A new genus for the Dipnoan species Ceratodus tuberculatus Tabaste, 1963 Charles S. CHURCHER Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario, M5S 3G5 (Canada) and Department of Palaeobiology, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario M5S 2C6 (Canada) [email protected] Gerardo DE IULIIS Faculty of Community Services and Health Sciences, George Brown College, 200 King Street East, Toronto, Ontario, M5A 1J5 (Canada) and Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario, M5S 3G5 (Canada) [email protected] Maxine R. KLEINDIENST Department of Anthropology, University of Toronto at Mississauga, Ontario, L5L 1C6 (Canada) and Department of Egyptology, Royal Ontario Museum, 100 Queen’s Park, Toronto, Ontario, M5S 2C6 (Canada) [email protected] Churcher C. S., De Iuliis G. & Kleindienst M. R. 2006. — A new genus for the Dipnoan species Ceratodus tuberculatus Tabaste, 1963. Geodiversitas 28 (4) : 635-647. ABSTRACT A tooth plate of the large lungfish referred to Ceratodus tuberculatus Tabaste, 1963 from Kharga Oasis, Egypt, allows reconsideration of its generic status. Comparisons with fossil Ceratodus and living Neoceratodus demonstrate the generic distinction of this taxon and Retodus n. gen. is proposed for this large KEY WORDS dipnoan. Tooth plates of R. tuberculatus n. comb. are characterised by four Dipnoi, Retodus n. gen., transverse ridges, broadly rounded crests, a reticular pattern of ridges and hol- Ceratodus tuberculatus, lows, and large adult size. The stratigraphic time span for specimens assigned Albian-Maastrichtian, to R. tuberculatus n. comb. is Albian-Early Cretaceous of southern Algeria, to Late Cretaceous, Egypt, Campanian-Late Cretaceous of Dakhleh and Kharga Oases, Egypt, and Maas- new genus. trichtian Late Cretaceous of Niger. GEODIVERSITAS • 2006 • 28 (4) © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 635 Churcher C. S. et al. RÉSUMÉ Un nouveau genre de dipneuste pour l’espèce Ceratodus tuberculatus Tabaste, 1963. Une plaque dentaire bien conservée du dipneuste Ceratodus tuberculatus Tabaste, 1963 de l’oasis de Kharga (Égypte) permet une révision de son statut générique. Des comparaisons avec les plaques dentaires du genre fossile Ceratodus et celles du genre actuel Neoceratodus montrent des différences morphologiques signifi- catives. En conséquence, la création du genre Retodus n. gen. est proposée. Les MOTS CLÉS plaques dentaires de R. tuberculatus n. comb. sont caractérisées entre autres par Dipnoi, Retodus n. gen., quatre crêtes transversales arrondies et des spécimens adultes de grande taille. Ceratodus tuberculatus, L’extension stratigraphique de R. tuberculatus n. comb. s’étend de l’Albien (Cré- Albien-Maastrichtien, tacé inférieur, sud de l’Algérie) au Campanien (Crétacé supérieur de Dakhleh Crétacé supérieur, Égypte, et Kharga, en Égypte). Des restes connus au Niger datent du Maastrichtien nouveau genre. (Crétacé supérieur). INTRODUCTION around its margins showing its denteon structure and some supporting bone. It preserves the third A partial right upper (or less likely, a left lower) and fourth ridges, with vestiges of the second, and tooth plate of Ceratodus tuberculatus (Fig. 1) was has lost the protuberant crests (Fig. 1). retrieved from a gravel-covered terrace surface in A previously recovered lower tooth plate with the Piedmont below the Libyan Escarpment in the prearticular bone still adhering (ROM 44609) Western Desert of Egypt, north of Ain Umm Da- assigned to C. tuberculatus also derives from this badib, 35 km north of Kharga City, Kharga Oasis, formation, but some 5 km southeast of Baris, about in New Valley (Wadi el-Gedid) Province (Fig. 2). 100 km south of Kharga City (Churcher 1995). It was collected on March 7, 1998 by Kleindienst Other fragments of C. tuberculatus tooth plates have while surveying terrace surfaces for earlier Middle been collected from the equivalent Mut Fm. in the Stone Age artifacts. Its provenience lies near the neighbouring Dakhleh Oasis, 150 km to the west head of the middle terrace, of a series of three, (Churcher & De Iuliis 2001). high-elevation terraces of probable Pleistocene age The speciesC. tuberculatus comprises a separate (cf. Gardner 1952), c. 4 km north of the ruined genus on the basis of crest morphology and size, Romano-Byzantine “fort” known as Ain Umm and is easily separable from both Ceratodus, the Dabadib. The terraces are formed on flaggy sand- genus to which Tabaste (1963) originally assigned stones and shales, probably of the Campanian Taref it, and Neoceratodus to which Martin (1981, 1982a, Formation, of Late Cretaceous (Maastrichtian) age b, 1984a, b) assigned it, on these characters. (El Deftar et al. 1978; Hermina 1990). The specimen has noin situ stratigraphic context ABBREVIATIONS but is presumed to be a lag derived from the under- Acronyms for Saharan localities that yielded dipnoan lying local Campanian Baris Formation (= Qusseir tooth plate materials are used in Martin (1984a, b) and Fm., Variegated Shales or “Qusseir Clastic Mem- reviewed in Churcher & De Iuliis (2001). Those cited here are: ber”), which overlies the Taref Formation and is MNHN Muséum national d’Histoire naturelle, Paris; exposed in the Escarpment to the north (El Deftar ROM Royal Ontario Museum, Toronto. et al. 1978: 61) (Fig. 1). The specimen is eroded HG series-Ahoggar Massif or Hoggar Mountains: 636 GEODIVERSITAS • 2006 • 28 (4) A new genus for Ceratodus tuberculatus (Dipnoi) HGO West (Ouest); “Neoceratodus” tuberculatus – Churcher 1999: 64, table HGN North (Nord); 2.2. HGS South (Sud). LECTOTYPE. — Mandibular tooth plate HGO 49 (Ct2) TERMINOLOGY (Tabaste 1963: pl. II, fig. 3a, b), designated by Martin The terminology for features of lungfish tooth plates (1984a: 244). (See also Fig. 4B). is not consistent and we use that previously used by us (Churcher & De Iuliis 2001: 309, text-fig. 3). It is REFERRED SPECIMENS. — Ct1, Ct3-Ct6 (Tabaste 1963: reproduced here as Figure 3. pl. II, fig. 3a), Albian-Early Cretaceous age. ROM 44609 (Churcher 1995: figs 2, 3), Campanian- Late Cretaceous age. SYSTEMATICS ROM 47638, probably Campanian-Late Cretaceous age. (See also Fig. 4D). Order CERATOFORMES Berg, 1937 TYPE LOCALITY. — Rouaix (Algeria). Albian-Lower Family CERATODONTIDAE Gill, 1872 Cretaceous. Subfamily CERATODONTINAE Gill, 1872 TYPE STRATA. — Erg Iller (Algeria) and Mt. Igdaman (Niger): Albian-Lower Cretaceous. Genus Retodus n. gen. DIAGNOSIS. — Same for genus and species. Four ridges TYPE SPECIES. — Ceratodus tuberculatus Tabaste, 1963. oriented almost transversely across the plate, concave distally (not straight) when unworn, and cross-linked ETYMOLOGY. — From the Latin, rete, net; -odus, Latinised by smaller lunate secondary ridges into a network of Greek -Óδούυς, toothlike, referring to a network of ridges crests and hollows, best seen in the Egyptian Campanian on the occlusal surface of a tooth plate. form. Tooth plate size is considerably larger than those of coeval Ceratodus or Neoceratodus. Length 76-100 × DIAGNOSIS. — The same as Retodus tuberculatus breadth 32.0-48.5 mm. n. comb. REFERRED STRATA. — Baris and Ain Umm Dabadib, REMARKS Kharga Oasis, Egypt: Baris (= Qusseir) Formation shale, The new lungfish tooth plate (ROM 47638) re- Campanian-Upper Cretaceous. Dakhleh Oasis, eastern ported here preserves features unknown in the area, Egypt: Mut (= Qusseir) Formation shale, Campa- nian-Upper Cretaceous. Bahariya Oasis, Egypt: Bahariya species previously known as Ceratodus tuberculatus Formation shale, Albian-Lower Cretaceous (probable and indicates that the species cannot be referred occurrence). to an already described genus. Although insuffi- cient material of the species is known to permit a DESCRIPTION AND COMPARISONS phylogenetic analysis, it is apparent that it forms a Upper right tooth plate (Figs 1; 4) distinct clade, and thus merits generic distinction When compared to other species placed within as Retodus n. gen. the genus Neoceratodus, the Ain Umm Dabadib fragment, representing the unworn condition of tooth plates of its taxon, does not fit easily within Retodus tuberculatus (Tabaste, 1963) n. comb. the previously observed tooth plate morphotypes. Compared with other dipnoan tooth plates from Ceratodus tuberculatus Tabaste, 1963: 444, 445, fig. 3, Saharan Africa, those of Ceratodus africanus (Haug, 448, pl. 2, figs 3, 4, pl. 3, figs 1-6, pl. 4, figs 1-3. — Cap- 1905) most closely resemble those of R. tubercu- petta 1972: 185. — Kemp 1997a: 729; 2001: 430, 434, fig. 16. — Lehman 1966: 271, fig. 27B, 291. — Martin latus n. comb. in that their six or seven ridges are 1984b: 233. — Schultze 1992: 192. arranged in a poorly radiating pattern, and the central ones, i.e. nos 2 and 3, are concave distally, Neoceratodus tuberculatus – Martin 1982a: 612; 1982b: and are oriented approximately across the axis of the 56, 60, 61; 1984b: 225, 226, 243, fig. 44non 46, 244, 245, fig. 49, 246, fig. 50, 248, 251-253, fig. 53, 257, plate fide Tabaste (1963: pl. I, figs 2-7) and Martin 258. — Schaal 1984: 44-46. — Churcher & De Iuliis (1981: pl. 1, figs 6, 12, 17, 18; 1982a: fig. 1.10), 2001: 305. contra Martin (1984a: 273, figs 24 [HGN 28], 26 GEODIVERSITAS • 2006 • 28 (4) 637 Churcher C. S. et al. FIG. 1. — Stereoscopic image of a partial tooth plate of Retodus tuberculatus (Tabaste, 1963) n. comb. (ROM 47638), from the sur- face of a Pleistocene terrace on the Libyan Escarpment near Ain Umm Dabadib, Kharga Oasis, Wadi el-Gedid, Egypt. It is presumed to derive from the underlying Campanian Baris Formation, of Late Cretaceous (Campanian) age. Compare with those illustrated by Tabaste (1963: fig. 3, pl. II, fig. 3a, b, pl. III, figs 1, 2, 4) and Churcher (1995: fig. 2). Scale bar: 12 mm. [HGO 7?]); 275, fig. 30 [HGN 30]) who assigns “Presque toutes les pièces (32) rapportées à cette specimens from north and west of the Ahoggar espèce proviennent du gisement Rouaix (Soudan). Massif (Hoggar Mountains) with only four crests to trois ont été trouvées à l’Erg Iller et une au Niger N. africanus. (N.B. HGS 114, from In Abangarit, (Mt.