Coleolus sp.

Malinky, John M. & Skovsted, Christian B., 2004, Hyoliths and small shelly fossils from the Lower Cambrian of North-East Greenland, Acta Palaeontologica Polonica 49 (4), pp. 551-578 : 570-571

Coleolus sp.

Figs.?10G, 13.

Hyolithus (Orthotheca) fistula ( Holl, 1865) ; Poulsen 1932: 21, pl. 3: 5.

Material.— MGUH 3527 ( Fig. 13C = Poulsen 1932: pl. 3: 5), MGUH 27119–27120 and 142 additional specimens from GGU samples 314807, 314809, 314835, 314906, 314918, 314919, and 314933.

Description.—Tubular conch with very slight helical coil; apical angle small such that the sides of tube appear to be parallel in more mature regions of conch; surface of shell covered with transverse elements of sculpture that appear to consist of widely spaced ribs with interspaces that range from shallow to deep; ribs have inclination of approximately 110° from long axis; cross−section circular. Both apical and apertural terminations unknown.

Remarks.— Coleolus sp. is represented in the collections from North−East Greenland by 145 very fragmentary speci−

MALINKY AND SKOVSTED— CAMBRIAN HYOLITHS AND SMALL SHELLY FOSSILS 571

mens, widely differing in prominence of the obliquely inclined ribs on the shell. Shell on the acid−isolated but generally less well−preserved individuals ( Fig. 13A, B ) is exfoliated in some places, whereas preservation of shell is much better on the smaller though more fragmentary specimen from Poulsen’s collections ( Fig. 13C ). Whether such variation between ornament falls within the range of normal variation of one species or warrants separate species status is unknown until more complete specimens become available for study. These specimens are referred to Coleolus , but referral to species is more difficult given that so few morphologic features are present on tubular fossils such as these. The oblique ribs somewhat resemble those of C. tenuicinctum Hall, 1879 from the Devonian of New York, but Hall’s (1879) specimen is more complete than any Greenland specimen.

Coleolus trigonus Syssoiev, 1962 from Siberia, the only other species of Coleolus reported from the Lower Cambrian, has much coarser ribs on its shell. Poulsen (1932) referred a specimen of Coleolus to Hyolithus (Orthotheca) fistula ( Holl, 1865) which was founded on phosphatic rather than calcareous tubes (Malinky, unpublished). In addition, a specimen referred to Helenia bella Walcott, 1890 by Poulsen (1932) may represent Coleolus as well ( Fig. 10G ). Helenia was the generic name used for the hyolithid skeletal pieces that subsequently were designated helens. The morphology of helens has been recently discussed by Marek et al. (1997), and the Greenland specimen bears only limited resemblance to any authentic helens. However, its tubular morphology and obliquely dipping ribs are not unlike Coleolus . If it indeed represents Coleolus , a separate species is probably required.

Stratigraphic range and distribution.—Lower Cambrian, North−East Greenland.

Figures

Fig. 13. Coleolus sp. A. MGUH 27119, from GGU sample 314933, lateral view. B. MGUH 27120, from GGU sample 314835; B1–B3, lateral views; B4, cross−section. C. MGUH 3527 from the collections of C. Poulsen, lateral view. Scale bars 1 mm.

Fig. 10. A–C. “Orthotheca bayonet var. groenlandica (Poulsen, 1932)”. A. MGUH 3521; A1, venter; A2, right lateral edge; A3, dorsum. B. MGUH 3523, venter. C. MGUH 3525; C1, dorsum; C2, venter; C3, cross−section. D. “Orthotheca communis (Billings, 1872)”, MGUH 3524; D1, cross−section; D2, dorsum; D3, right lateral edge with venter to right; D4, venter. E. “Orthotheca bayonet var. longa (Poulsen, 1932)”, MGUH 3526, venter. F. “Orthotheca billingsi (Walcott, 1886)”, MGUH 3528, venter. G. Coleolus sp.? MGUH 3517. All specimens from the collections of C. Poulsen. Scale bars 2 mm.