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B2: The anterior and posterior edges of the bridge-carapace suture are parallel or closely so with a prominent suture surface between them. There is no medial constriction.
B3: The bridge-carapace suture is expanded for its full length, but more so at extremes, there being an obvious medial constriction.
B4: The bridge-carapace suture narrows from its widest point proximal to the vertebral column, and constricts completely to form a ridge confluent with the edge formed by the ventral suture of the peripheral bones.
Rib/Gomphosis of Pleural 1
Character C: Rotation of the Rib/Gomphosis
C0: The ventral surface of the distal extent of the rib/gomphosis is rotated obliquely, to face ventrally but with posterior inflection.
C1: The rib/gomphosis shows no such torsion distally.
Dorsal Characters
Character D: Relative width of Vertebral 1
D1: First three vertebral scutes equal or sub-equal in width.
D2: First vertebral scute wider than second and third.
Character E: Cervical Scute
E0: Cervical scute typically present.
E1: Cervical scute typically absent.
Posterior Internal Carapace Characters
Character F: Carapace Pelvis Suture
F0: Ileum sutures to the seventh and eighth pleurals and the pygal (Fig. 1a).
F1: Ileum sutures to the eighth pleural and pygal only but is directly adjacent to the suture between the seventh and eighth pleurals (Fig. 1b).
F2: Ileum sutures to the eighth pleural and pygal only but is widely separated from the suture between the seventh and eighth pleural (Fig. 1c).
Comparative material: All names used for undescribed species are from Georges & Adams (1992, 1996). Abbreviations used: AM, Australian Museum; NTM, Museum and Art Galleries of the Northern Territory; QM, Queensland Museum; WAM, Western Australian Museum; UC, University of Canberra; UM, University of Michigan Field Series; UU, University of Utah.
Elusor macrurus: UC 0184-93, 0225-29 UU 19488, 19508; Elseya dentata: NTM 13319, 13521, 16330, QM 59265, 59277-80, UC 0307-18; Elseya georgesi: AM 138387-88, UM 02016-17; Elseya irwini: ANWC 0520; Elseya lavarackorum: QM F24121, QMJ 31939, 31942, 31944, 31946-47, 31949-50, 31952, 46284, 47908, 47911, 48544, 48547, 60255, UC0201; Elseya latisternum: AM 123037, 123039, 125474-75, QM 48054-55;
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Elseya novaeguineae: AM 42662, 125038; Elseya purvisi: AM 123040, 123042, QM 59289-90; Emydura macquarii: QM 48016, 48034, 48050- 51, 59275-76, UC 0175-76, 0303; Emydura subglobosa: NTM 5028, 8206, 13428, 13433, 16332, UC 0171-72, 0177; Emydura tanybaraga: AM 125470-71, 125491, NTM 8211, 8213, 17339; Emydura victoriae: NTM 13513-14, 32917, 32976, UC 0165; Elseya sp. aff. lavarackorum (Burnett): UC 0305-6, QM 2966, 28449, 36036, 36039, 36041-42, 36044-47, 37933, 38533, 59269-71; Elseya sp. aff. lavarackorum (Johnstone): QM 22694, 23175, 23299, 23300, 23322, 24938, 28449, 48060, 48068; Elseya sp. aff. dentata (South Alligator): AM 128002, 128004, QM 59285-89, NTM 5097, 13512, 13985, UC 0304; Elseya sp. aff. latisternum (Gwyder): AM 123028-29, QM 48028, 48038; Pseudemydura umbrina: UC 0178 WAM 29337; Rheodytes leukops: UC 0173.
Systematics
Order Testudines Linnaeus, 1758
Suborder Pleurodira Cope, 1864
Family Chelidae Ogilby, 1905
Elseya nadibajagu sp. nov. (Figure 1.)
Holotype: QM F30576a partially articulated carapace and associated plastron collected by Henk Godthelp during the 1992 Field Season. Upper Andrews Quarry.
Referred specimens: QM F30577 also collected at the same site.
Type Locality: Upper Andrews Quarry (19 43' S, 145 36' E). Allingham Formation, Bluff Downs, Bluff Downs Station, north eastern Queensland. The Allingham Formation was named by Archer & Wade (1976) for a sequence of terrigenous clays, silts, sands and calcareous sands that outcrop on Bluff Downs Station, along the banks of the Allingham Creek, a tributary of the Burdekin River. Several different quarries have been established to exploit these outcrops, all showing a similar and contiguous stratigraphy (BM unpubl.data). The sediments recovered are fluviatile and lacustrine in nature and represent a number of depositional events.
Age: Early Pliocene, based on the interpreted age of the overlying Allensleigh basalt (Archer & Wade 1976)
Diagnosis
The fossil is identified as an Elseya by the presence of steeply angled bridge struts, features diagnostic of Elseya sensu stricto, (see Thomson et al. 1997) and Emydura. The carapacial sutures for these struts are wide throughout their length that is diagnostic of the Elseya lavarackorum group within this genus (Thomson et al. 1997). Other diagnostic features include the first vertebral scute being wider than the second and third and the absence of a cervical scute (Thomson et al. 1997).
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