| Tetragraptus approximatus Temporal range:
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| Illustration of Tetragraptus approximatus | |
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| Original illustrations of Tetragraptus approximatus by Nicholson (1873). At the top is a magnified section of the stipes. A complete specimen is illustrated below. | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Hemichordata |
| Class: | Pterobranchia |
| Order: | †Graptoloidea |
| Family: | †Dichograptidae |
| Genus: | †Tetragraptus |
| Species: | †T. approximatus
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| Binomial name | |
| †Tetragraptus approximatus Nicholson, 1873
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Tetragraptus approximatus is a species of dichograptid graptolite belonging to the genus Tetragraptus. It existed during the Floian Age (477.1 million years ago) of the Ordovician. It is an important index fossil in biostratigraphy.