# Valvatida
**Valvatida** is an order of sea stars (class Asteroidea) that contains the greatest number of families, genera, and species of any order within the class, and whose members typically bear a well-defined series of marginal plates outlining the body periphery.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) Molecular phylogenetic studies have repeatedly shown that the order as traditionally circumscribed is not monophyletic, and its internal classification is under active revision.[2](https://www.sciencedirect.com/science/article/abs/pii/S1055790317301653)
| Key fact | Detail |
|---|---|
| Rank and group | Order within class Asteroidea, phylum Echinodermata[3](https://australian.museum/learn/animals/sea-stars/carpet-sea-star/) |
| Taxonomic richness | The most taxonomically numerous order in the Asteroidea at the levels of families, genera, and species[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) |
| Largest families | Goniasteridae, with 256 species, is the largest family in the Asteroidea; Ophidiasteridae, with 106 species, is the largest family in the tropical shallow-water Atlantic and Indo-Pacific[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/) |
| Defining morphology | Well-defined marginal plate series, clearly bounded plates, large disk with defined actinal regions, and a relatively heavily calcified skeleton[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) |
| Phylogenetic status | Recovered as paraphyletic in transcriptomic and mitogenomic analyses, while Forcipulatida, Velatida, Paxillosida, and Spinulosida were each monophyletic[2](https://www.sciencedirect.com/science/article/abs/pii/S1055790317301653) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/) |
| Deep-water divergence | Deep-sea and shallow-water Valvatida lineages split at an estimated 180.6 Ma (95% HPD 108.9–199.7 Ma)[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/) |
## Morphology
Most members of the Valvatida share a consistent skeletal framework. A marginal plate series frequently outlines the periphery of the body, boundaries between plates are relatively well defined, the disk is large with well-defined actinal regions, and the skeleton is relatively heavily calcified or otherwise modified.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) Some valvatidan taxa depart substantially from this body plan, including the Asterinidae, Ganeriidae, and Solasteridae.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/)
## Families and diversity
The order includes some of the most taxon-rich families in the Asteroidea. Traditionally recognized valvatidan families include the Acanthasteridae, Archasteridae, Asterodiscididae, Asteropseidae, Goniasteridae, Oreasteridae, Ophidiasteridae, and Odontasteridae.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) The Goniasteridae alone contains 256 species, the largest species count of any asteroid family, and the Ophidiasteridae, with 106 species, dominates tropical shallow-water habitats in the Atlantic and [Indo-Pacific](https://www.edgepedia.org/indo-pacific).[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/)
Familiar examples show the order's ecological range. The crown-of-thorns starfish *Acanthaster* falls on a valvatidan clade in COI phylogenies.[1](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/) The Carpet Sea Star (*Patiriella calcar*), an asterinid placed in the Valvatida, reaches about 5 cm, lives on Australian intertidal rocky shores to a depth of 3 m, and differs from most other echinoderms in being viviparous, giving birth to live young that develop within the parent.[3](https://australian.museum/learn/animals/sea-stars/carpet-sea-star/)
## Molecular phylogeny and the paraphyly problem
Classification within the broader group containing the Valvatida has been historically problematic, and molecular work has reshaped it substantially. A three-gene analysis of the Valvatacea by Christopher Mah of the [Smithsonian Institution](https://www.edgepedia.org/smithsonian-institution) and David Foltz of Louisiana State University, using 12S, 16S, and early-stage histone H3 and sampling 13 of the 16 living valvatidan families, moved the Solasteridae out of the [Velatida](https://www.edgepedia.org/velatida) and into the clade containing the Asterinidae, supported the Poraniidae as sister to the large valvatacean cluster, and found that the goniasterid-like ophidiasterids *Fromia* and *Neoferdina* are derived goniasterids rather than true Ophidiasteridae.[5](https://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2010.00659.x)
Later, larger datasets confirmed the core problem. A 2017 comparative transcriptomic study of extant starfish recovered the Valvatida as paraphyletic, while the orders Forcipulatida, Velatida, Paxillosida, and [Spinulosida](https://www.edgepedia.org/spinulosida) were each monophyletic; the earliest divergence among extant asteroids separated Velatida and Forcipulatacea from the remaining lineages.[2](https://www.sciencedirect.com/science/article/abs/pii/S1055790317301653) A mitogenomic study of deep-sea sea stars likewise found the Valvatida paraphyletic and reported that the phylogenetic positions of the Ophidiasteridae and Goniasteridae vary with the analytical method: nucleotide-based trees and amino-acid-based trees placed these families differently relative to the [Paxillosida](https://www.edgepedia.org/paxillosida), Notomyotida, and Spinulosida.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/) The order has also been described as splitting into two primary clades, with family placements varying by method.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC12912233/)
## Timing of divergences
A Bayesian relaxed-molecular-clock analysis of mitochondrial genomes estimated that the deep-sea and shallow-water Valvatida species split 180.6 Ma (95% HPD 108.9–199.7 Ma). Comparable splits in other asteroid orders, including 233.8 Ma for deep-sea Paxillosida and Notomyotida and 189.2 Ma for the Velatida, indicate that divergences between deep-sea and shallow-water asteroids coincided approximately with the Triassic–Jurassic transition, a period marked by a mass extinction event.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/)
## Enigmatic members
The genus *Podosphaeraster*, currently placed in the Valvatida, comprises seven species characterized by a distinctive spherical body, all known from seabed depths below approximately 70 m. Its placement has been debated: an initial suggestion of affinity with the fossil Sphaerasteridae was later attributed to convergent evolution, and a study of *Podosphaeraster toyoshiomaruae* from Japanese waters positioned it as the most basal lineage within the Valvatida, though with low statistical support possibly due to long-branch attraction from a rapid evolutionary rate. [Shotgun sequencing](https://www.edgepedia.org/shotgun-sequencing) of its mitochondrial genome revealed a translocation of the COX2 gene, the first discovery of a major protein-coding gene translocation within the Asteroidea, and micro-CT imaging showed mesentery skeletal connections suggesting its marginal plates may not be homologous with those of other asteroids.[7](https://pubmed.ncbi.nlm.nih.gov/42713091/)
## References
1. [Global Diversity and Phylogeny of the Asteroidea (Echinodermata), PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3338738/)
2. [The phylogeny of extant starfish (Asteroidea: Echinodermata) including Xyloplax, based on comparative transcriptomics, Molecular Phylogenetics and Evolution 115 (2017)](https://www.sciencedirect.com/science/article/abs/pii/S1055790317301653)
3. [Carpet Sea Star, The Australian Museum](https://australian.museum/learn/animals/sea-stars/carpet-sea-star/)
4. [Mitogenomics provides new insights into the phylogenetic relationships and evolutionary history of deep-sea sea stars (Asteroidea), Scientific Reports (2022)](https://pmc.ncbi.nlm.nih.gov/articles/PMC8933410/)
5. [Mah, C. and Foltz, D. (2011). Molecular phylogeny of the Valvatacea (Asteroidea: Echinodermata), Zoological Journal of the Linnean Society 161: 769–788](https://onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2010.00659.x)
6. [The complete mitochondrial genome of Atheraster arandae (Asteroidea: Valvatida: Goniasteridae) from the western Pacific](https://pmc.ncbi.nlm.nih.gov/articles/PMC12912233/)
7. [Phylogenetic position of the enigmatic starfish family Podosphaerasteridae (Asteroidea, Valvatida) with a morphological observation of the skeletal structure by micro-CT](https://pubmed.ncbi.nlm.nih.gov/42713091/)
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*Topic: Encyclopedia › Life and health › Animals › Invertebrates › Other invertebrate lineages › Echinoderms and nonvertebrate chordates › Echinodermata (phylum and living classes) › Sea stars (Asteroidea) › Sea star genera and species › Valvatida*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 11, 2026; Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license