The size of the siphuncle in cephalopod evolution

Björn Kröger

doi:10.1007/bf03043304

Molecular clocks indicate turnover and diversification of modern coleoid cephalopods during the Mesozoic Marine Revolution

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2016.2818 ◽

2017 ◽

Vol 284 (1850) ◽

pp. 20162818 ◽

Cited By ~ 36

Author(s):

Alastair R. Tanner ◽

Dirk Fuchs ◽

Inger E. Winkelmann ◽

M. Thomas P. Gilbert ◽

M. Sabrina Pankey ◽

...

Keyword(s):

Molecular Clocks ◽

Early Mesozoic ◽

Bony Fishes ◽

Unique Nature ◽

Molecular Dataset ◽

Divergence Estimates ◽

Mesozoic Marine Revolution ◽

Marine Vertebrates ◽

Cephalopod Evolution ◽

Coleoid Cephalopod

Coleoid cephalopod molluscs comprise squid, cuttlefish and octopuses, and represent nearly the entire diversity of modern cephalopods. Sophisticated adaptations such as the use of colour for camouflage and communication, jet propulsion and the ink sac highlight the unique nature of the group. Despite these striking adaptations, there are clear parallels in ecology between coleoids and bony fishes. The coleoid fossil record is limited, however, hindering confident analysis of the tempo and pattern of their evolution. Here we use a molecular dataset (180 genes, approx. 36 000 amino acids) of 26 cephalopod species to explore the phylogeny and timing of cephalopod evolution. We show that crown cephalopods diverged in the Silurian–Devonian, while crown coleoids had origins in the latest Palaeozoic. While the deep-sea vampire squid and dumbo octopuses have ancient origins extending to the Early Mesozoic Era, 242 ± 38 Ma, incirrate octopuses and the decabrachian coleoids (10-armed squid) diversified in the Jurassic Period. These divergence estimates highlight the modern diversity of coleoid cephalopods emerging in the Mesozoic Marine Revolution, a period that also witnessed the radiation of most ray-finned fish groups in addition to several other marine vertebrates. This suggests that that the origin of modern cephalopod biodiversity was contingent on ecological competition with marine vertebrates.

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Nectocaridid ecology, diversity, and affinity: early origin of a cephalopod-like body plan

Paleobiology ◽

10.1666/12029 ◽

2013 ◽

Vol 39 (2) ◽

pp. 297-321 ◽

Cited By ~ 16

Author(s):

Martin R. Smith

Keyword(s):

Body Plan ◽

Cambrian Explosion ◽

Burgess Shale ◽

Middle Cambrian ◽

Low Reynolds Number Flow ◽

Reynolds Number Flow ◽

Number Flow ◽

Early Origin ◽

First Time ◽

Cephalopod Evolution

Nectocaridids are soft-bodied early to middle Cambrian organisms known from Burgess Shale-type deposits in Canada, China, and Australia. Originally described as unrelated species, they have recently been interpreted as a clade; their flexible tentacles, camera-type eyes, lateral fins, internal gills, axial cavity, and funnel point to a relationship with the cephalopods. However, aspects of this reinterpretation, including the relevance of the group to cephalopod evolution, have been called into question.Here, I examine new and existing nectocaridid material, including a large new form that may represent a sexual dimorph of Nectocaris pteryx. Differences between existing taxa largely represent taphonomic variation between sites and specimens—which provides further constraint on the organisms' anatomy. I revise the morphology of the tentacles and fins, and describe mouthparts and phosphatized gills for the first time. A mathematical analysis supports the presence of the earliest known camera-type eyes, and fluid mechanical considerations suggest that the funnel is optimized for efficient jet propulsion in a low Reynolds number flow regime.Nectocaridids closely resemble coleoid cephalopods, but a position deeper within Cephalopoda raises fewer stratigraphic challenges. Whether its coleoid-like construction reflects common ancestry or profound convergence, the Nectocaris body plan adds substantially to Cambrian disparity, demonstrating the rapid colonization of nektobenthic niches after the Cambrian explosion.

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Nectocaris and early cephalopod evolution: reply to Mazurek & Zatoń

Lethaia ◽

10.1111/j.1502-3931.2011.00295.x ◽

2011 ◽

Vol 44 (4) ◽

pp. 369-372 ◽

Cited By ~ 5

Author(s):

MARTIN R. SMITH ◽

JEAN-BERNARD CARON

Keyword(s):

Cephalopod Evolution

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The contribution of molecular data to our understanding of cephalopod evolution and systematics: a review

Journal of Natural History ◽

10.1080/00222933.2013.825342 ◽

2014 ◽

Vol 49 (21-24) ◽

pp. 1373-1421 ◽

Cited By ~ 33

Author(s):

A. Louise Allcock ◽

A. Lindgren ◽

J.M. Strugnell

Keyword(s):

Molecular Data ◽

Cephalopod Evolution

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Jet propulsion of Nautilus: a surviving example of early Paleozoic cephalopod locomotor design

Canadian Journal of Zoology ◽

10.1139/z90-116 ◽

1990 ◽

Vol 68 (4) ◽

pp. 806-814 ◽

Cited By ~ 14

Author(s):

John A. Chamberlain Jr.

Keyword(s):

Sea Level ◽

Mantle Cavity ◽

Early Paleozoic ◽

Cavity Pressure ◽

Design Constraints ◽

Jet Propulsion ◽

Sea Level Fluctuations ◽

Propulsive Performance ◽

Slow Moving ◽

Cephalopod Evolution

Like its coleoid relatives, Nautilus swims by jet propulsion. However, in the structure and functioning of its motor, Nautilus differs markedly from its contemporaries. Compared with that of squids, Nautilus locomotion is based on small propellant volume, low mantle cavity pressure, low propellant velocity, and small propulsive muscle mass. Propulsive performance of Nautilus is consequently unspectacular, with as little as one-eighth the thrust and one-tenth the burst speed observed in squids of equivalent size. Nautilus survives as a result of its slow-moving, vertically mobile, foraging life-style limited to habitats where competition with fast-moving, agile swimmers is minimal. Fossil cephalopods faced similar design constraints, which may have contributed to their decline, but nonbiologic factors such as sea level fluctuations may also have been important in directing the course of cephalopod evolution.

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