Records of the Western Australian Museum 21: 167-201 (2002). The axial postcranial structure of Griphognathus whitei from the Upper Devonian Gogo Formation of Western Australia: comparisons with other Devonian Dipnoans K.S.W. Campbell and R.E. Barwick Geology Department, Australian National University, Canberra, 0200, Australia. e-mail [email protected]@anu.edu.au Abstract - The skeleton of the pectoral and pelvic girdles, the foremost axial region, and the scales of Griplwgnathus whitei, and the pectoral and pelvic girdles and scales of Chirodipterus australis, have been described previously. The posterior parts of the postcranial skeleton of these fishes have been commented on in passing, but new material permits a description of the centra, the neural and haemal arches and the incomplete medial fins of G. whitei. The limb skeletons have not been preserved in our material. The new material of G. whitei adds considerably to the information available on the axial skeleton and the medial fins of Devonian dipnoans. Of these dipnoans, only Dipterus has the axial skeleton without the centra well preserved, though fragments of the centra of some of the other genera are poorly preserved. The new specimens of G. whitei have well preserved centra along the full length of the body of the animal. The neural and haemal arches give the best information available on Devonian species. The medial fins are sufficiently well preserved to compare with those of Fleurantia and Scaumenacia from the Upper Devonian of Canada, and the Australian Barwickia and Howidipterus from the Givetian of Victoria. Gross differences occur between all the above genera in the structure of the medial fins. The function of the fins and the centra are discussed, and an attempt is made to show how the whole structure of the movement of G. whitei is related to the bottom dwelling environment in which the animals lived. INTRODUCTION of the fins are also partly known. In addition we From the Gogo Formation in the Canning Basin of have specimens of Griphognathus in which several Western Australia, the lungfishes Griphognathus ribs are preserved. The attachment of the ribs to the whitei and Chirodipterus australis have parts of the centra are well preserved and the shapes of the ribs postcranial skeleton preserved, and fragments of and their attachment surfaces are clear. These Holodipterus are available but we do not have features are not known from any other Devonian sufficient material at present to be worth describing. dipnoans. Of these Griphognathus is the best preserved, and In none of the previous works is there any work on the anterior vertebral column has already discussion of the articulations of the elements, been published (Campbell and Barwick 1988, 1999). presumably because they were not preserved. The Pridmore and Barwick (1993) also figured parts of Gogo material permits an examination of the the vertebral column and the median fins, but did articulations and hence a better understanding of not comment on the details. The structure of the the function of the fins and the body during pectoral girdle and the pelvic girdle have been locomotion. described (Young et al. 1989; Campbell and Barwick 1999). No examples of the pectoral or pelvic fins have been observed. TERMINOLOGY We now have a more or less complete body of We will not discuss the details of relationships Griphognathus whitei which lacks its caudal fin. between sarcopterygians, and so there will be no Nineteen other specimens have been prepared, need to become involved with a discussion of some of which show details of the posterior end of terminology as it might apply to other groups as the skeleton, others show the detail of a number of well as dipnoans. So that our work will fit in with axial segments, others show the centra and the ribs, what is being done in other Palaeozoic dipnoans, and still others show the support structures of the we will use the terminology used by Ahlberg and medial fins and their lepidotrichs. Scale coverings Trewin (1995) in describing the axial skeleton of 168 K.S.W. Campbell, R.E. Barwick Dipterus valenciennesi. In so doing we will provide a preserved, and few of the fine details were available basis for the direct comparison with the most for description. For example, no information on the recently described species which occurs in rocks internal structure of the centra, and no structures of older than our material. More recently, Cloutier the haemal or neural arches were available, the (1996) has described the postcranial exoskeleton of organisation of the ribs was not displayed, and the the Late Devonian Scaumenacia and Fleurantia from support structures for the median fins were only Canada, and these species show structures not partly exposed. known in Dipterus valenciennesi. Where appropriate More recently, Cloutier (1996) has provided a list we have used Cloutier's terminology. of the work previously done on the Canadian genera Scaumenacia and Fleurantia. Jarvik (1959, 1980) has also commented on these genera, PREVIOUS WORK ON THE POSTCRANIAL following up the work done by Graham-Smith and STRUCTURE OF DEVONIAN DIPNOANS Westoll (1937). Cloutier's work is more complete, Ahlberg and Trewin (1995) in a discussion of the and for the first time the postcranial skeleton of postcranial skeleton of Dipterus valenciennesi, Scaumenacia has been described in detail. This mentioned the lack of information on the work provides the best account of the Canadian postcranial skeleton of Devonian dipnoans. The genera. reason for this is clear; so few specimens have been Long (1993) described the postcranial ribs in a found showing the structures in position, and only number of Devonian dipnoan genera, especially a few genera have ossified centra. Specimens found Barwickia and Howidipterus from the Givetian in shale provide most of the data available. Their deposits at Mt Howitt in Victoria. He also has vertebrae were cartilagenous or were crushed, and further details of these genera in a manuscript, the fin supports are hidden beneath the strong which we have been given permission to examine. covering of scales. Isolated vertebral centra have These specimens are preserved in shale, and were been used to describe their internal structure studied by latex moulds. They are very useful in (Schultze 1970), but there are too few of these to that they give a better understanding of Australian make a consistent statement about Devonian material than we had previously. They will be dealt dipnoans. The discovery of postcranial skeletons with in a later part of this paper. from Gogo, sometimes in association with much of the body, offers the opportunity to develop this information in this "potentially important field" MATERIALS AND METHODS (Ahlberg and Trewin 1995: 159). All the specimens examined have been in the Schultze (1970) described the axial centra of collections of the Australian National University Griphognathus sculpta and G. multidens from Geology Department (ANU), the Western Germany, and Jarvikia and ?Soederberghia from Australian Museum (WAM), and the Australian Greenland. The main purpose of his paper was to Museum, Sydney (AMF). Apart from one specimen examine the vertebral structures, attempting to collected from South of Lloyd's Hill, all others were understand the similarities and differences between collected from Paddy's Valley, Gogo Station, dipnoans and other sarcopterygians. He came to the Canning Basin, Western Australia. conclusion that their structures "show that it is ANU 35641; 35645; 49114-49116; 49120; 491207; more convincing to place the dipnoans with 49282-49284; 49900. the teleostomes and near the crossopterygians, WAM 87.8.24; 86.9.25; 86.9.645; 86.9.650; 86.9.651. rather than place them with the elasmo­ AMF72402 branchiomorphs....". On the other hand he All specimens have been prepared by solution of concluded that the evidence indicated a "much the matrix in acetic acid, impregnating the exposed stronger comparison with the vertebrae of other bone with a dilute plastic, and continuing with the teleostomes or tetrapods". The axial skeleton of solution until the bone we wished to examine has Rhinodipterus ulrichi, Dipterus cf valenciennesi, and been exposed. Griphognathus sculpta, have been described from various localities in Europe by Schultze (1975), but they added little evidence because of the poverty of GROSS STRUCTURE OF GRIPHOGNATHUS the material available. WHITEI The most complete work on the European Devonian genera is that of Ahlberg and Trewin The Structure of the Centra (1995). This dealt with Dipterus valenciennesi. It As has been illustrated on several occasions discussed the evidence from a number of specimens (Miles 1977, figures 11, 12, 30; Campbell and from Scotland, and described parts of the axial Barwick 1999, figures 2,3), the posterior of the skull skeleton, the haemal and neural arches, and the has centra fused to it and these occupy all the space medial fins. Much of the material was poorly dorsal to the posterior part of the parasphenoid. Postcranial structure of Griphognathus whitei 169 Figure 1 Two views of ANU 49116. A shows the full specimen in lateral view, and B is slightly tilted to show the shapes of the caudal haemal arches. The arrow indicates an opening in the haemal arch for the exit of the caudal artery. Scales =10 mm. None of these elements have cranial ribs attached. Many segments of ANU 49116 (Figure 1A,B) are The free centra from Griphognathus whitei are well known, and in particular those of the proximal part preserved. They include large anterior centra, the of the caudal region are well preserved. These fulcral centra, and posterior centra from the caudal illustrate the reduction of the length of the centra at region of adults, and some juveniles with centra a clear cut point along the length of the vertebral from a variety of positions along the axial column.