FOSSIL INSECTS FROM THE JURASSIC DEPOSITS OF THE CENTRAL KUZBASS REGION

I. V. LEBEDEV

Introduction

The insect impressions described in the present note were collected by the author in 1945. Almost all of them were found on the left bank of the Tom’ River, 3.3 km below the village of Chernyi Etap, in exploratory ditch No. 7, and only a single specimen of a nymph of Mesoleuctra gracilis was obtained from the core of borehole Yu-31, drilled in the village of Rodnichki, Leninsk-Kuznetskii District.

The sediments exposed along the Tom’ River belong to the Sartakovo member of the conglomerate suite, while the sediments opened in the village of Rodnichki belong to the Barashevo member of the same suite. According to paleobotanical data, the age of the former is Middle Jurassic, and that of the latter is Lower Jurassic.

Near the village of Chernyi Etap, the insect remains have been preserved in a light-yellow argillite possessing very fine lamination, caused by alternation with coarser-grained material of pelitic-aleurolitic and aleurolitic composition. In the village of Rodnichki, rocks of the same composition are represented, but they have a greenish-gray color.

In the collection described there are only three species of insects in all; nevertheless, the fauna is of great interest, since it provides additional material for correlating the conglomerate suite of the Kuzbass with the deposits of the Cheremkhovo Formation of the Irkutsk Basin.

Description of the Material

Order Homoptera

Pseudocossus zemcuznicovi Mart.

Fig. 1.

Pseudocossus zemcuznicovi Mart. [2, p. 94, pl. VII, figs. 1–3].

The collection contains one incomplete impression of a forewing, the basal part of which is considerably narrower than the membrane. The latter at first widens (to Cu₂), and then rapidly narrows. The venation of the wing membrane found in Kuzbass coincides with the venation of the specimen figured in the work of A. V. Martynov. Radius R and the sector of the radius RS are almost parallel and simple. Median M divides into two branches, each of which, in turn, also divides into two branches. M₁ near the base is connected with RS, M₄ with the cubitus at the place of its division into two branches. The basal part of the wing has not been preserved in full, and its venation differs somewhat, which apparently is to a considerable degree connected with subsequent deformation. Thus, in our impression the costal field appears narrower, the costa itself appears narrow and weaker, the longitudinal depression between C and RS is almost not expressed, and the node N, apparently, was lower than in the specimens from the Irkutsk Basin.

The entire surface of the impression is covered with punctate depressions corresponding to traces of spines that covered the wing. Traces of spines have not been preserved on the veins.

The length of the preserved part of the wing reaches 33 mm, the greatest width—20 mm.

Pseudocossus zenczienicovi is known only from Ust-Baley.

Order Plecoptera

Samarura gigantea Brauer etc.

Fig. 2

Samarura gigantea Brauer etc. [1, p. 7, fig. 6].

The collection contains one impression representing the abdominal part of a larva. The head, thorax, and also part of the limbs have not been preserved. The length of the abdomen is 15.5 mm, the width—2.5 mm. The hind limbs are short, reaching only as far as the sixth abdominal segment. At the end of the abdomen there is an impression of two oval, lamellar tracheal gills, the length of which is equal to the length of the last two abdominal segments (2.5 mm).

The specimen described is identical with the image of the larva of Samarura gigantea given by Brauer et al. in fig. 6. Larvae of Samarura minor, close to this species, differ from our specimen in the presence of a keel on the tracheal gills and in relatively longer limbs. Samarura gigantea was described from Ust-Baley.

Order Plecoptera

Mesoleuctra gracilis Brauer etc.

Figs. 3 and 4

Mesoleuctra gracilis Brauer etc. [p. 9, fig. 11]

The collection contains more than two dozen impressions of nymphs, which do not differ from the forms described by Brauer from Ust-Baley under the name Mesoleuctra gracilis. The sizes of the nymphs reach 11–17 mm, but specimens of 15–16 mm predominate. The limbs are poorly preserved on the impressions, but on some they are present. The hind pair of legs reaches 9 mm in length, the forelegs are somewhat shorter. The antennae are thin, long, reaching 12 mm. The caudal filaments likewise reach 12 mm in length. On some impressions of nymphs there are traces of wing buds, which project somewhat to the side. Mesoleuctra gracilis was described from Ust-Baley.

Conclusion

In the Middle and Lower Jurassic deposits of Kuzbass, impressions of three species of insects have been found, belonging to three different orders. All these insects were previously known from the Jurassic deposits of Ust-Baley, belonging to the Cheremkhovo Formation (lower suite) of the Irkutsk coal basin, and on the basis of the finds of these insects the sediments of the Sartakovskaya member of the conglomerate suite should be regarded as an analogue of the Cheremkhovo Formation.

References

1. Brauer T., Redtenbacher I. und Ganglbauer.—Fossile Insecten aus der Juraformation Ost-Sibiriens. Mem. de l’Acad. Imper. des Sci de St. Petersbourg. VII serie. Tome XXXVI, No. 11, 1889.

2. Martynov A. V.—On the knowledge of Jurassic Palaeontinidae Handl. Morphology, systematic position, and description of a new genus from Ust-Baley, Yearbook of the Russian Paleontological Society, vol. 9, 1925.

Fig. 1, 2, 3, 4