Chalazoscolex pharkus, Morris & Peel, 2010

Morris, Simon Conway & Peel, John S., 2010, New palaeoscolecidan worms from the Lower Cambrian: Sirius Passet, Latham Shale and Kinzers Shale, Acta Palaeontologica Polonica 55 (1), pp. 141-156 : 154

Chalazoscolex pharkus sp. nov.

Figs. 1 , 2, 4B, G , 6B–D, F .

Etymology: From the Greek for wrinkled (pharkidos), in reference to the trunk ornamentation.

Holotype: MGUH 29133 ( Figs. 1A , 6B ).

Type locality: Peary Land, central North Greenland, situated at the south−western end of the broad valley (Sirius Passet) that connects J.P. Koch Fjord and Brainard Sund; latitude 82 ° 47.6’N, longitude 42 ° 13.3’W, altitude 450 m above sea level .

Type horizon: Lower part of the Buen Formation (lower Cambrian, provisional Series 2, Stage 3), equivalent to the Nevadella Zone of North American usage.

Material.— The holotype and MGUH 29134–29141 , 29148 , 29151 .

Diagnosis.—Palaeoscolecidan with introvert and trunk in two regions. Introvert with dense array of simple scalids. Anterior and median trunk with two types of ornamentation: ca. 140 segments with simple sclerites and longitudinal folds, separated by smoother zones. Posterior trunk with ca. 15 segments bearing more prominent sclerites. Gut includes anterior pharynx and straight intestine.

Stratigraphic and geographic range.—Buen Formation (Stage 3 of provisional Cambrian Series 2, equivalent to Nevadella Zone ), Peary Land (North Greenland).

Figures

Fig. 1. Palaeoscolecidan Chalazoscolex pharkus gen. et sp. nov., lower Cambrian (Series 2, stage 3), Buen Formation, Sirius Passet Fossil−Lagerstätte, Peary Land, North Greenland. A. MGUH 29133, entire specimen (A1) and enlargements of trunk (A2) and introvert (A3); see also Fig. 6B. B. MGUH 29134, entire specimen (B1) and enlargements of anterior (B2), trunk (B3), and introvert (B4). Scale bars 10 mm. All specimens coated with sublimate.

Fig. 4. Palaeoscolecidans Xystoscolex boreogyrus gen. et sp. nov. (A, C–F) and Chalazoscolex pharkus gen. et sp. nov. (B, G), lower Cambrian (Series 2, stage 3), Buen Formation, Sirius Fossil−Passet Lagerstätte, Peary Land, North Greenland. A. MGUH 29147, anterior with introvert. B. MGUH 29148, enlargement of introvert and anterior trunk (B1) and entire specimen with gut trace (B2); see also Fig. 6F. C. MGUH 29149, enlargement of posterior end (C1) and entire specimen with gut trace (C2). D. MGUH 29142, enlargement of introvert, see also Fig. 3A. E. MGUH 29150, entire specimen (E1) and enlargement of introvert with everted pharyngeal region (E2); see also Fig. 6A. F. MGUH 29151, gut trace containing arthropod Isoxys volucris Williams, Siveter, and Peel, 1996 with characteristic spinose extension arrowed. G. MGUH 29137, gut trace; see also Fig. 2C. Scale bars 5 mm in D, G; otherwise 10 mm. All specimens coated with sublimate.

Fig. 6. Scanning electron micrographs of Xystoscolex boreogyrus gen. et sp. nov (A, E) and Chalazoscolex pharkus gen. et sp. nov (B–D, F), lower Cambrian (Series 2, Stage 3), Buen Formation, Sirius Passet Fossil−Lagerstätte, Peary Land, North Greenland. A. MGUH 291560, scalids of the introvert, see also Fig. 4E. B. MGUH 29133, grooves and ridges on the introvert, see also Fig. 1A. C. MGUH 29136, segments of trunk showing longitudinal cuticular ridges, see also Fig. 2B. D. MGUH 29141, posterior trunk with larger sclerites, see also Fig. 2G. E. MGUH 29144, detail of scalid, distal point to upper right, see also Fig. 3C. F. MGUH 29148, segments with rows of sclerites and intervening unarmoured areas of cuticle (F1) and scalids of introvert (F2), see also Fig. 4B. Scale bars 400 µm (A+F1), otherwise 300 µm. All specimens coated with gold film.