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1. A new stem-octopod (Coleoidea: Cephalopoda) from the Late Jurassic Eichstätt Archipelago – juveniles or dwarfed adults?

Author

Fuchs, Dirk and Heyng, Alexander

Abstract

Teudopsinia grossheidei n. sp. from the Tithonian Eichstätt plattenkalks represents a new gladius-bearing species of the suborder Teudopseina (Teudopsidae), which is positioned as part of the octopod stem-lineage. This Late Jurassic record of Teudopsinia pushes the stratigraphic occurrence of the genus back by about 60 million years. None of the five recorded gladiuses is longer than 40 mm suggesting the specimens are either juveniles or dwarfed adults. The soft part morphology, specifically the relative arm length and putative gonads in the rear of the mantle, give conflicting ontogenetic information on the age of these squid-like octopods. The relatively short arms might indicate an immature life stage, while the absence of larger gladiuses combined with putative gonads indicate that the studied specimens represent adults of a very small-sized species.

Published
2024
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8. The Muensterelloidea: phylogeny and character evolution of Mesozoic stem octopods.

Author

Fuchs, Dirk, Iba, Yasuhiro, Heyng, Alexander, Iijima, Masaya, Klug, Christian, Larson, Neal L., Schweigert, Günter, and Brayard, Arnaud

Subjects
BIOLOGICAL evolution, CHARACTER
Abstract

The Muensterelloidea is a superfamily of teudopseid octobrachians with a posteriorly patella‐shaped gladius. A morphometric comparison based on 148 muensterelloid gladii has yielded five new species accommodated in three new genera: Engeseriteuthis arcuatus gen. et sp. nov., Muensterella jillae sp. nov., Muensterella spinosa sp. nov., Tyrionella fauseri gen. et sp. nov. and Muensterellina johnjagti gen. et sp. nov. Cretaceous taxa 'Tusoteuthis' cobbani and 'Muensterella' tonii are re‐combined and placed within the genus Enchoteuthis. We introduce categories for gladius proportions applicable for both muensterelloid and non‐muensterelloid octobrachian gladii. A 2D‐landmark analysis including 64 muensterelloid and non‐muensterelloid gladii statistically confirms that the Muensterelloidea possess the smallest median field sizes of all Mesozoic gladii. We consider the lateral field‐dominated 'gladius' of the family Patelloctopodidae (Patelloctopus, Pearceiteuthis) to be vestigial (i.e. shorter than the mantle length) suggesting that the Patelloctopodidae are the last shared ancestors of incirrate and cirrate octopods. According to a phylogenetic analysis based on 31 gladius characters, the Muensterelloidea mainly consists of the 'Muensterella‐Enchoteuthidae' and the 'patelloctopodid' clade. Ancestral character state reconstructions suggest that an increasing posterior growth front is accompanied by a continuous decrease of the median field length. This milestone in the evolution of the octopod gladius vestige occurred between the Early and Middle Jurassic. The benthic life style of incirrate octopods (including Cretaceous palaeoctopodids) was adopted by Jurassic Patelloctopodidae, which arose from nectonic to nectobenthic teudopseid ancestors. There is currently no evidence to suggest a pelagic origin for benthic octopods. [ABSTRACT FROM AUTHOR]

Published
2020
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9. Environmental changes in northern New Zealand since the Middle Holocene inferred from stable isotope records (delta N-15, delta C-13) of Lake Pupuke

Author

Heyng, Alexander M., Mayr, Christoph, Luecke, Andreas, Striewski, Bernd, Wastegård, Stefan, Wissel, Holger, Heyng, Alexander M., Mayr, Christoph, Luecke, Andreas, Striewski, Bernd, Wastegård, Stefan, and Wissel, Holger

Abstract

Maar lakes in the Auckland Volcanic Field are important high-resolution archives of Holocene environmental change in the Southern Hemisphere mid-latitudes. Stable carbon and nitrogen isotope analyses were applied on bulk organic matter and the green alga Botryococcus from a sediment core from Lake Pupuke (Auckland, North Island, New Zealand) spanning the period since 7,165 cal. year BP. The origin of organic matter was established using total-organic-carbon-to-nitrogen ratios (TOC/TN) as well as organic carbon (delta C-13(OM)) and nitrogen (delta N-15) isotope composition of potential modern sources. This approach demonstrated that the contribution of allochthonous organic matter to the lake sediment was negligible for most of the record. The sedimentary TOC/TN ratios that are higher than Redfield ratio (i.e. > 7) are attributed to N-limiting conditions throughout the record. Variations of nitrogen and carbon isotopes during the last 7,165 years are interpreted as changes in the dominant processes in the lake. While epilimnetic primary productivity controlled isotope composition before 6,600 cal. year BP, microbial processes, especially denitrification and methane oxidation, caused overall shifts of the delta N-15 and delta C-13 values since the Mid-Holocene. Comparisons with climate reconstructions from the Northern Island suggest that changes in the wind-induced lake overturn and a shift to more pronounced seasonality were the most likely causes for lake-internal changes since 6,600 cal. year BP., AuthorCount:6

Published
2012
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