Memoirs of the Queensland Museum | Nature 56 (1) © Queensland Museum PO Box 3300, South Brisbane 4101, Australia Phone 06 7 3840 7555 Fax 06 7 3846 1226 Email [email protected] Website www.qm.qld.gov.au National Library of Australia card number ISSN 0079-8835 NOTE Papers published in this volume and in all previous volumes of the Memoirs of the Queensland Museum may be reproduced for scientific research, individual study or other educational purposes. Properly acknowledged quotations may be made but queries regarding the republication of any papers should be addressed to the Director. Copies of the journal can be purchased from the Queensland Museum Shop. A Guide to Authors is displayed at the Queensland Museum web site www.qm.qld.gov.au A Queensland Government Project Typeset at the Queensland Museum The pachyrhizodontid teleosts from the marine Lower Cretaceous (latest mid to late-albian) sediments of the Eromanga Basin, Queensland, Australia Alan BARTHOLOMAI Alan Bartholomai, Director Emeritus, Queensland Museum, PO Box 3300, South Brisbane Qld 4101, Australia. Citation: Bartholomai, A. 2012 02 17: The pachyrhizodontid teleosts from the marine Lower Cretaceous (latest mid to late Albian) sediments of the Eromanga Basin, Queensland, Australia. Memoirs of the Queensland Museum–Nature 56(1): 119-148. Brisbane. ISSN 0079-8835. Accepted: 11 March 2010. ABSTRACT Two species of the fossil pachyrhizodontid teleost, Pachyrhizodus, are present in the marine Lower Cretaceous (mid to late Albian) Toolebuc and Allaru Formations of the Eromanga Basin in Queensland, Australia. New morphological data on P. marathonensis (Etheridge Jnr., 1905) is provided as part of a revision of the species. The smaller and much less common P. grawi sp. nov. is described and is shown to co-exist with P. marathonensis but has a more restricted distribution. Pachyrhizodus grawi is more gracile than the larger species, with a shorter premaxilla and with its jaw articulation positioned more anteriorly, below and just behind the back of the orbit. Pachyrhizodontidae, Pachyrhizodus, P. marathonensis, P. grawi sp. nov., Toolebuc Formation, Allaru Formation, Lower Cretaceous, Albian, Eromanga Basin, Queensland, Australia. As part of a general review of Queensland’s derived to be Upper Cretaceous. Bartholomai Lower Cretaceous fossil marine fishes, recently (1969) agreed with Bardack’s (1962) suggestion collected specimens added to the Queensland regarding the taxonomic position of the Museum collections expand representation of mat­ species, provided a more complete description erial referrable to the Family Pachyrhizodontidae. of its skeletal morphology, and corrected the age of the deposits from which it was derived This material was largely collected from to Lower Cretaceous (Albian). Forey (1977) poorly exposed surface exposures of both the has subsequently added further comments on Toolebuc and Allaru Formations, that occur as the morphology of P. marathonensis, based on an arc around the northern and western edge of a specimen, P 55858, in the collections of the the Eromanga Basin (part of the Great Artesian British Museum (Natural History). Basin) and that were deposited within the epeiric sea of that time. The thin, widespread and organic­rich Toolebuc Formation (and the contemporaneous but con­ For over a century, fossil teleosts that were siderably thicker Allaru Formation) is now dated originally described by Etheridge Jnr. (1905) as latest mid to late Albian, the Pseudoceratium as Ichthyodectes marathonensis appeared to ludbrookiae dinoflagellate zone/upper Coptospora represent the only pachyrhizodontid present in paradoxa- Phimopollenites pannosus spore­ pollen the Australian Cretaceous sediments. Bardack zone (Moore et al. 1986; McMinn & Burger (1962) suggested that this species should have 1986). Henderson (2004, Fig.1) has provided been referred to Pachyrhizodus but considered a map of the Great Artesian Basin and its the age of the deposits from which it was subdivisions that also illustrates the surface Memoirs of the Queensland Museum | Nature 2012 56(1) www.qm.qld.gov.au 119 Bartholomai expression of the Toolebuc Formation. He has acetic acid but that held externally on loan is suggested the age should be refined further often either unprepared or has been cleared to late Albian on the basis of ammonite and manually of supporting matrix. nannofossil biostratigraphy. However, the author prefers to retain the more conservative ABBREVIATIONS age determination for the purposes of the Material examinied listed with prefix ‘F’ refers current study. Material referred in the study to fossils in the palaeontological collection at the to a new, more gracile species has come from Queensland Museum at Hendra Brisbane. localities close to Richmond, CNQ, close to the oceanic inflow area over the basement Euroka Ang ..............................angular Ridge between the Eromanga and Carpentaria Ao ............................. antorbital Basins. Distribution of the larger species, Atfc. .anterior opening jugular canal P. marathonensis is wider, extending from near Asp ........................ autosphenotic the Euroka Ridge area to the western margin of Bhtp .................. basihyal tooth plate the Eromanga Basin, near Boulia, CWQ, east of the Northern Territory border. Boc ..........................basioccipital Bsp .........................basisphenoid Nearly all pachyrhizodontid material studied is neurocranial and only rarely are more than Cb ....................ceratobranchial (1­4) anterior parts of the body present. This reflects Cea ....................anterior ceratohyal the fact that the bulk of specimens have come Cl .............................cleithrum from the poorly layerered coquinite that re­ De ..........................dermethmoid presents the majority of the rare surface exposures of the Toolebuc Formation. Little Den ..............................dentary material has been collected from the Allaru df ..........................dilitator fossa Formation. Many preserved specimens form Dsp. dermosphenotic the nucleus of calcilutite concretions that are Eb ...................... epibranchial (1­3) developed within the coquinites and that Ect. .ectopterygoid are released and exposed on the surface by weathering and erosion of the containing Enpt .......................endopterygoid sediment. Excavation of exposed coquinites by Epo. epiotic the Kronosaurus Korner, Richmond, NCQ, has Exo ........................... exoccipital recently provided almost complete specimens of fm. .foramen magnum several of the early teleosts, including an almost complete skeleton and body outline identified fmcv .......foramen for middle cerebral vein by the author as S. achyrizodus sp. and a large focc .............foramen for occipital nerve specimen of the ichthyodectid, Cooyoo australis fVIIot ........ foramen for otic branch of VII (Smith Woodward, 1894). Similar excavations Fr ................................frontal have been undertaken below surface finds by the Stonehouse Museum, Boulia, CWQ but, to H ................................hypural date, success there has mostly been in regard Hm. hyomandibular to articulated remains of marine reptiles and Ic .............................. intercalar cranial remains of fishes. Recently exposed fish Io. infraorbital (1­5) remains are often of higher quality compared Le ........................ lateral ethmoid to those that have remained on the surface for longer periods. Much of the material in the Me. mesethmoid Queensland Museum has been prepared using Mpt ........................metapterygoid 120 Memoirs of the Queensland Museum | Nature 2012 56(1) Pachyrhizodontid teleosts from the marine Lower Cretaceous Mx ..............................maxilla following features: Dermethmoid broad, laterally Op ............................operculum with muted posteroventral processes, lacking definitive bone­enclosed ethmoid commissure. Ors .......................orbitosphenoid Exoccipitals meet above and below foramen Pa ...............................parietal magnum. Endochondral elements of posterior of Pal ...............................palatine otic region meet loosely without interdigitating Par .........................parasphenoid sutures. Dilitator fossa present, sometimes empha­ Ph ............................parhypural sised anteriorly by a large fenestra between auto­ sphenotic and pterotic below excavated frontal Pmx .......................... premaxilla margin behind autosphenotic ‘crest’; pterotic Pop ........................preoperculum roof of dilitator diminishes posteriorly to virtually Pro ...............................prootic disappear. Fenestration of anterior ceratohyal Psp ........................pterosphenoid variably present. Preoperculum varies from minimally expanded ventrally to significantly Pto ..............................pterotic expanded posteroventrally, with preopercular Pu ...................preural centrum (1­2) sensory canal moderately branched across Qu ..............................quadrate preopercular base. Rart .........................retroarticular Discussion. Forey (1977) undertook a complete Smx. supramaxilla redescription of the osteology of a number So ...........................supraorbital of Cretaceous teleosts referred to the genera Soc ........................ supraoccipital Notelops Smith Woodward, 1901, Rhacolepis Sop ........................suboperculum Agassiz, 1841 and Pachyrhizodus Dixon, 1850 (including its junior synonym, Thrissopater Sosc .............supraorbital