Glikmanius, Ginter & Ivanov & Lebedev, 2005

Ginter, Michał, Ivanov, Alexander & Lebedev, Oleg, 2005, The revision of “ Cladodus ” occidentalis, a late Palaeozoic ctenacanthiform shark, Acta Palaeontologica Polonica 50 (3), pp. 623-631 : 624

Genus Glikmanius nov.

Type species: Cladodus occidentalis Leidy, 1859 ; upper Coal Measures of Manhattan, Kansas, Pennsylvanian .

Etymology: In honour of the late Russian palaeontologist, Dr. Leonid Glikman, who thoroughly studied this genus and was the first to propose its ctenacanthiform affinity; the suffix − us indicates the masculine gen− der of the name.

Referred species.— Glikmanius occidentalis ( Leidy, 1859) , G. myachkovensis ( Lebedev, 2001) .

Diagnosis.—Sharks with cladodont teeth having a robust, triangular median cusp, strongly convex lingually and slightly convex or flattened labially, with a well developed depression in the basolabial part. There are usually from two to four pairs of lateral cusps, the outermost the largest. At least one pair of intermediate cusplets is not in line with the others, but positioned labially. The base is reniform, with two rounded, compact basolabial projections flanking the labial depression, and two widely spaced buttons on the oral−lingual side.

Differential diagnosis.—Teeth of Glikmanius gen. nov. present a unique combination of features, most of them observed in other cladodont shark taxa. They share the shape of the tooth−crown with Cladodus Agassiz, 1843 , and particularly with Cladodus bellifer St. John and Worthen, 1875 , but differ clearly from the latter by a greater depth of the basolabial depression and the presence of two pairs of separate basal articulation devices (buttons and basolabial projections). Similar basal features are observed in the teeth of Heslerodus Ginter, 2002 (= Phoebodus heslerorum sensu Williams 1985 ) which, however, are characterised by a phoebodont−like crown with delicate, slender cusps. Prominent, labially flattened median cusp, typical of Glikmanius , occurs in Ctenacanthus Agassiz, 1838 (see Dean 1909) and Symmorium Cope, 1893 , but in the latter two genera, as in the case of Cladodus , the articulation devices are in a form of an undivided orolingual ridge and a single basolabial shelf.

Remarks on tooth histology.—The observations on the internal morphology of Glikmanius teeth made by Mertiniene (1995) and a new study in transmitted light of a tooth immersed in aniseed oil ( Fig. 1F–H ) showed that the whole crown is covered by a thin, uniform layer of enameloid and pallial dentine ( Fig. 1G, H ). The internal part of the median cusp ( Mertiniene 1995: fig. 2) and larger lateral cusps ( Fig. 1H ) is composed of osteodentine. The basal vascular system consists of a network of numerous, thin, and sinuous canals which occupy the whole interior of the base ( Fig. 1F ). Between the buttons, usually about 2–4 larger labio−lingual canals occur. Stratigraphic range.— Carboniferous, Serpukhovian–Perm−

ian, Wordian (= Kazanian).

Figures

Fig. 1. A. Glikmanius occidentalis (Leidy, 1859), holotype, specimen ANSP 8394, from the upper Coal Measures (Pennsylvanian) of Manhattan, Kansas, in lingual (A1), aboral (A2), and labial/aboral (A3) views. B. Glikmanius sp., specimen CM 44504B, from the Namurian E3, Bear Gulch, Montana, in lingual view. C–E. G. occidentalis. C. Specimen USNM 14107, from undetermined Carboniferous of Illinois, labial view. D. Specimen BMNH P.7043 (labelled as Cladodus impressus Woodward), from the Moscovian of Myachkovo, Moscow District, in lateral view. E. The first ever published specimen, BMNH P.7364, from the Chance Pennystone, Coal Measures of Donnington, Coalbrook Dale, Shropshire, UK, labial view. F, G. Glikmanius sp., photographs in aniseed oil, parts of occlusal view, specimen MP30−1, from the Serpukhovian of the Kalinovskie Vyselki Quarry, Moscow District. F. Lingual part of the base. G. Intermediate cusp. H. Lateral cusp.