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  • 1.
    Doguzhaeva, Larisa
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Dunca, Elena
    Swedish Museum of Natural History, Department of Paleobiology.
    Siphonal zone structure in the cuttlebone of Sepia officinalis2015In: Swiss Journal of Palaeontology, article id 10.1007/s13358-015-0085-yArticle in journal (Refereed)
    Abstract [en]

    The evolutionary process through which the siphonal zone of the cuttlebone of Sepia replaced the tubular siphuncle seen in other shelled cephalopods is poorly understood. Recently, porous connecting stripes, interpreted as homologous to connecting rings of tubular siphuncles, were revealed in Sepia (Acanthosepion) cf. savignyi (Geobios, 45:13–17, 2012). New data on the siphonal zone structure are herein demonstrated through SEM testing of 16 beach-collected cuttlebones ofSepia officinalis from Vale do Lobo, southern Portugal. In examined cuttlebones, the organic connecting stripes are mineralized along their peripheries where they are attached to septa by inorganic–organic porous contacting ridges. The contacting ridges consist of globular crystalline units within an organic matrix; each globule is a stack of rounded alternating organic and mineralized microlaminas parallel to the septal surface; mineralized microlaminas contain carbonate microgranules. Porous connecting stripes together with the contacting ridges may serve as transport routes for the cameral liquid used in buoyancy regulation. The contacting ridges appear to reinforce contacts between the connecting stripes and septa, and may strengthen shell resistance to changing environments. Lamella–fibrillar nacre in septa is demonstrated in Sepia for the first time. Comparison of Sepia and Spirula reveals the common character of their phragmocones, the slit-like shape of the permeable zones between chambers and the siphuncle. Narrowing of the permeable zones may provide shell resistance to high hydrostatic pressure; however, the essentially dissimilar relative length of the permeable zones may results in different capabilities of two genera for buoyancy regulation. In Sepia, long narrow porous inorganic–organic permeable connecting stripes and contacting ridges may allow for rapid buoyancy regulation which would lead to environmental plasticity and higher species diversity.

  • 2.
    Doguzhaeva, Larisa
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Mapes, Royal
    North Carolina Museum of Natural Sciences.
    Arm hooks and structural features in the Early Permian Glochinomorpha Gordon 1971, indicative of its coleoid affiliation.2014In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931, article id DOI: 10.1111/let.12091Article in journal (Refereed)
    Abstract [en]

    Data on the re-examined-type specimens of the Early Permian Glochinomorpha stifeli Gordon 1971 (Coleoidea, Cephalopoda) gives new insight into the evolutionary origination of gladius-bearing coleoids in the Late Palaeozoic and suggests their parallel evolution with the belemnoids and phragmoteuthids. The iron-oxidized arm hooks are found in front of a gladius on an un-illustrated paratype (USNM 170614). Theyare dispersed in a maximum distance equal to 2.5 the gladius length from the incomplete anterior end of the rachis of the gladius. The hook height ranges from less than 1 mm to as much as 4 mm. They have a massive curved base, and a strongly curved shaft with a long thin distal part. The hooks confirm the cephalopod and the coleoid affiliation of G. stifeli that is widely rejected. The iron-oxidized gladii (preserved length is less than 20 mm) show micro-laminations and a fibrous ultrastructure; the fibre bundles are approximately 0.5 lm thick. Lack of calcium and the high content of nitrogen (up to 12% of total weight) confirm the originally non-biomineralized (apparently chitin) composition of the gladii suggested by their fibrous ultrastructure. These data lead to the conclusion that in the evolutionary history of gladius-bearing coleoids, the biomaterial (biochemical) development of the skeleton preceded its morphological transformation. This phenomenon resulted in a recombination of an advanced composition (being non-biomineralized) with archaic features (sensu morphological structure of the posterior part) in the gladius of G. stifeli. The data castdoubt on the hypothesized origination of a gladius from a phragmoteuthid pro-ostracum as well as the evolutionary origination of the gladius-bearing coleoids from pro-ostracum-bearing phragmoteuthids or belemnitids.

  • 3.
    Doguzhaeva, Larisa
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Mapes, Royal
    American Museum of Natural History, USA.
    Beak from the body chamber of the Early Carboniferous (Visean) shelled longiconic coleoid (Cephalopoda) from Arkansas, USA: -2017In: Lethaia: an international journal of palaeontology and stratigraphy, ISSN 0024-1164, E-ISSN 1502-3931Article in journal (Refereed)
    Abstract [en]

    Here we report the discovery of an Early Carboniferous (Late Visean) 3D cephalopod beak displaying significant similarity to the lower beak of Recent coleoids. It was uncovered in a fragmentarily preserved, longiconic shell from the Moorefield Formation in Arkansas, USA. This shell comprises a fractured 29-mm-long body chamber having a maximum diameter of ~14 mm and showing an indistinct pro-ostracum-like structure. The beak-bearing shell could easily have been mistaken for a bactritid or orthocerid if it were not for a coleoid-type, weakly mineralized, evidently organic-rich shell wall which shows a lamello-columnar ultrastructure of a bulk of shell wall thickness and plate ultrastructure of thin outer layer. The specimen is assigned to an as-yet unnamed shelled coleoid of a so far unknown high-level taxonomic group. A partially exposed, 4.0-mm-long portion of the beak is the lower beak in oblique view from its left side. It exhibits fractured anthracite-like black, apparently originally chitin material, helmet-like general shape, broad hood with narrow shallow median groove and small notch posteriorly, pronounced pointed, non-biomineralized upside belt rostrum, high shoulder and about a 90–100 degrees jaw angle. A broad hood and massive rostrum emphasize its similarity to the lower mandible of Recent Vampyroteuthis and signify that its unique, among living coleoids, structure has been existed for at least since Late Visean time (~333 my).

  • 4.
    Doguzhaeva, Larisa
    et al.
    Swedish Museum of Natural History, Department of Paleobiology.
    Mutvei, Harry
    Swedish Museum of Natural History, Department of Paleobiology.
    The Additional External Shell Layers Indicative of “Endocochleate Experiments” in Some Ammonoids2015In: Ammonoid paleobiology: From anatomy to ecology / [ed] Ch. Klug et al., Dordrecht: Springer, 2015, 2nd, p. 585-609Chapter in book (Refereed)
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