Geologica Balcanica, 25. I. Sofia, Febr. 1995, p. 61-70 Some fossil cephalopods from the Lovec Urgonian Group at the village of Pusevo, Veliko Tarnovo District (Lower Cretaceous, Central Fore-Balkan) 1 Todor Nikolov 2 1Petar Parashkevanov I 1 Geological-geographic Department, Sofia University "St. Kliment Ohridski", 1000 Sofia 2 5058 Village of Hotnica, Velika Tarnovo District (Received ll.04.1994; accepted 13.05. 1994) T. HuKOA06, II. IlapawKe6a/lo6 - HecKOAbKO ¢occuAbllblX !Je¢aAonoo U3 Ho6e~cKoii ypzoiiCKOii zpynnbl y c. IlyweBo BeAuKomblpllo6cKozo pauo11a ( IIUJICIIUii MeA, l.(ellmpaAblloe Ilpeo6aAKallbe) . OrnolKeHHJI Jioae'!cKoii yproHCKOH rpynnhi O'leHb 6oraTbl .!IBYCTBOp'laThiMH, racTpOllO,!IaMH, JJGIHOH,!IeaMH, KOpaJJJJaMH, XeTeTH,!IaMH, CllOHfiUIMH, aJJhfHliMH, HO cpe,!IH HHX cpaBHHTeJJbHO pe,!IKO BCTpe'!a!OTCJI ue<flaJJOllO,!Ihl. fiOJTOMY OC06hiH HHTepec npe,!ICTaBJIJIIOT HaXO,!IKH HeCKOJihKHX ue<flaJIOllO.!I B MblfblpCKOM KJIHHe DOJirapeHCKOH CBHThl H B ,[(e6eJibUOBCKO­ MJia,!leHCKOM KJIHHe 3MeHcKoi1 CBHThi B oKpecTHOCTJIX c. flyweao BeJIHKOThipHoBcKoro paiioHa. 0HH ,~:~arHpyiOT 6appeMCKHH B03paCT. Abstract. The sediments of the Lovec Urgonian Group are very rich in bivalves, gastropods, echinoderms, brachiopods, corals, chaetetids, sponges, algae, but quite rare in cephalopods. For that reason, the outcrops of some cephalopods in Magara Tongue of the Balgarene Formation and in the Debelcovo-Mladen Tongue of the Em en Forma,tion at the village of Pusevo, Veliko Ta.rnovo District are interesting. They all date the Barremian Age. Introduction The sediments of the Lovec Urgonian Group are very rich in bivalves, gastropods, echinoderms, brachiopods, corals, chaetetids, sponges, algae, but rare in cephalopods (X p H c 'I e B, 1966; H H K o JI o B, 1969). For that reason the findings of some cephalopods with heteromorph ammonite among them in the sediments of the Magara Tongue of the Balgarene Formation represent special interest. The locality is situated at the Drjankov Hill, to the north from the village of Pusevo, Veliko Tarnovo District (fig. 1) . The Magara Tongue of the Balgarene Formation in this section is represented by clayey slightly silty marls with lens of coral limestones. Rare intercalations of calcareous sandstones and sandy oolitic limestones are met in the top part, changing in aphanite and organogenic limestones of the Debelcovo-Mladen Tongue of the Emen Formation to the west. In a separate outcrop, to the south-east from the section studied and to the east from the village ofPusevo, the Barremian ammonite species Valdedorsella haugi B res k., was found in the limestones of the Debelcovo-Mladen Tongue years ago (I-I H K o JI o B, 1969, fig. 2). The character of the Magara Tongue of the Drjankov Hill is determined by the marls predominating the section. Lens of coral limestones are spread among them without any regularity. Usually, most of the lens are parallel or subparallel to the layers, while some of 61 19 · 0 fp 2p 3f1 km I· , - ; ..,.. ._,..r ·' ·- ._. .- ·1 Fig. I. Sketch-map of the investigated area I -principal locality Drjankov Hill the them are located obliguely, resembling chaotic internal structure determined by the landslides of separate lenses (fig. 2) . The thickness of the sediments in the outcrop is 20-25 m increasing from west to the east. The studies association of cephalopod species determined the Late Barremian Age of the locality. The specimens described are preserved in the Museum of Palaeontology at the Sofia University "St. Kliment Ohridski" (MP - US). Systematic Palaeontology Class CEPHALOPODA C u v i e r, 1897 Subclass NAUTILOIDEA A g a s s i z, 1847 Order NAUTILIDA Agassiz, 1847 Superfa mily NAUTILACEAE B I a i n vi I I e, 1825 Family CYMATOCERATIDAE Spath, 1927 Genus Heminautilus S p a t h, 1927 Type species. Nautilus saxbii Morris, 1848, Aptian, England, by original designation ofS path (1927, p. 22). G e n e r i c c h a r a c t e r s. Involute, compressed conchs with distinctly higher whorl section than wide. The lateral flanks are flattened, strongly converging towards ventral area. The venter is fiat or concave, with differently deep furrow, with or without median keel ; the umbilicus is narrow, while the umbilical area is rounded. Remarks. The genus includes also H. lallierianus (d'O r big n y, 1841) and H. sanctaecrucis C o n t e, 1980, besides the type species. The relations between the three species are very interesting but are beyond the purpose of this study. The major differences between them are related with the character of the ventral area mostly (fig. 3) . 62 w E I I -Gil ({ 1<3> (q; 1 ~ 1 p-c!!J it# 1w . --- .A'fr--- u!] a 1 cJ ) ---- -~- - -- - -~--- I I I I I 12 Fig. 2. The section of the Drjankov Hill to the north of Pusevo Village 1 - marls; 2 - limestones; 3 - oolitic limestones; 4 - sandy limestones; 5 - nodular limestones with corals H eminautilus sanctaecrucis C o n t e, 1980 Pl. I, fig . 1; pl. II, fig.•1; pl. III, fig . 1, 2, 2a; pl. IV. fig. 1, 1a, 2, 2a 1859. Nautilus lallierianus d'O r big n y sensu Pi c t e t & Campi c he, p. 148, pl. XIX, fig. 6a, b, c. V pars 1967. Xenocheilus /allierianus (d'O r big n y, 1840) sensu,[{ H M H T p o B a, p. 18, pl. IV. fig. 1, Ia, lb (=K, 1962, non K, 1963 & 1964). 1980. Heminautilus sanctaecrucis nov. sp. C o n t e, p. 138, pl. I, fig. I, 2. 1989. Heminautilus sanctaecrucis Conte, p. 30-31, fig. 5-7. N o m e n c I a t u r e. The holotype is a species from the P i c t e t & C a m p i c h e collection (1858-1860, pl. XIX_, fig. 6). Sainte-Croix (Jura suisse), "Marne jaune", Lower Aptian. 1 Dimensions : D H E L H~ EM L~ KL 1962 en: li M li T p 0 B a, 1967, pl. IV, fig. I, from Lipnica Village) 113 80 53 12 0.70 0.66 0.10 K 6001 (from Pusevo Village) 147 97 59 13 0 . 660 . 610.01 Description. Discoidal compressed involute conchs with average size and narrow umbilicus. The whorl section is considerably higher than wide. The lateral flanks are flat and definitely convergent towards the ventral area, at the end of which edges are formed. These edges are more distinct in the last whorl. In the initial whorls the ventral area is tabulate. By increasing of the shell, a distinct furrow with fine median keel is observed. The burrow itself is surrounded by well defined ventral board edges. The suture line is with a wide and shallow lateral lobe and relatively narrow and slightly curved saddle. C om p a r i s o n s. Heminautilus sanctaecrucis Conte is the closest to H. lallierianus (d' Orb.) differing from it by the development of median keel, as well as for its wider and shallow lateral lobe of the suture line. H. saxbii (M o r r i s) is with a flat and smooth ventral area, narrower and strongly curved lateral lobe and more oblique lateral saddle of the suture line. D i s t r i b u t i o n. Switzerland, France, Bulgaria. Barremian - Aptian. Material and deposits. Upper Barremian: MP- US, K 6001, to the north from the village of Pusevo, Veliko Tarnovo District; MP - US, K 6002, ~bid., MP - US, K 1 1 6003, ibid.; MP- US, K 6004, ibid.; Lower Aptian: MP- US, K 1692 (cool. N. Dimitrova), 1 village of Lipnica, Velikb Tarnovo District. 1 D - diameter; H - height of the last tour; E - thickness of the last tour; L - width of the ventral area. 63 Explanations of plates PLATE I 1. Heminautilus sanctaecrucis C o n t e. Drjankov Hill, Pusevo Village, Magiira Tongue of the Biilgarene Formation. Upper Barremian. MP - US, K, 6001 . PLATE II 1. Heminautilus sanctaecrucis Conte. Drjankov Hill, Pusevo Village, Magiira Tongue of the Biilgarene Formation. Upper Barremian. MP- US, K, 6001. PLATE III 1, 2, 2a. Heminautilus sanctaecrucis C o n t e. Drjankov Hill, Pusevo Village, Magiira Tongue of the Balgarene Formation. Upper Barremian. 1- MP-US, K, 6001 ; 2, 2a- MP-US K, 6002. PLATE IV 1, 1a, 2, 2a. Heminautilus sanctaecrucis Co n t e. Drjankov Hill, Pusevo Village, Magii ra Tongue of the Biilgarene Formation. Upper Barremian. I, Ia - MP-US, K, 6003; 2, 2a - MP-US K, 6004. PLA TE V I, Ia. Heminautilus sa.xbii (Morris). Drjankov Hill, Pusevo Village, Magii ra Tongue of the Biilgarene Formation. Upper Barremian. MP-US, K, 6005. PLAT E VI I. Lithancylus pushevensis sp. n. Holotype, x 0,5. Drjankov Hill, Pusevo Village, Magiira Tongue of the Biilgarene Formation. Upper Barremian. MP-US, K, 6006. PLATE VII 1. Lithancylus pushevensis sp. n. Holotype, x 0,5 . Ibid. PLATE VIII I, 2. Lithancylus pushevensis sp. n. Holotype, x 0,5. Ibid. PLATE IX I. Barremites waageni (S i m i o n e s c u). Drjankov Hill, Pusevo Village, Magiira Tongue of the Bftlgarene Formation. Upper Barremian. MP-US, K, 6007. PL ATE X 1. Barremites sp. D rjankov Hill, Pusevo Village, Magiira Tongue of the Bii lgarene Formation. Upper Barremian. MP-US, K, 6008. 2. Valdedorse/la haugi B res k o v ski. East of the Pusevo Village, Debelcovo-Mladen Tongue of the Balgarene Formation. Lower Barremian. MP-US, K, 305. a b c Fig. 3. Types of suture line and ventral area of the genus Heminautilus (after C o n t e, 1980) a- H. sanctaecrucis Conte; b- H.