Ammonoid Embryonic Development

Baets, Kenneth De; Landman, Neil H.; Tanabe, Kazushige

doi:10.1007/978-94-017-9630-9_5

Cited by 46 publications

(55 citation statements)

References 141 publications

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“…; De Baets et al . ; and references therein). The results of this study suggest that the hatchlings with a protoconch and no chamber, and thus a small embryonic shell diameter, are possibly a common feature between belemnites and ammonoids.…”

Section: Discussionmentioning

confidence: 99%

Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

et al. 2017

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Based on well-preserved belemnites, the ontogenetic trajectories of septal spacing between succeeding chambers were analysed. In the examined species (Passaloteuthis laevigata, Parapassaloteuthis zieteni and Pseudohasitites longiformis) that come from Buttenheim, Germany, and Lixhausen, France, the ontogenetic trajectories of septal spacing follow exponentially increasing trends with no decreasing phase of septal crowding during the earliest ontogenetic stage. The absence of a decreasing trend at the earliest ontogenetic stage is a unique character in contrast with those in modern cuttlefish and ancient and modern nautiloids, in which the decreasing trends are related to hatching events. These ontogenetic septal spacing trends suggest that the belemnite hatchlings had only a protoconch with no chamber. These belemnite hatchlings with no chamber and therefore small embryonic shell diameter are similar to those of ammonoids. Significant difference in a statistical test that compared the protoconch size between the two localities, might suggest that there was limited transportation at the embryonic stage, although it could also just indicate differences in regional environmental conditions, age and/or degree of time averaging which might differ between the examined taxa.

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Section: Discussionmentioning

confidence: 99%

Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

et al. 2017

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“…The adaptations required for a hatchling may vary greatly in comparison with those for a juvenile or adult (De Baets et al . ; Naglik et al . ).…”

Section: Discussionmentioning

confidence: 97%

“…; Tanabe ; De Baets et al . , ). Most ammonoid researchers assume that the hatchlings would have been planktonic in lifestyle due to their extremely small size (Landman et al .…”

Section: Discussionmentioning

confidence: 99%

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

Walton

Korn

2017

Palaeontology

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We measured longitudinal growth in conch cross-sections of 177 Devonian to Jurassic ammonoid species to test whether conch ontogenetic development parallels the iterative evolution of pachyconic or globular conch shapes. Ontogenetic trajectories of two cardinal conch parameters, conch width index and umbilical width index, show a few common recurring ontogenetic pathways in terms of the number of ontogenetic phases. The most common, with three phases in the conch width index (decrease-increase-decrease) and umbilical width index (increase-decrease-increase), is termed here C-mode ontogeny (after the Carboniferous genus Cravenoceras). Many of the studied globular Palaeozoic and Triassic species (of the latter, particularly the arcestid ammonoids) share principal patterns in the triphasic C-mode conch ontogeny in closely related groups but also between unrelated groups as well. The repetition of conch growth patterns is an example of convergent evolution of the entire life history of globular ammonoids. The studied Jurassic globular shaped ammonoids deviate from the growth patterns seen in earlier groups showing less pronounced ontogenetic trajectories with nearly isometric or weakly asymmetric growth without distinct phases. This trajectory is termed here M-mode ontogeny (after the Jurassic genus Macrocephalites). No major change in the ontogenetic modes of pachyconic and globular ammonoids occurred moving from the Palaeozoic into the Mesozoic; the survivors of the end-Permian extinction event iteratively developed conch ontogenies similar to those of Palaeozoic forms. In contrast, the Triassic-Jurassic boundary marks the major event with the evolution of some cardinal conch parameters relating to globular ammonoid ontogeny.

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“…; De Baets et al . , ); and (3) the facies of the rocks were they occur (Kulicki & Wierzbowski ; Landman ; Bucher et al . ; Mapes & Nützel ; Stephen et al .…”

Section: Discussionmentioning

confidence: 99%

Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study

et al. 2016

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In biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1) SDD is influenced by both spatial extent and sample size; (2) the potential effect of the phylogenetic level has yet to be tested; (3) the effect of a marked biogeographical structuring upon SDD patterns is largely unknown; and (4) the SDD relationship is usually explored with modern, mainly terrestrial organisms, whereas fossil taxa are seldom used in that perspective. Using this relationship, we explore the long‐distance dispersal of the Early Jurassic (early Pliensbachian, c. 190.8 Ma to 187.6 Ma) ammonites of the western Tethys and adjacent areas, in a context of marked provincialism. We show that the long‐distance dispersal of these ammonites is not related to shell size and shape, but rather to the environmental characteristics of the province to which they belong. This suggests that their long‐distance dispersal may have been essentially driven by passive planktonic drift during early juvenile, post‐hatching stages. Furthermore, it seems that the SDD relationship is not always an appropriate method to characterize the existence of a biogeographical structuring. We conducted SDD analyses at various spatial, sampling and phylogenetic scales in order to evaluate their sensitivity to scale effects. This multi‐scale approach indicates that the sampling scale may influence SDD rates in an unpredictable way and that the phylogenetic level has a major impact on SDD patterns.

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Ammonoid Embryonic Development

Cited by 46 publications

References 141 publications

Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study

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