Protacrodus sp. 1

Roelofs, Brett, Barham, Milo, Mory, Arthur J. & Trinajstic, Kate, 2016, Late Devonian and Early Carboniferous chondrichthyans from the Fairfield Group, Canning Basin, Western Australia, Palaeontologia Electronica (Barking, Essex: 1987) 262, pp. 1-28 : 16

Protacrodus sp. 1

Figure 6.2-4

v. 2011 Protacrodus sp. ; Habibi and Ginter, p. 39, pl. 2b-e.

Material. One tooth from sample TS-1, Laurel Formation, Laurel Downs, Tournaisian.

Description. Crown is thin labio-lingually with five cusps; a large triangular central cusp and two pairs of lateral cusps diminishing in size distally ( Figure 6.2 ). The central cusp is three times the size of the first lateral cusps and makes up approximately half the size of the crown ( Figure 6.2, 6.4 ). The second pair of lateral cusps is approximately half the size of the first pair and diverge at approximately 45 degrees from the centre of the crown. Coarse cristae are present on both faces of the crown. On the labial face, the cristae thicken around the crown base interface to the extent they resemble small cusplets ( Figure 6.3-4 ). In outline, the base is straight along the labial face with a gently curved lingual margin ( Figure 6.3 ). The lingual face of the base is perforated by a row of large canals that decrease in size toward the distal margins. The labial face of the base is thin and gently arched with a single row of small pores ( Figure 6.4 ).

Remarks. The tooth superficially resembles Deihim mansureae Ginter, Hairapetian and Klug, 2002 but differs in that the central cusp in Protacrodus sp. is more pronounced with the lateral cusps not as highly fused as they are in D. mansureae . In addition, the tooth described here bears a shorter lingual extension of the base and lacks the characteristic cusplets. The crown and basal morphologies bear a very strong resemblance to Protacrodus sp. teeth figured in Habibi and Ginter (2011, plate 2, figure b-e). The basal canals in the specimen from the Canning Basin are focused into a single row. The cristae around the crown-base interface on the labial side are also far coarser. These differences, however, do not appear significant enough to separate these species and so we determine this tooth belongs to the same species as Protacrodus sp. from the Central Alborz Mountains, Iran ( Habibi and Ginter, 2011).

Figures

FIGURE 6. Protacrodont teeth from Lower Carboniferous Laurel Formation, Laurel Downs, Lennard Shelf, Canning Basin, Western Australia. 1, Protacrodus aequalis, WAM 15.6.43, sample TS-1, in lingual view (1); 2-4, Protacrodus sp. 1, WAM 15.6.45, sample TS-1, in lingual (2), occlusal (3) and labial (4) views; 5-12, Deihim mansureae, WAM 15.6.17, in lingual view (5), WAM 15.6.18, sample 198408, in occlusal view (6), WAM 15.6.46, sample TS-1, in lingual view (7), WAM 15.6.48, sample TS-1, in lingual view (8), WAM 15.6.19, sample 198404, in labio-basal view (9), WAM 15.6.17, sample 198404, in labial view (10), WAM 15.6.49, sample TS-1, in labio-basal view (11), and WAM 15.6.18, sample 198404, in lateral view (12); 13-16, Dalmehodus cf. turnerae, WAM 15.6.30, sample LG-1, in lingual (13) and labial (14) views, WAM 15.6.44, sample TS-1, in occlusal (15) and lateral (16) views. Scale bar length: 1-4, 0.5 mm; 5- 12, 1 mm; 13-16, 0.25 mm.