Direct development of stem tetrapods across the fin-to-limb transition.
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| Title: | Direct development of stem tetrapods across the fin-to-limb transition. |
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| Authors: | Pardo, Jason D. (AUTHOR), Mann, Arjan (AUTHOR) |
| Source: | Science. 6/18/2026, Vol. 392 Issue 6804, p1292-1296. 5p. |
| Subjects: | Metamorphosis, Larvae, Tetrapods, Ontogeny, Biological evolution, Paleontology |
| Abstract: | Modern amphibians are characterized by an aquatic larval stage that ends abruptly with a period of widespread tissue remodeling (metamorphosis) upon transition to terrestrial adulthood. A transient larval stage ending in gradual metamorphosis is often assumed for the earliest digited tetrapods, but direct evidence of this larval stage is lacking. Exceptionally preserved stem tetrapod hatchlings show that a transient larval stage was absent in tetrapods both before and after the fin-to-limb transition; instead we identified soft- and hard-tissue evidence of direct development, falsifying hypotheses of an ancestral origin of metamorphosis or of a gradual larval-postlarval transition serving as a template for lissamphibian metamorphosis. We argue that a transient larval period culminating in metamorphosis originated near or within the tetrapod crown group as part of a broader suite of traits associated with terrestrialization. Editor's summary: The earliest tetrapod colonizers of land have been considered to have life histories somewhat similar to modern amphibians, including the presence of an aquatic larval stage, and it has been hypothesized that this transition may have facilitated the broader transition from water to land. Pardo et al. looked at many fossils of stem tetrapods from the Mazon Creek Lagerstatte and found no evidence of such larval morphological change. Instead, both before and after the fin-to-limb transition, hatchling to adult growth proceeded through a direct development model. —Sacha Vignieri [ABSTRACT FROM AUTHOR] |
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| Database: | Psychology and Behavioral Sciences Collection |
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| Abstract: | Modern amphibians are characterized by an aquatic larval stage that ends abruptly with a period of widespread tissue remodeling (metamorphosis) upon transition to terrestrial adulthood. A transient larval stage ending in gradual metamorphosis is often assumed for the earliest digited tetrapods, but direct evidence of this larval stage is lacking. Exceptionally preserved stem tetrapod hatchlings show that a transient larval stage was absent in tetrapods both before and after the fin-to-limb transition; instead we identified soft- and hard-tissue evidence of direct development, falsifying hypotheses of an ancestral origin of metamorphosis or of a gradual larval-postlarval transition serving as a template for lissamphibian metamorphosis. We argue that a transient larval period culminating in metamorphosis originated near or within the tetrapod crown group as part of a broader suite of traits associated with terrestrialization. Editor's summary: The earliest tetrapod colonizers of land have been considered to have life histories somewhat similar to modern amphibians, including the presence of an aquatic larval stage, and it has been hypothesized that this transition may have facilitated the broader transition from water to land. Pardo et al. looked at many fossils of stem tetrapods from the Mazon Creek Lagerstatte and found no evidence of such larval morphological change. Instead, both before and after the fin-to-limb transition, hatchling to adult growth proceeded through a direct development model. —Sacha Vignieri [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00368075 |
| DOI: | 10.1126/science.aeb7635 |
