MILIOLIDAE - Acta Palaeontologica Polonica

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28 EWA LUCZKOWSKA cont. 1 I 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 17 TrilocuZina anguZaris X X X X X f--- - eggeri X t--- gibba X X X X X t--- gUbkini X intermedia X X X neu,dorfensis X X X t--- - : georgiana \faridentella - lateZacunata pseudocostata reussi rosen rotunda , ... , sarmatica Sigmoilinita tenuis x " x \. X tenuissima x t--- tschok rakensis X x t--- sp. - Ntlnlmoloculina contraria Spirosigmoilina x X t--- - erenata x x t--- speciosa x x I-- t--- DETAILED PART MORPHOLOGY OF TESTS Three factors contribute to the diversity of shapes in the Miliolidae: morphological variability, dimorphism and ontogeny. They do not act all at the same time in particular species, but are all related to each other to a certain degree. For example, various sizes of tests may point to the presence of specimens representing different ontogenetic stages, from the juvenile to the gerontic one (this is visible only in sections), but they may also reflect specific environmental conditions responsible now for a larger now for a smaller growth of tests in the same species (e.g. Sarmatian species Varidentella reussi or V. rotunda). Dimorphism also influences the diversity of shapes to some extent. Although the micro and mega I generations cannot be distinguished one from another on the basis of their size and shape (Part I, p. 348), the mega II generation may stand out as specimens which are small but higher than the other generations of this species (e.g. in Quinqueloculina anagallis, Text-fig. 7/5, or Q. buchiana, PI. IV, Fig. 2). As regards morphological variability, it is observed in most species, chiefly in the form of variation in the shape of tests, elongated, widened or rounded to a various degree, and that of ornamentation, e.g. the number
<strong>MILIOLIDAE</strong> FROM MIOCENE OF POLAND 29 of ribs or striae, or their presence only in some specimens of a given species. There are only few species which have little varying morphological characters, e.g. Quinqueloculina regularis (Text-fig. 21/1, 2), Q. pygmaea (Text-fig. 21/3, 4) or Siphonaperta ovalis (Text-fig. 34/3). Cycloforina contorta is one of the most variable species as regards morphology. The periphery of its chambers has two longitudinal edges, which are sharp in typical forms but may be rounded to a various degree in other specimens (Text-fig. 26). Similarly, Cyclojorina vermicularis may have an angular truncate periphery or a more rounded one without any signs of the angles (Text-fig. 32). The ribs on the chamber surfaces in Lachlanella incrassata may be either well or ill developed (Text-fig. 33/1, 2). Sigmoilopsis foeda may be regularly oval or S-shaped (PI. XV, Figs 3, 4) and Triloculina intermedia has either keeled chambers or their edges are rounded (PI. XXIII, Fig. 1), etc. Great variation in shape is especially frequent in Sarmatian species, like Varidentella reussi (Text-fig. 49), Cycloforina karreri ovata (Text-fig. 30) or some species of Articulina (e.g. A. problema, A. multibullata and A. sarmatica). Some attention should also be given to the variation in the shape of the aperture and tooth, especially in such genera as Cycloforina, Miliolinella, Pyrgo, Pyrgoella and Varidentella. In Cycloforina the variable shape of the aperture occurs in the species that have the last chamber unextended and as a result the aperture may be round with a narrow tooth or slightly flattened at the base with a somewhat broader square tooth (e.g. in Cycloforina suturalis, C. toreuma, C. predcarpatica and C. stomata). In Miliolinella the shape of the tooth is differentiated and it assumes the form of a fairly broad or narrow apertural plate, e.g. in M. valvularis (PI. XX, Figs 4, 5). This is also true of Pyrgoella, whose apertural plate may be narrowed so much as to become a tongue-shaped tooth, as in P. controversa (PI. XXI, Figs 4-6). In Pyrgo the variation of the apertural shape can be seen particularly well in P. amphiconica (PI. XX, Figs 6-8), in which the width of aperture may be nearly equal to the diameter of the test. The most variable shape of the aperture and tooth is observed in the genus Varidentella, whose aperture ranges from a transverse slit with a broad tape-shaped tooth to a large semicircular opening with a short square tooth (e.g. in Varidentella sarmatica or V. latelacunata). ONTOGENY The ontogenetic stages can be observed in transverse sections, which show the shape of the chambers from the juvenile stage to the adult one, whereas the structure of the aperture and tooth in an early stage is exposed by the removal of the external chambers.
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