Icriodontidae Müller and Müller, 1957

Drygant, Daniel & Szaniawski, Hubert, 2012, Lochkovian conodonts from Podolia, Ukraine, and their stratigraphic significance, Acta Palaeontologica Polonica 57 (4), pp. 833-861 : 844-845

Family Icriodontidae Müller and Müller, 1957 Genus Caudicriodus Bultynck, 1976

Type species: Icriodus woschmidti Ziegler, 1960 ; Rhenish Slate Mountains , Hüinghaus Beds, lower Lochkovian .

Remarks.—Apparatuses of the Caudicriodus species are composed of the typical icriodontid Pa elements and five pairs of different coniform elements (see Serpagli 1982). All the coniform elements of Caudicriodus from Podolia were earlier assigned to the form species: Rotundacodina quadratibasis Drygant, 1974 , R. elegans Carls and Gandl, 1969 , R. noguerensis Carls and Gandl, 1969 , R. dubia (Rhodes, 1953) , Drepanodus ? curvatus (Rhodes, 1953), Acodina plicata Carls and Gandl, 1969 , A. curvata Stauffer, 1940 , A. retracta Carls and Gandl, 1969 ( Drygant 1974) and to Rotundacodina rotunda Drygant, 1984 ( Drygant 1984). However, the rare preservation of the M and transition series elements and their occurrence with Pa elements of different species restricts the reconstruction of the apparatuses to a few exceptional cases. Because of that only the Pa elements are determined and illustrated in the paper.

Ontogenetic development of Caudicriodus transiens ( Carls and Gandl, 1969) , C. postwoschmidti (Mashkova, 1968) , and C. serus ( Drygant, 1984) shows that their juvenile forms ( Figs. 9 , 10N, Q–S, U) strongly differ from the mature. In some cases ( Mashkova 1968b, 1970) the juveniles were described as separate species and subspecies, e.g. Caudicriodus eolatericrescens (Mashkova, 1968) , C. angustoides angustoides ( Carls and Gandl, 1969) , C. angustoides bidentatus ( Carls and Gandl, 1969) . Besides we noticed that among the left and right mature forms of Pa elements of some species ( Caudicriodus transiens , C. postwoschmidti , C. schoenlaubi , and C. serus ) considerable morphological difference occurs ( Figs. 5 , 9 ). The general shape of the elements is similar but their outline is different. Similar asymmetry of the conodont elements within one apparatus has been described in detail by Lane (1968).

Caudicriodus hesperius ( Klapper and Murphy, 1975) Figs. 9A , 10A, B.

For synonymy see Drygant (2010) and include:

1975 Icriodus woschmidti hesperius subsp. nov.; Klapper and Murphy 1975: 48, pl. 11: 1–19.

1980 Icriodus woschmidti hesperius Klapper and Murphy ; Klapper and Johnson 1980: pl. 2: 11.

2010 Caudicriodus hesperius (Klapper and Murphy) ; Drygant 2010: 56, pl. 2: 1, 2, 14–16.

Material.—Eleven Pa elements and thirty seven coniform elements (not separated from the elements of C. woschmidti ) from the lower part of the Khudykivtsi Formation, Tseliyiv Formation and lower part of Mytkiv Formation. Numbers of sections and samples: 14/−1,3, 16 and 25 m, 14 V /5, 104/1, 37/1, 12/1a ( Fig. 3 ).

Remarks.—Pa elements of the species characterize comparatively elongated spindle (0.9–1.0 mm) and occurrence of 4–5 transverse ridges which are formed by connected denticles of the lateral and median rows. In the juvenile specimens the longitudinal rows are not developed and the transverse ridges are flattened. Postero−lateral process long, straight, laterally compressed, bears a single ridge of denticles. Inner and outer lobes undenticulated. Basal cavity lobe−like, expanded behind the second transverse ridge. Primary and secondary cusps high and approximately equal in height.

The platform gets suddenly wider immediately behind the second or third transverse ridge. The angle between the median longitudinal row (axis of the spindle) and the postero−lateral process is up to 135 ° and does not differ much from the angle in the holotype and paratype (115–145 °).

Representatives of the species differ from Caudicriodus woschmidti ( Ziegler, 1960) by the lobe−like, expanded platform and possession of narrow, long, and straight postero−lateral process.

Elements asssigned to the Icriodus woschmidti hesperius by Schönlaub (1980b: pl. 6: 5 and 1980a: pl. 19: 1, 12) are close in outline of the basal cavity to the transitional forms between Caudicriodus woschmidti ( Ziegler, 1960) and C. ruthmawsonae Drygant, 2010 . Specimens identified by Simpson (1998) as Icriodus woschmidti hesperiu s are closest in morphology and denticulation to the trasitional forms between the genera Pedavis and Caudicriodus .

Stratigraphic and geographic range.—Uppermost part of Pridoli(?) and lower Lochkovian—the Caudicriodus hesperius Zone. Podolia , Sardinia, Marocco, Nevada, Texas, Western North America, Canadian Arctic Archipelago, and Australia (Queensland and New South Wales).

http://dx.doi.org/10.4202/app.2011.0124

Figures

Fig. 9. Ontogenetic development and morphological comparison of Pa elements of Podolian Caudicriodus species.

Fig. 5. A. Probable phyletic relationships within Caudicriodus, based on the evidence of the Podolian collection. B. Similar forms in other regions. D., Devonian; S., Silurian; Fm., Formation. For legend see Fig. 3.

Fig. 3. Stratigraphic range of conodonts in the Lochkovian sequence of Podolia.A. Lower part. B. Upper part (see next page). D., Devonian; S., Silurian.