Late Emsian Rutoceratoidea (Nautiloidea) from the Prague Basin, Czech Republic: morphology, diversity and palaeoecology

Abstract

Nautiloids of the superfamily Rutoceratoidea from the late Emsian (late Early Devonian) of the Prague Basin (Czech Republic) are commented upon. Species recognized include the hercoceratids Hercoceras mirum, H.? transiens, Ptenoceras proximum, P. nudum, P. minusculum and Anomaloceras anomalum, as well as the rutoceratids Adelphoceras bohemicum, Homoadelphoceras devonicans, Pseudorutoceras bolli and Goldringia? devonicans. In addition, four new species are described: Parauloceras regulare sp. nov., Roussanoffoceras chlupaci sp. nov., Otomaroceras sp. nov. and Goldringia sp. nov. Morphology and distribution patterns of Pragian and late Emsian rutoceratoid faunas from the Prague Basin are compared. They show that an increased diversity was accompanied by a higher level of specialization of rutoceratoids, which manifested itself in low abundance, increased facies dependence and greater variation in shell size during the Early Devonian. The evolution of sculpture and a contracted aperture, both regarded as protective adaptive features, was also examined, but no adaptive trend towards more pronounced sculpture and constriction of the aperture was found to have occurred in the Early Devonian. A more distinctive sculpture was, however, observed in shallow-water assemblages of P. proximum in comparison with deeper-water faunules, and two additional cephalopod species were examined in order to obtain comparative data. The presence of distinct sculpture patterns in coeval shallowand deeper-water assemblages suggests limited migration between them and consequently reflects some degree of territoriality in Devonian nautiloids. New data on early shell development in P. proximum are presented. During the Choteč Event, rutoceratoid generic diversity dropped dramatically, one family became extinct and the Early Devonian diversification of the group came to an end. The recovery of nautiloid faunas was slower than that of other cephalopods and associated, unrelated invertebrates. The absence of change in abundance patterns between Pragian and late Emsian rutoceratoid faunas, i.e. prior to and subsequent to ammonoid radiation, suggests that the appearance and radiation of the latter group in the early Emsian did not affect the structure of nautiloid assemblages, i.e. these two clades did not occupy the same niches.

Early ontogeny, anomalous growth, and healed injuries in the Silurian nautiloid Ophioceras Barrande - Implications for hatching and the autecology of the Tarphycerida

“…raised metabolic activity of the organism after hatching. A positive correlation between sculpture development and original content of calcium carbonate in seawater is highly probable (Graus 1974, Vermej 1987, Manda & Turek 2011. This is supported by the development of sculpture in specimens coming from different depth-related facies.…”

“…The difference in sculpture in conchs from shallow and deeper water settings documents partial limited migrations between populations of Ophioceras, a feature known so far only from Early Devonian oncocerid Ptenoceras Hyatt, 1894 (Manda & Turek 2011). A more prominent fine sculpture may be a phenotypic reaction to living in a more turbulent shallow-water domain.…”

Nautiloid cephalopods from the Rickard Hill facies of the Saugerties Member of the Schoharie Formation, eastern New York, USA (late Emsian, Devonian): A case study in taphonomy from glacial erratics

“…From Table 1, we infer that the RHf nautiloid assemblage represented part of a localized, biohermal community occurring along the lower shoreface of an inner shelf patch reef and was comprised of a diverse and abundant array of benthopelagic animals (e.g., Brett et al, 2007;Barskov et al, 2008;Manda and Turek, 2011). Other cooccurring and disarticulated benthic invertebrates including brachiopods, corals, and trilobites support this interpretation (Williams, 1980;Fagerstrom, 1983;Brett and Baird, 1986;Kaufmann, 1998;Becker and Bartholomew, 2013).…”

“…An alternative explanation proposed in this study for the large size of the nautiloids found in the RHf assemblage and Table 1 may be related to a life and reproductive strategy in which small juveniles lived separately and in a different depositional environment. Examples of juvenile and adult nautiloids from the Devonian occurring in different depositional environments that support this explanation include: 1) Wadleigh Formation of southeastern, Alaska, and Holy Cross Mountains near Chęciny, Poland, that contain multiple beds and concretions of concentrated juvenile nautiloids (Soja et al, 1996;Rakociński and Borcuch, 2016); 2) Cherry Valley Limestone of central New York that contains concentrations of large co-occurring orthoconic nautiloids and ammonoids (Klofak, 2002); and, 3) Třebotov and Choteč Limestones of the Prague Basin, Czech Republic that contains both juvenile and adult coiled nautiloids separated into distinct size populations (Manda and Turek, 2011). Proposed life and reproductive strategies in these studies that resulted in separation of juvenile and adult populations included: spawning, predation, and the efficiency of calcification in embryonic nautiloids in warm shallow water.…”

Environmental impact on ectocochleate cephalopod reproductive strategies and the evolutionary significance of cephalopod egg size

“…This is particularly true for ammonoids in which the strategy of early ontogenetic stages (expressed in protoconch and ammonitella size, shape, and ornament) was crucial for survival through extinction events and consequent quick radiation of survivors in contrast to slow recovery of nautiloid fauna (House 1996, Manda & Turek 2011.…”