Limulidae

Horseshoe crabs are arthropods of the family Limulidae and the only surviving xiphosurans. Despite their name, they are not crabs or even crustaceans; they are chelicerates, more closely related to arachnids like spiders, ticks, and scorpions. The body of a horseshoe crab is divided into three main parts: the cephalothorax, abdomen, and telson. The largest of these, the cephalothorax, houses most of the animal's eyes, limbs, and internal organs. It is also where the animal gets its name, as its shape somewhat resembles that of a horseshoe. Horseshoe crabs have been described as "living fossils", having changed little since they first appeared in the Triassic around 250 million years ago, and similar-looking fossil xiphosurans extend back to the Ordovician around 445 million years ago.

Limulidae

Shubham Chatterjee · 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
Also called
horseshoe crabPBDB
Sits inside
LimuloideaPBDB
Diet
carnivorePBDB, for Xiphosura
Life habit
nektobenthicPBDB, for Xiphosura
Motility
actively mobilePBDB, for Xiphosura
Vision
limitedPBDB, for Xiphosurida

Time the record covers

At least 308 million years on record.

The record covers at least 346.7 Mya to 37.71 Mya. No occurrence read is dated outside 358.86 Mya to 33.9 Mya.

Devonian — about 0 of 51 occurrencesCarboniferous — about 1 of 51 occurrencesCarboniferousPermian — about 0 of 51 occurrencesEarly Triassic — about 5 of 51 occurrencesMiddle Triassic — about 18 of 51 occurrencesLate Triassic — about 1 of 51 occurrencesLate TriassicEarly Jurassic — about 2 of 51 occurrencesMiddle Jurassic — about 1 of 51 occurrencesLate Jurassic — about 14 of 51 occurrencesEarly Cretaceous — about 2 of 51 occurrencesEarly CretaceousLate Cretaceous — about 6 of 51 occurrencesLate CretaceousPaleocene — about 0 of 51 occurrencesEocene — about 1 of 51 occurrencesOligocene — about 0 of 51 occurrences365–354 Mya — about 0.4 occurrences354–343 Mya — about 0.6 occurrences253–241 Mya — about 19 occurrences241–230 Mya — about 4 occurrences230–219 Mya — about 0.4 occurrences219–208 Mya — about 0.5 occurrences208–196 Mya — about 2 occurrences196–185 Mya — about 0.4 occurrences185–174 Mya — about 0.2 occurrences174–163 Mya — about 0.8 occurrences163–151 Mya — about 1 occurrence151–140 Mya — about 13 occurrences129–118 Mya — about 0.3 occurrences118–106 Mya — about 2 occurrences106–95 Mya — about 3 occurrences95–84 Mya — about 0.7 occurrences84–72 Mya — about 1.0 occurrences72–61 Mya — about 1 occurrence39–27 Mya — about 1 occurrence346.7 Mya37.71 Mya365 Mya27 Mya

51 occurrences of Limulidae on record, most of them in the Middle Triassic. The Paleobiology Database records this as a living group, and the chart stops with its fossils rather than at the present. 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

51 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

26 formations

Solnhofen — 48.91°N, 11.14°ESolnhofen — 49.00°N, 11.70°EGrès à Voltzia — 48.91°N, 7.20°EGrès à Voltzia — 48.82°N, 7.24°EGrès à Voltzia — 48.69°N, 7.38°EGrès à Voltzia — 48.78°N, 7.25°EGrès à Voltzia — 48.64°N, 7.45°EGrès à Voltzia — 48.53°N, 7.43°EGrès à Voltzia — 48.64°N, 7.44°EMuschelkalk — 41.27°N, 1.12°ERybinsk — 58.02°N, 39.04°EAkrabou — 30.51°N, 4.84°WLiegende Bankkalk — 48.12°N, 8.87°EShar Teg — 44.12°N, 95.82°EWingate Sandstone/Kayenta — 38.18°N, 109.26°WOuled Chebbi — 33.41°N, 10.42°EKirchaou — 33.41°N, 10.42°EBallagan — 55.80°N, 2.28°WStrelovec — 46.37°N, 14.66°EKcynia — 51.38°N, 20.14°EMarnes irisées supérieures — 48.78°N, 6.53°EGlen Rose Limestone — 32.23°N, 97.79°WJena — 51.14°N, 11.74°EFox Hills — 46.32°N, 100.27°WSannine — 34.13°N, 35.74°EPierre Shale — 40.50°N, 105.09°WNorthampton Sand — 52.28°N, 0.71°WGuanling — 24.78°N, 104.33°EBorna — 51.11°N, 12.01°EMoenkopi — 37.83°N, 110.45°WTalynzhansk — 51.53°N, 133.75°E

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The named rock units Limulidae has been recovered from, largest first. Drawn where the rock is now, not where it formed. 2 further formations hold fewer occurrences each and are not listed. 8 occurrences have no formation on record, which is common for older literature.

Limulidae and its relatives

Middle Triassic

Where Limulidae and its relatives were recorded in the Middle Triassic.

Found in the same rock

447 taxa

The Paleobiology Database records 42 sites for Limulidae, 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

39 references

Each of the 51 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. 27 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 Limulidae

Credit
Shubham Chatterjee
Licence
CC BY-SA 3.0
Commercial use
the licence allows it

No 3D scan of Limulidae was found in Sketchfab.

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 itLimuloidea through timeFormations of the Middle TriassicThe world it lived on

Occurrence data from the Paleobiology Database, CC BY 4.0. Leach 1819