© Copyright Australian Museum, 2000 Records of the Australian Museum (2000) Vol. 52: 103-128. ISSN 0067-1975 The Braincase, Mandible and Dental Structures of the Early Devonian Lungfish Dipnorhynchus kurikae from Wee Jasper, New South Wales K.S.W. Campbell and R.E. Barwick Geology Department, Australian National University, Canberra A.C.T. 0200, Australia ken. c ampbell @ anu. edu. au richard. bar wick @ anu. edu. au Abstract. Dipnorhynchus kurikae Campbell & Barwick was described from the Receptaculites Limestone Member at Wee Jasper. Our new specimens include material of the braincase, the snout, the nasal capsules, the palate and the mandible which were not previously available. The new specimens give new data on the pores in the snout, the arrangement of the soft tissues in the nasal capsule, the growth of the hard tissues on the surface of the dentary, the formation of the hard surface on the palate and the prearticulars, the arrangement of sacculus and the nerves VII, IX and X in the otic region, and the interpretation of the palatoquadrate. The lateral lines on the mandible have been exposed by excavation. Thin sections show that the bone on the overgrowth of the dentary is of the same ^nd as occurs in the cores of the ridges on the tuberosities and marginal ridges on the palate and prearticular. A thin layer of dentine-like columns which contain no dentine tubules overlie the bony cores. This, and the mode of growth, demonstrate that the dental plates—being made of a bony core—have different patterns of deposition from tooth plates in most later Palaeozoic genera, which are made of dentine. This throws light on the way tooth plates evolved from a dipnorhynchid pattern through a speonesydrionid pattern to true tooth plates. The complex tooth plates of Diabolepis are considered to be independently developed. Ventrally the parasphenoid of Dipnorhynchus kurikae does not divide the pterygoids, but stops short at the posterior end of the pterygoids. The semicircular canals and the superior sinus of the saccular cavity are described from the well-preserved material. In comparison with D. sussmilchi, this species has a number of distinctive features, and is easily recognised as a separate species. Campbell, K.S.W., & R.E. Barwick, 2000. The braincase, mandible and dental structures of the Early Devonian lungfish Dipnorhynchus kurikae from Wee Jasper, New South Wales. Records of the Australian Museum 52(1): 103-128. Dipnorhynchus kurikae Campbell & Barwick, 1985, was lower part of the neurocranium were well enough preserved, described from two partial skull roofs, three isolated palates, their relationships with other parts of the skull were unclear. two snout fragments, and two isolated mandibles. The Three new specimens of the mandible have been recovered neurocranium, the rostrum and the nasal capsules were from the type locality, including the smallest and the largest unknown, and though the palate and lateral wings and the known individuals. Two new crania, one of which comes 104 Records of the Australian Museum (2000) Vol. 52 from the type locality and the other from the same horizon Description about 5 km farther north, add considerably to our knowledge of the species and, though they lack roofs, they enable us to The palate demonstrate more clearly than we could when it was first described that the species is distinct from D. sussmilchi Incomplete palates from four specimens are known. The (Etheridge, 1906). The oldest Dipnorhynchus specimens most complete is ANU 48676, from which the braincase is have been found in the basal part of the Cavan Bluff described below (Eig. 1). Limestone below the appearance of Polygnathus dehiscens. The dermopalatines are not clearly defined, but they are This suggests that they are possibly Pragian in age, making long and extend back to the level of the preorbital wall (Eigs. the genus the oldest or the second oldest member of the Dipnoi 1 A, 6B). Their outer edge is ridged, the posterior end having known at present. Morphological details of D. kurikae are of three or four rounded eminences on the ridge. maximum importance because its preservation provides the The pterygoids (Eigs. lA, 2A) are well preserved and best information available on the external and endocranial have clear raised structures on their surfaces in some structures of primitive dipnoans. The new material has a section specimens, but flatter structures on others. The level of along the braincase which allows us to map out the neural expression of these features is not related to the size of the features directly. One nasal capsule is fully exposed, and specimens, implying a periodic reconstruction of the provides detail of the subdivision of the nasal capsule, as well surfaces. The lateral margins of the pterygoids are formed as the nerves entering it. of rounded ridges which, although continuous, show three The structure of the cheek is not known by direct or four slightly rounded eminences along their length. The observation, but reconstructions by Thomson & Campbell most anterior ones are the most prominent, and lie against (1971) and (Westoll, 1989), have drawn different the dermopalatines—they consist of swellings which extend conclusions. Westoll concluded that all these Australian into the more median parts of the palate. The remainder of Dipnorhynchus are very closely comparable. Of course, this the lateral margin of the pterygoids extends back to the is obvious because they are congeneric; alternatively he may posterior end of the dental-plate, becoming narrower have been implying that a single variable species has been posteriorly. The lateral facing edges of the pterygoids have unnecessarily split. The present specimens add data to irregular denticles where lateral growth took place. In a well indicate that such a view is untenable. Westoll also formed specimen, ANU 48676, the marginal ridge has a interpreted the cheek of Dipnorhynchus with a skull that is furrow against the large bosses (posterior tuberosities or flattened in comparison with that of Dipnorhynchus, and blisters) that form the posterior part of the palate. White with a mandibular canal exiting from bone 4 rather than (1966: 7) referred to these elevated surfaces as raised bone 5 as is normal for Devonian dipnoans. blisters. In this paper we will refer to the elevations on the The second partial cranium is not so well preserved, but it pterygoids and the prearticulars as tuberosities. On full exposes the posterior part of the neurocranium, and a large closure these marginal ridges fit medially to the marginal part of the otic region. This has been known only from the ridges on the mandible. The anterior lateral tuberosities fit into holotype of Dipnorhynchus sussmilchi, the posterior part of the cavities behind the anterior tuberosity on the mandible. which is poorly preserved, and the structures now observed The posterior tuberosities are variable in size and outline, permit a better reconstruction than we have had previously. but ANU 48676 (Eig. lA) has them beautifully preserved. The mandibles show details of structure and the dental The anterior edge of each tuberosity has a median projection plates are well enough preserved to section and to examine with two lobes on each side. The median projection extends under light microscopy and by Scanning Electron forward of the others, and has a definite embayment on Microscopy. These sections have been compared with each side. The posterior edge of the tuberosity is broken up sections of secondary growth on the mandibles, and they into irregular patches or denticles indicating that the growth are found to be closely comparable. This is of major took place by extension in that direction and by overgrowing significance for studies of the primitive dental plates in these irregularities. In front of the posterior tuberosity is a dipnoans. Similar structures are found in the tuberosities large cavity in the palatal surface. Dipnorhynchus sussmilchi on the palate. We conclude that the animal had dental plates has a smaller depression which is not so well defined which had a thin layer of dentine, and were able to grow (Thomson & Campbell, 1971: fig. 75). The anterior median periodically by addition to bone by internal growth. The tuberosity forms a pair towards the end of the pterygoids. lateral lines can be excavated and show in detail their These tuberosities are not equal in size on the one specimen, pattern. All of these features give more information on the and they fit unevenly into the median space in the mandible. most primitive dipnoans. Anterior to the pterygoids but between the dermopalatines, is an open space lying anterior to the paired anterior tuberosities Material. The material used for this paper is as follows. (Eigs. lA, 2A). In ANU 48676, the margins of the open Skulls: ANU 48676, from the type locality, the base of space are rough as though a bone has fallen out. Thomson the Receptaculites Limestone along a strike line of ca. 1 & Campbell (1971) referred to this space as being occupied km around L624, of Pedder et al. (1970). ANU 48678 from by a small bone in some specimens. Such a bone is present a similar horizon, ca. 5 km north of the type locality. Rocks in the specimen of D. sussmilchi labelled ANU 18815, but in this area were exposed near Cave Island during a drought. in other individuals it must have been a bone so loosely Mandibles: ANU 60028-60030, also from the type articulated with the surrounding bones that it has fallen locality. ANU 60030 is on loan from Ian and Helen Cathles out. With further evolution in which reduction of the of Cookmundoon Station, Wee Jasper. dermopalatines occurs, this bone becomes isolated at the Campbell & Barwick: Early Devonian lungfish Dipnorhynchus kurikae 105 Figure 1. Dipnorhynchus kurikae, all parts of this figure are of ANU 48676. A,B—ventral and dorsal views of a skull from which the roof was removed during preservation. In A, note the shape of the posterior and anterior palatal tuberosities, the position of the buccohypophyseal opening, and the shape of the anterior naris. In B, note the shape of the braincase, the closely spaced neurocranial walls, the swelling on the superior sinus of the sacculus, the space for nerve VIII and the back of the endocranial wall of the braincase where it joins the notochordal cavity (white arrow). C—^posterior view of the specimen. Note the end of the notochordal cavity, the position of the nerve VII on the left (white arrow), the superior sinus of the sacculus, the walls of the sacculus, and the foramen jugulare. D—view of the labial pouch and snout showing a small area of cosmine on the dermal roof. Note the large excavation for the labial pit. Scales = 10 mm. 106 Records of the Australian Museum (2000) Vol. 52 external ampjlle ar^teriar ampulla posterior ampulla Superior sinus of sacculus groove for N X anterior ampulla exterior ampulla pterygoidl groove honizontaJ canal auperior sinus posterior ampulla of the sacculus internal carotid artery ^ ramu& mentalls externus iniernal carotid parasphenoid artery & ramus mental is extern u3 Figure 2. Dipnorhynchus kurikae, an isolated palate and braincase, ANU 48678. A—ventral view. Note the shapes of the tuberosities on the palate, the gross form of the parasphenoid and the position of spiracular recess. B—dorsal view, left side worn through to the level of the horizontal semicircular canal and the position of the superior sinus of the sacculus. The three ampullae of the semicircular canals well shown. Anterior edge of the notochordal cavity marked with a white arrow. See also Fig. 4A. C—dorsolateral view of the braincase. Nerves IX and X and the ampullae marked. For detail see Fig. 5. Scales = 10 mm. Campbell & Barwick: Early Devonian lungfish Dipnorhynchus kurikae 107 front of the pterygoids (Miles, 1977: fig. 67). Although On the posterior wall a large recess, named the spiracular Miles (1977) refers to the isolated bone in front of the recess by Thomson & Campbell (1971), is also present in pterygoids of Chirodipterus australis as the vomer, we this species. This foramen was for the internal carotid artery consider that the bone is not homologous with the vomers and the ramus mentalis N VII. No matter how we interpret in any other group, but is a neomorphic feature in dipnoans. this opening, there is no structure like it in Diabolepis This is a highly significant point, as some workers consider (Chang, 1995). the presence of vomers to be of significance in discussing The buccohypophyseal foramen lies towards the relationships of dipnoans. For example, some workers posterior end of the palate, but its relation to the posterior consider that Diabolepis is the sister group of the Dipnoi, end of the palatal thickening varies from specimen to and it has an anterior pair of bones which are named the specimen. It is at the end of a tube which has been described vomers. We see no evidence that these paired bones in by Campbell & Barwick (1985). Diabolepis (Chang, 1995: fig. 11) are the homologues of the isolated bone in dipnoans. As was shown by Campbell & Barwick (1985: fig. 6d) The structure of the neurocranial walls cross sections of the palate show no signs of a boundary between a parasphenoid and the pterygoids on the buccal The inner perichondrium is made of continuous bone and surface, but its outline is seen anterior to the buccohypophyseal is separated from the outer perichondrium by only 1-2 mm tube on the dorsal surface. It was attached to the posterior end of endochondral bone (Fig. IB, 3, 4). Specimens of of the pterygoids, and the only way it could have increased in Holodipterus gogoensis (Pridmore et al., 1994: fig. 1) and size was by the addition to its posterior and lateral edges. of Chirodipterus australis of similar size have a greater On ANU 48676 only the anterior end of the parasphenoid separation between the inner and outer perichondral walls is preserved, but on ANU 48678 (Figs. 2A,B) most of it is than in D. kurikae, and the space between them is not filled present, even though the ventral surface is eroded. It rises with so much vesicular tissue (Fig. IB). The foramina for dorsally in a sharp even curve from the palate and then the nerves and vessels are well exposed on ANU 48676, turns posteriorly to make a short process. This is very similar and the canals in the bone have been removed by etching to that of D. sussmilchi, which also has a median furrow with acetic acid. It has been possible for the first time to that breaks through the bone in the same way. It seems to trace the canals by inserting fine nylon line into them and us that a thin layer of bone was present in this region, but it observing their points of emission. An examination of this is not preserved. Once again, there is no similarity between kind provides the basis for Figs. 3 and 4. The structure of the structure of the parasphenoid in these primitive dipnoans the braincase wall will be discussed below, beginning at and the parasphenoids in Diabolepis (Chang, 1995: figs. 4, the anterior end. The description will be based on the two 11) which is close to that of the porolepiforms. ANU specimens which will be referred to as required. ramus ophthalmicus profundus V, anterior lateral line nerve N VII hyomandibularis jugular vein ramus profundus N Vg anterior ophthalmic artery pituitary vein jugular vein Figure 3. Dipnorhynchus kurikae, dorsolateral view of ANU 48676 showing the lateral features of the braincase nd the otic region. Main structures indicated and details shown on Fig. 4. Scale = 10 mm. 108 Records of the Australian Museum (2000) Vol. 52 foramen ramus ophthalmicus sphenoticum profundus Vi majus NVIl \ ramus maxillaris V2 anterior ¥ophthalmic jugular vein jk' ¥^artery pituitary vein foramen / Sphenoticum _ minus lorbital artery orbital N X anterior ophthalmic N IX artery notch for base hypophyseal of superior sinus fossa foramen foramen NVIl sphenoticum sphenoticum canal majus minus N VII hyomandibularis jugular vein orbitai artery Figure 4. Dipnorhynchus kurikae. A—dorsolateral view of the specimen shown in Fig. 3. Nerves and vessels are indicated, with their courses shown as dotted lines where they are hidden in bone. B—^reconstruction of the braincase with the dorsal surface of the braincase restored from other specimens of D. sussmilchi. Nerves and vessels drawn around the outline structures shown in Fig. 4A, and the otic region as in Fig. 5. The outlines of the foramen sphenoticum minus and majus, and the notch for the base of the superior sinus in Fig. 4A, shown in dotted outline. Scale =10 mm. Olfactory canals. The two olfactory canals separate at a olfactory bulbs are pedunculated, and considered that this point half way between the anterior end of the notochordal is the primitive condition for lungfishes. This is chamber and the tip of the snout. Each runs for 1.5-2.0 cm undoubtedly correct, because all Gogo lungfishes and as before opening into the nasal capsules at a junction that is well as Dipnorhynchus and Speonesydrion specimens are marked by a slight but continuous bony rim. The walls of pedunculated. In other words, the best known Devonian the olfactory canals are perforated with a number of tubules species in which the snout region is well known have which are most common on the ventral and mesial sides, pedunculated olfactory regions. This is correlated with their the latter joining the two sides together. Northcutt (1987: expanded snouts containing a large number of tubuli 289) commented that in Latimeria and Neoceratodus the overlying the large olfactory bulbs. Campbell & Barwick: Early Devonian lungfish Dipnorhynchus kurikae 109 Telencephalon. As we have indicated for D. sussmilchi (Fig. 4). The jugular vein runs from a posterior position (Campbell & Barwick, 1982: fig. 25a), the floor of the and opens through the foramen sphenoticum minus slightly telencephalon drops slightly to the rear of, and also behind the pituitary vein. The anterior ophthalmic artery constricts laterally, posterior to the ends of the olfactory passes anteroventrally to the pituitary vein and opens low canals (Figs. IB, 4B). Northcutt (1987: 281) commented down on the lateral wall of the braincase just dorsal to the that in living dipnoans there is a distinctly expanded floor palate. The external opening for this artery is clearly visible on the telencephalon. In dipnorhynchids any expansion of on both sides of the specimen, but its internal opening is the floor of the braincase is barely perceptible. Similar concealed. Presumably the internal carotid enters the comments can be made about the floor of the telencephalon posterior swelling though we have not been able to establish in the Gogo dipnoans, and presumably this is a feature of this point. Posteroventrally the hypophyseal pouch passes primitive dipnoans. down into a long narrow buccohypophyseal canal, that A shallow depression, which is too small to photograph opens into the mouth almost at the posterior end of the in such a secluded position, lies on each side of the midline pterygoid dental plate. in the floor of the telencephalon of D. kurikae. At the anterior Internally within the braincase, oculomotorius N III, is end of each groove is a foramen, and this passes situated 2-3 mm above the anterior wall of the pituitary anterolaterally presumably into a tube. We have not been hypophysis. It leaves the braincase through a foramen that able to see where it emerges. Of particular interest is the is only 1 mm in diameter, and passes ventrolaterally into entry into the right foramen by four small holes; but on the the orbital chamber, opening about 7 mm posterior to the left a single perforation is present. The function of these optic foramen. structures remains unknown. As usual, the trochlearis N IV is situated high on the The dorsal surface of the telencephalon is not preserved wall of the braincase, and in this specimen is represented in either specimen. However the shape of the lateral and on each side by a notch on the upper edge of each side of anterior walls indicates that it was raised above the level of the neurocranium (Figs. 3, 4). With the palate held the more posterior parts of the braincase. We cannot horizontally, this foramen is slightly anterior to a line dorsal determine the extent to which it was divided medially. to foramen for oculomotorius N III. It is oriented anterolaterally from the inside outwards. Diencephalon. Behind the telencephalon the walls of the diencephalon swell slightly laterally, and ventrally they drop Mesencephalon and metencephalon. Behind the hypophyseal to a point where the base of the foramen for the opticus N foramen, the floor of the braincase is almost horizontal except II makes its exit (Fig. 4). The optic nerve passes from the for a broad slight median ridge along its length. The foramen braincase via a bone-lined tube and an external foramen 5 for the moderately large trigeminus N V lies well down on mm in diameter and oriented mainly anterolaterally, but also the wall, and leaves the braincase about 12 mm behind the a little ventrally. This is similar to the orientation shown by hypophyseal pouch. It is entered by a short groove which Campbell & Barwick (1983) but unlike that shown by starts anteriorly. Within a couple of millimetres after leaving Thomson & Campbell (1971: fig. 32) for D. sussmilchi. the inner perichondrium the tube splits; a thin tube that The optic foramen lies immediately behind the point where carried the profundus Vj, being directed forwards and the preorbital wall meets the lateral wall of the braincase. downwards to open through the external neurocranial wall In extant dipnoans the opticus N II passes out dorsal to in the foramen sphenoticum minus on the left side of the the base of the braincase, and generally it is smaller than specimen (Fig. 4B), but through a small foramen behind that of Dipnorhynchus. In Chirodipterus and Holodipterus that structure on the right side. This nerve is in an appropriate the opticus canal emerges from the base of the braincase, position to run through the floor of the orbital cavity, and though in both these genera its point of exit is further thence forwards to the sensory region of the snout. A second forward than in Dipnorhynchus. The position of the nerve much larger tube runs posterolaterally to open through the in these Devonian forms indicates that they display the foramen sphenoticum majus (Fig. 4A,B). This carried both primitive condition for dipnoans. In Diabolepis, the nerve V2 and V3, which serve the maxillary and mandibular rami. II is situated in a forward position, and the nasal capsule On the internal surface of the braincase, dorsal to the forward of it is also short (Chang, 1995: figs. 5, 11). This foramen for trigeminus N V, a shallow groove runs upwards, interpretation is supported by the position of the orbit as but the specimen does not show any foramen at its top. shown by Chang (1995: fig. 2). Other differences between This, presumably, is the result of erosion of the top of the Diabolepis and dipnoans, such as the massive differences braincase through weathering. in the posterior of the skull, are dealt with in a paper that The wall of the sphenoticum minus is a coarse open we have submitted for publication. structure (Figs. 3,4A), rather than being a continuous layer. Behind the opticus nerve foramina, the floor of the Immediately in front of the ventral edge of this structure is braincase rises slightly to form the front edge of a a small opening for the anterior ophthalmic artery, described commodious hypophyseal cavity. In this rise is a deep above. Between this foramen and around the opticus N II median groove that runs posteroventrally down into the foramen, the wall of the external endocranium is depressed hypophyseal pouch. The pouch swells laterally and and crinkled. A similar feature is found on some specimens posteriorly. The pituitary vein passes out laterally and of D. sussmilchi. slightly posteriorly within this pouch, and emerges into a Examination of the structure of extant dipnoans large cavity {the foramen sphenoticum minus) in the lateral Neoceratodus wndProtopterus (Northcutt, 1987) shows that wall of the braincase medial to the conical palatal process the facialis N VII and the accousticus N VIII leave the wall 110 Records of the Australian Museum (2000) Vol. 52 of the braincase close behind nerve V; in addition, a branch exit from the posterior part of the sacculus, which is its of the anterior lateral line nerve passes out dorsal to nerves standard position on Devonian dipnoans. It passes out in a VII and VIII. The two new specimens of D. kurikae do not lateral direction. show any exits close behind nerve V, and the interpretation The passage of nerve vagus N X is preserved as a groove of the existing foramina have to be understood in terms of passing below the posterior part of the superior sinus of the general principles. We reached the following conclusions. saccular cavity, and then parallel with the ventral edge of In the inner perichondrium about 7-8 mm posterodorsal the ampulla for the posterior semicircular canal. It passes to the trigeminus N V foramen, is a vertically elongated out of the bone in a posterolateral direction. foramen which runs laterally into a foramen in the top of The horizontal semicircular canal is not evenly curved, the foramen sphenoticum majus on the left side, and to a its external edge being almost straight. Its external ampulla small foramen dorsal to the same position on the right side. lies well behind the anterior end of a transverse line through This structure is in an ideal position for the anterior lateral the superior sinus of the saccular cavity. Below the external line nerve (Fig. 4B). Its position can be compared with that ampulla it turns ventrally into the sacculus. Posteriorly the of Neoceratodus, Protopterus and Latimeria as illustrated horizontal semicircular canal maintains its width throughout by Northcutt (1987). its length, and passes into the posterior end of the superior In the internal wall immediately below the above sinus of the saccular cavity. At the posteromedial corner foramen, a shallow but wide groove runs into the front wall the horizontal canal is connected with the marked swelling of the utriculus, and then runs posterolaterally into the thick that represents an ampulla at the base of the posterior vertical neurocranial wall. Within the wall the tube splits into two, semicircular canal. This is the largest ampulla of all three the dorsal one of these emerges in the dorsal extremity of preserved, and anteriorly it joins via a large foramen into the foramen sphenoticum minus, and probably carried the the posterior part of the superior sinus. This foramen superficialis ophthalmicus N VII. The ventral one enters a provided entry for a ramus of the accousticus N VIII. The long tube that runs postero-ventrolaterally to open through posterior semicircular canal that must have arched from this iht foramen prooticum basicraniale along with the jugular ampulla to the top of the superior sinus, would have been vein. It must therefore be the hyomandibularis N VII. aligned at a low angle to the axial plane. The anterior vertical Posterior to where facialis N VII leaves the braincase, ampulla is connected with the horizontal canal as expected, the walls expand laterally to form the inner face of the otic and it also opens down into a foramen opening into the top region. At the anterodorsal end of this expansion, incomplete of the sacculus. This must have carried a branch of nerve N gaps in the specimen show where nerves open out of the VIII. As well as opening into the horizontal canal, this braincase and pass laterally through the thick lateral walls. ampulla must have opened directly into the superior sinus This must have been for the nerve accousticus N VIII. Its of the saccular cavity, but this part of the specimen has been course is not preserved but it must have turned into the otic lost during preservation. We have reconstructed the canal region after a short distance. We assume that the brain stem so as to give a functional orientation with respect to the maintained a linear course through this region, and we have posterior canal. so represented it on Fig. 4B. The sacculus, which is exposed on both specimens, is large The walls of the braincase turn downwards in front of and has a convex well-rounded base extending ventrally to the otic region, and the anterior end of the notochordal the base of the notochordal canal. The lateral wall has a very chamber penetrates this wall for about 3-4 mm. This puts oblique surface sloping ventromediahy at about 45°. The lateral the end of the notochordal chamber anterior to the level margin is sharp and lies almost at the point where the jugular from which the nerve accousticus N VIII passes out. vein passes through the posterolateral wall. The second specimen, ANU 48678, shows the otic region Neither specimen has the anterior or posterior semicircular moderately clearly, except that the vertical semicircular canals preserved, and we have no direct means of determining canals are missing. Figure 5A shows the specimen with the the height of the superior sinus. We do know, however, that outlines of the canals and the otic region drawn onto it, and the roof of the other dipnorhynchids is high and is supported Figs. 5B and 5C are reconstructions of the soft tissues from the braincase on a high median septum and two high inferred from it. The right side of the specimen has been dorsolateral septa. One skull roof of D. kurikae has the weathered, exposing the internal structure of same. The left dorsolateral cristae partly preserved, and they are in a lateral side has been not so deeply weathered but exposes the position as in D. sussmilchi rather than close together as in horizontal part of the semicircular canals. This gives Chirodipterus australis. This implies that the vertical space sufficient information on the general structure of the region for the superior sinus or the space for the ductus to be able to reconstruct the overall pattern. endolymphaticus is large. Consequently we have restored The posterior part of the notochordal chamber has also these structures to the height implied by the space available been lost allowing observation of the sacculus, the utriculus, from the horizontal structures that are preserved. and the superior sinus. In addition this specimen shows the The only Devonian species with which a comparison of position of nerves N VII to N X more clearly than any other the labyrinth can be made are Chirodipterus australis Miles, Early Devonian form. The utriculus is large and extends Holodipterus gogoensis Miles and Griphognathus whitei across the anterior face anterodorsally to the terminus of Miles from the Late Devonian at Gogo, and C. wildungensis the notochord, and it is crossed by the facialis N VII as has Gross from the Late Devonian of Wildungen. Save- been described above. The accousticus N VIII is dealt with Soderbergh’s (1952) attempt to understand the Wildungen in the section below dealing with the semicircular canals. specimen depended on his destruction of the specimen with Nerve glossopharangeus N IX is known only from its a hammer and chisel. His illustration (1952: fig. 9, pi. 5, Campbell & Barwick: Early Devonian lungfish Dipnorhynchus kurikae 111 fig. 4) of the otic region shows a clear outline similar to The nasal capsule that given by Miles (1977: figs. 47-48), but the horizontal semicircular canal is not present on his photograph and is The capsule is preserved on the left side cf. ANU 48676, reconstructed on fig. 9. Despite this incompleteness, the two and is quite uncrushed. Miles (1977: 123) commented on species of Chirodipterus are very close indeed. Neither of these the Gogo dipnoans that the surface of the neurocranium species has the large ampulla on the posterior semicircular was evidently without a perichondral bone layer. The dorsal canal, the large utricular recess, and the laterally compressed view of this specimen shows the junction between the horizontal canal, as found in D. kurikae. In Chirodipterus, the dermal bone and the endocranium, and a perichondral layer horizontal canal is semicircular in outline in dorsal view. lies around the endocranium (Figs. 3, 6A). We have also Holodipterus is discussed by Miles and is said to be close observed a similar layer in C. australis. The boundary to that of Chirodipterus. Griphognathus whitei has a similar between the neurocranium and the dermal bone is clearly arrangement to that of Chirodipterus, but its proportions outlined, and it is exactly like the boundary between the are different because of the flattened shape of the skull. neurocranium and the dermal bone of the palate illustrated These differences are small in comparison with the obvious by Campbell & Barwick (1985: fig. 6d). The tubules over similarities between the species, and its occurrence in all the top of the capsule, that is in the ethmoid capsule, were the Devonian species in which the labyrinth is preserved, situated in a cartilage matrix (Miles, 1977: 133). leads us to conclude that it is the primitive dipnoan pattern. An internasal septum {septum nasi), is narrow and rather Details of the comparison between the otic region of sharp crested towards the rear, but fades away almost primitive dipnoans was discussed by Miles (1977: 98-103). completely anteriorly (Fig. 6B). It is formed of endocranial superior sinus posterior of saccular cavity anterior semicircular semicircular canal canal horizontal posterior semicircular semicircular canal canal anterior horizontal —^ semicircular semicircular 11 canal canal ampulla N X posterior anterior ampulla ampulla N IX N VIII median sacculus N IX axis sacculus superior sinus left N I of saccular cavity posterior semicircular anterior canal semicircular canal posterior anterior ampulla ampulla horizontal N VIII semicircular canal exterior ampulla N IX utricular recess sacculus Figure 5. Dipnorhynchus kurikae. A—dorsolateral view of ANU 48678, the same specimen shown on Fig. 2. The semicircular canals were stripped off during preservation, but the details of the superior sinus of the sacculus, the ampullae of all three canals, and features more ventral to it are preserved. The height of the superior sinus is restored according to the height in the dorsolateral process supporting the braincase. The median axis is drawn along the base of the braincase. B—reconstruction of the left otic region viewed from the medial side. Outlines of structures on the lateral side are dotted. The same viewed from the lateral side. Nerve VIII is based on a canal and foramina in the specimen, and nerve IX is based on a foramen in the posterior wall of the specimen behind the sacculus. Scale =10 mm. 112 Records of the Australian Museum (2000) Vol. 52 olfactory canal internasal septum I palatine^ J nerve r roof of nasal capsule ^ Figure 6. Dipnorhynchus kurikae, A-C from ANU 48676. A—dorsal view of the nasal capsule and snout, showing the dermal bone (innermost boundary arrowed) with pores in the outer layer, the gap between the dermal bone and the neurocranium with no tubules crossing into the dermal bone. The roof of the nasal capsule shows few structures because it was largely removed during preservation, and the black spots on it are bubbles in the impregnating plastic. B—view of the palate and snout with the snout tilted towards the observer. In the snout, note the pores some of which are in groups, the perforations for the palatine nerves, and the opening of the olfactory canal. C—same specimen tilted in the opposite direction, showing the flattened surface without pores on the inside of the snout, and the boundary (arrow) between the roof of the nasal capsule and the dermal bones of the snout (arrowed). D—Dipnorhynchus sussmilchi, anterior end of the snout of ANU 18815 showing the hard surface lying in front of the cosmine-bearing plates, the course of the lateral line canals, and the small pores on the anterior surface. Scales = 10 mm. material, and its surface is smooth without any evidence nasi certainly has a curious appearance (Miles, 1977: 134- that it continued ventrally as cartilage. Unlike Chirodipterus 135). Beyond its anterior end of the septum nasi, the edge australis, it has no flattened surface to which a palatal bone of the anterior lip has a pronounced embayment within (identified as a vomer by Miles) was attached. This is as which is a foramen. This and foramina under the projections would be expected, as the so-called vomer lies in a more forming the embayment apparently connected with the posterior position between the dermopalatines in this tubules in the ethmoid capsule. species, and in comparison with C. australis the septum