Peel—Problematic Cambrian cnidarian (Octocorallia?)
in consequence of which, Cambroctoconida is tentatively placed within the anthozoan Class Octocorallia. While the presence of pores is not established in Tretocylichne on account of its rela- tively coarse preservation (Engelbretsen, 1993), the octagonal form and eight-fold septation support its assignment to Cambroctoconida. Material of Lipopora is coarsely silicified, but the cylindrical coralla display eight or sixteen septa, which seem to confirm their affinity with Cambroctoconus. Cambroctoconida (Cambrian Series 2–3) is readily distin-
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Formation, Ptychagnostus gibbus Biozone, Cambrian Series 3, Stage 5. PMU 31718 from GGU sample 315879, Freuchen Land, Henson Gletscher Formation, Cambrian Series 3, Stage 4.
Other material.—More than 30 specimens from GGU sample 271718.
guished from other octocorals by the massively calcified, cup- shaped corallum. Soft tissues in present day octocorals are supported by spicules, although a few taxa (e.g., Tubipora Linnaeus, 1758; Heliopora de Blainville, 1830; Epiphaxum Lonsdale, 1850; and Nanipora Miyazaki and Reimer, 2015) develop calcified tubes or spicular frameworks containing polyps that rise above sometimes massively calcified stolon platforms. Heliopora, Epiphaxum, and Nanipora are grouped together within a separate order Helioporacea Bock, 1938, known to occur already in the Cretaceous (Lozouet and Molodtsova, 2008), while Tubipora is placed within the alcyonacean octocorals (Pérez et al., 2016).
Genus Cambroctoconus Park et al., 2011
Type species.—Cambroctoconus orientalis Park et al., 2011, from the Changhia Formation (Cambrian Series 3, Drumian) of Shandong Province, China.
Remarks.—A detailed comparison between Cambroctoconus and the related genera Tretocyclichne and Lipopora was given by Park et al. (2016). In terms of its turbinate corallum and budding pattern of daughter corallites, Cothonion resembles Cambroctoconus, but it lacks the octagonal shape and eight-fold symmetry of septa. Cothonion is also distinguished by its pro- minent operculum with septa on the inner surface. Apart from the type locality in Australia, Cothonion is only described from the Paralleldal Formation (Cambrian Series 4, Stage 4) of Peary Land, North Greenland (Peel, 2011), which is the same age as GGU sample 315879 from southern Freuchen Land (Fig. 1). Dzik (1993) considered Cothonion to be a rugose coral, but
this was rejected by Fedorowski (1997). As is the case with cambroctoconids, Cothonion was considered to represent one of several independent calcification events in anthozoan evolu- tionary history by Scrutton (1997, 1999; see also Oliver and Coates, 1987 and Peel and McDermott, 2016). Aploconus Debrenne et al., 1990 from Cambrian Series 2,
Stage 4, of Nevada differs in that the wall of its simple conical skeleton is laminated (Zhuravlev et al., 1993).
Cambroctoconus koori new species Figures 3, 4
Holotype.—PMU 31705 from GGU sample 271718, upper Henson Gletscher Formation, Ptychagnostus gibbus Biozone, Cambrian Series 3, Stage 5, Løndal, Peary Land (Fig. 2).
Paratypes.—PMU 31703, 31704, 31707–31717 from GGU sample 271718, Løndal, Peary Land; PMU 31706 from GGU sample 271492, Lauge Koch Land; upper Henson Gletscher
Diagnosis.—A small species of Cambroctoconus in which the corallum is variable in shape, but most commonly turbinate, becoming cylindrical in later growth stages; octohedral form only rarely developed, budding not observed.
Occurrence.—Currently known only from the Henson Gletscher Formation of North Greenland.
Description.—The description is based on phosphatized mate- rial, both in the form of phosphatized coralla and molds of the calice, showing varying degrees of phosphatization. The corallum is highly variable in shape, ranging from turbinate (Fig. 3.3, 3.4) and trochoid (Fig. 4.9), both of which may become cylindrical in later growth stages (Figs. 3.10, 4.6), to patellate (Fig. 4.1, 4.2). Maximum preserved height is 3mm, in cylindrical forms. One specimen is attached to a shell fragment (Fig. 3.12), but the flattened or broken base of several coralla (Fig. 4.8) suggests that this was often the case. The holotype is turbinate, with a shallowly convex lateral
profile (Fig. 3.3, 3.4); calical margins of the corallum are not preserved. The base is pointed, without an obvious attachment scar, although such a scar might not be recognized on an internal mold. Eight rounded ridges (width 100–150 µm) are equally
disposed over the specimen surface, rising abruptly from the floor of intervening depressions, which increase in width (circumferential) away from the base, as the corallum expands. The depressions are filled with vermiform pore-infillings (diameter 20–50 µm) that arise both from the floor of the depressions and the eight ridges. The pore-fillings are well ordered, labyrinthine in form, and may branch. Near the base, pore-fillings also extend out abaxially from the corallum beyond the outer surface of the rounded ridges. The turbinate holotype clearly represents an internal mold
of the basal portion of the corallum after dissolution of the corallum wall. Thus, the eight rounded ridges represent channels on the inside of the corallum wall comparable to those preserved in silicified coralla of Cambroctoconus orientalis (arrows in Fig. 1.1, 1.5). Pores extended from these channels and from the inner surface of the calice into the corallum wall. The channels inC. orientalis lie between a pair of thin perforated septa (Park et al., 2011, fig. 2), which are not preserved in the holotype of Cambroctoconus koori n. sp. The abaxial extension of pore-infillings from the upper surface of the rounded ridges in the holotype of C. koori n. sp. indicates that the thickness of the corallum wall was at least twice the height of the ridges. The texture of the outer surface of the corallum (Fig. 3.10) suggests that the pores extended to the outer surface of the corallum as in Cambroctoconus kyrgyzstanicus (Fig. 1.2, 1.4). In other specimens, septa on the outer surface of the
phosphatized molds are preserved as grooves in the surface of the mold (Fig. 3.1, 3.5, 3.6). Deep grooves representing septa on
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