The Battery Point formation of the Gaspé Peninsula in Quebec (Canada) hosts a diverse assemblage of Early Devonian (Emsian, c. 395 Ma) permineralized plant fossils. One of these fossils is a previously unidentified type of euphyllophyte represented by a small axis fragment c. 1 mm in diameter. The axis has a highly irregular cross-sectional outline, due to both emission of lateral appendages and taphonomic distortion. The epidermis consists of rectangular cells 37 µm in size containing dark bodies. Abrupt indentations with rectangular to U-shaped profile or irregular profile (up to 129 µm deep and 119 µm wide) affect the epidermis and outer cortical layers all along the axis. The parenchymatous cortex is up to 140 µm wide. A thin layer of phloem with narrow, thin-walled cells is variably preserved around the primary xylem, which forms a five-lobed actinostele. The xylem lobes protrude up to 360 µm from the central core of xylem, which is c. 390 µm wide. Metaxylem tracheids, angular to oval in shape and up to 50 µm in diameter, have densely distributed circular bordered pits with large oval apertures. Each lobe of xylem has a conspicuous mesarch protoxylem strand located approximately midway between its tip and base. Lacunae are present in the position of protoxylem strands in undistorted portions of the axis. At the center of the xylem, an area up to 200 µm wide is occupied by large thin-walled parenchyma cells. At the contact between this central area and the innermost xylem tracheids, a fine layer of cells have features consistent with those of the phloem cells external to the xylem. Terete traces (c. 140 µm diameter) to lateral appendages possessing a central protoxylem strand (lacuna), diverge radially from the tips of the xylem lobes. The appendages follow a 2/5 helical taxis, are filiform (c. 250-300 µm wide in basal portions and 300-400 µm distally), extensive (>9 mm long), and branch dichotomously several times. This new Gaspé plant is similar to the cladoxylopsid Adelocladoxis praecox (described from the same strata), from which it differs in the single protoxylem strand of its appendage traces (and, possibly, the taxis of appendages) and its central parenchyma. This is a, thus, new species closely related to Adelocladoxis praecox and possibly belonging to the same genus. Importantly, the parenchymatous area at the center of the stele is a true pith, as the layer of phloem bordering it demonstrates that the new plant possesses a bona fide siphonostele with amphiphloic organization (rather than a medullated protostele). The oldest previously documented euphyllophytes with parenchyma at the center of steles are Middle Devonian (Givetian): the cladoxylopsid Arachnoxylon and the putative progymnosperm Actinoxylon. However, it is unclear whether either of these plants had true siphonosteles or if those were amphiphloic. Therefore, this new Gaspé plant represents the oldest siphonostele occurrence among euphyllophytes, pre-dating by at least 10 million-years previously known occurrences and demonstrating much deeper origins of this structural feature in the clade.