Undichna septemsulcata, Wisshak & Volohonsky & Blomeier, 2004

Wisshak, Max, Volohonsky, Eden & Blomeier, Dierk, 2004, Acanthodian fish trace fossils from the Early Devonian of Spitsbergen, Acta Palaeontologica Polonica 49 (4), pp. 629-634 : 632

Undichna septemsulcata isp. nov.

Fig. 2 .

Derivation of name: Latin septem, seven, and sulcus, a furrow, groove, referring to the characteristic number of groove marks exhibited by well−preserved specimens in “full morphology”.

Type material: Slab with two traces, the more prominent of which is defined as the holotype ( Fig. 2A–C ; PMO 169.565).

Type locality and horizon: Wigdehlpynten (UTM:4 79 516 E; 88 14 111 N), West Andrée Land , Northern Spitsbergen , Svalbard. Middle Wood Bay Formation , Dicksonfjorden Member .

Diagnosis.—One unpaired median groove and three pairs of lateral grooves, all with a regular in−phase sinusoidal wave pattern of equal wavelength. The lateral grooves have a lower amplitude and may or may not be discontinuous while the continuous median groove has the largest amplitude and does not cross any lateral groove. Differs from all previously described Undichna ichnospecies by its outer paired double−groove with a very low amplitude, and by all seven sinusoidal scratch marks being in−phase.

Description.—The holotype trace is 30 mm wide and extends over 0.5 m across the slab. The wavelength (λ) of all waves is ca. 60 mm, and their amplitudes (A) decrease outward from 10 mm (median groove) and 5–6 mm (inner lateral grooves) to 1–2 mm (outer lateral grooves). All waves are nearly or completely in−phase. The median groove is central or laterally slightly displaced, and does not crosscut any of the lateral grooves. The inner lateral groove occasionally crosscuts the inner one of the outer lateral pair of grooves. Individual grooves are sharply incised and up to 1 mm wide. The width of individual pairs (w) is generally near−constant. In contrast to the median groove, the lateral grooves are intermittent, disappearing in the range of their outer maximum amplitude.

Remarks.—Since the preservation of the holotype is excellent, the figured pattern is regarded as fully developed and may be modified by the effect of undertracking as well as by the assumed trace maker swimming at slightly varying elevations above the sediment−water interface. The well−preserved “full morphology” and the significant difference to all (fully or incompletely developed) other ichnospecies of Undichna justifies the establishment of a new ichnospecies even though it is based on limited material.

Figures

Fig. 2. Undichna septemsulcata isp. nov., Early Devonian, Spitsbergen. A. Sandstone slab (PMO 169.565) with two specimens of the fish trace Undichna septemsulcata isp. nov., and numerous arthropod trackways (ichnogenera: Merostomichnites, Diplichnites) preserved as delicate positive hyporelief. B, C. Enlarged section and line drawing of the holotype specimen of Undichna septemsulcata isp. nov., overprinted by two arthropod trackways (Diplichnites). D, E. Enlarged section and line drawing of the second, less well−preserved and narrower specimen.