<i>Nectocaris</i>
            and early cephalopod evolution: reply to Mazurek &amp; Zatoń

Smith, Martin R.; Caron, Jean‐Bernard

doi:10.1111/j.1502-3931.2011.00295.x

Cited by 7 publications

(16 citation statements)

References 32 publications

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“…Given that a number of Cambrian groups such as the nectocariids [31,32] and amiskwiids [33] remain in phylogenetic limbo (but see [34,35]), the only option might be to add the vetulicolians to this roster and continue our efforts to find even better preserved material and/or related taxa that might serve to pinpoint their relationships.…”

Section: Discussionmentioning

confidence: 99%

“…As already noted we argue that a position within the stem-group deuterostomes is the best phylogenetic solution, but as is often the case in such problematic animals from the Cambrian the correct identification of homologies is crucial. In this context the case of the putative cephalopod Nectoccaris [31,32,34,35] provides a useful parallel. Thus any attempt to link the vetulicolians to one or other group within either the ambulcrarians or chordates is largely frustrated not only by the paucity of obvious homologies, but in addition evidence for radical reorganization of some bodyplans (notably echinoderms [43]) as well as both molecular [44] and fossil [45] data that suggest other groups (notably amphioxus) are more or less degenerate.…”

Section: Discussionmentioning

confidence: 99%

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Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

Morris

Han

et al. 2012

BMC Biol

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BackgroundVetulicolians are a group of Cambrian metazoans whose distinctive bodyplan continues to present a major phylogenetic challenge. Thus, we see vetulicolians assigned to groups as disparate as deuterostomes and ecdysozoans. This divergence of opinions revolves around a strikingly arthropod-like body, but one that also bears complex lateral structures on its anterior section interpreted as pharyngeal openings. Establishing the homology of these structures is central to resolving where vetulicolians sit in metazoan phylogeny.ResultsNew material from the Chengjiang Lagerstätte helps to resolve this issue. Here, we demonstrate that these controversial structures comprise grooves with a series of openings. The latter are oval in shape and associated with a complex anatomy consistent with control of their opening and closure. Remains of what we interpret to be a musculature, combined with the capacity for the grooves to contract, indicate vetulicolians possessed a pumping mechanism that could process considerable volumes of seawater. Our observations suggest that food captured in the anterior cavity was transported to dorsal and ventral gutters, which then channeled material to the intestine. This arrangement appears to find no counterpart in any known fossil or extant arthropod (or any other ecdysozoan). Anterior lateral perforations, however, are diagnostic of deuterostomes.ConclusionsIf the evidence is against vetulicolians belonging to one or other group of ecdysozoan, then two phylogenetic options seem to remain. The first is that such features as vetulicolians possess are indicative of either a position among the bilaterians or deuterostomes but apart from the observation that they themselves form a distinctive and recognizable clade current evidence can permit no greater precision as to their phylogenetic placement. We argue that this is too pessimistic a view, and conclude that evidence points towards vetulicolians being members of the stem-group deuterostomes; a group best known as the chordates (amphioxus, tunicates, vertebrates), but also including the ambulacrarians (echinoderms, hemichordates), and xenoturbellids. If the latter, first they demonstrate that these members of the stem group show few similarities to the descendant crown group representatives. Second, of the key innovations that underpinned deuterostome success, the earliest and arguably most seminal was the evolution of openings that define the pharyngeal gill slits of hemichordates (and some extinct echinoderms) and chordates.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

Morris

Han

et al. 2012

BMC Biol

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“…They noted the absence of key cephalopod characters, including a molluscan radula and a siphunculate shell, and drew attention to some similarities between Nectocaris and coeval Cambrian panarthropods such as Anomalocaris . However, they were not comparing homologous characters as Smith & Caron (2011) easily showed. For example, the paired unsegmented anterior ‘tentacles’ of Nectocaris bear no resemblance in construction or presumed mode of operation to the jointed ‘great appendages’ of the anomalocarids.…”

mentioning

confidence: 99%

“…If the ‘axial cavity’ is a gut and the ‘ctenidia’ are not gills then all other similarities to structures found in crown‐group cephalopods become dubious (Smith & Caron 2011, table 1). A pair of stalked eyes that are found only in highly derived squids?…”

mentioning

confidence: 99%

“…I may be misinterpreting Smith & Caron’s (2010, 2011) concept of Nectocaris and why they believe it is a stem‐group cephalopod. If so, a broader discussion of these matters in response to Mazurek & Zatoń’s critique – perhaps with key characters mapped on to a tree that includes Nectocaris , Odontogriphus , and some of the conchiferan molluscs – would be very helpful.…”

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confidence: 99%

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Once again: is Nectocaris pteryx a stem‐group cephalopod?

Runnegar

2011

LET

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An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda

Smith

2019

J. Paleontol.

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Nectocaridids are soft-bodied Cambrian organisms that have been controversially interpreted as primitive cephalopods, at odds with the long-held belief that these mollusks evolved from a shell-bearing ancestor. Here, I document a new nectocaridid from the Whetstone Gulf Formation, extending the group's range into the Late Ordovician. Nectocotis rusmithi n. gen. n. sp. possesses a robust internal element that resembles a non-mineralized phragmocone or gladius. Nectocaridids can be accommodated in the cephalopod total group if the earliest cephalopods (1) inherited a non-mineralized shell field from the ancestral mollusk; and (2) internalized this shell field. This evolutionary scenario would overturn the traditional ectocochleate, Nautilus-like reconstruction of the ancestral cephalopod, and indicate a trend towards increased metabolic efficiency through the course of Cambrian–Ordovician evolution.UUID: http://zoobank.org/ed594200-37b9-4642-bd8f-4fb72dc544eb

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Nectocaris and early cephalopod evolution: reply to Mazurek & Zatoń

Cited by 7 publications

References 32 publications

Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

Evidence for gill slits and a pharynx in Cambrian vetulicolians: implications for the early evolution of deuterostomes

Once again: is Nectocaris pteryx a stem‐group cephalopod?

An Ordovician nectocaridid hints at an endocochleate origin of Cephalopoda

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