Turinia composita, Karatajūtē-Talimaa, 2002

Karatajūtē-Talimaa, Valentina N., 2002, Lower Devonian (Lochkovian) thelodonts from October Revolution Island (Severnaya Zemlya Archipelago, Russia), Geodiversitas 24 (4), pp. 791-804 : 792-799

Turinia composita n. sp. ( Figs 1 ; 2 )

Turinia sp. 1 – Märss & Karatajūtē- Talimaa 2002: fig. 1. HOLOTYPE. — Trunk scale (LIG 35-496) ( Fig. 1J ).

ETYMOLOGY. — Composita (Latin): compound, composite.

TYPE LOCALITY AND AGE. — Outcrop 69, bed 26, the Pod”emnaya River section, October Revolution Island, Pod”emnaya Fm., Lochkovian, Lower Devonian.

MATERIAL EXAMINED. — About 100 scales, mainly in the rock.

OCCURRENCE. — Type locality is outcrop 69, bed 26 at the Pod”emnaya River: the upper part of the Pod”emnaya Fm., Lochkovian, Lower Devonian. T. composita n. sp. scales are also found in the upper part of the Pod”emnaya Fm. outcropping at the Spokojnaya River.

DIAGNOSIS. — Comparatively large scales (1.0- 3.3 mm). Head scales with high, ridged, sometimes thorn-like crown and high base. Transitional scales have crowns of oval, “oak-leaf” form, or ridged, with separated posterior area and forward displaced base. Trunk scales, the largest, to 3.3 mm long. Crown form very variable. Some scales have composite crowns, with distinct shorter central area and wide marginal strip, divided into separate parts, ornamented with short ridgelets. Lower side of crown plate covered with longitudinal ribs. Anterior part of base large, with spur-like projection. Crowns of other morphologic varieties consist of the central area and one or two pairs of laterals. Lower surface of crown plate with strong longitudinal ribs. Base may reach a large size.

DESCRIPTION

The set of principal morphologic varieties of scales ( Fig. 1 ) was composed using isolated scales not taken from associated specimen ( Fig. 2 ). Surfaces of sandy siltstones resistant to dissolution have yielded numerous scales of two species, Turinia composita n. sp. and Nikolivia elongata . Head scales with rather high, ridged, more symmetrical crowns, having a truncated ( Fig. 1A ) and asymmetric thorn-like tips ( Fig. 1B ) have been found. Neck is low, base is high.

To transitional scales are ascribed two varieties, with “oak-leaf” crowns ( Fig. 1C ) and ridged crowns with distinct posterior area and large, anteriorly placed base ( Fig. 1D ). This scale type, already defined earlier as transitional, however, based on unusual crown structure, was identified as Turinia sp. indet. (Karatajūtē- Talimaa 1978: pl. XLII, fig. 3).

Trunk scales display a great diversity. Several main morphologic types can be recognized:

– type A: crown consists of short central area and wide marginal strip, divided into separate parts ( Fig. 1E, J ) and ornamented with short ridgelets;

– type B: crown comparatively monolithic, with high ribbed neck; crown plate smooth, its posterior edge finely notched; base large, flattened, anteriorly vaulted ( Fig. 1G, K );

– type C: crown covered with longitudinal ridgelets ( Fig. 1F, H, J, M, N, Q, S ); narrow central area higher, compared to remaining plate; the lower crown surface contains distinct longitudinal ribs; neck clearly developed; base strongly in advance of crown, large to moderately large, sometimes with marginal ledges ( Fig. 1N, Q );

– type D ( Fig. 1R, V ): crown elongated, with large smooth ( Fig. 1R ) or concave central area ( Fig. 1V ) and pair of narrow laterals with small laterally pointed tips;

– type E: crown large, flattened, with smoothened (rounded) ridges ( Fig. 1P ); base low, striplike;

– type F: narrow, modified scales with ridged crown ( Fig. 1 U-Y), displaced posteriorly; base small ( Fig. 1U, V, T ) or strongly anteriorly extended, spur-like ( Fig. 1O, X, Y ).

COMPARISON

T. composita n. sp. scales, especially trunk scales, are the largest as compared with other

Turinia species, distributed within the Lower Devonian of the northern hemisphere. The maximum length of trunk scales are: Turinia pagei 1.9 mm, T. polita 1.5 mm, T. composita n. sp. 3.3 mm. A similar length (3.5 mm) is reached also by trunk scales of Turinia gondwana Turner, 1988 (in Gagnier et al. 1988) from the Lower Devonian Catavi Fm. of Bolivia ( Gagnier et al. 1988), whereas the trunk scales of Turinia australiensis Gross, 1971 from the Pragian of Australia do not exceed 1.6 mm ( Gross 1971). Trunk scales of the A, B and C types are only characteristic for T. composita n. sp. and are not observed within the squamation of other species. Head, transitional and trunk scales of types D and F are identical in form to those of T. pagei . Generally, crown structure of T. composita n. sp. is more complex as compared with T. pagei and especially with T. polita . Most scales also have more complicated bases. The scale in Fig. 1V is nearly identical in form to T. gondwana , referred by Gagnier et al. (1988: fig. F).

Several scales of T. composita n. sp. resemble in crown complexity and general shape scales to Turinia antarctica Turner & Young, 1992 from the Middle Devonian of Antarctica, and also to other Turinia species, which have large scales and are characteristic of the Middle and early Late Devonian of Gondwana ( Gross 1971; Turner & Dring 1981; Long et al. 1988; Turner & Young 1992; Turner 1997).

Genus Boreania Karatajūtē- Talimaa, 1985

TYPE AND ONLY SPECIES. — Boreania minima Karatajūtē- Talimaa, 1985. The new genus and species Boreania minima were briefly described in 1985. B. minima was also considered characteristic of thelodont assemblages from the Pod”emnaya Fm. of the October Revolution Island (Karatajūtē- Talimaa 1985).

OCCURRENCE. — Middle part of the Pod”emnaya Fm. (Lochkovian) of October Revolution Island (Matusevich River, outcrop 4, bed 3). Boreania minima scales are found together with scales of Goniporus alatus (Gross, 1947) in a sample from talus of outcrop 45 in the Krasnaya Bukhta section, Pridoli, Upper Silurian. It also occurs in lower Dittonian of the Welsh Borderland ( Turner 1984, 1999), in the.

Tilze Fm. and basal part of the Stoniskiai Fm. in Baltic, Domachevo Fm. of the Brest Depression (Western Byelorussia), and the lower part of the Ovinparma Regional Stage in the Polar Urals. The North Timan Subregion (the Velikaya River section) has yielded B. minima together with Katoporodus timanicus (Karatajūtē- Talimaa, 1967) from the second Member of the Eptarma Fm., whereas it occurs in the Varandei-Adzva Zone of the Khoreyver Depression (Timan-Pechora region) – from the uppermost Silurian – together with scales of Katoporodus lithuanicus (Karatajūtē- Talimaa, 1967). Many boreholes of the Timan-Pechora region bore Boreania scales from Lower Lochkovian sequences ( Talimaa 2000).

DIAGNOSIS. — Small scales – circular, oval, rhombic, keel-like – 0.2-0.8 mm long. Head scales circular or irregularly shaped, having low, flattened crown with notched margins. Crown of transitional scales flat. Central anterior area separated from laterals by deep cuts. Trunk scales larger, with elongated crown, composed of longer central area and pair of laterals. Scales of all morphologic types with distinct, but low necks. Bases of circular or irregular form, smaller than crowns, convex, anteriorly vaulted and displaced forward. Short spur-like process observed only on several trunk scales. Pulp opening centrally in the base or displaced slightly posteriorly. Pulp cavity small, of complicated outline, with pocket-like branches. Dentine tubules comparatively smooth, long, parabasally widened.

COMPARISON

In scale size, general shape, crown ornamentation, size and form of base, size and displacement of pulp opening, resembles scales of Thelodus Agassiz, 1839 , especially several morphologic varieties of T. sculptilis Gross, 1967 . In presence of single pulp cavity and in form, diameter and branching style of dentine tubules, Boreania scales can be attributed to the “ Thelodus ” histologic type. Widened proximal parts of dentine tubules complicate outline of pulp cavity. This feature slightly links Boreania with Turinia scales, and strongly separates them from the other genera of Thelodontida , having a large pulp cavity with distinct outline ( Thelodus , Apalolepis Karatajūtē- Talimaa, 1967, Nikolivia Oervig, 1969 and Amaltheolepis ). This suggested placement of Boreania within family Turiniidae .

Boreania minima Karatajūtē- Talimaa, 1985

( Figs 3 ; 4 A-H; 5)

For synonymy see Karatajūtē- Talimaa (1985: 54).

HOLOTYPE. — Trunk scale (LIG 35-456) ( Fig. 3R ).

TYPE LOCALITY AND HORIZON. — Matusevich River, outcrop 4, bed 3. Pod”emnaya Fm., Lochkovian.

MATERIAL EXAMINED. — About 500 well-preserved scales.

OCCURRENCE. — B. minima scales are found on the Severnaya Zemlya Archipelago only on October Revolution Island (outcrop 4, bed 3 at the Matusevich River, middle part of the Pod”emnaya Fm., Lochkovian, Lower Devonian and in a sample from talus of outcrop 45 of the Krasnaya Bukhta section, Pridoli, Upper Silurian).

DIAGNOSIS. — As for genus.

DESCRIPTION

Morphology

The set of principal morphologic varieties is shown in Fig. 3 . Transitional or trunk scales are very conventional.

Head scales ( Fig. 3 A-C, E) may be circular or of irregular form, asymmetric, with lower or higher spine-like crown and lateral ledges all around margins or situated only anteriorly. Base of moderate height with centrally placed pulp opening. Neck distinct, but low. Transitional scales ( Fig. 3D , F-H, K, M, O) with comparatively monolithic, flat crown having sharp short anterior cuts. Asymmetric scales may have unequal numbers of cuts on each side ( Fig. 3D ). Some transitional scales have more distinctive central area. Lateral crown areas displaced slightly lower. Distal crown area flat, three- or five-pointed ( Figs 3M ; 4A, B ). Base may be high ( Fig. 3F, K ), equally convex or with central convexity. Several scales have bases smaller than crowns ( Fig. 3M ), the bases protruded anteriorly.

Trunk scales crowns ( Figs 3I, J, L, N , P-Z; 4C-H) more elongated and more distinctly divided into central and lateral areas. Crown ornamentation varies widely. Type A ( Figs 3I, J, N, V ; 4D, E ): crown rather monolithic, elongated, with deep anterior cuts; crowns overhang base posteriorly; posterior crown tip monopointed. Type B ( Figs 3L , P-T, Y, Z; 4C, H): anterior central area higher than laterals and separated from them by groovelets extend- ed throughout the crown; distal crown part three- or five-pointed with enlarged central area. There are scales with keel-like crowns ( Figs 3W ; 4F, G ), having medial area separated by deep grooves. Bases of all varieties, ascribed to trunk scales, are low, anteriorly vaulted, rarely developing short spur-like projection. Neck low.

Histology

Vertical sections of two trunk and one transitional scale are shown in Fig. 5 . Pulp cavity comparatively small. Dentine tubules long, rather smooth, linear, branching at several levels. Proximal canal edges widened, as a rule, complicating outline of pulp cavity.

COMPARISON

Comparison is given with the generic description.

Family NIKOLIVIIDAE Karatajūtē- Talimaa, 1978

Genus Nikolivia Karatajūtē- Talimaa, 1978

TYPE SPECIES. — Nikolivia oervigi (Karatajūtē- Talimaa, 1967).

Figures

FIG. 1. — Turinia composita n. sp., set of scales; A, B, head scales; C, D, transitional scales; E-I, K-N, P-S, trunk scales; J, trunk scale (holotype); O, T-Y, undivided trunk and fin scales; A, B, scales in lateral view; C-H, J-M, O, R, T, V, X, Y, scales in crown view; I, P, scales in anterior-lateral view; N, Q, S, U, W, scales in base view; collection numbers: LIG 35-492-LIG 35-516 (holotype J: LIG 35-496). Sample 69-26, Pod”emnaya River, Pod”emnaya Formation, Lochkovian, Lower Devonian. Scale bar: 0.3 mm.

FIG. 2. — Turinia composita n. sp., scales on the surface of sandy siltstones of bed 26, outcrop 69, Pod”emnaya River, Pod”emnaya Formation, Lochkovian, Lower Devonian. Scale bar: 2 mm.

FIG. 3. — Boreania minima Karatajūtē-Talimaa, 1985, set of scales (see Karatajūtē-Talimaa 1985: fig. 1); A-E, head scales; F-H, K, M, transitional scales; I, J, L, N-Z, trunk scales; A-E, G-J, L-Z, scales in crown view; F, K, scales in lateral view; collection numbers: LIG 35-433, LIG 35-434, LIG 35-436-LIG 35-444, LIG 35-447, LIG 35-449-LIG 35-456, LIG 35-458-LIG 35-464 (holotype R: LIG 35- 456). Sample 4-3, Matusevich River, Pod”emnaya Formation, Lochkovian, Lower Devonian. Scale bar: 0.2 mm.

FIG. 4. — A-H, Boreania minima Karatajūtē-Talimaa, 1985; A, B, transitional scales; C-H, trunk scales; A-C, E-G, scales in crown view; D, scale in lateral view; H, scale in base view; collection numbers: LIG 35-808-LIG 35-815; I-R, Canonia sp. cf. C. grossi Vieth, 1980; I-O, scales in crown view; P-R, scales in base view; collection numbers: LIG 35-816-LIG 35-825. Sample 4-3, Matusevich River, Pod”emnaya Formation, Lochkovian, Lower Devonian. Scale bars: A-H, 0.1 mm; I-R, 0.1 mm.

FIG. 5. — Boreania minima Karatajūtē-Talimaa, 1985, histological structure of scales; A, vertical longitudinal section of trunk scale with high base (see Karatajūtē-Talimaa 1985: fig. 2), No. 1089; B, vertical transverse section in anterior part of transitional scale, No. 1074; C, vertical longitudinal section of trunk scale, No. 1091. Sample 4-3, Matusevich River, Pod”emnaya Formation, Lochkovian, Lower Devonian. Abbreviations: b, base; cr, crown; dt, dentine tubules; pcv, pulp cavity. Scale bars: 0.1 mm.