers suggest they may have lacked specialized tissues like xylem and phloem, relying instead on simpler conductive pathways.

Fossil evidence for arthrocormous plants is limited to impressions or casts, such as those found in the Rhynie chert deposits in Scotland, which preserve some of the earliest known vascular plants. These fossils provide clues about their growth habits, including upright stems and possible branching patterns. However, the lack of complete specimens makes definitive classification challenging, leading to ongoing debate among paleobotanists about their exact affinities and ecological roles.

The study of arthrocormous plants is significant for understanding the early colonization of land by vascular flora. Their segmented structure may have offered advantages in nutrient absorption and stability, contributing to their survival in the challenging Devonian environment. While not a formal taxonomic group, the concept of arthrocormous morphology remains a key reference point in discussions of early plant evolution.