Palaeontology (Impact Factor: 1.8). 02/2007; 50(2):467 - 478. DOI: 10.1111/j.1475-4983.2007.00635.x

ABSTRACT Forty-five specimens of Leptomitus conicus sp. nov. have been collected from the base of the Murero Formation (Caesaraugustan, Middle Cambrian) in the Murero area of Zaragoza, north-east Spain. The new species is a small obconical sponge, which has coarse oxeas forming parallel rods that run the whole length of the specimens in the manner typical of the genus. The biostratigraphy and facies of the levels with Leptomitus conicus have been analysed. Palaeoecological information derived from associated trilobites, brachiopods and ichnofossils shows that L. conicus lived in a soft substrate of a sublittoral environment of low to low/moderate energy. According to established Cambrian palaeogeographical reconstructions, a tropical distribution is inferred for the genus Leptomitus. Based on body shape, wall structure and stratigraphical distribution, a phylogenetic tree of the various Leptomitus species is proposed, with a central stock of simple cylindrical sponges branching out to other morphs.

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    ABSTRACT: E. 2009. Middle Cambrian gogiid echinoderms from Northeast Spain: Taxonomy, palaeo− ecology, and palaeogeographic implications. Acta Palaeontologica Polonica 54 (2): 253–265. DOI: 10.4202/app.2008.0010 Gogia parsleyi Zamora sp. nov. and Gogia sp. are described from two different echinoderm assemblages, both from the middle Cambrian of the Murero Formation (Iberian Chains, NE Spain). Gogia parsleyi is reconstructed and described on the basis of fifteen complete or partial specimens and numerous isolated plates. It is characterised by spiralled brachioles, simple epispires, sometimes covered by stereomic domes or tiny cover plates, and by thecal plates arranged in subregular circlets. This gogiid population comprises juveniles, advanced juveniles and mature individuals. The material was found in the upper part of the Murero Formation (upper Caesaraugustian–lower Languedocian). Gogia sp. is represented by two almost complete specimens and several isolated plates from the lower part of the Murero Formation (lower Caesar− augustian). The genus Gogia was first described in Western Gondwana from the Languedocian (upper middle Cambrian) of France, but the material from Spain is older and represents the oldest record of this genus in Gondwana, suggesting an early migration from Laurentia. The gogiids are well preserved in two echinoderm Lagerstätten, which, together with other echinoderms, comprise the majority of the fossil fauna. Both levels are derived from obrution deposits produced in calm and open marine conditions, sometimes affected by sporadic storms. Their holdfast morphology suggests that these gogiids were low−tier suspension feeders, living attached to trilobite fragments in a soft, muddy environment.
    Acta Palaeontologica Polonica 06/2009; 54(2). · 1.72 Impact Factor
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    ABSTRACT: The Cambrian Substrate Revolution refers to a substantial and “rapid” change to the nature of marine sedimentary substrates in the early Cambrian and is widely interpreted as a biologically-driven event, a direct response to evolutionary innovations in metazoan burrowing and the development of new shelly faunas. However, abiotic factors such as tectonic and climatic evolution also had the potential to restructure Cambrian substrates, and are here shown to be more plausible drivers of change in the benthic faunas of western Gondwana. The western Mediterranean region underwent a southward drift during Cambrian times, which drove a switch from subtropical carbonates to temperate siliciclastic substrates with short-term episodes of temperate carbonate productivity. As a result, microbial and shelly carbonates disappeared diachronously in a stepwise manner across the lower–middle Cambrian boundary interval. Archaeocyathan-microbial reefs were replaced by chancelloriid-eocrinoid-(spiculate) sponge meadows, in which the stepwise immigration of new echinoderm taxa was primarily controlled by extensional tectonic events, first recorded in rifting settings and later in passive-margin platforms. Availability of new kinds of substrate was thus the primary factor that controlled where and when evolutionary innovations in benthic strategies arose. Examples of this include the early Cambrian colonization of phosphatic hardgrounds and thrombolite crusts by chancelloriids, archaeocyathan and spiculate sponges, and the exploitation by benthos to the increasingly widespread availability of shelly grounds and carbonate firmgrounds by early-diagenetic cementation. A microbial mat/epifaunal antagonistic relationship is demonstrated for echinoderm pelmatozoans based on the non-overlapping palaeogeographic distributions of microbial reefs and mats versus mud-sticker pelmatozoans. Cambrian benthic communities thus evolved in parallel with substrates in response to abiotic factors rather than being the primary drivers of substrate change.
    Earth-Science Reviews 03/2013; 118:69-82. · 7.14 Impact Factor
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    ABSTRACT: Esteve, J., Zamora, S., Gozalo, R. & Liñán, E. 2010: Sphaeroidal enrolment in middle Cambrian solenopleuropsine trilobites. Lethaia, 10.1111/j.1502-3931.2009.00205.xFifty specimens belonging to species of Solenopleuropsis and Pardailhania from Spain and France demonstrate sphaeroidal enrolment in Cambrian trilobites for the first time. These solenopleuropsines show novel coaptative structures in different regions of the exoskeleton: in the cephalon there are vincular furrows and notches; in the thorax an articulating facet is developed at the pleural margins, with a ball and socket connection on the adaxial most portion, and an articulating half-ring axially; the pygidium possesses an articulating facet. The interaction of these coaptative structures resulted in a sphaeroidal enrolment that was a progressive act from the first articulation between the occipital ring and the first segment to the pygidial articulating facet. A similar type of sphaeroidal enrolment is observed in the Devonian trilobite Phacops. Both Cambrian and Devonian trilobites developed a vincular furrow in the ventral surface of the cephalon to close their bodies tightly. In both cases, this is probably a convergent adaptation to protect against predators and obrution. Indeed, the enrolled trilobites are very common in obrution deposits restricted to shallow and soft muddy substrates. □Coaptative structures, convergence, Murero Formation, Pardailhania, Solenopleuropsinae, Solenopleuropsis.
    Lethaia 10/2010; 43(4):478 - 493. · 2.49 Impact Factor

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