Tortilicaulis D.Edwards is a genus of long-standing unknown affinity in which there are two species: the holotype T. transwalliensis D.Edwards, known only from coalified compressions and T. offaeus D.Edwards, Fanning et J.B.Richardson, known from an assemblage of minute, exceptionally well preserved charcoalified fossils from a Lochkovian deposit in the Welsh Borderland. It has previously been interpreted as bryophyte-like after comparisons based on twisted cells in both stems and sporangia were made with certain extant liverwort and moss genera, there being no evidence of vascular tissues. It has previously been grouped within the horneophytes in cladistic analyses. Subsequent studies of T. offaeus confirmed the presence of stomata on their isotomously branching stems and dehiscence of the sporangium into two valves, but the absence or presence of tracheids has not been demonstrated. Despite numerous attempts to observe the internal anatomy of stems through physical splitting followed by scanning microscopy, we turned to synchrotron radiation x-ray tomography microscopy. Here we describe five Tortilicaulis specimens that were selected for scanning and demonstrate simple annular tracheids within their twisted stems. We conclude that Tortilicaulis was an early diverging tracheophyte, although whether a member of the stem or crown group awaits further detailed cladistic analyses. While architecturally similar to Psilophyton Dawson, the hypothesis that Tortilicaulis was ancestral to the trimerophytes remains unproven.