Phragmoteuthida (Cephalopoda: Coleoidea) From the Lower Jurassic of Dorset, England

Donovan, D. T.

doi:10.1111/j.1475-4983.2006.00552.x

Cited by 23 publications

(22 citation statements)

References 9 publications

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“…It has even been suggested that they were not very active [78], as expected for deepwater organisms [64], [65]. The other coleoid lineage in the Triassic, namely phragmoteuthids, had a limited geographic distribution [78] and, judging from the phragmocone angle [79] and generalization by [75], probably lived in shallower waters. Thus, aulacocerids would have been the only possible prey coleoid group for deep-diving air-breathers.…”

Section: Discussionmentioning

confidence: 99%

Absence of Suction Feeding Ichthyosaurs and Its Implications for Triassic Mesopelagic Paleoecology

Motani

Tomita

et al. 2013

PLoS ONE

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Mesozoic marine reptiles and modern marine mammals are often considered ecological analogs, but the extent of their similarity is largely unknown. Particularly important is the presence/absence of deep-diving suction feeders among Mesozoic marine reptiles because this would indicate the establishment of mesopelagic cephalopod and fish communities in the Mesozoic. A recent study suggested that diverse suction feeders, resembling the extant beaked whales, evolved among ichthyosaurs in the Triassic. However, this hypothesis has not been tested quantitatively. We examined four osteological features of jawed vertebrates that are closely linked to the mechanism of suction feeding, namely hyoid corpus ossification/calcification, hyobranchial apparatus robustness, mandibular bluntness, and mandibular pressure concentration index. Measurements were taken from 18 species of Triassic and Early Jurassic ichthyosaurs, including the presumed suction feeders. Statistical comparisons with extant sharks and marine mammals of known diets suggest that ichthyosaurian hyobranchial bones are significantly more slender than in suction-feeding sharks or cetaceans but similar to those of ram-feeding sharks. Most importantly, an ossified hyoid corpus to which hyoid retractor muscles attach is unknown in all but one ichthyosaur, whereas a strong integration of the ossified corpus and cornua of the hyobranchial apparatus has been identified in the literature as an important feature of suction feeders. Also, ichthyosaurian mandibles do not narrow rapidly to allow high suction pressure concentration within the oral cavity, unlike in beaked whales or sperm whales. In conclusion, it is most likely that Triassic and Early Jurassic ichthyosaurs were ‘ram-feeders’, without any beaked-whale-like suction feeder among them. When combined with the inferred inability for dim-light vision in relevant Triassic ichthyosaurs, the fossil record of ichthyosaurs does not suggest the establishment of modern-style mesopelagic animal communities in the Triassic. This new interpretation matches the fossil record of coleoids, which indicates the absence of soft-bodied deepwater species in the Triassic.

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Section: Discussionmentioning

confidence: 99%

Absence of Suction Feeding Ichthyosaurs and Its Implications for Triassic Mesopelagic Paleoecology

Motani

Tomita

et al. 2013

PLoS ONE

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“…Macfadyen 1941; Barnard 1949; Howarth 1957; Hallam 1960; Zeuner 1962; Palmer 1966; Lord 1974; Whalley 1985) and accounts of individual fossil finds (e.g. Martill 1995; Donovan 1998, 2006; McGowan and Milner 1999). The diversity data from the literature were supplemented by collection records from the British Geological Survey, Keyworth (BGS), Bristol City Museum (BRSMG) and Dorset County Museum, Dorchester (DORCM).…”

Section: Methodsmentioning

confidence: 99%

Completeness of the fossil record and the validity of sampling proxies at outcrop level

Dunhill

Benton

Twitchett³

et al. 2012

Palaeontology

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Most studies of the adequacy of the fossil record have been carried out at a global or continental scale, and they have used sampling proxies that generally do not incorporate all aspects of sampling (i.e. rock volume, accessibility, effort). Nonetheless, such studies have identified positive correlations between apparent diversity and various sampling proxies. The covariation of fossil and rock record signals has been interpreted as evidence for bias or for a common cause, such as sea level change, or as evidence that the signals are in some ways redundant with each other. Here, we compare a number of proxies representing the three main aspects of sampling, (1) sedimentary rock volume, (2) rock accessibility and (3) worker effort, with palaeodiversity in a geographically and stratigraphically constrained data set, the marine Lower Jurassic outcrop of the Dorset and East Devon Coast. We find that the proxies for rock volume and accessibility do not correlate well with the other sampling proxies, nor with apparent diversity, suggesting that the total amount of sedimentary rock preserved does not influence apparent diversity at a local scale, that is, the rock record at outcrop has been sampled efficiently. However, we do find some correlations between apparent diversity and proxies for worker effort. The fact that the proxies do not correlate significantly with each other suggests that none can be regarded as an all‐encompassing sampling proxy that covers all aspects of bias. Further, the presence of some correlations between sampling proxies and diversity most probably indicates the bonanza effect, as palaeontologists have preferentially sampled the richest rock units.

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“…Cephalopod arm hooks from the Mesozoic (onychites) are usually attributed to belemnoids. Rare, articulated belemnoid animal fossils with soft−part preservation show rows of hooks along the arms (Reitner and Engeser 1982;Engeser and Reitner 1992;Donovan and Crane 1992;Doyle and Shakides 2004;Donovan 2006;Klug et al 2009; reviewed by Stevens 2010).…”

Section: Introductionmentioning

confidence: 97%

Large onychites (cephalopod hooks) from the Upper Jurassic of the Boreal Realm

Hammer¹,

Hryniewicz²,

Hurum³

et al. 2012

APP

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Phragmoteuthida (Cephalopoda: Coleoidea) From the Lower Jurassic of Dorset, England

Cited by 23 publications

References 9 publications

Absence of Suction Feeding Ichthyosaurs and Its Implications for Triassic Mesopelagic Paleoecology

Absence of Suction Feeding Ichthyosaurs and Its Implications for Triassic Mesopelagic Paleoecology

Completeness of the fossil record and the validity of sampling proxies at outcrop level

Large onychites (cephalopod hooks) from the Upper Jurassic of the Boreal Realm

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