Papers and ProceedinRs of the Royal Society of ]clsmania, Volume J23, 1989 37 LATE CAMBRIAN BRACHIOPODS FROM THE DENISON RANGE, SOUTHWESTERN TASMANIA by J. B. Jago (with one text-figure and two plates) JAGO, LB., 1989 (3I:x): Late Cambrian brachiopods from the Denison Range, southwestern Tasmania. Pap. Proc R. Soc. Tasm. 123: 37-42. ISSN 0080-4703. Department of Applied Geology, South Australian Institute of Technology, The Levels Campus, South Australia 5095. Eight unnamed species of brachiopods and one indetenninate hyolithid species are described and figured from three stratigraphic intervals within the early Late Cambrian Singing Creek Formation, Denison Range, southwestern Tasmania. Key Words: brachiopod, hyolithid, Cambrian, Tasmania. INTRODUCTION 1==;.;- = G"daUonal conlact w,'h Great Dome Sandstone The purpose of this paper is to document the brachiopods and hyolithids from the Singing Creek Top fauna Formation of the Denison Range in southwestern Tasmania. The Middle Cambrian to Lower Ordovician stratigraphy of the Denison Range area (Corbett 1975) may be summarised as follows: Middle fauna Denison Group - Squirrel Creek Formation 600 m Reeds Conglomerate 1560 m Great Dome Sandstone 510 m Singing Creek Formation nOm angular unconformity Bottom fauna Trial Ridge Beds 500 m o 100km ~ The upper part of the Trial Ridge Beds contains fossils of the late Middle Cambrian Lejopyge laevigata Zone (Jago 1979). The Great Dome Sandstone is a shallow marine-deltaic-fluvial sequence which contains abundant trace fossils, Unconformity on rare inarticulate brachiopods, and a gastropod Trial Ridge aeds similar to Kobayashiella (Corbett 1975). The Singing Creek Formation comprises no m of quartzwacke turbidites interbedded with Sandstone, conglomerate fossiliferous siltstone, siliceous conglomerate and and slump sheets slump sheets, deposited as a submarine fan D Siltstone with isolated complex in a fault-controlled basin (Corbett 19n, sandstone beds 1973, 1975). In the Denison Range, fossils are D found over three stratigraphic intervals (fig. I). Jago (1987) described the trilobites; the FIG. I - Stratigraphic position of the faunas brachiopods and hyolithids are described herein. from the SinginR Creek Formation, Denison The specimens were collected by K.D. Corbett in Range, southwestern Tasmania. Rock types after 1967 and 1968 as bulk samples rather than on a Corbett (1975: fig. 2). The location of Denison bed-by-bed basis, because of the nature of the Range is shown. 38 J. B, Jago outcrop and the difficulties of collection in this three Idamean Zones, i.e. Proceratopyge cryptica, rather inaccessible area. Erixanium sentum and Stigmatoa diloma Zones. All The lowest fauna, occurring between about 185 specimens described here are preserved as internal and 240 m above the base of the Singing Creek and external moulds in weathered siltstone or very Formation, contains the following: fine sandstone. In order to prepare them for Trilobita (see Jago 1987): Micragnostus, description, silicone rubber casts were prepared. Pseudagnostus idalis denisonensis, Denagnostus These rubber casts were then photographed after corbetti, Eugonocare, Dokimocephalidae and being whitened with magnesium oxide. Proceratopyge. Unfortunately the brachiopods, particularly the Brachiopoda: Lingulella (7) sp., Acrotretidae, gen. inarticulate brachiopods, are generally poorly et sp. indet. I, and Billingsella sp. 1. preserved. Only Pseudagnostus idalis denisonensis and The terminology used for brachiopods is after Billingsella sp. I are reasonably abundant. Williams & Rowell (1965a,b). All specimens are The middle fauna, occurring between about 410 housed in the collection of the Geology and 430 m above the base of the Singing Creek Department, University of Tasmania. The catalogue Formation, contains the following: numbers refer to this collection. Trilobita: Denagnostus corbetti, Aphelaspis cantori, Proceratopyge gordonensis, P. sp., Pseudoyuepingia vanensis and trilobite tracks. SYSTEMATIC DESCRIPTIONS Hyolithida: Hyolithid, gen. et sp. indet. Brachiopoda: Lingulella (7) sp., and Obolus (7) sp. In this fauna Proceratopyge gordonensis, P. sp. and Phylum BRACHIOPODA Dumeril 1806 Pseudoyuepingia vanensis are common. Class INARTICULATA Huxley 1896 By far the richest fauna is the top one which Order LINGULIDA Waagen 1885 occurs between about 540 and 610 m above the Family OBOLIDAE King 1846 base of the Singing Creek Formation. The Subfamily LINGULELLINAE Schuchert following fossils are present: 1893 Trilobita: Micragnostus, Pseudagnostus idalis Genus LINGULELLA Salter 1866 denisonensis, P. sp., Denagnostus corbetti, Asphelaspis cantori, a member of the Type species: Lingula davisii M'Coy 1851: 405. Leiostegiacea, Proceratopyge gordonensis, P. sp" and trilobite tracks. Hyolithida: Hyolithid, gen. et sp. indet. Lingulella (?) sp. (pI. lA-C) Brachiopoda: Obolus (7) sp.; Obolidae, gen. et sp. indeL I; Obolidae, gen. et sp. indet. 1; Remarks: The available material comprises three Acrotretidae, gen. et sp. indet. 2 and Billingsella internal and one external mould, all of which sp.2. appear to belong in the one species. They belong in Jago (1987) suggested that the faunas of the Lingulella or a related genus, as is indicated by Singing Creek Formation are of early Late their outline and ornamentation. They are too Cambrian age and fall within the range of the top poorly preserved to warrant description. PLATE 1 (A-C) Lingulella (?) sp.1: (A) UT89445 , internal mould of pedicle valve, x 7, (B) UT89515, internal mould of pedicle valve, x 6. (C) UT89449 , external mould of pedicle valve, x 5. (D-H) Obolus (?) sp.4: (D) UT89430, internal mould of brachial valve, x 6, (E) UT88427, internal mould of pedicle valve, x 4.5. (F,G) UT89431, counterparts showing both valves; (F) xS, (G) x 6, (H) UT88433 , internal mould of (?)pedicle valve, x 6. (l) Aerotretidae, gen, et sp. indet. 1, UT89515, internal mould of pedicle valve, x 12. (J-L) Obolidae, gen, et sp. indet. I: (J) UT88432 , internal mould, x 3.5; (K) UT88423 , internal mould, x 6. (L) UT88435 , internal mould, x 5.5. (M) Obolidae, gen. et sp. indet. 2. UT88429, internal mould, x 3.5, (N,O) Acrotretidae, gen. et sp. indet, 2: (N) UT88431, external mould of brachial valve, x 6, (0) UT88410, internal mould of brachial valve, x 9, Late Cambrian brachiopods, Tasmania 39 40 J. B. Jago S.ubfamily OBOLINAE King 1846 lamellae. Their outline is similar to that of Genus OBOLUS Eichwald 1829 Quadrisonia minor of Rowell & Henderson (1978) from the Upper Cambrian of North America, but Type species: Obolus apollinis Eichwald 1829: 274 until better preserved material is available this (pI. 4, figs SA-B). material must be left in open nomenclature. Obo/us (7) sp. (pI. lD-H) Class ARTICULATA Huxley 1869 Material: Three pedicle and two brachial valves Order ORTHIDA Schuchert and Cooper preserv ed as either internal or external moulds. 1932 Remarks: If it is assumed that the two valves Suborder ORTHIDINA Schuchert and which occur together on specimen UT89431 Cooper 1932 (pI. IF,G) originally belonged to the same Superfamily BILLINGSELLACEA individual, then the pedicle valve is slightly larger Schuchert 1893 than the brachial valve. Both valves are gently Family BILLINGSELLIDAE Schuchert 1893 convex and have a circular to oval outline; both Genus BILLlNGSELLA Hall and Clarke 1893 show fine concentric growth lamellae. The general appearance of the available specimens suggests that Type species: Orthis pepina Hall 1863: 134, pI. 6, they belong in Obulus, to which genus they are figs 23-27. tentatively assigned. Comment: As noted by Mackinnon in Shergold et al. (1976) Billingsella is a cosmopolitan genus of Obolidae, gen. et sp. indet. no. 1 (pI. lJ-L) Middle Cambrian to Early Ordovician age. Although it has been recorded from Late Cambrian Remarks: Internal moulds of three valves of a sequences in Tasmania by various authors (e.g. probable member of the Obolidae are figured. The Banks 1962, Corbett 1975, Jago 1979), the details are such that it can not be determined specimens dealt with below are the first to be whether they are brachial or pedicle valves. described and figured from Tasmania. Obolidae, gen. et sp. indet. no.2 (pI. 1M) Billingsella sp.l (pI. 2A-J) Remarks: One partially preserved valve exhibits Material: All specimens are disarticulated. Six closely spaced growth lamellae. There are minute brachial and twelve pedicle valves are available. spines on the surface of the valve, particularly in Description: Gently convex pedicle valve with the posterior region. Discontinuous vascular subtrapeziform outline, widest at hinge line; markings are visible, particularly in the anterior apsacline ventral interarea about four times as wide part of the valve. as long; posterolateral margins of ventral interarea slightly concave; gently convex pseudodeltidium covers apical half of delthyrium; cardinal Order ACROTRETIDA Kuhn 1949 extremities angular, acute to right-angled; low Suborder ACROTRETIDINA Kuhn 1949 median fold; slightly concave posterolateral slopes; Superfamily ACROTRETACEA Schuchert external ornamentation parvicostellate with 1893 costellae most prominent on fold margins; variably Family ACROTRETIDAE Schuchert 1893 developed concentric growth lines; details of Acrotretid, gen. et sp. indet.l (pI. II) teeth and musculature not clear on available material. Remarks: One poorly preserved small conical Almost flat, subrectangular brachial valve, widest pedicle valve of an acrotretid is present. It is too at hinge line; cardinal extremities