Paleocene genus Incisiochiton Van Belle, 1985 (Mollusca: Polyplacophora) with the description of a new species from Ukraine

Sirenko, Boris I.; Dell’Angelo, Bruno

doi:10.31610/trudyzin/2023.327.1.128

Cited by 2 publications

(1 citation statement)

References 8 publications

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“…S8). Our time-calibrated phylogeny indicates shell eyes evolved in the last common ancestor of Acanthopleurinae + Toniciinae between 150 and 100 million years (Ma) ago and in Schizochitonidae between 250 and 200 Ma ago, estimates considerably older than the earliest verified fossil evidence of shell eyes in fossil Toniciinae from the middle Eocene (48 to 38 Ma ago) and fossil Schizochitonidae represented by two species of Incisiochiton from the Lower Paleocene (66 to 59.2 Ma ago) ( 48 – 50 ). Time-calibrated phylogeny and fossil evidence together indicate that both instances of shell eyes in chitons represent the most recent origins of camera-type eyes known.…”

Section: Chitons Rapidly Evolved Visual Systems Four Times In Two Dis...mentioning

confidence: 99%

A morphological basis for path-dependent evolution of visual systems

Varney,

Speiser,

Cannon

et al. 2024

Science

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Path dependence influences macroevolutionary predictability by constraining potential outcomes after critical evolutionary junctions. Although it has been demonstrated in laboratory experiments, path dependence is difficult to demonstrate in natural systems because of a lack of independent replicates. Here, we show that two types of distributed visual systems recently evolved twice within chitons, demonstrating rapid and path-dependent evolution of a complex trait. The type of visual system that a chiton lineage can evolve is constrained by the number of openings for sensory nerves in its shell plates. Lineages with more openings evolve visual systems with thousands of eyespots, whereas those with fewer openings evolve visual systems with hundreds of shell eyes. These macroevolutionary outcomes shaped by path dependence are both deterministic and stochastic because possibilities are restricted yet not entirely predictable.

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Section: Chitons Rapidly Evolved Visual Systems Four Times In Two Dis...mentioning

confidence: 99%

A morphological basis for path-dependent evolution of visual systems

Varney,

Speiser,

Cannon

et al. 2024

Science

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Phylogenomic analyses shed light on the relationships of chiton superfamilies and shell-eye evolution

Liu,

Sigwart,

Sun

2023

Mar Life Sci Technol

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Mollusca is the second-largest animal phylum with over 100,000 species among eight distinct taxonomic classes. Across 1000 living species in the class Polyplacophora, chitons have a relatively constrained morphology but with some notable deviations. Several genera possess "shell eyes", true eyes with a lens and retina that are embedded within the dorsal shells, which represent the most recent evolution of animal eyes. The phylogeny of major chiton clades is mostly well established, in a set of superfamily and higher-level taxa supported by various approaches including multiple gene markers, mitogenome-phylogeny and phylotranscritomic approaches as well as morphological studies. However, one critical lineage has remained unclear: Schizochiton was controversially suggested as a potential independent origin of chiton shell eyes. Here, with the draft genome sequencing of Schizochiton incisus (superfamily Schizochitonoidea) plus assembly of transcriptome data from other polyplacophorans, we present phylogenetic reconstructions using both mitochondrial genomes and phylogenomic approaches with multiple methods. Phylogenetic trees from mitogenomic data are inconsistent, reflecting larger scale confounding factors in molluscan mitogenomes. A consistent robust topology was generated with protein coding genes using different models and methods. Our results support Schizochitonoidea is a sister group to other Chitonoidea in Chitonina, in agreement with established classification. This suggests that the earliest origin of shell eyes is in Schizochitonoidea, which were also gained secondarily in other genera in Chitonoidea. Our results have generated a holistic review of the internal relationship within Polyplacophora, and a better understanding on the evolution of Polyplacophora.

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Paleocene genus Incisiochiton Van Belle, 1985 (Mollusca: Polyplacophora) with the description of a new species from Ukraine

Cited by 2 publications

References 8 publications

A morphological basis for path-dependent evolution of visual systems

A morphological basis for path-dependent evolution of visual systems

Phylogenomic analyses shed light on the relationships of chiton superfamilies and shell-eye evolution

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