Macquarie University ResearchOnline This is the published version of: Paterson JR and Jago, JB (2006) New trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, South Australia. Memoirs of the Association of Australasian Palaeontologists 32, 43‐57. Copyright: Copyright the Publisher 2006. Version archived for private and non‐commercial use with the permission of the author and according to publisher conditions. For further reproduction rights please contact the publisher at http://www.gsa.org.au. Further information regarding the copyright applicable to this article can be obtained from Association of Australasian Palaeontologists, http://www.gsa.org.au/specialgroups/aap.html. New trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, South Australia JOHN R. PATERSON & JAMES B. JAGO PATERSON, J.R. & JAGO, J.B., 2006:07:29. New trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, South Australia. Memoirs of the Association of Australasian Palaeontologists 32, 43-57. ISSN 0810-8889. Two new trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, are described. Megapharanaspis nedini gen. et sp. nov. is placed in the Megapharanaspidae, a new family of the Emuelloidea. Holyoakia simpsoni sp. nov. represents the first occurrence of the genus outside Antarctica, providing further confirmation of the close faunal affinity between Cambrian trilobite faunas from Australia and East Antarctica. New specimens of Redlichia takooensis are documented that provide new morphological information, including a description of the rostral plate and hypostome. J.R. Paterson ([email protected]), South Australian Museum, Division of Natural Science, North Terrace, Adelaide, SA 5000 and Department of Earth & Planetary Sciences, Macquarie University, NSW 2109, Australia; J.B. Jago ([email protected]), School of Natural and Built Environments, University of South Australia, Mawson Lakes, SA 5095, Australia. Received 21 March 2006. Keywords: Early Cambrian, Australia, East Gondwana, Trilobita, Redlichia, Megapharanaspis, Holyoakia. TRILOBITES, brachiopods and hyoliths were the these stratigraphic horizons, the known biota first reported fossils from the Emu Bay Shale type is of relatively low diversity compared to other section in Emu Bay (Sprigg et al. 1954; Sprigg Cambrian Lagerstätten such as the Chengjiang 1955; Daily 1956) thus establishing an Early and Burgess Shale faunas (Briggs et al. 1994; Cambrian age. Numerous studies on the Emu Bay Hou et al. 2004). We describe two new trilobites, Shale fauna (Pocock 1964, 1970; Glaessner 1979; Megapharanaspis nedini gen. et sp. nov. and Conway Morris & Jenkins 1985; Conway Morris Holyoakia simpsoni sp. nov., and provide new 1989; Bengtson et al. 1990; McHenry & Yates information about Redlichia takooensis from the 1993; Nedin 1995a, 1997, 1999; Briggs & Nedin Emu Bay Shale at Big Gully. 1997; Nedin & Jenkins 1999; Dzik 2004; Paterson & Edgecombe 2006) have recorded the trilobites STRATIGRAPHIC SETTING AND AGE Redlichia takooensis Lu, 1950, Estaingia bilobata Big Gully is situated to the east of Emu Bay and Pocock, 1964, Emuella dalgarnoi Pocock, 1970 approximately 1.5 km west of White Point on the and Balcoracania dailyi Pocock, 1970, the northern coast of Kangaroo Island (Fig. 1). The arachnomorphs Naraoia sp. and Xandarella Emu Bay Shale crops out to the east of the mouth sp., the bivalved arthropods Isoxys communis of Big Gully and is approximately 78 m thick Glaessner, 1979 and Tuzoia australis Glaessner, (Daily et al. 1979). Here the unit unconformably 1979, the anomalocaridids Anomalocaris overlies the White Point Conglomerate and briggsi Nedin, 1995a and Anomalocaris sp., the conformably underlies the Boxing Bay Formation palaeoscolecid priapulan Palaeoscolex antiquus (Daily et al. 1979; Briggs & Nedin 1997). Most Glaessner, 1979, the problematic forms Myoscolex fossils occur in the dark grey silty shales within ateles Glaessner, 1979, Vetustovermis planus the basal 8 m of the unit (Briggs & Nedin 1997), Glaessner, 1979 and Wiwaxia sp., in addition to although Daily et al. (1979) recorded fossils up to undescribed phosphatic brachiopods, hyoliths, 23.5 m above the base of the formation. chancelloriids and complete sponges. Fossils Trilobites are by far the most common occur at several stratigraphic horizons throughout constituent of the Emu Bay Shale Lagerstätte at the unit at Emu Bay and Big Gully (Fig. 1); Big Gully, representing approximately 60% of however, the Lagerstätte is only preserved at the the total assemblage (Nedin 1995b). The majority latter locality (Nedin 1995a, b, 1997; Briggs & of specimens are partially or fully articulated, Nedin 1997). Although fossils are abundant in but a high proportion represent moults, which 44 AAP Memoir 32 (2006) Fig. 1. Location of Big Gully on the northern coast of Kangaroo Island, South Australia and the Cambrian geology along the coast between Cape D’Estaing and Point Marsden; modified from Nedin (1995b). may exaggerate the apparent dominance of also supports correlation with the Tsanglangpuan trilobites in the fauna (Briggs & Nedin 1997). The Stage, based on the occurrence of this species in most abundant taxa at Big Gully are Redlichia China (see Zhang et al. 1980) and in the Lolab takooensis and Estaingia bilobata (Nedin 1995b) Formation in Kashmir (Jell & Hughes 1997; of which several hundred specimens are available Hughes & Jell 1999). in the South Australian Museum collections. The only previously described species of Rarer species include Balcoracania dailyi and Holyoakia is the type species, H. granulosa, from the new taxa described herein, Megapharanaspis a small fauna within the Shackleton Limestone of nedini gen. et sp. nov. and Holyoakia simpsoni the Central Transantarctic Mountains. It occurs sp. nov., each of which is known from only five in association with the trilobites described in specimens. Palmer & Rowell (1995) as Calodiscidae gen. et The occurrence of Estaingia bilobata and sp. undetermined A, Berabichia cf. B. subditus Balcoracania dailyi allows correlation with the (Palmer & Gatehouse, 1972) and Pensacola? sp. Pararaia janeae Zone of South Australia (Jell 2. The fauna was assigned a late Atdabanian age in Bengtson et al. 1990; Paterson & Edgecombe on the basis of Berabichia being closely related to 2006; Paterson & Brock, in press). Paterson Chorbusulina from the late Atdabanian of Siberia & Brock (in press, fig. 5) have correlated this (Palmer & Rowell 1995). If this age determination zone with the early-mid Tsanglangpuan Stage of is indeed correct, then Holyoakia simpsoni sp. China and the mid-late Botoman of Siberia. The nov. is younger than H. granulosa. However, the occurrence of Redlichia takooensis at Big Gully paucity of age diagnostic taxa from the Shackleton AAP Memoir 32 (2006) 45 Limestone assemblage and its weak correlation 1997 Redlichia takooensis Lu; Jell & Hughes, with Siberia based on generic affinities casts doubt p. 22, pl. 2, figs 4-12 (see for additional on a late Atdabanian age. Other occurrences of synonymy). Berabichia appear to indicate a Botoman age. For 1999 Redlichia takooensis Lu; Nedin, p. 988, example, it occurs in the uppermost Banian Stage fig. 2B. of Morocco (Geyer 1990a, b, 2005), equivalent 2005 Redlichia takooensis Lu; Vannier & Chen, to the Botoman Stage of Siberia (Geyer & p. 14, fig. 9. Shergold 2000; Geyer 2005); while its occurrence in Avalonia indicates a Botoman (or perhaps Material. Over 100 internal and external moulds younger) age (Westrop & Landing 2000). of complete specimens, isolated cranidia and The occurrence of Holyoakia in South librigenae are available as well as several Australia provides further confirmation of the separate pygidia and hypostomes; registered close faunal affinity between Cambrian trilobite and unregistered specimens are housed in faunas from Australia and Antarctica (Brock the palaeontological collection of the South et al. 2000; Lieberman 2003, 2004; Meert & Australian Museum. There are two specimens Lieberman 2004). In addition to Holyoakia, in which the hypostome is associated with the there are five other Early Cambrian congeneric rostral plate. Figured specimens: SAMP35566, occurrences between Australia and East Antarctica, 40181, 41173-41182. including Balcoracania, Estaingia, Pagetides (Discomesites), Redlichia and Yunnanocephalus Remarks. This species has been well documented (Palmer & Gatehouse 1972; Bengtson et al. 1990; (see synonymy). However, new specimens from Palmer & Rowell 1995; Paterson 2005; Paterson the Emu Bay Shale at Big Gully, (illustrated & Brock, in press). Paterson (2005) demonstrated herein and others housed in the South Australian that the respective species of Estaingia and Museum), warrant further discussion. In light Pagetides (Discomesites) from the Cymbric Vale of this new material, Jell’s (in Bengtson et al. Formation in western New South Wales, Australia 1990) description of the Big Gully population and the Shackleton Limestone in the Central of Redlichia takooensis requires minor revision. Transantarctic Mountains are actually conspecific, Firstly, Jell noted that the tenth thoracic segment and suggested that a continuous carbonate-detrital possesses a long, slender medial spine, but the shelf along the East Gondwanan margin allowed new specimens clearly indicate its position on faunal exchange between the two regions. the eleventh segment. This was, in fact, suggested