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Journal of Paleontology 91(1):116–145
remainder of the tubarium; and the occurrence of the robust, ventrally projecting ‘pseudolip’. Comparison with the Chinese specimens of Pseudoretiolites tianbaensis is somewhat difficult because they are flattened and only moderately well preserved. However, two observations give support to the possible affinities of the Arctic material with that species. These are the smooth merging of the rather round ancora umbrella with the remainder of the tubarium, and the possession of a reticulum of small reticular meshes of near–uniform size (this feature is well shown in Ge, 1990, pl. 10, fig. 4), although there is no hint of the unique ‘pseudolip’ in Ge’s illustrations. Thecal spacing and maximum tubarium width of the Chinese and Arctic specimens are very similar.
Pseudoretiolites hyrichus new species Figure 10.1–10.6
Holotype.—Holotype GSC137635, Paratype specimens GSC137632-137634, 137636.
Diagnosis.—Ancora umbrella deep with four to five whorls of spiral lists. Two large rounded lateral orifices on obverse and reverse walls, ventral orifices small. Thecal zigzag floors long, inclined ~30o to nema, overlapping minimally. Thecae with straight, moderately inclined ventral walls. Reticulum a moderately dense meshwork made of polygons that vary in size. Sicula preserves complete prosicula and most of metasicula.
Materials.—11 specimens, all immature, except for two speci- mens without the ancora umbrella.
Occurrence.—R. orbitus Zone and L. convolutus Zone, Cape Manning, Cornwallis Island.
Description.—Tubarium narrow. Width across firstthecalpair 1.2–1.3mm, maximum width (one specimen) 1.65mm. 2TRD ~1.5mm (~13.3 in 10mm) (single specimen). Sicula comprises complete prosicula and most of metasicula, the latter generally having only approximately one-half of fusellar wall preserved. Sicula 0.7–0.8mmlong, prosicula ~0.45mm. Prosicula possesses longitudinal rods. Ancora umbrella U-shaped or broadly V-shaped, almost as deep aswide, 0.6–1.0mmwide, composed of four to five whorls of spiral lists, enclosing the aperture of the prosicula (Fig. 10.1). Paired large, rounded to broadly ovate lateral orifices on both obverse and reverse walls; small ventral orifices below first thecae. Thecae with straight ventral walls, distal part
composed of a mid-ventral list and five pairs of zigzag lists, inclined ~30o to nema, overlapping only to a small degree. Mid-ventral list of theca 11 originates within the inside surface of the ancora umbrella. Pleural lists present, inclined inward. Ancora sleeve meshwork moderately coarse, meshes irregular in size; stomata present, somewhat rounded, rims level with reticular meshwork. List surfaces smooth to very finely striated.
Etymology.—hyrichus: Gr., basket; referring to deep ancora umbrella.
Remarks.—Specimens of this species, although being pre- dominantly preserved in juvenile stages, are distinctive among species of this genus in a number of ways: relatively narrower width; its ancora umbrella is deep and V- to U-shaped; and large, paired lateral orifices are present on obverse and reverse sides. The thecae are inclined at a low angle, and its sicula is more completely preserved than the other species of this genus described above. There is no evidence of preservation of con- tinuous fusellar thecal membranes.
Pseudoretiolites? sp. Figure 11.1–11.10
Materials.—34 poorly preserved specimens, all fragmentary, predominantly of sicula and ancora umbrella; most distal frag- ments partially or fully flattened.
Occurrence.—D. triangulatus/D. pectinatus Subzone to
R. orbitus Subzone and possibly lower L. convolutus Zone, from Cape Manning, Cornwallis Island, and Dundas Island.
Description.—Tubarium widening rapidly, width at first thecal pair 2–2.5mm, distal width at least 3.7mm in dorsoventerally compressed specimen. 2TRD cannot be reliably measured. Prosicula and metasicula complete, total length ~1.05mm, prosicular length ~ 0.3mm. Prosicula possesses longitudinal rods. Theca 11 mid-ventral list appears to arise from metasicula. Proximal portion of theca 11 is preserved, revealing visible porus near metasicular rim (Fig. 11.2, 11.6). Ancora umbrella deep, bowl-shaped, with five to six whorls of spiral lists, 1.3mm wide. Distal portion of mid-ventral list attached to numerous zigzag lists defining the distal thecal floor, some with com- pletely preserved fusellum (Fig. 11.9, 11.10). Ancora sleeve reticulum of moderately coarse polygonal meshes of various sizes. List surfaces smooth to very finely striated.
Figure 12. Scanning electron microscopy images of Rotaretiolites exutus, Bates and Kirk, 1992, Rotaretiolites cf. exutus Bates and Kirk, 1992, Pseudoplegmatograptus obesus (Lapworth 1877) and Pseudoplegmatograptus? sp.. (1, 2, 5, 7) Rotaretiolites cf. exutus Bates and Kirk, 1992: (1, 5) GSC137661, (1) stereopair of distal part of tubarium, arrows point to spines on lateral margins of thecal apertures (a), and mid-ventral list of thecae (b), (5) enlargement of list showing very coarse parallel striae, section LL1-77, guerichi Zone?; (2) GSC137662, specimen with basal pair of thecae, arrows point to spines on lateral margin of thecal aperture (a), and mid-ventral list (b), and also to prosicular ring (c), section MSC07, 3m above 01G, S. guerichi Zone?; (7) GSC137663, proximal fragment with one thecal pair and prosicular ring; arrows point to spines on lateral margins of thecal apertures (a), and mid-ventral lists (b), and prosicular ring (c), section LL1-77, S. guerichi Zone?. (3, 4) Pseudoplegmatograptus obesus (Lapworth 1877): (3) GSC78423, distal portion of tubarium with paired apertural spines and two stomata, missing the ancora umbrella, arrow indicates partly preserved mid-ventral list on distal theca, section LL1-77, S. guerichi Zone?; (4) GSC137664, immature specimen with shallow ancora umbrella, and two thecal pairs with long paired spines emerging from apertural rims, arrows indicate pleural list (a), lateral apertural rod (b), and partly preserved prosicula (c), section MSC07, 3m above 01G-1, S. guerichi Zone?. (6) Rotaretiolites exutus Bates and Kirk, 1992, GSC114225; proximal end with very simple ancora umbrella, prosicular ring and one thecal pair; note absence of spines. (8, 9) Pseudoplegmatograptus? sp.: GSC137665, (8) stereopair of distal part of tubarium with well-developed paired thecal spines and three stomata, (9) stereopair enlargement of portion of tubarium to show zigzag thecal floors, long paired spines and three stomata, unknown location on Cornwallis Island, ?L. convolutus Zone.
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