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Ž. Žigaite. New telodont from Tuva and Mongolia 161
with large anterior spur-like process. Pulp opening allocated just behind the vertical
projection of the base. Only one well-defined pulp canal present. Straight separate
dentine canals, rather thin in the periphery, anostomose and become thicker close to the
pulp canal. Pore scales of sensory line-system present.
Description.
Morphology. Five major morphological types of the scales have been distinguished –
the rostral, cephalo-pectoral, postpectoral, precaudal and pinnal (according to Märss
1986a, b; Märss and Ritchie 1998). Rostral scales (Fig. 1 A-D; Fig. 2 A-C) are slightly
rhombic to oval, with a massive basal plate which is usually larger than the crown. The
crown has isometrically serrated edges. The surface of the crown is smooth and lacks
any kind of sculpture. Cephalo-pectoral scales (Fig. 1 E-L; Fig. 2 D-L) are large, elongate
and relatively flat, with distinct crown sculpture. The crown surface contains a sharp
longitudinal central depression or groove, surrounded by symmetrical ribs on both sides,
and one or two pairs of lateral ribs. The crown goes over the smooth base. The neck is
not well expressed. The posterior edge of the crown is notched and stretches over the
base. The base is large, wedge shaped, often with a specific strong anterior spur-like
process. Postpectoral scales (Fig. 1 M-P) are characterized by a wide and shallow
central crown depression and one pair of lateral ribs. The crown is usually wider and
longer than the base. The difference between cephalo-pectoral and postpectoral scales
is transitional. Precaudal scales (Fig. 1 Z; Fig. 2 M) are comparatively tiny, up to 0.5
mm long. The crown sculpture, the central groove and ridges are not very clear. Pinnal
(fin) scales (Fig. 1 R-V; Fig. 2 N, O) are narrow and elongate as are crown sculpture
elements. The base is strongly wedge-shaped, its vertical projection lies almost at a
right angle with the crown. The crown is rather needle shaped, so called “cuneata” type
(Märss 1986a, b). These scales might have been allocated on the fins of this thelodont.
The shape of the scales reflects the higher flexibility of fins. The scales possessing
pores of the sensory-line system are also established (Fig. 2 H).
Histology. The internal structure of Talimaalepis rimae gen. et sp. nov. is rather similar
to that of genus Helenolepis. The horizontal longitudinal thin sections of the scales
show thin dentine canals which are directed from the periphery towards the pulp canal,
gradually thickening and anastomosing. In the central part of the scale, several thick
dentine canals enter into a wide single pulp canal which takes approximately 2/3 of the
crown length (Fig. 3).
Comparison. The morphology of rostral and cephalo-pectoral scales of Talimaalepis
rimae gen. et sp. nov. is rather similar to that of Helenolepis obruchevi Karatajūte-
Talimaa, 1978. A common feature is the extremely high vertical projection of the base
of adult scales. The internal scale structure and the possession of thick dentine canals
display a close relation to genus Helenolepis too. Though possession of a single pulp
K, LGI M-1/237, cephalo-pectoral scale; L, LGI M-1/227, cephalo-pectoral scale; M, LGI M-
1/207, post-pectoral scale ; N, LGI M-1/208, post-pectoral scale; O, LGI M-1/223, post-pectoral
scale; P, LGI M-1/235, post-pectoral scale; R, LGI M-1/220, pinnal scale; Q, LGI M-1/238,
pinnal scale; S, LGI M-1/213, pinnal scale; T, LGI M-1/214, pinnal scale; U, LGI M-1/226,
pinnal scale; Y, LGI M-1/200, pinnal scale; V, LGI M-1/206, pinnal scale; Z, LGI M-1/239,
precaudal scale. Scale bars: A, D, E, H, N, P, 200 µm; B, C, G, I, K, M, O, R-T, V, 300 µm; F, J,
L, U, Y, Z, 400 µm.