Helcionelloida

Helcionelloida is an extinct group of ancient molluscs. These are the oldest known conchiferan molluscs, that is, they had a mineralised shell. Some members of this class were mistaken for Monoplacophorans. The class was erected by Peel in 1991.

Helcionelloida

Apokryltaros at English Wikipedia · CC BY-SA 3.0 · 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
MolluscaPBDB
Diet
detritivorePBDB
Life habit
low-level epifaunalPBDB
Motility
slow-movingPBDB
Vision
limitedPBDB
Environment
marinePBDB

Time the record covers

At least 49 million years on record.

The record covers at least 530.7 Mya to 481.1 Mya. No occurrence read is dated outside 538.8 Mya to 477.1 Mya.

Cambrian — about 2025 of 2031 occurrencesCambrianOrdovician — about 6 of 2031 occurrencesOrdovician540–538 Mya — about 12 occurrences538–536 Mya — about 28 occurrences536–534 Mya — about 28 occurrences534–531 Mya — about 28 occurrences531–529 Mya — about 59 occurrences529–527 Mya — about 79 occurrences527–525 Mya — about 116 occurrences525–523 Mya — about 258 occurrences523–521 Mya — about 244 occurrences521–519 Mya — about 123 occurrences519–517 Mya — about 124 occurrences517–514 Mya — about 226 occurrences514–512 Mya — about 256 occurrences512–510 Mya — about 116 occurrences510–508 Mya — about 73 occurrences508–506 Mya — about 70 occurrences506–504 Mya — about 73 occurrences504–502 Mya — about 41 occurrences502–499 Mya — about 32 occurrences499–497 Mya — about 17 occurrences497–495 Mya — about 5 occurrences495–493 Mya — about 3 occurrences493–491 Mya — about 3 occurrences491–489 Mya — about 6 occurrences489–487 Mya — about 6 occurrences487–484 Mya — about 1 occurrence484–482 Mya — about 1 occurrence482–480 Mya — about 1 occurrence480–478 Mya — about 2 occurrences478–476 Mya — about 0.7 occurrences530.7 Mya481.1 Mya540 Mya476 Mya

2,031 occurrences of Helcionelloida on record, most of them in the Cambrian. 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

2,031 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

175 formations

Zhujiaqing — 25.64°N, 103.07°EZhujiaqing — 27.93°N, 103.56°EZhujiaqing — 26.38°N, 103.07°EZhujiaqing — 24.73°N, 102.57°EZhujiaqing — 24.67°N, 102.65°EZhujiaqing — 26.28°N, 103.22°EZhujiaqing — 24.65°N, 103.13°EZhujiaqing — 25.52°N, 103.07°EZhujiaqing — 26.38°N, 103.21°EPestrotsvet — 58.75°N, 128.00°EPestrotsvet — 58.75°N, 127.00°EPestrotsvet — 60.83°N, 125.33°EPestrotsvet — 61.00°N, 126.00°EPestrotsvet — 57.35°N, 131.20°EPestrotsvet — 57.67°N, 131.83°EPestrotsvet — 57.17°N, 132.00°EPestrotsvet — 60.70°N, 124.72°EPestrotsvet — 60.92°N, 125.77°EPestrotsvet — 60.83°N, 125.40°EPestrotsvet — 58.50°N, 129.50°EPestrotsvet — 66.40°N, 112.28°EPestrotsvet — 71.83°N, 107.00°EPestrotsvet — 71.50°N, 105.00°EPestrotsvet — 61.13°N, 126.80°EPestrotsvet — 57.40°N, 132.73°EParara — 34.73°S, 137.63°EParara — 34.70°S, 137.71°EParara — 34.06°S, 138.02°EParara — 34.80°S, 137.69°EParara Limestone — 34.92°S, 137.80°EAjax Limestone — 30.59°S, 138.33°EDengying — 26.33°N, 103.17°EDengying — 26.42°N, 103.50°EDengying — 25.08°N, 102.98°EDengying — 25.48°N, 103.03°EDengying — 33.00°N, 107.92°EDengying — 32.35°N, 106.82°EDengying — 28.27°N, 103.40°EDengying — 30.73°N, 111.13°EDengying — 30.77°N, 111.12°EDengying — 25.52°N, 103.07°EDengying — 24.72°N, 102.56°EDengying — 33.67°N, 109.46°EHenson Gletscher — 82.00°N, 42.00°WHenson Gletscher — 82.50°N, 36.33°WHenson Gletscher — 82.20°N, 30.08°WHenson Gletscher — 82.25°N, 29.75°WHenson Gletscher — 82.17°N, 39.67°WHenson Gletscher — 82.29°N, 39.68°WHenson Gletscher — 82.15°N, 42.42°WHenson Gletscher — 82.16°N, 42.45°WHenson Gletscher — 82.17°N, 40.40°WHenson Gletscher — 82.30°N, 37.05°WChapel Island — 46.92°N, 56.00°WChapel Island — 47.00°N, 56.00°WChapel Island — 47.07°N, 55.87°WMernmerna — 31.19°S, 138.87°EMernmerna — 31.41°S, 138.43°EMernmerna — 31.41°S, 138.56°EMernmerna — 30.81°S, 140.69°EMernmerna — 31.55°S, 140.79°EMernmerna — 30.79°S, 139.14°EBastion — 74.10°N, 23.00°WBastion — 74.35°N, 22.77°WBastion — 73.52°N, 24.68°WBastion — 72.85°N, 25.03°WBystraya — 52.00°N, 119.00°EXinji — 33.27°N, 112.98°EXinji — 34.53°N, 110.87°EXinji — 33.38°N, 113.43°EXinji — 34.90°N, 106.85°EJbel Wawrmast — 32.00°N, 6.00°WJbel Wawrmast — 30.67°N, 8.17°EJbel Wawrmast — 30.67°N, 8.17°WJbel Wawrmast — 30.58°N, 7.20°WJbel Wawrmast — 31.21°N, 7.88°WJbel Wawrmast — 31.08°N, 8.13°WJbel Wawrmast — 31.52°N, 5.02°WJbel Wawrmast — 31.37°N, 5.02°WEmyaksin — 62.00°N, 129.67°EEmyaksin — 70.72°N, 112.88°EEmyaksin — 70.22°N, 113.70°EEmyaksin — 70.72°N, 112.76°EEmyaksin — 68.52°N, 111.93°EHuangshandong — 30.70°N, 111.28°EHuangshandong — 30.83°N, 111.17°EMedvezhyn — 71.00°N, 102.00°EMedvezhyn — 70.64°N, 103.43°EMedvezhyn — 70.62°N, 103.53°EMedvezhyn — 71.50°N, 102.50°EMedvezhya — 71.33°N, 99.50°EMedvezhya — 70.14°N, 114.00°EWilkawillina Limestone — 30.81°S, 140.69°EWilkawillina Limestone — 30.72°S, 139.20°EWilkawillina Limestone — 31.85°S, 140.63°EWilkawillina Limestone — 30.12°S, 137.16°EWilkawillina Limestone — 31.85°S, 140.01°EBrowns Pond — 42.22°N, 73.73°WBrowns Pond — 43.60°N, 73.32°WMedvezhin — 70.50°N, 103.40°EMedvezhin — 70.67°N, 103.00°EYanjiahe — 30.73°N, 111.08°EYanjiahe — 30.73°N, 111.03°EYanjiahe — 30.78°N, 111.35°EMernmerna Formation — 30.72°S, 139.18°EMernmerna Formation — 31.85°S, 140.63°EMernmerna Formation — 31.00°S, 139.26°EMernmerna Formation — 31.01°S, 139.24°EShackleton Limestone — 82.21°S, 160.33°WShackleton Limestone — 82.22°S, 160.31°EKuonamka — 70.74°N, 112.98°EKuonamka — 70.75°N, 116.75°EKuonamka — 70.22°N, 113.70°E

Loading coastlines…

The named rock units Helcionelloida has been recovered from, largest first. Drawn where the rock is now, not where it formed. 151 further formations hold fewer occurrences each and are not listed. 34 occurrences have no formation on record, which is common for older literature.

Helcionelloida and its relatives

Cambrian

Where Helcionelloida and its relatives were recorded in the Cambrian.

Found in the same rock

1,176 taxa

The Paleobiology Database records 748 sites for Helcionelloida, and this reads 240 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

228 references

Each of the 2,031 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. 216 further references are 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 Helcionelloida

Credit
Apokryltaros at English Wikipedia
Licence
CC BY-SA 3.0
Commercial use
the licence allows it

No 3D scan of Helcionelloida 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 itMollusca through timeFormations of the CambrianThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. Peel 1991