Skovsted, C.B., Brock, G.A. & Paterson, J.R., 2006. Bivalved arthropods from the Lower Cambrian...

Bivalved arthropods from the Lower Cambrian Mernmerna Formation, Arrowie Basin, South Australia and their implications for identification of Cambrian ‘small shelly fossils’

CHRISTIAN B. SKOVSTED, GLENN A. BROCK & JOHN R. PATERSON

A WIDE RANGE OF ARTHROPODS with bivalved head-shields are known from the Cambrian. Many of these arthropods did not have mineralised exoskeletons, and consequently are known mainly from celebrated Cambrian Lagerstätten such as the Burgess Shale of British Columbia and the Maotianshan Shale of Chengjiang, China (Briggs 1983; Hou & Bergström 1997). The vast majority of Cambrian arthropods with bivalved head-shields belong to the orders Bradoriida Raymond, 1935 and Phosphatocopida Müller, 1964. The shields of both these groups were often mineralised by calcium phosphate, facilitating their preservation as fossils in different environments (Siveter & Williams 1997). The shields of bradoriids and phosphatocopids are superficially similar to ostracods, to which they have often been referred, but modern studies show only a distant relatationship to extant and fossil Ostracoda (Hou et al. 1996; Shu et al. 1999; Siveter et al. 2003; Maas et al. 2003). The first bradoriids appear slightly below the oldest trilobites in China (Hou et al. 2002) and were thus among the first arthropods to leave identifiable remains in the fossil record. Both bradoriids and phosphatocopids continued to form

important components in many Cambrian faunas, and persisted into the early and possibly middle Ordovician (Copeland 1974; Shu 1990; Siveter & Williams 1997; Williams & Siveter 1998). They may be very common locally, such as at the Chengjiang Lagerstätte, where bradoriids are the most abundant of all fossils (Hou et al. 1996). Ecologically, bradoriids may have been among the most common microscavengers/recyclers of nutrients in Cambrian benthic communities (Shu et al. 1999) and appear to have been an important food source for larger animals (Vannier & Chen 2005).

In Australia, bradoriids and phosphatocopids from the uppermost Lower and Middle Cambrian (Ordian and Templetonian) of Queensland have been well studied (e.g. Öpik 1961, 1968; Fleming 1973; Jones & McKenzie 1980; Hinz-Schallreuter 1993a, 1999; and references therein), but faunas from pre-Ordian rocks, or from other parts of Australia are less well known. Chapman (1918) was the first to describe bradoriids from the Lower Cambrian of South Australia, and limited faunas have since been described by Bengtson (in Bengtson et al. 1990) and Melnikova (in Gravestock et al. 2001).

SKOVSTED, C.B., BROCK, G.A. & PATERSON, J.R. 2006:07:29. Bivalved arthropods from the Lower Cambrian Mernmerna Formation, Arrowie Basin, South Australia and their implications for identification of Cambrian ‘small shelly fossils’. Memoirs of the Association of Australasian Palaeontologists 32, 7-41. ISSN 0810-8889.

An assemblage of bivalved arthropods from the Mernmerna Formation on ‘Angorichina’ Station in the Flinders Ranges, South Australia contains six bradoriid species, one phosphatocopid, and the spine of Isoxys. The assemblage includes several species that facilitate correlation with the Stansbury Basin of South Australia, but also with faunas from other Cambrian palaeocontinents, including Antarctica, China and Laurentia. One new taxon, Spinospitella coronata gen. et sp. nov. is described. This species is represented by both complete shields and numerous characteristic spines and fragments, fuelling a general discussion on the possible identification of bradoriid remains among the numerous problematic ‘small shelly fossils’ of the Lower and Middle Cambrian.

Christian B. Skovsted ([email protected]), Glenn A. Brock ([email protected]) & John R. Paterson ([email protected]), Centre for Ecostratigraphy and Palaeobiology, Department of Earth & Planetary Sciences, Macquarie University, NSW 2109, Australia. Received 21 March 2006.

Keywords: Lower Cambrian, Arrowie Basin, South Australia, small shelly fossils, Australia, Bradoriida, Phosphatocopida, Isoxys.

AAP Memoir 32 (2006)8

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Other bivalved arthropods from the Cambrian of Australia have been reported by Glaessner (1979), Jell (1983), Kruse (1990, 1998), Jago & Anderson (2004) and Jones & Laurie (2006). In a further contribution to the study of early Palaeozoic bivalved arthropods from Australia, we describe six bradoriid and one phosphatocopid species from the Lower Cambrian Mernmerna Formation in the Bunkers Range outcropping on ‘Angorichina’ Station in the Flinders Ranges, South Australia (Figs 1, 2). In the Mernmerna Formation, bradoriids are represented mainly by isolated and frequently fragmented valves. Two taxa, Mongolitubulus henrikseni Skovsted & Peel, 2001 and Spinospitella coronata gen. et sp. nov., are almost exclusively represented by fragments, mainly their characteristic spines. The description of these spines and their identification as bradoriid remains facilitates a general discussion of Cambrian so called ‘small shelly fossils’, and the identification of different problematic forms as possible arthropod remains.

LOCALITY, STRATIGRAPHY AND AGEAll bradoriid specimens were collected from the Mernmerna Formation on ‘Angorichina’ Station in the Wirrealpa area of the Flinders Ranges, South Australia. ‘Angorichina’ Station is located approximately 11 km east of the town of Blinman and borders ‘Wirrealpa’ Station to the east and the Flinders Ranges National Park to the

south. Material was sampled from a measured stratigraphic section through the Mernmerna Formation (MMF; base of section coordinates: 31°11’38.4”S, 138°52’28.7”E; map datum: WGS84; see Fig. 3), located on the eastern side of The Bunkers, approximately 1 km south of Balcoracana Creek and 7.5 km NNW of the type section at Wilkawillina Gorge (Figs 1, 2).

The stratigraphy and sedimentology of the Mernmerna Formation at section MMF has been documented in considerable detail by Brock & Paterson (2004) and Paterson & Brock (in press) and is thus summarised here. The MMF section correlates with the Third Plain Creek Member of the middle Mernmerna Formation at Wilkawillina Gorge type section in the Bunkers Graben based on similar lithologies, sedimentary structures and the occurrence of the trilobite Pararaia bunyerooensis Jell (in Bengtson et al., 1990). The Mernmerna Formation at section MMF unconformably overlies the Wilkawillina Limestone and is disconformably overlain by the Bunkers Sandstone (Brock & Paterson 2004; Paterson & Brock, in press). Evidence to support this hiatus includes the presence of a thin red microstromatolite horizon at the contact between these units, representing the Flinders Unconformity (James & Gravestock 1990; Gravestock & Cowley 1995), in addition to the co-occurrence of the trilobite Elicicola calva Jell (in Bengtson et al., 1990), the paterinate brachiopod Askepasma Laurie, 1986 and the tannuolinid Micrina Laurie, 1986 in horizon MMF/0.0. This indicates that a considerable hiatus exists at the MMF section with the absence of the Second Plain Creek Member of the Wilkawillina Limestone (Clarke 1990b) and the Six Mile Bore and Linns Springs Members of the lower Mernmerna Formation (Clarke 1990a) equating to sequence Є1.2 transgressive deposits of Gravestock & Cowley (1995, p. 23).

Lithology of the Mernmerna Formation at section MMF is dominated by interbedded black turbiditic wackestone-packstone and laminated lime silt and mud with rare sandstone beds. Grain flow deposits are common and contain intraclasts, ooids and peloids. Irregular and nodular bedding is relatively common and slump structures are also evident. The Mernmerna Formation at the MMF section contains an abundance of silicified and phosphatic macro- and microfossils, including six species of trilobites (Paterson & Brock, in press), the helcionellid mollusc Tannuella elinorae Brock & Paterson, 2004, in addition to undocumented molluscs, brachiopods, archaeocyaths, chancelloriids, sponge spicules, and other enigmatic small shelly fossils (Brock et al. in prep.). The occurrence of P. bunyerooensis

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AAP Memoir 32 (2006) 11

also provides an age constraint on the MMF section to the Pararaia bunyerooensis Zone, indicating a Botoman age (Bengtson et al. 1990; Jago et al. 2002; Paterson & Brock, in press).

BRADORIID AND PHOSPHATOCOPID REMAINS AND SMALL SHELLY FOSSILSTogether with bivalved arthropods and familiar fossil groups such as trilobites, sponges and echinoderms, Lower and Middle Cambrian rocks often contain an abundance of minute skeletal fossils of uncertain biologic origin, so called ‘small shelly fossils’ (Rozanov et al. 1969; Matthews & Missarzhevsky 1975; Rozanov 1986; Bengtson 2004). These fossils are usually composed of calcium phosphate, either by original composition or by diagenetic phosphatisation, and are commonly retrieved from carbonate rocks by treatment with weak acids. During the last 40 years our understanding of these fossils has increased dramatically. After an early tendency to regard every little shelly element as an independent biological species, many of the small shelly fossils are now regarded as elements (sclerites) of multi-component skeletons (scleritomes). In some cases, this interpretation is based on remarkably preserved specimens revealing the morphology of the entire animal and the structure of its skeleton (e.g. halkieriids: Conway Morris & Peel 1995; Microdictyon: Chen et al. 1995; palaeoscolecidans: Müller & Hinz-Schallreuter 1993, Brock & Cooper 1993, Hou & Bergström 1994, Ivantsov & Wrona 2004). In other cases, a multi-element, scleritome reconstruction is inferred from studies of morphology, distribution and variability in assemblages of disarticulated skeletal components (e.g. tommotiids: Landing 1984; Bengtson et al. 1990). It should be noted that among the small shelly fossils are also commonly included forms such as helcionelloid molluscs and hyoliths which are known to possess only one or a few skeletal components, and some of the more problematic small shelly fossils may still be best reconstructed in a similar way (e.g. mobergellans: Bengtson 1968). However, a large number of Cambrian small shelly fossil taxa remain highly problematic. Some of these fossils are known only from fragmentary material, and their morphology may thus be largely attributed to random processes. Only by study of fine details, including shell microstructure and composition, using large collections of complete specimens can the true morphology and biologic affinities of these fossils be deduced.

It has already been suggested that some of the more problematic small shelly fossils are in fact fragmented remains of the head-shields

of bradoriid arthropods (e.g. Melnikova 2000; Skovsted & Peel 2001; Skovsted 2005). Some of the fossil taxa discussed below substantially predate the oldest known undoubted bradoriids and phosphatocopids, and this age difference may justifiably be taken as an argument against arthropodan affinity for the fossils in question. However, trace fossils tentatively attributed to arthropods are known from older strata (e.g. Budd & Jensen 2000), and in South China at least one phosphatocopid and five bradoriid families are present already in the Parabadiella trilobite Zone of the Qiongzhusian Stage (Atdabanian equivalent; Luo et al. 1994; Hou et al. 2002). These observations suggest that arthropods in general, and bradoriids and phosphatocopids in particular, have a hidden pre-Atdabanian history. All age determinations discussed below are based on the correlation charts of Geyer & Shergold (2000).

Mongolitubulus and SpinospitellaThe ornamented , sp ine-shaped foss i l Mongolitubulus was first discovered by Missarzhevsky (1977) from Lower Cambrian strata in Mongolia, and has subsequently been documented from Antarctica (Gazdzicki & Wrona 1986; Wrona 2004), Siberia (Meshkova 1985), Malyi Karatau (Missarzhevsky & Mambetov 1981; Dzik 2003), Greenland (Peel & Blaker 1988; Skovsted & Peel 2001), the Taconic Allochthon of Quebec (Landing et al. 2002), and Australia (Demidenko in Gravestock et al. 2001; Brock & Percival 2006 [this volume]). Ornamented spines from the Lower Cambrian of New York (Landing & Bartowski 1996) and the Middle Cambrian of China (Zhu & Dong 2004) also probably belong to Mongolitubulus. In many ways Mongolitubulus exemplifies the problem of interpreting small shelly fossils; it is almost always imperfectly preserved with obviously broken margins and its biological function and affinity has been widely debated. Missarzhevsky (1977, 1989) regarded Mongolitubulus as a protoconodont, while Landing et al. (2002) described it as a pseudoconodont. Esakova & Zhegallo (1996) questioned the conodont affinity of Mongolitubulus, while Rozanov (1986) suggested a relationship to the tubular hyolithelminths. Conway Morris & Bengtson (in Bengtson et al. 1990) considered Mongolitubulus to be a problematic fossil and refrained from speculating on the functional or biological affinities of this taxon, but Dzik (2003) suggested that Mongolitubulus should be restored as defensive spines of a lobopod animal. Other authors favouring a defensive function for the spines have suggested an affinity to bradoriid


arthropods (Melnikova 1996, 2000; Skovsted & Peel 2001), and similar ornamented tubes from the Middle Cambrian of China were recently referred to as bradoriid spines (Zhu & Dong 2004). This interpretation was recently strengthened by the find of a complete bivalved shield of Mongolitubulus henrikseni Skovsted & Peel, 2001 from North-East Greenland preserving multiple spine bases (Fig. 1A; Skovsted 2005).

The fact that isolated spines of Mongolitubulus were found in abundance at multiple localities around the world before the first reasonably complete shield was found, may mean that the spines were more strongly mineralised than the rest of the shield. However, the complicated topography of the valves, with multiple, long and slender spines (spines up to at least 3 mm long with a diameter of only 0.21 mm were reported by Skovsted & Peel 2001, p. 142), would probably be mechanically fragile and would easily break around the bases of the spines, either during compaction in the sediment or during acid preparation.

In the Mernmerna Formation of South Australia, Mongolitubulus henrikseni occurs together with a second bradoriid carrying ornamented spines, Spinospitella coronata gen. et sp. nov. (Figs 6-9). Like M. henrikseni, S. coronata is thus far exclusively known from acid residues, and most specimens are almost always fragmented. The prominent spines and domes are the most common fossil remains of S. coronata, but pieces of convex shell also occur (Fig. 7A-I). All spines and shell fragments are covered with a fine reticulate network and a multitude of hollow second order spines. By themselves, the spines, domes and concave shell fragments would not yield any unequivocal evidence for the biological affinity of the species. However, in combination with two reasonably complete valves and a single articulated (although deformed) head-shield, the fragments can be confidently identified as bradoriid remains. The head-shield of Spinospitella has one first order spine and one anterodorsal node or dome on each valve (Fig. 9A, D). The first order spine is generally covered by a multitude of pointed second order spines, but on adult valves second order spines occur over all parts of the shield. The second order spines are hollow and not readily comparable to the scales of Mongolitubulus. The two fossils may not necessarily be closely related, but both illustrate the difficulties in correctly identifying arthropods from fragmented material.

A range of bradoriids with prominent unornamented or weakly ornamented spines are known from complete specimens (e.g. Monasterium oepiki Fleming, 1973, Capricambria cornucopiae

Hinz, 1991 and Flemingopsis ventrospinata Hinz-Schallreuter, 1993a from the Middle Cambrian of Australia, Preaechmina jiangshanensis Shu, 1990 from the Lower Cambrian of China, Tubuterium ivantsovi Melnikova, 2000 from the Middle Cambrian of Siberia (Fig. 4B) and the possible bradoriid Chegetella Kanygin, 1977 from the middle Ordovician of Siberia; Hinz et al. 1990). Monasterium has one curved spine attached to the anterodorsal region of each valve. Based on the relative position of shields and spines on slabs, the same configuration was suggested for Tubuterium by Melnikova (2000), although superficially similar associations from the Cambrian of Tasmania were interpreted by Jago & Anderson (2004) as antennae of waptiid arthropods. Chegetella has a long spine on each valve close to the ventral margin, while Capricambria has two stout spines in the middle of each valve and Preaechmina has one central spine close to the dorsal margin. In general morphology the spines of Monasterium, Chegetella and Capricambria are comparable to those of Mongolitubulus, although the ornamentation of broad, rounded knobs in Monasterium (Fleming 1973; Hinz 1992b) and Capricambria (in the latter combined with weakly expressed horizontal bands) can be used to discriminate these forms (Hinz 1991). The Cambriid bradoriid Monceretia Vannier et al., 2005 from the Lower Cambrian of France shows some resemblance to Spinospitella in that it has an ornament of minute tubercles on the posterolateral part of the valves and on the posterior node. However, the relationship between the tubercles in Monceretia and the second and third order spines of Spinospitella is difficult to evaluate.

The bradoriid genus Duibianella Shu, 1990 from the Lower and Middle Cambrian of China (Shu 1990; Zhang & Pratt 1993) and the Lower Cambrian of Siberia (Melnikova 1998) is characterised by a reticulate ornamentation in combination with abundant nodes and occasional spines. The distribution of nodes in Duibianella sp. of Zhang & Pratt (1993) is comparable to the distribution of spines in Mongolitubulus henrikseni with a few large nodes in a sub-central position with the majority of nodes located along the ventral margin (Fig. 4C). Additionally, Duibianella sp. bears one short spine close to the posterodorsal corner of each valve (Zhang & Pratt 1993, figs 1, 2). In the largest illustrated growth-stage (Zhang & Pratt 1993; fig. 1D), these spines are ornamented by what appears to be rounded scales, suggestive of the characteristic ornamentation of Mongolitubulus spines. A second species of Duibaniella, D. elongata Shu, 1990, show some similarities to juveniles

AAP Memoir 32 (2006) 13

of Spinospitella, indicating that Duibaniella, Mongolitubulus and Spinospitella may form a natural group.

A number of phosphatocopids from the Upper Cambrian of Sweden have prominent spines on the cardinal corners. At least in two species, Hesslandona necopina Müller, 1964 (see Maas et al. 2003, pl. 14A, C) and H. curvispina Maas et al., 2003 (Maas et al. 2003, pl. 29A, B), these spines are ornamented by small spiniform protuberances comparable in morphology to the scales of Mongolitubulus. Disassociated spines of phosphatocopids and bradoriids would probably be difficult to distinguish from each other, unless the basal part of the spine is preserved. In phosphatocopids the cardinal spines are not attached to the valves proper, but to the interdorsum, a narrow plate separating the main valves of many phosphatocopids (Hinz-Schallreuter 1993a; Maas et al. 2003). The basal part of phosphatocopid cardinal spines exhibit straight and well defined margins, while the circular flaring base of Mongolitubulus reflects the insertion of the spines on the convex surface of the valves.

Ornamented cones and spine-shaped SSFsThe rich literature of Early and Middle Cambrian small shelly fossils contains many groups of problematic taxa that, in light of the discussion above, may be reinterpreted as bradoriid or phosphatocopid remains. It should be noted that in the absence of articulated material any such interpretation is highly speculative, but may nevertheless be worthwhile, if only to spur continued research and debate. One group of small shelly fossils that may originate from bivalved arthropods include various ornamented spine- or tube-shaped fossils. Some of these fossils, including Tommotitubulus Fedorov, 1986, Kazakhstanotubulus Gridina, 1991 Rushtonites Hinz, 1987, Rhombocorniculum Walliser, 1958 and Nicolarites Vasilieva, 1994 were discussed briefly by Skovsted & Peel (2001) in connection with Mongolitubulus. Of these forms, Rhombocorniculum and Tommotitubulus are difficult to associate with arthropods. Rhombocorniculum (Fig. 4D) grew continuously by basal-internal deposition of phosphate (Landing et al. 1980) in a manner comparable to some other Cambrian conodontiform fossils, and Landing (1995) proposed the name pseudoconodonts to describe such fossils. Tommotitubulus is known only from internal moulds ornamented by broad flat-topped projections of variable shape and dimensions, but without any directionality (Fig. 4E, F; Fedorov 1986), and may be related to hyolithelminths (Rozanov 1986).

Similarities in ornamentation, shell structure and the presence of an expanded base make Rushtonites from the Lower Cambrian of England very similar to Mongolitubulus (Fig. 4G; Hinz 1987; Brasier 1989; Skovsted & Peel 2001). Ornamented spines closely comparable to Rushtonites have been reported from the Middle Cambrian of the Mackenzie Mountains, Canada (Butterfield & Nicholas 1996) and from Siberia (Melnikova 2000). In Siberia, these spines were found in association with the bradoriid Tubuterium ivantsovi. Melnikova (2000) suggested that the Siberian spines were originally attached to an anterior node on each valve of T. ivantsovi (Fig. 4B), and the same interpretation may apply also to Rushtonites from England, although Landing (1995) favoured a grasping function for this fossil.

Kazakhstanotubulus from the Kiikbay Formation (Tommotian?-Atdabanian) of central Kazakhstan (Fig. 4H) and Ornamented tube form A from South Australia (Fig. 4I; Conway Morris & Bengtson in Bengtson et al. 1990) are tubular fossils with short, hollow spines irregularly arranged over the surface. Both forms are from the Lower Cambrian and are known from only a few specimens. There is no indication of incremental growth and the shell structure is not accurately known, although Conway Morris & Bengtson (in Bengtson et al. 1990) expressed uncertainty regarding the original composition of Ornamented tube form A. The small spines of these fossils are reminiscent of the hollow second order spines of Spinospitella coronata from the Mernmerna Formation, and could be reconstructed in a similar manner. The best known taxon, Ornamented tube form A, combines the general morphology of Mongolitubulus henrikseni (e.g. long, curved and essentially parallel-sided spines with a cone-shaped apex) with the hollow second order spines of Spinospitella. Although the scales of Mongolitubulus henrikseni are occasionally developed as small spines, they are massive structures formed by the dense outer shell layer (Skovsted & Peel 2001). Little variation in morphology is observable among the three illustrated specimens of Ornamented tube form A (Bengtson et al. 1990, fig. 101), but this form may be reconstructed with multiple spines along the ventral margins in a manner similar to the spines of M. henrikseni or the nodes of Duibianella sp.

Nicolarites spasskyi Vasilieva, 1994 from the Lower Cambrian of Yakutia is known from curved spines and a single composite “sclerite” combining one long spine and one cone-shaped node on a convex plate (Fig. 4J). Morphologically similar fossils are also found in Lower Cambrian strata of North Greenland (J.S. Peel, pers. comm. 2005),


Quebec (Nodose cone of Landing et al. 2002) and possibly North-East Greenland (Skovsted, in press). Nicolarites from Yakutia are covered by a reticulate network and evenly distributed scales or second order spines (Vasilieva 1994, fig. 1, pl. 2, figs 1-3). This configuration is very close to that of Spinospitella coronata, but the reticulate network continue over the second order scales/spines. Vasilieva (1994) reconstructed Nicolarites as a sclerite and referred it with uncertainty to the cambroclavid family Zhijintidae Qian, 1978, but differences in morphology, ornamentation and shell composition makes this assignment dubious. The margins of the “complete” specimen illustrated by Vassilieva (1994, pl. 2, fig. 1c) do not preserve any obvious original margins, and its shape is best accounted for by breakage of some larger structure, presumably the valve of a bradoriid species morphologically similar to Spinospitella coronata.

Luo et al. (1982) referred curved cones with short, broad spines from the Meishucunian of South China to the archaeocyathid genus Tumuliolynthus Zhuravleva, 1963 and similar fossils were described as ‘Rushtonites’ asiatica by Landing (1991) from the Callavia Zone of eastern Newfoundland. Identical ornamented cones, together with specimens with more rapidly expanding bases, but with the same type of ornament, have since been described as Acanthocassis He & Xie, 1989 from a number of Chinese localities (e.g.; He & Xie 1989; Qian et al. 2001; Steiner et al. 2004). Acanthocassis was compared to Mongolitubulus by Qian et al. (2001), but the shape and ornamentation of the cones are more similar to Spinospitella. However, Steiner et al. (2004) showed that four or five cone-shaped elements of Acanthocassis occur in ring-like aggregates, mounted on a long annulated stalk (such aggregates were also found in association with Acanthocassis by Qian et al. (2001), who did not realise their relationship to the ornamented cones). Although individual cones of Acanthocassis may resemble bradoriid spines such as Mongolitubulus or Spinospitella, the circular arrangement of these fossils on an

annulated stalk is difficult to reconcile with an arthropodan origin.

Stoibostrombus crenulatus Conway Morris & Bengtson (in Bengtson et al. 1990) is a widespread fossil in acid residues from the Lower Cambrian of South Australia (Bengtson et al. 1990; Brock & Cooper 1993; Demidenko in Gravestock et al. 2001), and abundant specimens occur together with bradoriids in the Mernmerna Formation (CBS and GAB pers. obs.). Stoibostrombus is a cone-shaped and gently curved fossil, apparently with an open perforation at the apex. The exterior is generally smooth close to the apex, but the antapical end exhibits a distinct crenulated or ‘pulvinate’ ornament (Bengtson et al. 1990, figs 93-97; Brock & Cooper 1993, figs 8.4-8.6). Conway Morris & Bengtson (in Bengtson et al. 1990) interpreted Stoibostrombus as dermal, defensive sclerites of a vagrant benthic animal, while Demidenko (in Gravestock et al. 2001) noted similarities to sensory papillae of recent onychophorans and priapulids.

Smooth cones and spinesBilaterally symmetrical or asymmetrical cones and spines with smooth surfaces have been described from the Lower Cambrian under a variety of names. Some of these fossils presumably had a grasping function and are referred to protocontodonts, paraconodonts or pseudoconodonts (e.g. Bengtson 1976; Qian & Bengtson 1989; Landing 1995; Sweet & Donoghue 2001). However, a range of fossils are more problematical, and may represent arthropod spines.

Shingeinella indefinita Esakova in Esakova & Zhegallo, 1996 from the Mongolitubulus squamifer Zone (Botoman equivalent) of Mongolia (Fig. 4M) and Samsanoffoclavus matthewi Landing, 1991 from the Camenella baltica Zone (Atdabanian equivalent) of Cape Breton Island (Fig. 4N) are rapidly expanding cones, usually with an oval cross-section, that may be bilaterally symmetrical or slightly asymmetrical. The original composition is not well known for either of the two taxa, but may

Fig. 4. Cambrian bradoriids, phosphatocopids and small shelly fossils. A, Mongolitubulus henrikseni Skovsted & Peel, 2001. Reconstruction of right valve with multiple spines, (based on Skovsted 2005, fig. 1). B, Tubuterium ivantsovi Melnikova, 2000. Reconstruction of left valve with anterodorsal curved spine, (based on interpretations of Melnikova 2000, p. 184). C, Duibianella sp. Left valve, (based on Zhang & Pratt 1993, fig. 1D). D, Rhombocorniculum cancellatum (Cobbold, 1921). Lateral view of wide, flattened specimen, (based on Landing et al. 1980, pl. 2, fig. 20). E, F, Tommotitubulus savitzkii Fedorov, 1986; E, Lateral view of tube fragment; F, Detail of ornamented tube section (based on Rozanov 1986). G, Rushtonites spinosus Hinz, 1987. Lateral view of curved specimen with spine tip intact, (based on Hinz 1987, pl. 11, fig. 8). H, Kazakhstanotubulus aculeatus Gridina, 1991. Lateral view of spine fragment with second order spines intact, (based on Gridina 1991, fig. 2A). I, Ornamented tube form A. Lateral view of spine with multiple second order spines, (based on Bengtson et al. 1990, fig. 101E). J, Nicolarites spasskyi Vasilieva, 1994. Lateral view of ‘sclerite’ with one spine and one node, (based on reconstruction of Vasilieva 1994, fig. 1). (continued opposite)

AAP Memoir 32 (2006) 15

K, Stoibostrombus crenulatus Conway Morris & Bengtson in Bentson et al., 1990. Lateral view of spine, (based on specimen from the Mernmerna Formation of Angorichina Station, sample MMF 15.5). L, Acanthocassis orthacanthus (Yang & He, 1984). Lateral view of stalked specimen with a crown of ornamented cones, (based on Steiner et al. 2004, fig. 4.13). M, Shingeinella indefinita Esakova in Esakova & Zhegallo, 1996. “Ventral” view, (based on Esakova & Zhegallo, pl. 8, fig. 1). N, Samsanoffoclavus matthewi Landing, 1991. Right lateral view of internal mould, (based on Landing 1991, fig. 11.2). O, Seletellus seletinicus Gridina, 1991. Lateral view of plate with curved spine, (based on Gridina 1991, fig. 2i). P, Hesslandona ventrospinata Gründel in Gründel & Buchholz, 1981. Lateral view of left valve, (based on Hinz-Schallreuter 1998, fig. 3). Q, Salanacus voronini Grigorieva in Voronin et al., 1982. Oblique lateral view, (based on Rozanov 1986, fig. 23). R, Koksodus serratus Missarzhevsky in Missarzhevsky & Mambetov, 1981. Lateral view, (based on Rozanov 1986, fig. 24).


have been phosphate, although Landing (1991) speculated that Samsanoffoclavus may have had a calcareous shell. In both Samsanoffoclavus and Shingeinella the antapical end is widely flaring and may grade into a convex plate, the margins of which always appear to be broken. Both taxa differ from the ornamented bradoriid spines discussed above in their smooth surface, the shorter length and in having an oval rather than circular cross-section. Although bradoriids with smooth or almost smooth spines are known (see above), Samsanoffoclavus and Shingeinella show more similarities to the ventral spines of phosphatocopids such as Hesslandona ventrospinata Gründel in Gründel & Buchholz, 1981 (Fig. 4P) and Bidimorpha bidimorpha Hinz-Schallreuter, 1993b (e.g. Hinz-Schallreuter 1998, pls 3-7). Presently, phosphatocopids with ventral spines are known only from Middle and Upper Cambrian strata (Hinz-Schallreuter 1998), and all taxa described from the Lower Cambrian lack comparable structures, although small spines may be developed at the anterior and posterior cardinal angles (e.g. Dabashanella herein).

Small convex plates with curved spines from the Kiikbay Formation (Tommotian?-Atdabanian) of central Kazakhstan were described as Seletellus Gridina, 1991 (Fig. 4O). A second spine is occasionally developed on the same plate. The plates are about 0.1-0.2 µm wide, and apparently phosphatic by original composition. Seletellus was found in association with Kazakhstanotubulus in central Kazakhstan, and in shape resembles the second order spines of that taxon. However, the second order spines of Kazakhstanotubulus are only 20-25 µm long compared to 80-180 µm for Seletellus. Gridina (1991) compared Seletellus to conodonts, but alternatively the fossils could be interpreted as parts of the same organism as Kazakhstanotubulus, perhaps as larger second order spines on the valves, in analogy to the combination of large and small spines on the valves of Mongolitubulus henrikseni.

Convex plates of variable shape with multiple smooth spines were described from the Lower Cambrian (Tommotian equivalent) of Mongolia and China as Salanacus vorononi Grigorieva in Voronin et al., 1982 (Voronin et al. 1982; Jiang 1984; Esakova & Zhegallo 1996). Specimens with three to eight spines have been described, and the exact configuration of spines is highly variable. Some specimens are composed of a large subcentral spine surrounded by smaller spines of decreasing length (Fig. 4Q), while the spines of other specimens are linearly arranged. Koksodus serratus Missarzhevsky in Missarzhevsky & Mambetov, 1981 from the Lower Cambrian (Tommotian equivalent) of Malyi Karatau is

similar to Salanacus in the presence of multiple spines. Unfortunately, the only illustrated specimen of Koksodus (Missarzhevsky & Mambetov 1981, pl. 26, fig. 1; Rozanov 1986, fig.24) is a side view. The fossil appears to have three pointed spines on its “upper” surface and additional spines projecting horizontally from the sides (Fig. 4R). By analogy with the description of Spinospitella coronata below, both Salanacus and Koksodus may be interpreted as the fragmented and possibly deformed shields of some bradoriid or phosphatocopid arthropod with multiple spines. The weakly mineralised shield of S. coronata is sometimes subjected to folding, and the resulting fossils are contorted pieces of shell with the characteristic spines diverging in different directions (e.g. Figs 8A, B, 9A).

PHYLOGENETIC POSITION OF BRADORIIDS AND PHOSPHATOCOPIDSIn size and general morphology, the head-shields of Cambrian to lower Ordovician bradoriids and phosphatocopids are comparable to Ordovician–Recent crustaceans of the Class Ostracoda Latreille, 1806, and have traditionally been regarded as ostracods (Matthew 1902; Ivanova 1960; Sylvester-Bradley 1961; Müller 1964, 1979; Shu 1990). However, Ulrich & Bassler (1931) regarded bradoriids to be conchostracans and Raymond (1935) suggested an affinity to malacostracans, while Öpik (1968) and Fleming (1973) preferred an association with phyllocarids. The most obvious difference between bradoriids and phosphatocopids on one hand, and the post-Cambrian ostracods on the other, is the composition of the shell. While true ostracods have calcareous carapaces, bradoriids and phosphatocopids have either phosphatic or weakly mineralised shields (Müller 1979; Briggs et al. 1993; Hinz-Schallreuter 1993c, 1999; Siveter & Williams 1997). In addition, phosphatocopids and bradoriids lack a true articulating hinge between the valves comparable to that of ostracods (Hou et al. 1996).

The most convincing evidence for the phylogenetic position of bradoriids and phosphatocopids comes from studies of limb and soft part morphology of exceptionally preserved specimens. The limb-morphology of phosphatocopids from the Upper Cambrian Orsten fauna of Sweden (Müller 1979; Maas et al. 2003) and the Lower Cambrian of England (Siveter et al. 2001, 2003) shows that although phosphatocopids are crustaceans, they form a sister group to the Eucrustacea (sensu Walossek 1999; e.g. Malacostraca and Entomostraca; see also Siveter et al. 2001, 2003; Maas et al. 2003). Bradoriids may not be a monophyletic grouping

AAP Memoir 32 (2006) 17

(Jones & McKenzie 1980; Hinz-Schallreuter 1999), but the only bradoriid for which limb morphology is presently known, Kunmingella douvillei (Mansuy, 1912) from the Lower Cambrian Chengjiang fauna of China (Hou et al. 1996; Shu et al. 1999), appears not to be closely related to phosphatocopids, and may fall outside the crustacean clade (Hou et al. 1996; Walossek 1999) or represent an early off-shoot of the crustacean stem lineage (Shu et al. 1999). Consequently, the bivalved head-shield and presumably the ‘ostracod’ mode of life evolved multiple times among Cambrian arthropods, before true ostracods appeared (Briggs 1983; Hou et al. 1996; Shu et al. 1999; Maas et al. 2003).

A few authors have maintained phosphatocopids and bradoriids as Ostracoda (e.g. Hinz-Schallreuter 1993b, 1998, 1999; McKenzie et al. 1999; Gozalo & Hinz-Schallreuter 2002). Hinz-Schallreuter (1999) noted similarities in shell morphology between bradoriids and various modern ostracods as evidence for their close phylogenetic relationship. Gozalo & Hinz-Schallreuter (2002) also claimed that many modern Ostracoda exhibit modified limb-morphologies comparable to those documented from Cambrian phosphatocopids and bradoriids. Hinz-Schallreuter (1999, p. 27) suggested that instead of excluding bradoriids and phosphatocopids, the concept of the Ostracoda should be expanded to include these groups. However, an expanded Ostracoda that would include the phosphatocopids, would also (to remain monophyletic) have to include all other modern crustaceans as well, if indeed the Phosphatocopida is the sister group to the Eucrustacea (e.g. Maas et al. 2003; Siveter et al. 2003).

SYSTEMATIC PALAEONTOLOGYTerminology. The terminology used to describe the bradoriids largely follows that employed to describe Ordovician and later ostracods (as adapted in Siveter & Williams 1997, Williams & Siveter 1998, Hou et al. 2002 and Siveter et al. 2003). We follow Siveter et al. (2003, p. 13) in using the more neutral term ‘head-shield’, or simply ‘shield’ instead of the ostracod term ‘carapace’.

Repository. All specimens illustrated herein are housed in the palaeontological collection of the South Australian Museum (acronym SAMP).

Class UNCERTAINOrder BRADORIIDA Raymond, 1935

Discussion. The order Bradoriida is a diverse group of Early Cambrian to Lower Ordovician

arthropods and some authors have suggested it may be polyphyletic (e.g. Jones & McKenzie 1980; Hinz-Schallreuter 1999; Vannier et al. 2005). Information on the morphology of the limbs and other soft parts is essential for elucidating arthropod phylogenies (Siveter et al. 2003; Maas et al. 2003), but unfortunately the limb morphology is presently known for only one bradoriid species, Kunmingella douvillei, from the Chengjiang biota of China (Hou et al. 1996; Shu et al. 1999). Thus, the monophyly of the Bradoriida is, and will continue to be, difficult to test until the limbs and soft parts are known for a wider array of bradoriids. The shields of bradoriids share a number of characteristics (see Siveter & Williams 1997; Williams & Siveter 1998), and although the Bradoriida may include a number of different arthropod lineages, it is here treated as a natural group.

In their recent discussion of the phylogenetic position of the Phosphatocopida, Maas et al. (2003) listed a number of autapomorphies distinguishing this group. Many of these characteristics relate to limb and soft part morphology, and are impossible to apply to taxa known only from head-shields (i.e. many phosphatocopids and all known bradoriid species except Kunmingella douvillei). Of the shield characteristics used by Maas et al. (2003, p. 160, points 1-3) to distinguish the phosphatocopids, only one, the presence of a doublure on the free margin, consequently excludes bradoriids from the Phosphatocopida. Maas et al. (2003, appendix B) included in the Phosphatocopida a number of Early and Middle Cambrian taxa that are better regarded as bradoriids. Following Jones & McKenzie (1980), they regarded the comptalutid taxa Oepikaluta Jones & McKenzie, 1980, Alutella Kobayashi & Kato, 1951 and Zepaera Fleming, 1973 as phosphatocopids, although Hinz-Schallreuter (1999) and Hou et al. (2002) have shown that comptalutids lack a doublure and form a natural group which shares many characters with other bradoriids (e.g. reticulate surface ornament and lobe morphology). Following Müller (1964, 1979), Jones & McKenzie (1980) used the phosphatic shell composition to differentiate phosphatocopids from bradoriids, but several typical bradoriids have since been shown to include phosphate in their shields (Hinz-Schallreuter 1993c; Siveter et al. 1996; Siveter & Williams 1997; but see Briggs et al. 1993 for a different view). Maas et al. (2003) also regarded Monasterium Fleming, 1973 and Epactridium Bengtson in Bengtson et al., 1990 as phosphatocopids, again following arguments based on shell composition (e.g. Jones & McKenzie 1980; Bengtson in Bengtson et al. 1990). The internal morphology of Monasterium


and Epactridium is poorly known, but no evidence exists for the presence of a doublure, and both taxa resemble typical bradoriids such as Bradoria Matthew, 1899 and Hipponicharion Matthew, 1886. Lastly, Maas et al. (2003) included Liangshanella Huo, 1956 in the Phosphatocopida. This genus is widespread in the Lower Cambrian, and at least L. sayutinae (Melnikova, 1988) from the Trans-Baikal area of Siberia and North-East Greenland and L. burgessensis Siveter & Williams, 1997 from the Middle Cambrian Burgess Shale of western Canada have a margin without a doublure and consequently fall outside the concept of the Phosphatocopida (see Skovsted, in press, fig. 6.10; Siveter & Williams 1997, pl. 8, fig. 5).

Hinz-Schallreuter (1993a) described Biaurina punctata as a bradoriid with a punctate shield, lobation of bradoriid type and a doublure. However, the presence of a doublure is not apparent in the accompanying illustrations (Hinz-Schallreuter 1993a, fig. 3.1a, b) and this taxon needs reinvestigation.

Family UNDETERMINED

Discussion. Mongolitubulus and Spinospitella show some similarities both to each other and to various bradoriid genera such as; Duibianella, Monasterium, Flemingopsis , Chegetella , Capricambria, Tubuterium and Monceretia (see discussion above). These bradoriid genera have been placed in different families by various authors, and they may not all be closely related. Without detailed restudy of relevant type material it is impossible to fully evaluate the potential relationships between the taxa, and the same applies to potential relationships with various small shelly fossils. Therefore, at this stage we refrain from proposing any supragenetic affiliation within the Bradoriida for Mongolitubulus and Spinospitella.

Mongolitubulus Missarzhevsky, 1977

1977 Mongolitubulus Missarzhevsky, p. 13.2001 Mongolitubulus Missarzhevsky; Skovsted

& Peel, p. 137.

Type species. Mongolitubulus squamifer Missarzhevsky, 1977.

Species included. Type species and M. henrikseni Skovsted & Peel, 2001.

Discussion. The many hypotheses regarding the function and affinity of Mongolitubulus are outlined above. Skovsted (2005) recently

showed that at least Mongolitubulus henrikseni is a bradoriid with multiple spines of different size attached to each valve. The similarities of Mongolitubulus to a range of ornamented spine-shaped fossils from the Lower and Middle Cambrian is discussed above. The most notable similarities among spine-shaped small shelly fossils are to Rushtonites Hinz, 1987 from the Lower Cambrian of England, which occasionally preserve an expanding base similar to M. henrikseni (Brasier 1989, pl. 7.2, fig. 5) and to fossils from the Lower Cambrian of western Canada (Butterfield & Nicholas 1996) and the Middle Cambrian of Siberia (Melnikova 2000). Among bradoriids known from complete valves, the most similar are Duibianella sp. (sensu Zhang & Pratt 1993) from the Lower Cambrian of China and Spinospitella coronata gen. et sp. nov. from South Australia described below.

Distribution. Upper Lower Cambrian of Mongolia, Malyi Karatau, Antarctica, Greenland, eastern United States and Canada, South Australia, England. Middle Cambrian of Siberia and possibly China.

Mongolitubulus henrikseni Skovsted & Peel, 2001 (Fig. 5A-J)

1990 Ornamented tube C; Conway Morris & Bengtson in Bengtson et al., p. 158, fig. 103 a-h.

1996 Ornamented tubes; Landing & Bartowski, p. 759, fig. 9.10.

2001 Mongolitubulus henrikseni; Skovsted & Peel, p. 140, figs 3, 4.

2002 Mongolitubulus squamifer? Missarzhevsky, 1977; Landing et al., p. 301, fig. 4.19.

2005 Mongolitubulus henrikseni Skovsted & Peel; Skovsted, figs 1, 2.

in press Mongolitubulus henrikseni Skovsted & Peel; Skovsted, fig. 6.12-14.

Material. SAMP 41403-41409 and 2 additional specimens from the Mernmerna Formation [samples MMF15.5, 44.6, 66.0 and 94.8].

Description. Fragmentary to almost complete, isolated spines of a bradoriid with multiple external spines. The spines are long (length of preserved specimens and fragments 0.6 to 1.6 mm) and slender, with circular cross-section (0.1 to 0.2 mm in diameter). The spines sometimes taper very gently towards the pointed apex (Fig. 5H), but most specimens are of uniform thickness through much of the length (Fig. 5B, C, G). Close to the tip of the spine, the rate of tapering increases resulting in a conical apex (Fig. 5D).

AAP Memoir 32 (2006) 19

Fig. 5. Mongolitubulus henrikseni Skovsted & Peel, 2001. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All except H from sample MMF 44.6. A, SAMP41403, lateral view of spine with flaring base, x160. B, SAMP41404, lateral view of curved spine with flaring base, x100. C, D, SAMP41405; C, lateral view of spine with pointed apex, x90; D, detail of spine apex, x250. E, SAMP41406, lateral view of spine with blunt apex, x100. F, G, SAMP41407; F, Detail of spine apex with partially subdued ornament, x120; G, lateral view of curved spine with both apex and flaring base, x55. H, SAMP41408 from sample MMF 94.8, lateral view of exfoliated curved spine, x55. I, J, SAMP41409; I, lateral view of spine with deformed apex and flaring base, x140; J, detail of deformed apex, x420.


The antapical end of the spine is widely flaring, with an increase in diameter of approximately 2 times, but the flaring margins are always broken (Fig. 5A, G, I). The external surface of the spines exhibits an ornamentation of small scale-like or occasionally spiniform protuberances, 10 to 20 µm long and wide. The arrangement of the scales is dense and apparently chaotic (Fig. 5A, E-G). Certain specimens appear smooth over large stretches with only a few scales preserved, presumably an effect of abrasion (Fig. 5B, H). Sometimes, a subdued ornamentation of low, undulating ridges is present on the inner side of curved specimens (Fig. 5F).

Discussion. Only a few isolated spines of Mongolitubulus are available from the Mernmerna Formation, but based on the irregular surface ornamentation, the parallel-sided form with a conical apex and the flaring base, they can readily be assigned to Mongolitubulus henrikseni. Apparently identical fossils have been reported from the Ajax Limestone at Mt Scott Range in South Australia as Ornamented tubular fossil C (Conway Morris & Bengtson in Bengtson et al. 1990). The original composition of Ornamented tubular fossil C was considered problematic by Conway Morris & Bengtson (in Bengtson et al. 1990, p. 158). The fossils were preserved in acid residues as epitaxial coatings and internal moulds, suggestive of a calcareous original composition. However, these specimens could also represent weakly mineralised specimens of M. henrikseni. Similar, very weakly mineralised specimens of M. henrikseni are present in acid residues from the Forteau Formation of western Newfoundland (CBS pers. obs.). Two other types of ornamented tubes from South Australia were described in the same publication (Conway Morris & Bengtson in Bengtson et al. 1990). Ornamented tube A has hollow second order spines and is most similar to the spines of Spinospitella n. gen., while Ornamented tube B have a roughly linear arrangement comparable to specimens of M. squamifer from the Lower Cambrian of western New South Wales (Brock & Percival 2006 [this volume]) and Ornamented tube form 1 from the Middle Cambrian of China (Zhu & Dong 2004).

Demidenko (in Gravestock et al. 2001) described ornamented spines from the Stansbury Basin of South Australia as Mongolitubulus ex. gr. M. squamifer. The specimens are straight, cone-shaped and have an unusual ornamentation, but unfortunately only one specimen is figured. One side of the cone is smooth, while the other is ornamented with large, rounded scales. The rounded scales are reminiscent of M. henrikseni,

but the overall shape of the spine is more similar to straight specimens of M. squamifer (e.g. Skovsted & Peel 2001, fig. 1F). Skovsted & Peel (2001) observed that individual specimens of Mongolitubulus may be difficult to assign to any species due to the commonly extensive variation, and until additional material of Mongolitubulus ex. gr. M. squamifer is available, these specimens will remain problematical.

One specimen of Mongolitubulus from the Mernmerna Formation is unusual in that it apparently preserves both the apex and parts of the flaring base (Fig. 5G). This specimen has a highly recurved spine tip and is characterised by subdued ornamentation on the inside of the curvature, and in this respect it approaches the morphology of certain specimens of M. squamifer from North Greenland (e.g. Skovsted & Peel 2001, fig. 2G). However, curved specimens of M. henrikseni with subdued ornamentation were also documented from North-East Greenland by Skovsted & Peel (2001, fig. 3C, M). A second, unusually short specimen from the Mernmerna Formation combines a deformed, laterally compressed, apex with an extensively folded valve fragment at the antapical end. Specimens of M. henrikseni with similar deformed spine tips were documented from Greenland by Skovsted (2005, fig. 2E-J). All in all, the specimens of M. henrikseni from the Mernmerna Formation exhibit considerable differences in overall morphology and ornamentation, but a similar range of variability was documented among almost 2000 specimens of M. henrikseni from the Bastion Formation of North-East Greenland (Skovsted & Peel 2001; Skovsted 2005). The high variability is not unexpected, as the valves of a complete specimen of M. henrikseni from North-East Greenland was shown by Skovsted (2005, fig. 1) to bear a multitude of spines in different positions and of variable dimensions. Such a configuration would allow a considerable degree of variation in spine morphology.

Mongolitubulus henrikseni is presently known to occur along the present day eastern margin of Laurentia (Skovsted & Peel 2001) and in Australia. Skovsted & Peel (2001) suggested that specimens referred to M. squamifer from Malyi Karatau (Missarzhevsky & Mambetov 1981) and Antarctica (Wrona 1989) represented M. henrikseni, but later studies have shown that this interpretation was incorrect (e.g. Dzik 2003; Wrona 2004).

Distribution. Upper Lower Cambrian of Northeast Greenland, Labrador, Quebec, New York State, South Australia and western New South Wales.

AAP Memoir 32 (2006) 21

Spinospitella gen. nov.

Type species. Spinospitella coronata gen. et sp. nov.

Diagnosis. Slightly postplete bradoriid arthropod with gently curved (in lateral view) hinge-line and a narrow lateroadmarginal ridge. One hollow, sub-centrally placed and backwardly curving spine and one anterodorsal cone-shaped node. All parts of the adult shield covered by a reticulate network and hollow second order spines.

Etymology. Derived from Latin spina, thorn. For the prominent first order spines covered with second order spines.

Discussion. Spinospitella gen. nov. differs from other bradoriids by the existence on each valve of one curved sub-central spine and one anterodorsal node ornamented by a reticulate network and numerous hollow second order spines. In juvenile specimens, the second order spines are concentrated to the sub-central spine and to a zone close to what is probably the ventral margin of the valve (Fig. 8A, B). This configuration is reminiscent of Mongolitubulus, where the majority of smaller spines are concentrated to a zone along the valve margins (Skovsted 2005, fig. 1). It is possible that the smaller, marginal spines of Mongolitubulus are homologous to the second order spines of Spinospitella. The characteristic scales on the spines of Mongolitubulus is an integrated part of the outer shell layer only (Skovsted & Peel 2001, fig. 3a) and may be comparable to the crown of small scales of the hollow second order spines of S. coronata. The valve surface between the spines of Mongolitubulus may also exhibit a reticulate ornamentation (Skovsted & Peel 2001, fig. 4e). Mongolitubulus differs from Spinospitella by having at least seven large spines attached to each valve.

Spinospitella differs from Duibianella by the development of the sub-central spine and the numerous second order spines. However, juveniles of Spinospitella share several characters with Duibianella including dome-shaped processes and irregularly distributed minute knobs/vestigial second order spines (compare Fig. 9D, E with Shu 1990, pl. 5, fig. 4a, b). Spinospitella differs from other spinose bradoriids, including Capricambria, Flemingopsis, Monasterium, Chegetella, Tubuterium and Preaechmina, by the number and position of the first order spines, as well as the presence of second and third order spines.

As outlined above, the large ornamented

spine of Spinospitella exhibits similarities to Nicolarites from the Lower Cambrian of Yakutia and Laurentia, Kazakhstanotubulus from central Kazakhstan and Ornamented tube form A of Bengtson et al. (1990) from Yorke Peninsula, South Australia, indicating that these small shelly fossils may belong to related bradoriid species. However, in the absence of better preserved material, the exact relationships between these fossils must remain unresolved at the present time.

Distribution. Upper Lower Cambrian (Botoman, Pararaia bunyerooensis Zone), Mernmerna Formation, Flinders Ranges, South Australia.

Spinospitella coronata gen. et sp. nov. (Figs 6A-L; 7A-I, 8A-G, 9A-G).

Holotype. Bivalved head shield SAMP41425, from sample MMF 44.6, Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia (Fig. 9A-C).

Diagnosis. As for genus.

Etymology. Derived from Latin corona, crown. For the crown of scales or third order spines close to the apex of the second order spines.

Material. SAMP41410-41426 and a large number of fragments, including 93 first order spines, 17 domes and 101 additional valve fragments [from samples MMF15.5, 29.0, 37.8, 44.6 and 82.6].

Description. Equivalved bradoriid arthropod, slightly postplete. The hinge line is gently convex in lateral view and the anterodorsal angle has a short marginal spine (Fig. 9D). The ventral margin is evenly curved and the valves have a narrow margin (Fig. 9F). Valves are ornamented by three levels of spines. A low, cone-shaped node is located in the anterodorsal corner, while a hollow first order spine is present slightly posteriorly of, and below, the valve centre. First order spine is straight, with a rounded tip in juvenile valves (Fig. 9G), but in mature specimens it is gently curved, with apex probably directed backwards, and with a closed, pointed tip (Figs 6A-E, 9A, B). External shield surface, including the anterodorsal node and the first order spine, is covered by a fine polygonal network (each polygon 10 to 15 µm wide; Figs 6L, 7H-I, 9B, C).

Juvenile and young adult specimens exhibit rounded knobs at the junction of the nodes of the polygonal network, while the walls of the network are weakly expressed (Figs 8F, G, 9G). Hollow, second order spines are also present


Fig. 6. Spinospitella coronata gen. et sp. nov. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All from sample MMF 44.6. A, SAMP41410, lateral view of spine. B, SAMP41411, oblique lateral view of spine. C, SAMP41412, lateral view of spine. D, SAMP41413, lateral view of abraded spine. E, J-L, SAMP41414; E, lateral view of spine; J, detail of internal surface with pores, x225; K, detail of internal surface with pore and reticulate ornament, x650; L, detail of external surface with second order spines and reticulate ornament, x400. F, G, SAMP41415; F, oblique lateral view of dome; G, top view of dome. H, I, SAMP41416; H, oblique lateral view of dome; I, top view of dome. All x60, except J-L.

AAP Memoir 32 (2006) 23

Fig. 7. Spinospitella coronata gen. et sp. nov. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All from sample MMF 44.6. A, SAMP41417, fragment of ventral? valve margin. B, SAMP41418, oblique lateral view of valve fragment. C, SAMP41419, fragment of ventral? valve margin. D, SAMP41420, oblique interior view of fragmentary ventral? valve margin. E, SAMP41421, detail of broken valve edge with internal pores and one external second order spine, x400. F-H, SAMP41422; F, fragment of ventral? valve margin; G, oblique view of fragment edge, x70; H, detail of shell exterior, x300. I, SAMP41423, detail of shell exterior, x300. All x60, except E, H, I.


on most specimens. In the smallest specimen recovered (length 0.75 mm), rudimentary second order spines are found only in a zone close to the dorsal valve margin (Fig. 9E). In an incomplete specimen, presumably of intermediate size (0.84 mm), second order spines are found along all valve margins and on the first order spine (Fig.

8A, B). In the largest specimen (1.3 mm long, but is compressed lengthwise), almost all surfaces of the shield are covered by second order spines (Fig. 9A), but their concentration is highest along the shield margins, on the first order spine and anterodorsal node. The second order spines are narrow, straight or evenly curved cones (25 to 50

Fig. 8. Spinospitella coronata gen. et sp. nov. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. Deformed valve fragment with spine and ventral? valve margin. SAMP41424 from sample MMF 44.6. A, top view, x62. B, lateral view, x95. C, oblique view of spine, x220. D, detail of second order spines with crown of scales, x1500. E, top view of spine, x220. F, detail of valve margin and parse second order spines, x400. G, detail of valve margin and parse second order spines, x800.

AAP Memoir 32 (2006) 25

µm long), with a circular cross-section (12 to 23 µm in diameter) and a closed apex (Figs 6L, 7H, I, 8D, 9B). They appear to be randomly arranged over much of the shield and the bases of two or three spines may coincide (Figs 7H, I, 8D). Close

to the valve margin the second order spines may form uneven rows perpendicular to the shield margin (Fig. 7F), and on the first order spine and the anterodorsal node they may be arranged in uneven whorls surrounding the apex (Figs 6G,

Fig. 9. Spinospitella coronata gen. et sp. nov. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. Both from sample MMF 44.6. A-C, SAMP41425 (holotype), deformed bivalved shield; A, right lateral view (stereo image), x45; B, lateral detail of subcentral spine, x180; C, top view of anterodorsal node, x240. D-G, SAMP41426, juvenile right valve; D, lateral view, x80; E, oblique dorsal view, x80; F, oblique ventral view, x80; G, detail (dorsal view) of subcentral spine, x300.


I, 8E). The surface of the second order spines is smooth, with the exception of a crown of 5 to 10 third order spines or low rounded knobs or scales close to the apex (Figs 6L, 8D). Occasionally, a second crown of low knobs are present at about mid-length (Fig. 6L). The internal surface of the shield exhibits circular openings corresponding to the second order spines (Figs 6A, E, 7D, E), and intervening areas may be ornamented by a fine reticulation (Fig 6J, K).

Discussion. Spinospitella coronata gen. et sp. nov. is almost exclusively represented in the Mernmerna Formation by irregular fragments, low cones representing the anterodorsal node and curved spines representing the first order spine. However, the morphology of the valves is evident from three more complete specimens, one juvenile right valve (Fig. 9D-G), one fragmented young adult valve (Fig. 8) and one bivalved, but deformed adult specimen (Fig. 9A-C). Even small fragments are readily identifiable by the characteristic ornament of hollow second order spines with a crown of third order spines or scales (Figs 6-7). As almost all specimens of S. coronata are fragmented and/or deformed it is likely that the valves were weakly mineralised.

Distribution. Upper Lower Cambrian Mernmerna Formation, Flinders Ranges, South Australia.

Family HIPPONICHARIONIDAE Sylvester-Bradley, 1961

Albrunnicola Martinsson, 1979

Type species. Longispina oelandica Andres, 1969.

Species included. Type species and A. bengtsoni Hinz-Schallreuter, 1993c.

Discussion. Albrunnicola is a widespread hipponicharoniid genus characterised by a strongly developed anterodorsal lobe and a weaker, node-like posterodorsal lobe. The type species is known from the Middle Cambrian of Sweden (Andres 1969) and Morocco (Hinz-Schallreuter 1993c), while A. bengtsoni occurs in the Lower Cambrian of Antarctica and Australia. Albrunnicola is also represented by at least one unidentified species in the Lower Cambrian of North-East Greenland (Skovsted, in press). Hinz-Schallreuter (1993c) regarded specimens described as Beyrichona longquanxiensis Cui in Cui et al., 1987 and the possibly synonymous Pseudobeyrichona longquanxiensis Cui in Shu, 1990 from the Lower Cambrian of China to represent a new species of

Albrunnicola, but Hou et al. (2002) assigned both taxa to Neokunmingella Zhang, 1974.

Distribution. Lower Cambrian of Australia, Antarctica and Greenland; Middle Cambrian of Baltica and Morocco.

Albrunnicola bengtsoni Hinz-Schallreuter, 1993c (Fig. 10A-H)

1986 Hipponicharion sp.; Gazdzicki & Wrona, fig. 7e.

1990 Hipponicharion sp.; Bengtson in Bengtson et al., p. 325, fig. 207a.

1993c Albrunnicola bengtsoni; Hinz-Schallreuter, p. 424.

2001 Albrunnicola bengtsoni Hinz-Schallreuter; Melnikova in Gravestock et al., p. 210, fig. 26.

Material. SAMP41426-41430 and 9 additional fragmentary specimens [samples MMF15.5, 29.0, 44.6, 64.5 and 82.6].

Description. High, weakly postplete bradoriid with subtriangular lateral outline (1.3 to 1.5 mm long and 1.15-1.3 mm high; Fig. 10A, C). The valves are moderately inflated with maximum height almost at centre of the valve. The hinge line is straight and continues anteriorly into a short, triangular spine (Fig. 10H). Both the anterior and posterior borders extend slightly beyond the hinge line. The lateroadmarginal ridge is narrow but slightly bulging and is separated from the lobal area by a deep furrow (Fig. 10D, F). Both anterior and posterior lobes are best developed in the dorsal half of the valves, although they sometimes continue as low ridges into the ventral half (Fig. 10F). The anterior lobe is strongly developed, almost spine-like and somewhat inclined anteriorly, sometimes slightly overhanging (Fig. 10A, B, D, E). The posterior lobe is node-like and much lower with its maximum height closer to the dorsal edge compared to the anterior lobe (Fig. 10A). The central lobe is situated close to the dorsal margin, weakly developed and slightly elongated towards the anterior (Fig. 10C, E). The valve surface is smooth or sometimes ornamented by small pits (Fig. 10H).

Discussion. The species Albrunnicola bengtsoni was defined by Hinz-Schallreuter (1993c) based on a single specimen from the Lower Cambrian of South Australia originally described as Hipponicharion sp. by Bengtson (in Bengtson et al. 1990, p. 325, fig. 207A). Albrunnicola bengtsoni differs from the type species, A. oelandicus, by

AAP Memoir 32 (2006) 27

Fig. 10. Albrunnicola bengtsoni Hinz-Schallreuter, 1993c. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All from sample MMF 44.6. A, B, SAMP41427, right valve; A, lateral view (stereo image), x50; B, oblique view from posterior, x45. C-E, SAMP41428, left valve; C, lateral view (stereo image), x40; D, oblique ventral view, x45; E, oblique dorsal view, x45. F, SAMP41429, lateral view of ventral part of left? valve, x35. G, SAMP41430, lateral view of posterior part of right valve, x40. H, SAMP41431, lateral view of anterodorsal part of left valve, x45.


the more strongly developed posterior lobe and was considered intermediate between typical species of Albrunnicola and Hipponicharion Matthew, 1886 by Hinz-Schallreuter (1993c, p. 424). Melnikova (in Gravestock et al. 2001) illustrated two hipponicharioniid specimens from South Australia and referred them to A. bengtsoni. However, these specimens are poorly preserved and at least one (Gravestock et al. 2001, fig. 26b) has small, sub-equal anterior and posterior lobes comparable to those of Bicarinella evansi Rode et al., 2003 from the Lower Cambrian of East Antarctica. Melnikova (in Gravestock et al. 2001) also included in A. bengtsoni a specimen from the Lower Cambrian of Antarctica (Glacial erratics on King George Island) illustrated by Gazdzicki & Wrona (1986, fig. 7e).

Distribution. Upper Lower Cambrian of South Australia and Antarctica (glacial boulders on King George Island).

Family COMPTALUTIDAE Öpik, 1968

1968 Comptalutidae; Öpik, p. 27.1980 Comptalutidae Öpik; Jones & McKenzie,

p. 209.1980 Oepikalutidae; Jones & McKenzie, p. 211.1999 Oepikalutidae Jones & McKenzie; Hinz-

Schallreuter, p. 27.2002 Comptalutidae Öpik; Hou et al., p. 379.

Discussion. Jones & McKenzie (1980) referred their new family Oepikalutidae Jones & McKenzie, 1980 to the Phosphatocopida and distinguished it from the morphologically very similar (bradoriid) family Comptalutidae mainly by the phosphatic composition of the shields. This interpretation was followed by Maas et al. (2003), although the chemical composition of the valves has been shown to be irrelevant for separating bradoriids and phosphatocopids (see above). Hinz-Schallreuter (1999) recognised these fossils as bradoriids, although she retained the name Oepikalutidae. As discussed by Hou et al. (2002), Oepikalutidae is a junior synonym of Comptalutidae.

Zepaera Fleming, 1973

1973 Zepaera; Fleming, p. 7.1980 Zepaera Fleming; Jones & McKenzie, p.

213.1999 Zepaera Fleming; Hinz-Schallreuter, p.

30.

Type species. Zepaera rete Fleming, 1973.

Species included. Type species, Z. bandeli Hinz-Schallreuter, 1999 and possibly Z. brevidorsa Huo & Shu, 1985 and Z. primitiva Shu, 1990.

Diagnosis. See Hinz-Schallreuter (1999, p. 30).

Discussion. The genus Zepaera was erected by Fleming (1973) for comptalutid bradoriids with distinctive lobes forming W-shaped ridges in the anterior half of juvenile valves. However, in larger growth stages the lobes are effaced, and eventually disappear completely (e.g. Jones & McKenzie 1980, fig. 5C-H), a phenomenon also observed among other comptalutids (Hinz-Schallreuter 1999, p. 28).

In her discussion on the phylogeny of the Comptalutidae, Hinz-Schallreuter (1999) regarded the Middle Cambrian (late Templetonian) Quetopsis katarcha Hinz-Schallreuter, 1999 (type and only species of Quetopsis Hinz-Schallreuter, 1999) as the most primitive of all comptalutids. However, Q. katarcha is presently only known from four specimens from one locality (its stratigraphic range in fig. 3 of Hinz-Schallreuter 1999 is presumably inferred). Quetopsis was described as a comptalutid lacking lobes altogether (beyond the V-shaped anterodorsal sulcus) throughout ontogeny. Unfortunately, almost all Australian specimens referred to Quetopsis by Hinz-Schallreuter (including the holotype) are large, incompletely preserved and exhibit a pitted surface ornamentation unlike the reticulate network of other comptalutids. Only one juvenile specimen lacking distinct lobes was found and Hinz-Schallreuter (1999, p. 38) observed that the majority of specimens of Quetopsis could very well represent the largest growth stages of the co-occurring Zepaera rete. However, she regarded this as unlikely as Z. rete would then have had too many ontogenetic growth stages in comparison with Ordovician and later ostracods. We consider that at least the holotype and other large specimens of Quetopsis may belong to Zepaera, although the pitted surface ornamentation may suggest these specimens are not comptalutids at all (see discussion of Euzepaera sp. below). According to Hinz-Schallreuter (1999) specimens of Alutella nakamurai Kobayashi & Kato, 1951 described by Huo et al. (1991; p. 97, pl. 10, figs 1, 2) may belong to Quetopsis, but Hou et al. (2002, p. 388) suggested that the lack of distinct lobes in the Chinese material is a consequence of abrasion.

Indianidae gen. et sp. indet. B and C from the Ajax and Parara Limestones of South Australia, respectively, were described by Bengtson (in Bengtson et al. 1990). Both forms have a reticulated micro-ornamentation and a wide anterodorsal border comparable to that of

AAP Memoir 32 (2006) 29

Fig. 11. Zepaera sp. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. A, F, G, SAMP41432 from sample MMF 64.5; A, oblique right lateral view of bivalved shield (stereo image), x50; F, detail of valve reticulate valve surface, x235; G, posterior view of shield, x40. B, SAMP41433 from sample MMF 64.5, left lateral view of deformed bivalved shield (stereo image), x35. C, SAMP41434 from sample MMF 64.5, left lateral view of deformed bivalved shield (stereo image), x28. D, SAMP41435 from sample MMF 44.6, lateral view of deformed right valve, x45. E, SAMP41436 from sample MMF 44.6, lateral view of posterior part of right valve, x45.


Zepaera, but both forms are represented by single, poorly preserved specimens.

Distribution. Lower Cambrian of Australia and China, Middle Cambrian of Australia.

Zepaera sp. (Fig. 11A-G)

Material . SAMP41432-41436 additional specimens, including 1 right valve, 2 left valves and 29 fragmentary specimens [sample MMF15.5, 44.6, 61.2 and 64.5].

Description. Comptalutid bradoriid with postplete and strongly convex valves with a straight dorsal margin (1.2 - 1.5 mm long). Anterior and posterior margins are strongly curved and project slightly beyond the cardinal corners. Ventral margin is more gently curved. The lateroadmarginal ridge is entire between the cardinal corners and is wide, bulging and separated from the lobal area by a wide furrow. All specimens are affected to varying degrees by soft deformation. A flattened, V-shaped anterodorsal sulcus is present, but the remainder of the lobal area is strongly convex, without any obvious lobes or nodes. The surface of the valves are ornamented by a fine reticulate network (Fig. 11A, E, F)

Discussion. The highly postplete valves with a wide and bulging lateroadmarginal ridge and an undifferentiated lobal area makes the specimens described above very similar to large specimens of Zepaera rete from the Middle Cambrian of Queensland (e.g. Jones & McKenzie 1980, fig. 5C-H; Hinz-Schallreuter 1999, pl. 2, fig. 6). All reasonably complete specimens from the Mernmerna Formation lie within the upper size-range reported for Z. rete (e.g. Hinz-Schallreuter 1999, fig. 4). The imperfect preservation of all specimens and the lack of well preserved juveniles (which are more likely to exhibit the characteristic lobal patterns distinguishing different comptalutid taxa) precludes specific determination. Based on similar arguments Hinz-Schallreuter (1999) suggested that Z. brevidorsa Huo & Shu, 1985 and Z. primitiva Shu, 1990 from the Lower Cambrian of China are indistinguishable from Z. rete.

Family ZHEXIELLIDAE Shu, 1990

Euzepaera Shu, 1990

1990 Euzepaera; Shu, p. 44.2003 Euzepaera Shu; Melnikova, p. 397

Type species. Euzepaera hunanensis Shu, 1990.

Species included. Type species, E. zhejiangensis Shu, 1990, E. foveata Melnikova 2003 and Euzepaera sp.

Diagnosis. Preplete to weakly postplete zhexiellid with moderately convex valves, a V-shaped anterodorsal sulcus and a narrow lateroadmarginal ridge. Surface ornamentation consists of evenly distributed circular pores covering all parts of the valves except close to the margins and on the anterodorsal sulcus. Internally, pores are sealed by dome-shaped phosphatic pads.

Discussion. A punctate shell or pitted micro-ornamentation is not uncommon among bradoriids and is found in many taxa of different families. In Bradoria scrutator Matthew, 1899 (Bradoridae) from the Lower Cambrian of England and Avalonian North America the punctae were not open exteriorly and are only observable on exfoliated surfaces (Siveter & Williams 1997). However, in taxa such as Biaurina punctata Hinz-Schallreuter, 1993a (family uncertain) from the Middle Cambrian of Queensland, Hipponicharion geyeri Hinz-Schallreuter, 1993c (Hipponicharionidae) from the Middle Cambrian of Morocco and Epactridion portax Bengtson (in Bengtson et al., 1990) (?Monasteridae) from the Lower Cambrian of South Australia, the punctae appear to have been open to the exterior as was probably the case in Euzepaera. In H. geyeri and E. portax pores are restricted to certain parts of the valves and in E. portax they are reduced in number and distribution during ontogeny (Bengtson et al. 1990). The internal surfaces of bradoriid shields have not been extensively studied and it is unclear if any of the punctate forms mentioned above have internally open punctae, although the pores in E. portax were reported to have a “smooth rounded bottom” (Bengtson et al. 1990, p. 323). In modern ostracods open punctae are commonly occupied by setae, and the cylindrical depressions adjacent to the pore openings in the Australian Euzepaera may indicate a similar function.

E u z e p a e r a d i f f e r s f r o m B i a u r i n a , Hipponicharion and Epactridion by the presence of a v-shaped anterodorsal sulcus and in the absence of well developed lobes or ridges. The genus can be distinguished from Zhexiella Shu, 1990 by the well developed lateroadmarginal ridge and absence of a centrodorsal node, and from Almazina Melnikova, 2003 by the larger and less densely distributed pores.

Distribution. Lower Cambrian of South Australia, Middle Cambrian of Malyi Karatau and Upper Cambrian of China and Malyi Karatau.

AAP Memoir 32 (2006) 31

Fig. 12. Euzepaera sp. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All except A, B from sample MMF 44.6. A, SAMP41437 from sample MMF 8.8, lateral view of left valve (stereo image), x38. B, SAMP41438 from sample MMF 19.0, lateral view of deformed right valve, x38. C, SAMP41439, exterior surface of fragmentary right? valve with anterodorsal sulcus, x38. D, SAMP41440, external surface of domed valve fragment, x40. E-F, SAMP41441. E, external surface of fragmentary valve margin, x38. F, detail of external surface with pustules and a few pores, x165. G, H, SAMP41442; G, internal surface of valve fragments with dome-shaped pads, x45; H, detail of internal surface, x175.


Euzepaera sp. (Fig. 12A-H)

Material. SAMP41437-41442 and 127 additional fragmentary specimens [sample MMF8.8, 15.5, 19.0, 29.0, 44.6, 64.5 and 82.6].

Description. Bradoriid with moderately convex valves (most complete specimen 1.7 mm long and 1.5 mm high). Valve margins are not completely preserved in any specimen but the dorsal margin appears to be straight (Fig. 12B, C). Anterior and posterior margins are curved close to the cardinal corners but almost straight close to the strongly curved ventral margin, resulting in a sub-triangular lateral outline (Fig. 12A). Lateroadmarginal ridge appears to be entire between the cardinal corners. It is narrow but well defined and separated from the lobal area by a furrow. A flattened V-shaped sulcus is present close to the anterodorsal corner and is separated from the anterior border by a poorly defined anterodorsal lobe (Fig. 12A-C). The lobal area is ornamented by a large number of evenly distributed pore-like openings (diameter 10 to 22 µm; Fig. 12A-F). Diameter of the pores decrease close to the valve margins and the region closest to the margins, as well as the anterodorsal sulcus, which lacks pores altogether (Fig. 12A, C, E). These areas are ornamented by fine pustules (average diameter 5 µm; Fig. 12F). Close to the dorsal margins the pore openings are associated with vaguely defined cylindrical depressions extending ventrally (Fig. 12E, F). On internal valve surfaces the external pores are sealed by circular dome-like structures (30 to 44 µm in diameter; Fig. 12G, H).

Discussion. Euzepaera sp. from the Mernmerna Formation is similar to E. hunanensis Shu, 1990 from China and E. foveata Melnikova, 2003 from Malyi Karatau, but differs from both species in the development of a low node in front of the anterodorsal sulcus and in its subtriangular lateral outline. Euzepaera sp. is only represented by two reasonably complete specimens in the Mernmerna Formation, but a large number of fragmentary valves are also referred to the same species. The fragmentary specimens are referred to Euzepaera sp. based on the presence of characteristic external pores sealed internally by dome-like pads. The vast majority of the fragments represent the central convex area of large valves, but occasionally parts of the dorsal margin or the anterodorsal sulcus are preserved.

The largest of the two almost complete valves is 1.6 mm long (Fig. 12A), but many of the fragmentary specimens appear to represent much larger individuals, up to at least 4 mm in length. Some of these fragments resemble larger

specimens of Quetopsis katarcha from the Middle Cambrian of Queensland (Hinz-Schallreuter 1999, pl. 3, figs 6, 7). Quetopsis was considered to be a comptalutid by Hinz-Schallreuter (1999), despite the pitted ornamentation of the holotype and other large specimens. It is possible that larger specimens of Q. katarcha (including the holotype) represent a species of Euzepaera, although restudy of the relevant Queensland specimens would be required to assess this possibility.

Family HAOIIDAE Shu, 1990

Haoia Shu, 1990

Type species. Haoia shaanxiensis Shu, 1990.

Diagnosis. Weakly postplete bradoriids with a V-shaped anterodorsal sulcus and multiple, ridge-like lobes. Close to the ventral, and sometimes dorsal, margins secondary ridges connect the lobes, producing a honey-comb like pattern. Areas between lobes and ridges ornamented by a reticulate network or fine pustules.

Discussion. The family Hipponicharionidae includes bradoriids with three or more lobes (Siveter & Williams 1997; Williams & Siveter 1998). Shu (1990) proposed the new family, Haoiidae Shu, 1990 to include the multilobate genus Haoia Shu, 1990 from the Lower Cambrian Huoshaodian Member of the Shujingtuo Formation, Shaanxi Province, South China, but Haoia, as well as the somewhat similar Ushkarella Koneva, 1978 from the Lower Cambrian of central Kazakhstan, resembles the hipponicharoinid genus Septadella Stubblefield in Smith, 1933 from the Middle Cambrian to Tremadocian of Avalonian Canada and England (Williams & Siveter 1998). Haoia differs from Septadella by having narrow, ridge-like lobes separated by wide furrows (Williams & Siveter 1998) and from Ushkarella by the network of secondary ridges connecting the lobes close to the valve margins. The secondary ridges and resulting honey-comb ornament of Haoia is not found in other Hipponicharionidae.

Distribution. Lower Cambrian of South China and South Australia.

Haoia cf. shaanxiensis Shu, 1990 (Fig. 13A-D).

cf. 1990 Haoia shaanxiensis; Shu, p. 42, pl. 1, figs 1-8.

cf. 1990 Haoia primitiva; Shu, p.43, pl.1, fig. 9.

AAP Memoir 32 (2006) 33

Material. SAMP41443-41445 [sample MMF 44.6].

Description. Moderately convex and weakly postplete bradoriid (most complete specimen 0.83 mm long and 0.54 mm high). The dorsal margin is not completely preserved, but appears to be straight (Fig. 12A). The valves have a shallow, V-shaped anterodorsal sulcus and at least five dorso-ventrally extending lobes. The lobes are developed as high, narrow ridges and are separated by much wider, gently concave furrows (80 to 130 µm wide) (Fig. 12B). The anteriormost lobe is subparallel to the anterior margin but the remaining lobes are subparallel to the posterior margin. The lobes are highest at

about mid-valve and become successively lower towards the dorsal and ventral margins (Fig. 12A, B). Close to the dorsal and ventral margins multiple additional ridges connect the main lobes, resulting in a honey-comb pattern (Fig. 12A, C, D). The valve surface between the lobes and ridges is ornamented by densely spaced, circular pustules (Fig. 12C, D)

Discussion. Haoia cf. shaanxiensis from the Mernmerna Formation differs from H. shaanxiensis from the Lower Cambrian of China by the higher number of dorso-ventral lobes (five instead of four) and in the development of interconnecting ridges close to the dorsal margin. The only reasonably complete specimen

Fig. 13. Bivalved arthropods from the Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. A-D, Haoia cf. shaanxiensis Shu, 1990. All from sample MMF 44.6. A, B, SAMP41443; A, right lateral view of bivalved shield (stereo image), x75; B, dorsal view, x75. C, SAMP41444, lateral view of fragment of ventral? part of valve, x60. D, SAMP41445, lateral view of fragment of posteroventral? part of valve, x50. E, F, Isoxys? sp., SAMP41455 from sample MMF 8.8; E, lateral view of spine, x70; F, oblique ventral view of spine with median slit, x70.


is smaller than the material described from China, and the two additional valve fragments appear to represent considerably larger individuals. The development of the ridges and the honeycomb pattern is very different between the specimens. In the large fragmentary specimens the height of the lobes is lower and the number of interconnecting ridges is higher, resulting in a more homogeneous honeycomb pattern. This is interpreted as ontogenetic variation, which means that the exact configuration of lobes and interconnecting ridges may be unreliable characters for taxonomy. The specimens of Haoia from the Mernmerna Formation probably belong to the type species, although the poor preservation and limited number of specimens makes this interpretation uncertain. Haoia primitiva Shu, 1990 occur together with H. shaanxiensis in China and although the only illustrated specimen is incomplete, appear to be identical to H. shaanxiensis.

Order PHOSPHATOCOPIDA Müller, 1964

Discussion. Maas et al. (2003) redefined the Phosphatocopida based on numerous exceptionally preserved specimens exhibiting limb and soft part morphology from the Upper Cambrian Orsten fauna of Sweden. Well preserved limbs and soft parts are also known from a phosphatocopid species (Phosphatocopida sp. of Maas et al. 2003 = Klausmuelleria salopensis Siveter et al., 2003), from the Lower Cambrian of England (Siveter et al. 2001, 2003). Klausmuelleria differs from Middle and Upper Cambrian phosphatocopids in a number of characters, including the univalved head-shield (Siveter et al. 2003), and was separated by Maas et al. (2003) from all other phosphatocopids (i.e. the Euphosphatocopida of Maas et al. 2003). A univalved shield also occurs in the widespread Lower to Middle Cambrian Dabashanella Huo, Shu & Fu in Huo et al., 1983 (see below), as well as in the Australian Middle Cambrian Pejonesia Hinz, 1992a.

Family DABASHANELLIDAE Zhao, 1989

Dabashanella Huo, Shu & Fu, 1983

1983 Dabashanella; Huo, Shu & Fu in Huo et al., p. 68.

2002 Dabashanella Huo, Shu & Fu; Hou et al., p. 402 (full synonymy).

Type species. Dabashanella hemicyclica Huo, Shu & Fu, 1983.

Discussion. In their recent review, Hou et al. (2002) synonymised a multitude of phosphatocopid

species from China with Dabashanella hemicyclica. The authors also noted that Indiana sipa Fleming, 1973, Indiana? sipa Jones & McKenzie, 1980 and Dielmyella? dubia Jones & McKenzie, 1980 from the Middle Cambrian of Queensland probably belong to Dabashanella. Hou et al. (2002, p. 404) considered Dabashanella to be monospecific, but did not place any of the Queensland specimens in formal synonymy with D. hemicyclica. The illustrated specimens from Queensland (e.g. Fleming 1973, pl. 1, figs 1-3; Jones & McKenzie 1980, fig. 8A-I), are similar to D. hemicyclica, but appear to lack spines at the cardinal angles and may belong to a second species of Dabashanella.

Distribution. Lower Cambrian of South China, Malyi Karatau and South Australia, Middle Cambrian of China and Australia.

Dabashanella hemicyclica Huo, Shu & Fu, 1983 (Fig. 14A-E)

1983 Dabashanella hemicyclica gen. et sp. nov.; Huo, Shu & Fu in Huo et al., p. 68, pl. 5, figs 18-20.

1990 Dabashanella retroswinga Huo, Shu & Fu; Melnikova & Mambetov, p. 60, pl. 7, figs 1-8.

1997 Dabashanella retroswinga Huo, Shu & Fu; Melnikova, Siveter & Williams, pl. 1, fig. 9.

2002 Dabashanella hemicyclica Huo, Shu & Fu; Hou, Siveter, Williams & Feng, p. 403, fig. 25a-g (and synonyms therein).

Material. SAMP41446-41448 and 53 additional specimens [sample MMF23.0, 44.6, 66.0 and 91.8].

Descript ion . Small , s t rongly biconvex phosphatocopids (length: 0.6-0.65 mm, height: 0.40-0.45 mm). Dorsal outline is straight with a small process in each cardinal corner. Ventral outline is evenly convex, resulting in a more or less hemicircular profile (Fig. 14A, B). The shield is univalved but the “hinge” is marked by a fold on the dorsum (Fig. 14C). External surface is smooth, but all specimens are affected by folds or other types of soft deformation. The only part of the internal surface that can be observed is a well developed ventral doublure (Fig. 14D, E).

Discussion. All phosphatocopid specimens from the Mernmerna Formation are deformed or damaged, but are well enough preserved to be identified as Dabashanella hemicyclica based on the small size of the univalved shield, the absence of lobation, the hemicircular lateral

AAP Memoir 32 (2006) 35

outline, the small processes in the cardinal corners and the doublure. Dabashanella hemicyclica is widespread in the Lower Cambrian of South China where it also ranges into the Middle Cambrian (see Hou et al. 2002).

Dabashanella retroswinga was described from the Lower Cambrian (Atdabanian-Botoman) of Malyi Karatau by Melnikova & Mambetov (1990). The Chinese type material of D. retroswinga was synonymised with D. hemicyclica by Hou et al. (2002) and the specimens from Malyi Karatau fall within the expanded concept of D. hemicyclica.

Distribution. As for genus.

Class, Order and Family UNCERTAIN

Isoxys Walcott, 1890

Type species. Isoxys chilhoweanus Walcott, 1890.

Isoxys? sp. (Fig. 13E, F)

Material. SAMP41455 [from sample MMF8.8].

Fig. 14. Dabashanella hemicyclica Huo, Shu & Fu in Huo et al., 1983. Mernmerna Formation of ‘Angorichina’ Station, Flinders Ranges, South Australia. All from sample MMF 44.6. A, SAMP41446, lateral view of slightly deformed left valve (stereo image). B, C, SAMP41447; B, left lateral view of complete shield; C, dorsal view of complete shield with partial median fold. D, E, SAMP41448; D, oblique ventral view of deformed shield with doublure; E, left? lateral view of deformed shield. All x100.


Discussion. A single spine (1.5 mm long) with a wide median slit on one side is very similar to specimens referred to Isoxys? sp. by Bengtson (in Bengtson et al. 1990). The median slit extends almost to the pointed apex, but the antapical end of the fossil is evidently broken and deformed (Fig. 12E, F). Complete carapaces of Isoxys have been described from the Lower Cambrian of the Emu Bay Shale on Kangaroo Island, South Australia by Glaessner (1979).

ACKNOWLEDGEMENTSFinancial support towards fieldwork and laboratory costs come from a Macquarie University Research Development Grant to GAB and a Macquarie University Postgraduate Research Fund grant to JRP. Funding support for CBS was provided by a postdoctoral grant from the Swedish Research Council (VR). We extend warm thanks to Ian and Di Fargher (owners of Angorichina Station) for access to the field area. We are indebted to MUCEP members P. Bell, H. Caldon, P. Cockle, B. Jonak, R. Morgan, B. Pyemont, D. Smith, L. Strotz and N. Wilson for their assistance during the 2003 and 2004 field seasons when this material was collected. Initial picking of the MMF samples was completed by Phil Bell, Bo Jonak and Luke Strotz. We thank Dr. Peter Jones (Australian National University) for his constructive comments on an earlier draft of this manuscript. Dr Xu Shanhong kindly provided English translation of some pivotal Chinese papers. We are indebted to Dean Oliver (Dean Oliver Graphics) for drafting Figures 1–3 with characteristic skill and speed. The manuscript benefited from the constructive reviews of M. Williams and an anonymous referee.

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