Hemicyclaspis

Hemicyclaspis is an extinct genus of primitive jawless fish, closely related to Cephalaspis, that lived in the Late Silurian (Pridoli) to Devonian period in what is now Europe and North America. A typical cephalaspid, Hemicyclaspis had a heavily armored, shovel-shaped headshield. It is thought to have been a better swimmer than most of its relatives because of its powerful tail, stabilizing dorsal fin and the keel-shaped hydrodynamic edges of its head shield. Hemicyclaspis probably foraged the ocean floor for food.

Hemicyclaspis

the paleobear · CC BY 2.0 · 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
AteleaspididaePBDB
Motility
actively mobilePBDB, for Chordata

Time the record covers

At least 7 million years on record.

The record covers at least 426.7 Mya to 419.62 Mya. No occurrence read is dated outside 432.9 Mya to 413.02 Mya.

Silurian — about 7 of 8 occurrencesSilurianDevonian — about 1 of 8 occurrencesDevonian433–433 Mya — about 0.0 occurrences433–432 Mya — about 0.1 occurrences432–431 Mya — about 0.1 occurrences431–431 Mya — about 0.1 occurrences431–430 Mya — about 0.1 occurrences430–429 Mya — about 0.1 occurrences429–429 Mya — about 0.1 occurrences429–428 Mya — about 0.1 occurrences428–427 Mya — about 0.1 occurrences427–426 Mya — about 0.1 occurrences423–422 Mya — about 0.8 occurrences422–422 Mya — about 1 occurrence422–421 Mya — about 1 occurrence421–420 Mya — about 1 occurrence420–419 Mya — about 1 occurrence419–419 Mya — about 0.1 occurrences419–418 Mya — about 0.1 occurrences418–417 Mya — about 0.1 occurrences417–417 Mya — about 0.1 occurrences417–416 Mya — about 0.1 occurrences416–415 Mya — about 0.1 occurrences415–415 Mya — about 0.1 occurrences415–414 Mya — about 0.1 occurrences414–413 Mya — about 0.1 occurrences413–413 Mya — about 0.0 occurrences426.7 Mya419.62 Mya433.4 Mya412.5 Mya

8 occurrences of Hemicyclaspis on record, most of them in the Silurian. 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

8 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

7 formations

Ledbury — 51.95°N, 2.88°WCowie — 56.95°N, 2.20°WTemeside Shale — 52.37°N, 2.73°WPeel Sound — 73.25°N, 93.50°WSomerset Island — 73.98°N, 95.28°WDownton Castle Sandstone — 52.53°N, 2.14°WDownton — 52.21°N, 3.04°W

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The named rock units Hemicyclaspis has been recovered from, largest first. Drawn where the rock is now, not where it formed.

Hemicyclaspis and its relatives

Silurian

Where Hemicyclaspis and its relatives were recorded in the Silurian.

Found in the same rock

64 taxa

The Paleobiology Database records 7 sites for Hemicyclaspis, 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

6 references

Each of the 8 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. 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 content2

Picture of Hemicyclaspis

Credit
the paleobear
Licence
CC BY 2.0
Commercial use
the licence allows it

3D model

Source
Sketchfab
Licence
CC Attribution-NonCommercial
Commercial use
the licence does not allow it

Smithsonian Open Access and MorphoSource were 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 itAteleaspididae through timeFormations of the SilurianThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. Lankaster 1870