4


Journal of Paleontology 90(1):1–9


Other species.—Rankenella hamdii Kruse and Zhuravlev, 2008. Late Cambrian Series 3 (Guzhangian)–early Furongian (Paibian), Mila Formation, northern Iran.


Diagnosis.—“Smooth-walled conicocylindrical, digitate or explanate sponges with deep, cylindrical spongocoels in the former. Skeletal spicule net of regular anthaspidellid type, trabs parallel to gastral surface, and diverging upward toward dermal surface. Differentiated canal systems absent. Some spicular modification in dermal layer” (Kruse, 1983, p. 51; 1996, p. 164).


Remarks.—Rankenella represents one of the oldest sponges of the family Anthaspidellidae, which occurs from the late Cambrian Series 2 to the early Furongian. There are two other anthaspidellid genera reported from Cambrian reefs, Wilbernicyathus Wilson, 1950, and Gallatinospongia Okulitch and Bell, 1955 (Table 1). Both Wilbernicyathus and Gallatinospongia have canal system, and can be easily differentiated from Rankenella. Two other non- reefal anthaspidellid sponges, Capsospongia Rigby, 1986, and Fieldospongia Rigby, 1986, both from the early–middle Cambrian Series 3 Burgess Shale, are also different from Rankenella (Table 1). Capsospongia, a thin-walled, obconical sponge with vertical trabs, has major canals parallel to the trabs. Fieldospongia lacks an organized canal system, but it has vertically arranged trabs.


Rankenella zhangxianensis new species Figures 3–5


Diagnosis.—Trabs parallel/subparallel to gastral surface, diverging outward and almost perpendicularly meet dermal surface. Approximately 7–12 trabs occur between dermal and gastral surfaces. Between trabs, 3–7 ladderlike series of dendroclones occur. Spicular modification in dermal layer absent.


Description.—Mostly obconical in shape with deep cylindrical spongocoels (Fig. 4.1, 4.2). Digitate or planar forms absent. Length ranges up to 610mm (Fig. 4.1). Transverse sections of obconical structure have diameter 3–21mm, with spongocoels 1–14mm in diameter, although most are 5–10mm total diameter and 3–6mm spongocoel diameter (Figs. 4.1–4.7, 5.1, 5.2, 6). Ratio of spongo- coel diameter/total diameter is 17%–69%, andmany are 39%–58% (Fig. 6). Wall generally thicker in larger specimens, with higher ratio of spongocoel diameter/total diameter. Several specimens have holdfasts, which have similar spicule arrangements as other parts of body (Figs. 4.2, 5.1–5.3). Dermal and gastral surfaces generally smooth. Secondary thickening of skeletal net is absent, except for boundary between


Figure 4. Photomicrographs of Rankenella zhangxianensis in Zhangxia Formation, Beiquanzi section. All photomicrographs are taken from bedding-parallel thin sections. For location, see Figure 2. (1) Holotype NIGPAS159373. Longitudinal section. (2) NIGPAS519388. Two individuals in longitudinal section and five individuals in transverse section. Two Cambroctoconus orientalis (longitudinal and transverse sections; white arrows), characterized by octagonal conical shape, occur with R. zhangxianensis.(3) NIGPAS519385. Oblique section of the largest identified individual. (4) NIGPAS519382. Transverse section of four individuals. (5) NIGPAS519389. Longitudinal section of the wall. (6) NIGPAS519390. Oblique and transverse sections. (7) NIGPAS519391. Transverse section. Note occurrence of microstromatolite within the spongocoel. Scale bars: (1, 3, 4: 10mm; 2, 5–7:5mm).


Table 1. Summary of reported Cambrian anthaspidellid sponges Genus


Occurrence Rankenella


Australia, Iran, China


Wilbernicyathus Colorado and Texas, USA


Gallatinospongia California and Nevada, USA


Age


Stage 4– Paibian


Jiangshanian– Stage 10


Paibian


Outer morphology


Conicocylindrical with deep, cylindrical spongocoels, digitate or explanate


Crudely discoidal to obconical to almost cylindrical, with moderately thick wall and spongocoel extending nearly to base


Obconical stalked sponge with broad open spongocoel and thin walls


Canal Absent


Transverse radial canals longitudinally stacked and nearly straight. Longitudinal canals often present, scattered in endosomal spiculature


Coarse transverse canals generally normal to gastral and dermal surfaces in outer half of wall; fine, closely spaced, sublongitudinal canals that curve gently and gastrally in inner part of wall


Capsospongia Fieldospongia


Canadian Rockies Drumian


Annulate, conicocylindrical, thin walled


Canadian Rockies Drumian Moderately thin walled, conical to cylindrical with deep spongocoel


Canals parallel upwardly divergent skeleton.


Absent


Skeletal net


Trabs parallel to gastral surface, and diverging upward toward dermal surface. Some spicular modification in dermal layer.


One trab between radial canals; trabs cored by bundled oxeas; amphiarborescent dendroclones dominate and connect adjacent trabs transversely.


Rodlike trabs oriented longitudinally in gastral part of wall but curve upward and outward to become approximately normal to dermal surface; trabs cored by a few parallel monaxial spicules but largely formed of combined branched terminal rays of dendroclones whose principal shafts extend runglike between trabs in ladderlike structures.


Irregular, vertical trabs formed by combined tips of horizontal dendroclones to produce septate-appearing wall


Possible dendroclones that cross connect vertical strands; strands may be arranged in bladelike elements.


Reference


Kruse, 1983, 1996; Kruse and Zhuravlev, 2008; this study Johns et al., 2007


Shapiro and Rigby, 2004


Rigby, 1986 Rigby, 1986


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