Omnisaura
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Footprint type

Plesiornis

Hitchcock 1858

Plesiornis is a footprint type: the name is for the fossil footprints themselves. The animal that made them is not known for certain. Its footprints are found in rocks 227.3–192.9 million years old in the United States and Poland.

Confidence labels
How sure are we?0 high5 medium6 lowHow we rate confidence

Confidence labels are switched off. Facts with low confidence, or where sources disagree, still carry a small dot: tap it for the reason.

At a glance

Data as of 12 October 2026
227.3–192.9 Ma
Triassic
Jurassic
Cretaceous
252 million years ago20114366

The last non-bird dinosaurs died out 66 million years ago. That's as far from us as the end of this bar.

Named by
Hitchcock 1858
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Described in
R. S. Lull (1953). Triassic life of the Connecticut Valley (revised). State of Connecticut State Geological and Natural History Survey Bulletin 81: 1–336.
lowlow: PBDB gives this publication for the name, but its author or year differ from the naming authority (Hitchcock 1858): it may be a later work, such as one that renamed or redefined the genus.
Sources

Given by: Paleobiology Database. The publication the Paleobiology Database gives as the authority for this genus name, usually the one that first named and described it.

Dated to
Norian to Sinemurian, 227.3–192.9 million years ago
mediummedium: Only PBDB gives this; nothing contradicts it.
Omnisaura calculation227.3–192.9 million years ago, from its dated fossil records
mediummedium: Omnisaura's calculation from 4 confirmed PBDB records.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Found in
United States
mediummedium: Only PBDB records it (3 records).
Poland
lowlow: Only one PBDB record.
mixedmixed: Levels differ between entries; each has its own.
Sources

Given by: Paleobiology Database. How it was chosen: Union of all sources (ISO 3166).

Rock formations
Manassas Sandstone
lowlow: Only one PBDB record.
Portland Formation
lowlow: Only one PBDB record.
Przysucha
lowlow: Only one PBDB record.
Turners Falls
lowlow: Only one PBDB record.
Sources

Given by: Paleobiology Database. How it was chosen: Canonical names, automatic and editor-approved matches applied.

Parent group
Saurischia
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

Given by: Paleobiology Database. How it was chosen: PBDB leads.

Known from
Footprints and traces
Sources

Given by: Paleobiology Database (what the name was based on).

Made by
Not known for certain. Footprints rarely show which animal made them.
Sources: Paleobiology Database (CC BY 4.0), Natural History Museum Data Portal (CC0 1.0)Confidence levels and gaps are Omnisaura's own assessment.

Gaps are answers

What isn't known yet

  • The animal that made them: not known for certain, as for most footprint types.
  • Type species: no source we use gives it yet.
  • Order: no source we use gives it yet.
  • Family: no source we use gives it yet.
  • Common names: no source we use gives it yet.
  • What it was named after: no source we use gives it yet.
  • Held back: 1 fossil record left out: identified only tentatively (for example "cf." or "?").
  • Resting on one source: 4 facts come from a single source with nothing against them (rated medium): name (PBDB); authority (PBDB); parent group (PBDB); age (headline) (PBDB).

Size, diet and behaviour aren't covered yet. Omnisaura leaves them out rather than guess.

Where sources disagree

None open. Where our sources overlap, they agree on everything shown here.

Did it meet…?

?

No. Plesiornis had gone at least 109.3 million years before Tyrannosaurus appears in the fossil record, a longer gap than the 66 million years between Tyrannosaurus and today.

Going by the ages and rock formations of their dated fossils, as on the map. Compare their fossil sites on the map.

Found in the same rocks

Genera and other fossil types from the same formations, from rocks of the same age.

EubrontesGrallatorAnomoepusArgoidesPlatypternaPlectropternaSauropusOtozoumKayentapusAnchisauripusAnchisaurusTrihamusXiphopezaAnticheiropusPlectropusSelenichnusand 2 more

Same parent group

Other genera in Saurischia with a full profile.

AlwalkeriaAnticheiropusArgoidesChindesaurusCoelurosaurichnusDaemonosaurusDeuterotetrapousParachirotheriumPlatypternaTawaTrihamus

Credits

Where this page comes from

  • Paleobiology DatabaseCC BY 4.0 · fossil records, ages, classification
  • Natural History Museum Data PortalCC0 1.0 · catalogued specimens
  • OmnisauraOmnisaura editorial · confidence levels and gaps
  • PaleoMAP PaleoCoastlines (Kocsis and Scotese 2021)CC BY 4.0 · ancient coastlines on the small map
  • Natural EarthPublic domain · today's coastlines