DOI: 10.5061/dryad.7m6kg
title: Data from: Nectocaridid ecology, diversity, and affinity: early origin of a cephalopod-like body plan

description: 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.
description: Fig. 1a: ROM 59658 –
 Nectocaris pteryx from the Burgess ShaleExternal body tissue is
 intact, obscuring internal structuresRQ93-0376_338.g1.JPGFig. 1b: ROM 49585 – Nectocaris pteryx from the Burgess ShaleSlight decay reveals internal anatomy but not fin structureUE88-0106A_071.g.JPGFig. 1c: ROM 59660 – Nectocaris pteryx from the Burgess ShaleModerate decay reveals internal anatomy and fin structureUE88-0012A_067.g2.JPGFig. 1d: ROM 60089 – Nectocaris pteryx from the Burgess ShaleDecayed specimen, many organs are visible but no detail is preservedEZ88-0174A_513.g.JPGFig. 1e: ROM 60133 – Nectocaris pteryx from the Burgess ShaleHeavily decayed specimen, no detail visible.RQ91-0892A_058.g.JPGFig. 2a: Elemental distribution in Nectocaris pteryx, ROM 60079Pixel brightness in elemental maps corresponds to elemental abundance. Scale bars: 1 mm.WT98-1378B Elemental.pngFigs. 2b & 9e: ROM 60079 – Nectocaris pteryx from the Burgess ShaleWT98-1378B.pngFigs. 2c, 6b & 8b: ROM 60146 — Nectocaris pteryx (head) from the Burgess Shale, direct illuminationSpecimen with well-preserved soft tissue has smooth, unornamented tentacle margins. Robustly lined funnel canal is surrounded by fleshy tissue.BW97-2549A_708.JPGFigs. 2c, 6b & 8b: ROM 60146 — Nectocaris pteryx (head) from the Burgess Shale, crossed polarsSpecimen with well-preserved soft tissue has smooth, unornamented tentacle margins. Robustly lined funnel canal is surrounded by fleshy tissue.BW97-2549A_709.JPGFigs. 2c, 6b & 8b: ROM 60146 — Nectocaris pteryx (head) from the Burgess Shale, interference imageInterference image, using images under direct illumination and crossed polars. Specimen with well-preserved soft tissue has smooth, unornamented tentacle margins. Robustly lined funnel canal is surrounded by fleshy tissue.BW97-2549A_709 gex 708.bw.jpgFig 2d: ROM 60146 — Elemental distribution in eye and head of Nectocaris pteryx from the Burgess ShaleROM 60146 Elemental.pngFig. 3a: Bioturbation in Nectocaris ?pteryx from ChengjiangHKMF-50001Petalilium_HK-MF-00001A_098.g2.JPGFig. 3b: Bioturbation in Nectocaris ?pteryx from ChengjiangHKMF-50001 — Magnification of head regionPetalilium_HK-MF-00001A_114.g2.JPGBioturbation in Nectocaris pteryx from the Burgess ShaleROM 60117, Burgess Shale specimen with minimal burrowing, infill of axial cavity undisturbedUE90-1114A_257.g.JPGBioturbation in Nectocaris ?pteryx from ChengjiangHK-MF-00002, Chengjiang specimen; axial cavity decimated by burrowing.Petalilium_HK-MF-00002A_091.g1.JPGFigs. 4a & 9a: ROM 59658 – Nectocaris pteryx from the Burgess ShaleROM 59658, composite interference image of part and counterpart, showing coarse stripes, fine striations, and folding of fin marginRQ93-0322 AB overlay.bw.jpgFig. 4a: ROM 59658 – Nectocaris pteryx from the Burgess ShalePart, under crossed polarsRQ93-0322B_714.g.tifFig. 4a: ROM 59658 – Nectocaris pteryx from the Burgess ShalePart, direct illuminationRQ93-0322B_713.g.tifFig. 4a: ROM 59658 – Nectocaris pteryx from the Burgess ShaleCounterpart, crossed polarsRQ93-0322A_710.g.tifFig. 4a: ROM 59658 – Nectocaris pteryx from the Burgess ShaleCounterpart, direct illuminationRQ93-0322A_711.g.tifFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShaleROM 60079, composite interference image of part and counterpart, showing coarse stripes and fine striationsWT98-1378 AB multiply.JPG.jpgFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShaleCounterpart, crossed polarsWT98-1378B_705.g1.JPGFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShaleCounterpart, direct illuminationWT98-1378B_703.g.JPGFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShalePart, direct illuminationWT98-1378B_700.g.tifFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShalePart, crossed polarsWT98-1378B_699.g.tifFig. 4b: ROM 60079 – Nectocaris pteryx from the Burgess ShalePart, interference image of crossed polars and direct illuminationWT98-1378B_699 gx 700.JPGFigs. 4c & 10c: ROM 60144 – Nectocaris pteryx from the Burgess ShaleComplementary preservation of lineations: broad stripes are visible anteriad, fine striations posteriad. Assuming that this represents a single individual, the anterior portion of this specimen is somewhat oblique to the sediment. Interference image.WT94-0628A ROM 60144_370g gex 371g.g.JPGFigs. 4c & 10c: ROM 60144 – Nectocaris pteryx from the Burgess ShaleCrossed polarsWT94-0628A ROM 60144_370.g.JPGFigs. 4c & 10c: ROM 60144 – Nectocaris pteryx from the Burgess ShaleDirect illuminationWT94-0628A ROM 60144_371.g.JPGFig. 4d: ROM 60091 – Nectocaris pteryx from the Burgess ShaleFine striations associated with relief, stripes not visibleUE88-0133B_377.g.JPGFig. 4d: ROM 60091 – Nectocaris pteryx from the Burgess ShaleComplete specimen; low angle lightUE88-0133B_114.g.tifFig. 4d: ROM 60091 – Nectocaris pteryx from the Burgess ShaleFull specimen, crossed polarsUE88-0133B_113.g.tifFig. 4e: ROM 60141 – Nectocaris pteryx from the Burgess ShaleFine striations have distinct composition, stripes not visibleRQ93-1088B_110.g.JPGFig. 5a: ROM 60084 — Nectocaris pteryx from the Burgess ShaleROM 60084, stain lines axial cavityEZ88-0021A_118.g3.JPGFig. 5c: ROM 59661 — Nectocaris pteryx (lateral view) from the Burgess ShalePart, lateral specimen with staining in axial canalUE90-1394IA_127.g.JPGFig. 5c: ROM 59661 — Nectocaris pteryx (lateral view) from the Burgess ShaleCounterpartUE90-1394IB_315.g.JPGFig. 6a: ROM 59660 – Nectocaris pteryx (anterior) from the Burgess ShaleIterated transverse stripes with diffuse margins in twisted, partly decayed tentacleUE88-0012A_079.g.JPGFig. 6b: ROM 60146 – Nectocaris pteryx (head) from the Burgess ShaleSpecimen with well-preserved soft tissue has smooth, unornamented tentacle margins; interference image under plane and crossed polars.BW97-2549A_709 gex 708.JPGTentacle curvature in Nectocaris pteryx from the Burgess ShaleLeft tentacle demonstrates flexible curvatureUE88-0052B.g.jpgTentacle flexibility in Nectocaris pteryx from the Burgess ShaleRight tentacle (arrowed) is folded back over bodyRQ96-0371A_136.pngFig. 7a: ROM 59668 — Nectocaris pteryx mouthparts from the Burgess ShaleROM 59668, denticles associated with reliefUE88-0015A_439.g.JPGFig. 7b: ROM 59662 — Nectocaris pteryx mouthparts from the Burgess ShaleTwo opposed chevrons forming a crossEZ84-0561A_507.g.JPGFig. 7c: ROM 60100 — Nectocaris pteryx (head) from the Burgess Shaledenticles of posterior chevron demonstrate relief; anterior chevron putatively represented by crackUE90-0502B ROM 60100_412.g.JPGFig. 7c: ROM 60100 — Nectocaris pteryx mouthparts from the Burgess ShaleDirect illuminationUE90-0502B_177.g3.JPGFig. 7c: ROM 60100 — Nectocaris pteryx mouthparts from the Burgess ShaleLow-angle light, emphasizing reliefUE90-0502B ROM 60100_412.g.JPGFig. 7d: ROM 59661 — Nectocaris pteryx head (lateral view) from the Burgess ShaleLateral specimen illustrating curved belt-like structure with serially repeated linear notches projecting radially.UE90-1394A_115.g.JPGFig. 8a: ROM 60129 – Nectocaris pteryx from the Burgess ShaleCanal has robust dark lining, lateral voids visible in axial cavityUE90-1439A_304.g.JPGFig. 8c: ROM 59662 – Nectocaris pteryx from the Burgess ShaleCanal narrows within the internal portion of the funnel.UE90-0561_087.g.JPGFig. 9b: ROM 59664 – Nectocaris pteryx from the Burgess ShaleGill laminae distend from zig-zagging lateral axisUE90-1348A_327.g.JPGFig. 9c: ROM 59672 – Nectocaris pteryx from the Burgess ShaleDark components of gills have thick edges, suggesting a cylindrical profileUE90-1395a_492.g.JPGFig. 9d: ROM 60132 – Nectocaris pteryx from the Burgess ShaleGill blades are laterally connectedUE90-1498_324.g.JPGFig. 9f: ROM 59663 – Nectocaris pteryx from the Burgess ShaleSediment interdigitates between gill blades; blades are deflected posteriadUE90-0414A_135.g.JPGFig. 9g: ROM 59656 – Nectocaris pteryx from the Burgess ShaleAnterior gill blades deflected backwards by interdigitating sediment; undeformed posterior blades canalize the sedimentEZ84-0668B_343.g.JPGFig. 10a: ROM 59659 – Nectocaris pteryx from the Burgess ShaleBars preserved as dark two-dimensional regions lateral to the gills.UE88-0007B_055.g.JPGFig. 10b: ROM 59664 – Nectocaris pteryx from the Burgess ShaleBars preserved as dark two-dimensional regions, not in phase with gill blades.UE90-1348B_043.g.JPGFig. 10d: ROM 60131 – Nectocaris pteryx from the Burgess ShaleLow angle lighting highlights irregular fracture pattern between bars and flat surfaces of fins.UE90-1450A_034.g.JPGFig. 10e: ROM 60088 – Nectocaris pteryx from the Burgess ShalePale white sheath surrounds barsUE88-0126_050.g.JPGFig. 10f: ROM 59670 – Nectocaris pteryx from the Burgess ShaleDistinct colouration in lateral bodyUE88-0052a_006.g2.JPGFig. 10g: ROM 59656 – Nectocaris pteryx from the Burgess ShaleComplete specimenEZ84-0688A_349.g.JPGFig. 10g: ROM 59656 – Nectocaris pteryx from the Burgess ShalePosterior region. Stripes represent a taphonomic feature produced by the barsEZ84-0688A_354.g2.JPGFig. 10i: Reconstruction of nectocaridid internal anatomyModel showing relationship between bars (brown, interpreted as being associated with muscle), gills (mauve), fins (cream), and axial cavity (blue). Model generated in Blender.Reconstruction_16-out.jpgFig. 10i: Reconstruction of nectocaridid internal anatomy (3D model)3D model used to generate Fig. 10i. Blender file format.Nectocaris interior schematic.blendFig. 11a: HK-MF-00002 — Nectocaris ?pteryx, large morph from ChengjiangInfill of funnel canal appears braided; axial cavity reworked by burrowingPetalilium_HK-MF-00002A_091.JPGFig. 11a: HK-MF-00002 (head) — Nectocaris ?pteryx, large morph from ChengjiangDenticulate chevron structure between tentacles; planar lateral surface of eyePetalilium_HK-MF-00002A_063.g.JPGFig. 11a: HK-MF-00002 (posterior) — Nectocaris ?pteryx, large morph from ChengjiangDark posterior structurePetalilium_HK-MF-00002A_076.g.JPGFig. 11b: HK-MF-00001 — Nectocaris ?pteryx, large morph from ChengjiangShowing striated funnel infill, pervasive bioturbation in axial cavity, projections from head, relief associated with fin striations, and bars with ?shrinkage-related wrinklingPetalilium_HK-MF-00001A_114.g.JPGFig. 11b: HK-MF-00001 (anterior) — Nectocaris ?pteryx, large morph from ChengjiangShowing striated funnel infill, pervasive bioturbation in axial cavity, and projections from headPetalilium_HK-MF-00001A_155.g.JPGFig. 11b: HK-MF-00001 (fin) — Nectocaris ?pteryx, large morph from ChengjiangShowing relief associated with fin striations, and bars with ?shrinkage-related wrinklingPetalilium_HK-MF-00001A_127.g.JPGFig. 11c: SK-Z-00001 — Nectocaris ?pteryx, large morph from ChengjiangLong tentacles, funnel folded laterally; bars and texture of infilling sediment apparentPetalilium_SK-Z-00001_007.g2.JPGFig. 11c: ANSK-20001 — Nectocaris ?pteryx, large morph from ChengjiangANSK-20001 (=SK-Z-00001), long tentacles, funnel folded laterally; bars and texture of infilling sediment apparentPetalilium_SK-Z-00001_007.g6.jpgFig. 11c: ANSK-20001 — Nectocaris ?pteryx, large morph from ChengjiangLow angle lighting to accentuate relief. Illuminated from top left when anterior of specimen is at bottom of page.Petalilium_SK-Z-00001_045.g2.JPGFig. 11c: ANSK-20001 — Nectocaris ?pteryx (anterior), large morph from ChengjiangMagnification of anterior region of specimenPetalilium_SK-Z-00001_019.g.jpgAdditional Chinese material of Nectocaris ?pteryx (large morph)ZIP file containing images of two specimens, with scalesChina_Nectocaris.zipFig. 11d: ROM 61496 — Large morph of Nectocaris from the Burgess ShaleFull size, high-resolution images as displayed in Fig. 11d, plus original (pre-interference) images.Fig 11d - WQ94-3486.zipCounterpart of ROM 61496 — Large morph of Nectocaris from the Burgess ShaleImages of the counterpart of ROM 61496; one (_271) under cross polars, the other (_265) in low angle light to highlight relief.WQ94-3486_counterpart.zipLarge and small morphs of Nectocaris, to scale (reconstruction)A reconstruction of the large and small morphs of <i>Nectocaris</i>, to scale, constructed in Blender, using fossil material to constrain shape and proportions.Nectocaris reconstruction.jpg3D model of Nectocaris (large and small morphs)A Blender model of the large and small morphs of Nectocaris, to scale, constructed in Blender, using fossil material to constrain shape and proportions.Nectocaris reconstruction.blend