Occurrence of Giant Borings of Osprioneides kampto in the Lower Silurian (Sheinwoodian) Stromatoporoids of Saaremaa,Estonia

The distribution of Osprioneides is more environmentally limited than that of Trypanites in the Silurian of Baltica. Osprioneides probably occurred only in large hard substrates of relatively deepwater muddy bottom open shelf environments. Osprioneides were relatively rare, occurring in 4.7% of all stromatoporoid specimens in that environment, in contrast to small Trypanites-Palaeosabella borings, which occur in 88.4% of stromatoporoids and 88.9% of heliolitid corals. Osprioneides is reported only from the lower Sheinwoodian stromatoporoids of the exposed Silurian of Saaremaa (Wenlock to Pridoli). Osprioneides borings probably played a minor role in the general bioerosion in the Silurian of Baltica.     

Improving the parameterization of stromatoporoid shapes – a detailed approach to stromatoporoid morphometry

Eight specimens of Devonian stromatoporoids with well visible latilaminae arrangement exposed on polished slabs were subjected to a detailed morphometric analysis. The studies have revealed that the so far used stromatoporoid parameterization method leaves a broad field of uncertainty concerning the exact definitions of particular parameters. The possible ways of making the measurements and the propositions of more precise definitions of the parameters used in the method, both of the growth form above the sea bottom and of the whole skeleton are therefore presented in this paper. The B_m - basal length of the skeleton, has been defined as a straight line joining the two ends of the basal surface, which have been pointed basing on the stromatoporoid's overall shape, latilaminae arrangement and angular relation to the main growth axis position in ontogenetical development, length. The B_n - basal length of the growth form above the sea bottom, is to be measured along a straight line joining the ends of the last visible latilamina. From among a number of possible definitions of the V_m - vertical height of the whole skeleton, a straight line joining the initial growth nucleus and the highest point on the specimen's surface above the B_m line has been selected. The V_n - vertical height of the growth form above the sea bottom is defined as the height of the point on the stromatoporoid surface highest above the B_n measured perpendicularly to it. A parameter of burial ratio, BR=(V_m-V_n)/V_m, is introduced.     

湖南邵东中泥盆统棋梓桥组层孔虫生物群及其生态环境

湖南中部泥盆纪地层和生物礁相当发育。湖南邵东中泥盆世棋梓桥期的泥质石灰岩中层孔虫广泛分布,本文共描述邵东廉桥马鞍山棋梓桥期层孔虫12属18种,其中Stromatopora wenshanensis为一新名,代替1982年根据一个云南标本定名为Stromatopora irregularis的种名。 马鞍山礁是—发育在海底平台上的厚度稍有变化的层状礁,马鞍山礁的沉积相变化过程,是由近岸浅海到展状礁普遍发育的开阔台地,再到封闭或半封闭的泻湖或潮坪环境。生物组合和沉积物也随沉积环境的变化而发生相应的变化。     

The limited value of traditional morphometric features in stromatoporoid taxonomy

The morphological variation of stromatoporoids, which are solitary organisms, is partitioned into its presumably genetic and environmental components. Potentially heritable, environmentally mediated and residual components of morphological variability were estimated in a test set containing Devonian stromatoporoids of the genus Gerronostromaria from southern Poland using analysis of variance. The taxonomic importance of traditional morphometric features is limited, because they are dominated by the intra‐skeletal component of variance. Conventional metrics were therefore replaced by stereological and textural quantities. Both stereological and textural features are dominated by the inter‐skeletal and inter‐locality components of variation and thus may be valuable in taxonomic and environmental studies of stromatoporoids. Statistical analyses of these characters (principal component analysis and cluster analysis) were performed. Of 13 characters considered most useful in taxonomic studies, only five have been used previously in conventional species definitions.     

Indigenous demosponge spicules in a Late Devonian stromatoporoid basal skeleton from the Frasnian of Belgium

This paper records the first example of a demosponge spicule framework in a single specimen of a Devonian stromatoporoid from the Frasnian of southern Belgium. The small sample (2.5 × 2 cm) is a component in a brecciated carbonate from a carbonate mound in La Boverie Quarry 30 km east of Dinant. Because of the small size of the sample, generic identification is not confirmed, but the stromatoporoid basal skeleton is similar to the genus Stromatopora. The spicules are arranged in the calcified skeleton, but not in the gallery space, and are recrystallized as multi‐crystalline calcite. The spicules fall into two size ranges: 10–20 μm diameter and 500–2000 μm long for the large ones and between 5–15 μm diameter and 50–100 μm length for the small ones. In tangential section, the spicules are circular, they have a simple structure, and no axial canal has been preserved. The large spicules are always monaxons, straight or slightly curved styles or strongyles. The spicules most closely resemble halichondrid/axinellid demosponge spicules and are important rare evidence of the existence of spicules in Palaeozoic stromatoporoids, reinforcing the interpretation that stromatoporoids were sponges. The basal skeleton may have had an aragonitic spherulitic mineralogy. Furthermore, the spicules indicate that this stromatoporoid sample is a demosponge.     

Early symbiotic rugosan endobionts in stromatoporoids from the Rhuddanian of Estonia (Baltica)

The earliest known symbiotic rugosan endobionts occur in stromatoporoids from the early Rhuddanian of Estonia. The stromatoporoid Ecclimadictyon nikitini from the Tamsalu Formation contains the rugosan Donacophyllum middendorffii endobiont. A stromatoporoid Clathrodictyon boreale from the Varbola Formation contains Streptelasma estonica and Bodophyllum sp. endobionts. There are up to three endobiotic rugosans per stromatoporoid host. Stromatoporoid hosts were beneficial for symbiotic rugosans as elevated substrates on a seafloor that offered a higher tier for feeding; they also offered enhanced substrate stability. Stromatoporoids of the end‐Ordovician mass‐extinction recovery fauna hosted a diverse fauna of symbiotic endobionts. There were few if any negative effects of this mass extinction on the symbiotic endobionts.     

广西六寨中泥盆统台地边缘丘状叠置礁内的层孔虫生物礁

南丹六寨中泥盆统台地边缘层孔虫生物群内的层孔虫头骨有块状、柱状、板状、短粗枝状及皮壳包覆状等五大类型(其中块状又可分为孤立的11种类型和复合的9种类型,它们是丘状礁主要的建造格架块状体),分属8个属,可鉴定15个种。层孔虫大多分布于礁相,少数分布于礁相和非礁相,极少数只在非礁相出现。有三点结论:1.造架层孔虫共骨外形表现出较高的稳固性。这些形态基本上限于礁相。它们都具有较强的生长扩展特征。2.共骨外形在礁相的远较在非礁相的多样化,并具多变性。3.环境中底质性质和沉积速率是造架层孔虫生长发育的制约因素;也是层孔虫格架礁形成和发育规模的制约因索。     

Symbiotic interactions in the Silurian of Baltica

Thirteen symbiotic associations occur in the Silurian of Baltica. Symbiosis was especially prominent among colonial animals, most commonly with stromatoporoids. These sponges hosted the most diverse fauna of endobiotic symbionts (including rugosans, Syringopora, ‘polychaetes’, cornulitids and lingulids). This pattern can be explained by the abundance of stromatoporoids in the Silurian of Baltica and their large skeletal volume, making them attractive hosts for smaller invertebrates. There is an evolutionary trend of an increasing number of different pairs of symbiotic taxa from the Llandovery to the Ludlow, with a remarkable increase in the Ludlow. This is likely related to an increase in the number of mutualistic taxa that could have had evolutionary advantages over organisms less amenable to symbiosis. The number of different pairs of symbiotic taxa also increased in the Wenlock, which may be linked to delayed recovery from the end‐Ordovician mass extinction.     

湖南新邵巨口铺泥盆纪棋梓桥组的层孔虫及其造礁特征

湖南新邵巨口铺泥盆纪生物礁出现在中泥盆统棋梓桥组中上部,根据沉积特征的差异,礁体分上下两部分;下部成层性明显,以厚层生物格架灰岩为主;上部以灰白色块状徽晶一亮晶灰岩为主,灰岩成层性很差,生物也较单调。礁体可划分8种沉积微相,其发展过程有明显阶段性。这些阶段性与礁体群落的发展和演替相联系。它是开阔浅海与台地浅海相变过渡带上的一种层状礁。礁体内有丰富的层孔虫,计16属近40种。该文选择了较为常见、保存较好的10属18种进行了描述和研究。