Alvarezsauridae

Alvarezsauridae is a family of small, long-legged dinosaurs. Although originally thought to represent the earliest known flightless birds, they are now thought to be an early diverging branch of maniraptoran theropods. Alvarezsaurids were highly specialized, with tiny, stout forelimbs ending in compact, bird-like hands. Their skeletons suggest that they had massive breast and arm muscles, possibly adapted for digging or tearing. They had long, tube-shaped snouts filled with tiny teeth. They have generally been interpreted as myrmecophagous, adapted to prey on colonial insects such as termites, with the short arms acting as effective digging instruments to break into nests. Alternative hypotheses of ovivory interpret the manus as specialized shell-cracking apparatuses, using the large claws and robust forelimbs to puncture eggs.

Alvarezsauridae

★Kumiko★ · CC BY-SA 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
AlvarezsauroideaPBDB
Diet
carnivorePBDB, for Coelurosauria
Life habit
ground dwelling, solitaryPBDB, for Theropoda
Motility
actively mobilePBDB, for Theropoda
Environment
terrestrialPBDB, for Theropoda

Time the record covers

At least 37 million years on record.

The record covers at least 110.1 Mya to 72.2 Mya. No occurrence read is dated outside 113.2 Mya to 66 Mya.

Early Cretaceous — about 2 of 40 occurrencesEarly CretaceousLate Cretaceous — about 38 of 40 occurrencesLate CretaceousPaleocene — about 0 of 40 occurrences114–113 Mya — about 0.4 occurrences113–111 Mya — about 1 occurrence111–109 Mya — about 0.5 occurrences95–93 Mya — about 0.4 occurrences93–91 Mya — about 0.6 occurrences91–90 Mya — about 0.6 occurrences90–88 Mya — about 0.5 occurrences88–86 Mya — about 0.5 occurrences86–85 Mya — about 1 occurrence85–83 Mya — about 2 occurrences83–81 Mya — about 2 occurrences81–80 Mya — about 2 occurrences80–78 Mya — about 2 occurrences78–77 Mya — about 2 occurrences77–75 Mya — about 2 occurrences75–73 Mya — about 2 occurrences73–72 Mya — about 3 occurrences72–70 Mya — about 5 occurrences70–68 Mya — about 5 occurrences68–67 Mya — about 5 occurrences67–65 Mya — about 2 occurrences110.1 Mya72.2 Mya114.1 Mya65.1 Mya

40 occurrences of Alvarezsauridae on record, most of them in the Late Cretaceous. 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

40 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

15 formations

Hell Creek — 47.68°N, 106.43°WHell Creek — 47.65°N, 106.38°WHell Creek — 47.57°N, 106.91°WHell Creek — 47.71°N, 106.57°WHell Creek — 47.87°N, 107.26°WHell Creek — 47.11°N, 104.71°WHell Creek — 45.70°N, 104.72°WHell Creek — 45.00°N, 103.19°WNemegt — 43.54°N, 99.60°ENemegt — 43.48°N, 99.80°ENemegt — 43.87°N, 100.01°ENemegt — 43.50°N, 100.33°EBaruungoyot — 43.47°N, 101.52°EBaruungoyot — 43.15°N, 99.45°EBaruungoyot — 43.47°N, 99.83°EBaruungoyot — 43.49°N, 101.28°EBaruungoyot — 43.51°N, 101.08°EDjadokhta — 43.66°N, 100.90°EDjadokhta — 44.22°N, 103.27°EDjadokhta — 44.00°N, 104.00°EBajo de la Carpa — 39.12°S, 67.63°WBajo de la Carpa — 38.95°S, 68.23°WSînpetru — 45.55°N, 22.91°EWulansuhai — 41.74°N, 106.74°ECandeleros — 39.71°S, 68.60°WCandeleros — 39.63°S, 68.70°WPortezuelo — 38.90°S, 69.55°WHorseshoe Canyon — 52.00°N, 112.88°WMajiacun — 33.29°N, 111.47°EJavkhlant — 44.39°N, 109.35°ERâul Mare — 45.58°N, 22.93°EQiupa — 33.82°N, 111.63°EBissekty — 42.12°N, 62.66°E

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

Alvarezsauridae and its relatives

Late Cretaceous

Where Alvarezsauridae and its relatives were recorded in the Late Cretaceous.

Found in the same rock

298 taxa

The Paleobiology Database records 39 sites for Alvarezsauridae, 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

32 references

Each of the 40 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. 20 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 Alvarezsauridae

Credit
★Kumiko★
Licence
CC BY-SA 2.0
Commercial use
the licence allows it

No 3D scan of Alvarezsauridae was found in Smithsonian Open Access and Sketchfab.

MorphoSource 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 itAlvarezsauroidea through timeFormations of the Late CretaceousThe world it lived on

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