A simplified correlation between vertebrate evolution and Paleozoic geomagnetism
- Published
- Accepted
- Subject Areas
- Paleontology
- Keywords
- Paleozoic, geomagnetism, vertebrates, evolution, paleontology
- Copyright
- © 2019 Staub
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2019. A simplified correlation between vertebrate evolution and Paleozoic geomagnetism. PeerJ Preprints 7:e28002v1 https://doi.org/10.7287/peerj.preprints.28002v1
Abstract
Background. Despite a fifty-year failure of paleontologists to find a viable connection between geomagnetic polarity reversals and evolutionary patterns, recent paleobiology databases show that the early appearance, radiation, and diversification of Paleozoic vertebrates tends to occur during periods having frequent collapses of the Earth’s geomagnetic field. The transition time during the collapse of the Earth’s protective magnetic shield can last thousands of years, and the effects on biota are unknown. Solar and cosmic radiation, volcanism, climate alteration, low-frequency electromagnetic fields, depletion of ozone, the stripping of atmospheric oxygen, and increasing production of Carbon14 in the stratosphere have been proposed as possible causes, but previous studies have found no effects.
Methods. Using published databases, we compiled a spreadsheet showing the first appearance of 2210 age-dated genera with each genus assigned to one of eleven major taxonomic groups. From Gradstein’s Geologic Time Scale 2012, we delineated 17 Paleozoic zones with either high or low levels of polarity reversals.
Results. From our compilation, 737 Paleozoic vertebrates represent the initial radiation and diversification of individual Paleozoic vertebrate clades. After compensating for sample-size and external geologic and sampling biases, the resulting Pearson’s correlation coefficient between the 737 genera and geomagnetic polarity zones equals 0.89. These results suggest a strong relationship exists between Paleozoic vertebrates and geomagnetism.
Discussion. The question: is this apparent connection between geomagnetism and the evolution of Paleozoic vertebrate due to environmental or biologic factors. If biologic, why are vertebrates the only biota effected? And after an indeterminate period of time, how do vertebrates become immune to the ongoing effects of polarity reversals?
Author Comment
This is a preprint submission to PeerJ Preprints
Supplemental Information
Figure 1 Polarity Reversals and Distribution of Paleozoic vertebrates
Columns (1) and (2): geologic periods and stages (Gradstein 2012). Column (3): geomagnetic polarity reversals from multiple sources (black is normal polarity; white is reversed; gray represents multiple reversals). Column (4): high (red) and low polarity (blue) zones. Column (5): FAD of originating genus of 28 clades. Column (6) shows the “early-phase” ranges of 11 major groups of Paleozoic vertebrates. Column (7): Possible age-dated phylogeny of Paleozoic vertebrates, with sources.
Table 1: Distribution of early phase genera assigned to clades and placed in individual polarity zones
Table 1: The early-phase genera represent the early radiation of a clade, but an exact definition is needed. Using our replacement concept, the early-phase of a clade continues until it is replaced by a subsequent clade. The early phase of chordata and conodonts lasts until the scales of Anatolepis are found in the Upper Cambrian (HPZ-3); the armored Agnatha, Pteraspidomorphi, until the appearance of fish with cartilage, Chondrichthyes, in the Upper Ordovician (HPZ-5); the Osteostraci and Galeaspida until the earliest placoderm (Shimenolepis) of the Early Silurian (HPZ-7); the shark-like Chondrichthyes until the earliest Osteichthyes (Andreolepis) of the Upper Silurian (HPZ-9); the bony fish until the first Sarcopterygian (Guiyu) of the Upper Silurian (HPZ-9); the lobe and lung fish until the early “tetrapods” (Livoniana, Tiktaalik, Acanthostega, Ichthyostega, Hynerpeton) of the Upper Devonian (HPZ-11); the basal tetrapods until the earliest Reptiliomorpha (Casineria) of the Upper Visean (HPZ-13); the egg-laying Amniota until the Reptilia (Hylonomus) of Westphalian A (HPZ-15), which is immediately prior to the Kiaman Superchron; the reptiles and pelycosaurs until the therapsids of the Upper Permian (HPZ-17). Note: if we used the geologic stage date instead of polarity zones as the end-point of these clades, Pearson’s Correlation Coefficient would have dropped from 0.89 to 0.86.
Table 2 | Distribution of Paleozoic vertebrates within polarity zones
Table 2 shows the 17 high (red) and low polarity zones (blue), their range and duration (Ma), number of polarity reversals, reversals per million years, and distribution of total genera in each polarity zone showing early-phase genera, total genera, and percentage found in each polarity zone. Note that the Reversals per million years and percentage of genera are used to ascertain Pearson’s correlation coefficient.