_________________________________________________________________________________________________________ Kölner Forum Geol. P<strong>al</strong>äont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, <strong>Liège</strong>, August 19-29, 2011 _________________________________________________________________________________________________________ 80 Unique Early Cr<strong>et</strong>aceous <strong>de</strong>velopment of phaceloid pachythec<strong>al</strong>iines (Scleractinia?, Hexanthiniaria?): Upper Barremian, Bulgaria Bogusław KOŁODZIEJ 1 , Vyara IDAKIEVA 2 & Marin IVANOV 2 1 Institute of Geologic<strong>al</strong> Sciences, Jagiellonian University, Oleandry str., 2a, 30-063 Kraków, Poland; boguslaw.kolodziej@uj.edu.pl; 2 Department of Geology, P<strong>al</strong>eontology and Fossil Fuels, Sofia University, Sofia, Bulgaria; idakieva@gea.uni-sofia.bg, mivanov@gea.uni-sofia.bg The subor<strong>de</strong>r Pachythec<strong>al</strong>iina ELIÁŠOVÁ 1976 (=Amphiastraeina ALLOITEAU 1952) represents an unique cor<strong>al</strong> group among the or<strong>de</strong>r Scleractinia BOURNE 1900 or – as assume some authors – belongs to the subor<strong>de</strong>r Hexanthiniaria MONTANARO-GALLITELII 1975 (e.g. ELIÁŠOVÁ 1976; RONIEWICZ 2008). Their skel<strong>et</strong><strong>al</strong> architecture, especi<strong>al</strong>ly of Late Triassic zardionophyllids, similar to late P<strong>al</strong>aeozoic plerophyllines causes that their rugosan ancestry is <strong>al</strong>so consi<strong>de</strong>red (see RONIEWICZ & STOLARSKI 2001). The other question is the taxonomic position of h<strong>et</strong>erocoeniids, usu<strong>al</strong>ly classified to the subor<strong>de</strong>r H<strong>et</strong>erocoeniina BEAUVAIS 1974, but <strong>al</strong>so to Pachythec<strong>al</strong>iina (e.g., KOŁODZIEJ 2003; BARON-SZABO 2002). Abundant and highly diversified pachythec<strong>al</strong>iines have been recognized recently in three loc<strong>al</strong>ities (Rus<strong>al</strong>ya, Vishovgrad, Zarapovo) of Upper Barremian limestones of the Emen Formation, north-west of Veliko Tarnovo, Centr<strong>al</strong> Northern Bulgaria (Centr<strong>al</strong> Fore-B<strong>al</strong>kan). They represent 14 species (3 new) and 9 genera (3 new) (families: Amphiastraeidae, Carolastraeidae, Donacosmilliidae, ?H<strong>et</strong>erocoeniidae). Most of them – 10 species, 7 genera represent phaceloid (pseudocoloni<strong>al</strong>) growth form (Fig. 1). Particularly common are specimens of the genus Pleurophyllia. Their large skel<strong>et</strong>ons commonly preserved in growth position attain 1 m in high. In contrast, cor<strong>al</strong> assemblages from other loc<strong>al</strong>ities of the Emen Fm and other formations (both siliciclastic and carbonate) contain only cerioid amphiastreids (Amphiaulastraea), and h<strong>et</strong>erocoenids (Latusastraea) (IDAKIEVA 2003). Pachythec<strong>al</strong>iines are known from the Late Triassic to Late Cr<strong>et</strong>aceous. Except of h<strong>et</strong>erocoenids, they were poorly diversified during Cr<strong>et</strong>aceous times. Till now the richest Early Cr<strong>et</strong>aceous pachythec<strong>al</strong>iines were <strong>de</strong>scribed by BARON-SZABO & STEUBER (1996) from the Aptian of Greece. However among 11 species, only 3 are phaceloid. Thus, the assemblage from the Emen Fm dominated by phaceloid forms is the most remarkable during Cr<strong>et</strong>aceous. Pachythec<strong>al</strong>iines, mostly phaceloid, were more common only during Late Jurassic, and are particularly highly diversified in the Tithonian–lowermost Cr<strong>et</strong>aceous Štramberk Limestone (Czech Republic; 35 species, 17 genera; e.g., ELIÁŠOVÁ 1978) and their equiv<strong>al</strong>ents (exotic pebbles/boul<strong>de</strong>rs) in the Polish Outer (Flysch) Carpathians (22 species, 14 genera; e.g., KOŁODZIEJ 2003). The section in the Rus<strong>al</strong>ya quarry provi<strong>de</strong>s the sedimentary and environment<strong>al</strong> context of the pachythec<strong>al</strong>lines-bearing limestones. This section consists of five units: (1) The lower part (ca. 10 m thick) is composed of bioclastic limestone with boundstone patches with sm<strong>al</strong>l cor<strong>al</strong> colonies (without Pachythec<strong>al</strong>iina) and their fragments, cha<strong>et</strong><strong>et</strong>ids, stromatoporoids, microproblematicum Lithocodium aggregatum–Bacinella irregularis, and subordinately microbi<strong>al</strong> crusts; (2) Rudist limestone with bioclastic <strong>al</strong>ternations (ca. 15 m); (3) Bioclastic limestone with cha<strong>et</strong><strong>et</strong>ids, stromatoporoids, subordinately rudists and sm<strong>al</strong>l cor<strong>al</strong>s (without Pachythec<strong>al</strong>iina) (ca. 8 m thick); (4) Biostromes (ca. 2 m thick) composed of <strong>de</strong>nse assemblages of sm<strong>al</strong>l rudists Mathesia dar<strong>de</strong>ri (ASTRE) and cor<strong>al</strong>s, mostly phaceloid pachythec<strong>al</strong>iines, rarely others. Mathesia dar<strong>de</strong>ri and cor<strong>al</strong>s appear to occur mostly as separate patches, but they <strong>al</strong>so occur closely associated (Fig. 1A, B; FENERCI-MASSE <strong>et</strong> <strong>al</strong>. 2011). Associated macrobiota are poorly diversified and consist mainly of gastropods; (5) Limestone composed of large rudists and subordinately cha<strong>et</strong><strong>et</strong>ids (ca. 6 m thick). In gener<strong>al</strong> this section shows a transition from the outer to inner platform. Biostromes built by rudists and Pachythec<strong>al</strong>iina were possibly <strong>de</strong>veloped in the outer part of the platform, but rather in its more inner part, with lower energy, in comparison with the lower part of the section at Rus<strong>al</strong>ya. Environment<strong>al</strong> factors which permitted flourishing growth of sm<strong>al</strong>l rudists and pachythec<strong>al</strong>iine cor<strong>al</strong>s are not well established. Co-occurence of Mathesia dar<strong>de</strong>ri and pachythec<strong>al</strong>iines was recognized only in the Emen Fm in the studied
_________________________________________________________________________________________________________ Kölner Forum Geol. P<strong>al</strong>äont., 19 (2011) M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.) Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, <strong>Liège</strong>, August 19-29, 2011 _________________________________________________________________________________________________________ 81
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