Chasmataspidida

Chasmataspidids, sometime referred to as chasmataspids, are a group of extinct chelicerate arthropods that form the order Chasmataspidida. Chasmataspidids are probably related to horseshoe crabs (Xiphosura) and/or sea scorpions (Eurypterida), while more recent studies suggest that they form a clade (Dekatriata) with Eurypterida and Arachnida. Chasmataspidids are known sporadically in the fossil record through to the mid-Devonian, with possible evidence suggesting that they were also present during the late Cambrian. Chasmataspidids are most easily recognised by having an opisthosoma divided into a wide forepart (preabdomen) and a narrow hind part (postabdomen) each comprising 4 and 9 segments respectively. There is some debate about whether they form a natural group.

Chasmataspidida

James C. Lamsdell, Gerald O. Gunderson and Ronald C. Meyer · CC BY-SA 4.0 · via Wikipedia/Commons. May be a photograph of a specimen, or an artist’s reconstruction — an interpretation of a skeleton, since colour and soft tissue are almost never preserved.

On record

Recorded, not inferred
Sits inside
DekatriataPBDB
Motility
actively mobilePBDB, for Arthropoda

Time the record covers

At least 83 million years on record.

The record covers at least 477.1 Mya to 393.47 Mya. No occurrence read is dated outside 486.85 Mya to 382.31 Mya.

Cambrian — about 0 of 21 occurrencesOrdovician — about 4 of 21 occurrencesOrdovicianSilurian — about 3 of 21 occurrencesSilurianDevonian — about 14 of 21 occurrencesDevonian489–485 Mya — about 0.2 occurrences485–482 Mya — about 0.4 occurrences482–478 Mya — about 0.4 occurrences478–474 Mya — about 0.1 occurrences471–467 Mya — about 0.1 occurrences467–464 Mya — about 0.4 occurrences464–460 Mya — about 0.4 occurrences460–456 Mya — about 0.2 occurrences453–449 Mya — about 0.3 occurrences449–445 Mya — about 2 occurrences445–442 Mya — about 0.1 occurrences442–438 Mya — about 0.2 occurrences438–435 Mya — about 0.2 occurrences435–431 Mya — about 0.2 occurrences431–427 Mya — about 0.9 occurrences427–424 Mya — about 0.4 occurrences424–420 Mya — about 0.8 occurrences420–416 Mya — about 5 occurrences416–413 Mya — about 5 occurrences413–409 Mya — about 1 occurrence409–406 Mya — about 0.7 occurrences406–402 Mya — about 0.7 occurrences402–398 Mya — about 0.4 occurrences395–391 Mya — about 0.2 occurrences391–387 Mya — about 0.3 occurrences387–384 Mya — about 0.3 occurrences384–380 Mya — about 0.1 occurrences477.1 Mya393.47 Mya489 Mya380 Mya

21 occurrences of Chasmataspidida on record, most of them in the Devonian. Bar height is expected occurrences, not a count: each fossil is spread across the span it is dated to, so a tall narrow bar means tight dating and a low wide one means loose.

When

21 occurrences

These are dates about fossils, not the animal: the record can only begin after it arose and end before it died out, so either end may reach further. Shares are expected occurrences: a fossil dated to a span is counted partly in each period it straddles. More on what this infers.

Found in

13 formations

Zub — 69.33°N, 88.10°EZub — 76.00°N, 104.00°EZub or Kureika — 74.00°N, 95.00°EBig Hill — 45.78°N, 86.86°WSundvollen — 60.17°N, 10.30°EBlackford — 35.96°N, 83.54°WSiegen — 50.58°N, 7.47°EKureika — 66.51°N, 87.24°EUpper Zub or Lower Kureika Formation — 72.02°N, 102.84°EPatrick Burn — 55.65°N, 3.92°WSevernaya Zemlya — 79.50°N, 96.00°EDundee Flagstone — 56.00°N, 2.00°WFiddlers Green — 42.96°N, 75.06°WFezouata — 30.50°N, 5.85°W

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The named rock units Chasmataspidida has been recovered from, largest first. Drawn where the rock is now, not where it formed. 3 occurrences have no formation on record, which is common for older literature.

Chasmataspidida and its relatives

Devonian

Where Chasmataspidida and its relatives were recorded in the Devonian.

Found in the same rock

134 taxa

The Paleobiology Database records 16 sites for Chasmataspidida, and this reads all of them. The number is how many of those sites it was catalogued from too. The 24 sharing the most are listed.

This is not a list of everything alive at the time. It is only what has come out of the same ground as this animal and been written down.

Entered from

13 references

Each of the 21 occurrences read was entered from one of these publications, ordered by how many each accounts for. This is not a search for papers mentioning the name. 1 further reference is not listed. Entries link to doi.org where the Paleobiology Database holds an identifier, and to its own record where it does not. Relayed as the Paleobiology Database holds them, not checked against what they resolve to.

Media and terms

Media content1

Picture of Chasmataspidida

Credit
James C. Lamsdell, Gerald O. Gunderson and Ronald C. Meyer
Licence
CC BY-SA 4.0
Commercial use
the licence allows it

No 3D scan of Chasmataspidida was found in MorphoSource and Sketchfab.

Smithsonian Open Access was not reached for this taxon, so this list is what the others held rather than everything there is.

The description on this site

Licence
CC BY-SA 4.0

This is what the site found, which is not the same as what exists.

Keep going

What may have been alongside itDekatriata through timeFormations of the DevonianThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. (Caster and Brooks 1956)