Syn vivo hydrostatic and hydrodynamic properties of scaphitid ammonoids from the U.S. Western Interior

Peterman, David J.; Hebdon, Nicholas; Ciampaglio, Charles N.; Yacobucci, Margaret M.; Landman, Neil H.; Linn, Tom

doi:10.1016/j.geobios.2020.04.004

Cited by 24 publications

(32 citation statements)

References 52 publications

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“…The unique shell of this genus raises questions regarding how its changes in coiling may reflect the modification of syn vivo hydrostatic properties. Such a tactic was suggested for other morphologies of heteromorph ammonoids [17,19,20,[34][35][36][37][38][39]. These physical properties are vital to understand if Nipponites was a benthic crawler, a planktic drifter, an active swimmer, or just an atypical genus with a morphology that was not detrimental for survival or reproduction.…”

Section: Plos Onementioning

confidence: 99%

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The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): Managing hydrostatics throughout a complex ontogeny

2020

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Nipponites is a heteromorph ammonoid with a complex and unique morphology that obscures its mode of life and ethology. The seemingly aberrant shell of this Late Cretaceous nostoceratid seems deleterious. However, hydrostatic simulations suggest that this morphology confers several advantages for exploiting a quasi-planktic mode of life. Virtual, 3D models of Nipponites mirabilis were used to compute various hydrostatic properties through 14 ontogenetic stages. At each stage, Nipponites had the capacity for neutral buoyancy and was not restricted to the seafloor. Throughout ontogeny, horizontally facing to upwardly facing soft body orientations were preferred at rest. These orientations were aided by the obliquity of the shell's ribs, which denote former positions of the aperture that were tilted from the growth direction of the shell. Static orientations were somewhat fixed, inferred by stability values that are slightly higher than extant Nautilus. The initial open-whorled, planispiral phase is well suited to horizontal backwards movement with little rocking. Nipponites then deviated from this bilaterally symmetric coiling pattern with a series of alternating U-shaped bends in the shell. This modification allows for proficient rotation about the vertical axis, while possibly maintaining the option for horizontal backwards movement by redirecting its hyponome. These particular hydrostatic properties likely result in a tradeoff between hydrodynamic streamlining, suggesting that Nipponites assumed a low energy lifestyle of slowly pirouetting in search for planktic prey. Each computed hydrostatic property influences the others in some way, suggesting that Nipponites maintained a delicate hydrostatic balancing act throughout its ontogeny in order to facilitate this mode of life.

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Section: Plos Onementioning

confidence: 99%

“…restricted to horizontal or diagonally-upwards soft body positions [20,29,[34][35][36][37][38][39][42][43][44][45]. These living cephalopods would have assumed some static orientation when their centers of buoyancy and mass were vertically aligned [41,46,47] (Fig 1).…”

Section: Plos Onementioning

confidence: 99%

The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): Managing hydrostatics throughout a complex ontogeny

2020

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“…Where V wd and ρ wd are the volume and density of the water displaced, V sb and ρ sb are the volume and density of the soft body, V sh and ρ sh are the volume and density of the shell, ρ cl is the density of cameral liquid, ρ cg is the density of cameral gas, and V ct is the total cameral volume of the phragmocone. A soft body density of 1.049 g/cm 3 is preferred based on the measurement of Nautilus soft body by Hoffmann & Zachow [73] that was later averaged by a seawater-filled mantle cavity and thin mouthparts by Peterman et al [38]. A shell density of 2.54 g/cm 3 was adopted from Hoffman & Zachow [73].…”

Section: Methodsmentioning

confidence: 99%

“…The directional efficiency of movement (thrust angle) depends upon the relative position of the source of thrust (the hyponome) and the center of rotation (the midpoint between the centers of buoyancy and mass; Fig 1A, B). Thrust energy produced by jet propulsion is more efficiently transmitted into movement in the direction where the hyponome and center of rotation are aligned [20,38,39,48,49]. If these two points were horizontally aligned (thrust angle of zero), more energy would be transmitted to horizontal movement with minimal rocking.…”

Section: Introductionmentioning

confidence: 99%

The balancing act ofNipponites mirabilis(Nostoceratidae, Ammonoidea): managing hydrostatics during a complex ontogenetic trajectory

Peterman

Mikami

Inoué

2020

Preprint

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Nipponites is a heteromorph ammonoid with a complex and unique morphology that obscures its mode of life and ethology. The seemingly aberrant shell of this Late Cretaceous nostoceratid seems deleterious. However, hydrostatic simulations suggest that this morphology confers several advantages for exploiting a quasi-planktic mode of life. Virtual, 3D models of Nipponites mirabilis were used to compute various hydrostatic properties through 14 ontogenetic stages. At each stage, Nipponites had the capacity for neutral buoyancy and was not restricted to the seafloor. Throughout ontogeny, horizontally facing to upwardly facing soft body orientations were preferred. These orientations were aided by the obliquity of the shell’s ribs, which were parallel to former positions of the aperture during life. Static orientations were somewhat fixed, inferred by stability values that are slightly higher than extant Nautilus. The initial open-whorled, planispiral phase is well suited to horizontal backwards movement with little rocking. Nipponites then deviates from this coiling pattern with a series of alternating U-shaped bends in the shell. This modification allows for proficient rotation about the vertical axis, while possibly maintaining the option for horizontal backwards movement by redirecting its hyponome. These particular hydrostatic properties likely result in a tradeoff between hydrodynamic streamlining, suggesting that Nipponites assumed a low energy lifestyle of slowly pirouetting in search for planktic prey. Each computed hydrostatic property influences the others in some way, suggesting that Nipponites maintained a delicate hydrostatic balancing act throughout its ontogeny in order to facilitate this mode of life.

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“…1). The more compressed shell shapes of Hoploscaphites criptonodosus, H. macer, and H. sargklofak would have been more advantageous in such an environment compared to the more depressed shell shapes of H. crassus, H. plenus, and H. peterseni (for a recent discussion of hydrodynamics in ammonites, in general, see Naglik et al, 2015, and in scaphites, in particular, see Peterman et al, 2020). Similarly, the increased tuberculation in the geologically younger species may also be related to the transition to a more nearshore environment, with a simultaneous increase in the number and kinds of predators.…”

Section: Evolutionary Patternsmentioning

confidence: 99%

Large Scaphitid Ammonites (Hoploscaphites) from the Upper Cretaceous (Upper Campanian–Lower Maastrichtian) of North America: Endless Variation on a Single Theme

Landman

Kennedy

Grier³

et al. 2020

Bulletin of the American Museum of Natural History

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Syn vivo hydrostatic and hydrodynamic properties of scaphitid ammonoids from the U.S. Western Interior

Cited by 24 publications

References 52 publications

The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): Managing hydrostatics throughout a complex ontogeny

The balancing act of Nipponites mirabilis (Nostoceratidae, Ammonoidea): Managing hydrostatics throughout a complex ontogeny

The balancing act ofNipponites mirabilis(Nostoceratidae, Ammonoidea): managing hydrostatics during a complex ontogenetic trajectory

Large Scaphitid Ammonites (Hoploscaphites) from the Upper Cretaceous (Upper Campanian–Lower Maastrichtian) of North America: Endless Variation on a Single Theme

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