Neoproscinetes penalvai

Meunier, François J., Alvarado-Ortega, Jesús, Machado, Lúcio P. C. & Brito, Paulo M., 2021, The paleohistology of bone and teeth in Cretaceous Pycnodontidae (Neopterygii: Pycnodontiformes): the case of Neoproscinetes penalvai and Tepexichthys aranguthyorum, Cybium 45 (3), pp. 193-203 : 194

Neoproscinetes penalvai

External morphology ( Figs 1 , 2 )

The prearticulars and the vomer show numerous stout teeth with a roundish apex ( Fig. 2A, C, D ). They are of a molariform type ( Fig. 2A, D ). Presence of partly eroded teeth associated with a small somewhat round tooth in one hand (white arrow-heads in Fig. 2D ), and of teeth roots without their crown in a second hand (black arrows in Fig. 2D ), shows that there is a renewal of the dentition, in where the renewing teeth, although small in size, present the same shape as the worn teeth. Poyato-Ariza and Wenz (2005) proposed that successional teeth could occasionally be replaced in pycnodonts; this replacement can happen with a new tooth growing to occupy the space of a wear or broken tooth, and not just by erupting in the posterior extremity of the bone. However, Neoproscinetes shows that this replacement can happen with a new tooth growing directly underneath a functional tooth, and not just by erupting in the posterior extremity of the bone.

Figures

Figure 1. – A: Neoproscinetes penalvai. Complete specimen, UERJ PMB 593. The white arrows point to the molariform teeth. B: Tepexichthys aranguthyorum. Complete specimen, IGM 3286. Scale bars:A = 20 mm; B = 30 mm.

Figure 2. – Neoproscinetes penalvai. A: External view of the studied fossil material showing some teeth (white and black arrowheads). Lines aa’ and bb’ correspond to the first sections series of the specimen. B: View of the right side (bloc No 2), showing the vomer (Vo), the two prearticulars (PA). C: Polished surface bb’ of sample No 2, showing the relations between teeth (asterisks) and the bony skeleton. One can see two teeth inserted on the vomer (Vo) on the right, and several other ones on the two prearticulars (PA) on the left. On the top a dermal bone (Db) with an odontode (arrow-head). D: Neoproscinetes penalvai. Occlusal view of the lower jaw (left prearticular) showing i) two shed teeth (black arrows), the scars of which show pleats indicating a plicidentine organization, ii) three resorbing teeth (black arrow-heads), and iii) two young growing teeth (white arrow-heads). Upper left inset. Detail of the left shed tooth showing the crenulated dentine in the pulp cavity (arrow). Scale bar = 1 mm. E: Tepexeichthys aranguthyorum. External view of the studied fossil material showing fin rays (on the upper right) and some bony plates (black asterisks). The lines aa’ and bb’ wrap the area of cross sections. Scale bars:A, B, C, D, E = 5 mm.