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Dinosaur genus

Hylaeosaurus

Mantell 1833

Hylaeosaurus is a dinosaur genus known from bones, found in rocks 139.1–110.1 million years old, in the United Kingdom, Germany and France.

Confidence labels
How sure are we?3 high6 medium8 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
139.1–110.1 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
Mantell 1833
mediummedium: Only PBDB gives this; nothing contradicts it.
Sources

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

Described in
G. A. Mantell (1833). The Geology of the South-East of England: xix–415. Read it
mediummedium: Only PBDB gives this; its author and year match the naming authority (Mantell 1833).
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.

Lived
Berriasian to Albian, 139.1–110.1 million years ago
highhigh: PBDB and NHM agree.
Omnisaura calculation139.1–110.1 million years ago, from its dated fossil records
mediummedium: Omnisaura's calculation from 10 confirmed PBDB records.
Sources

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

Fossils found in
United Kingdom
highhigh: NHM and PBDB both record it.
France
lowlow: Only one PBDB record.
Germany
lowlow: Only one PBDB record.
mixedmixed: Levels differ between entries; each has its own.
Sources

Given by: Paleobiology Database; Natural History Museum Data Portal. How it was chosen: Union of all sources (ISO 3166).

Rock formations
Tunbridge Wells Sand Formation
mediummedium: Only PBDB records it (3 records).
Ashdown Formation
lowlow: Only one PBDB record.
Bückeberg
lowlow: Only one PBDB record.
Greensand Formation
disputedlow: Only NHM gives this name and it matches no PBDB formation; awaiting an editor.
Wadhurst Clay Formation
lowlow: Only one PBDB record.
Weald Clay Formation
lowlow: Only one PBDB record.
West Melbury Marly Chalk Formation
disputedlow: Only NHM gives this name and it matches no PBDB formation; awaiting an editor.
mixedmixed: Levels differ between entries; each has its own.
Sources

Given by: Paleobiology Database; Natural History Museum Data Portal. How it was chosen: Canonical names, automatic and editor-approved matches applied.

Family
Nodosauridae
highhigh: PBDB and NHM agree.
Sources

Given by: Paleobiology Database; Natural History Museum Data Portal. How it was chosen: PBDB leads.

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

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

Order
Ornithischia
mediummedium: Only NHM gives this; nothing contradicts it.
Sources

Given by: Natural History Museum Data Portal. How it was chosen: Gap filled from NHM.

Known from
Bones
Sources

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

Sources: Paleobiology Database (CC BY 4.0), Natural History Museum Data Portal (CC0 1.0), Wikidata (CC0 1.0)Confidence levels and gaps are Omnisaura's own assessment.

Gaps are answers

What isn't known yet

  • Type species: 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: 2 fossil records left out: identified as a related genus rather than this one.
  • Held back: 2 fossil records left out: identified only to a broader group, not to this genus.
  • Resting on one source: 3 facts come from a single source with nothing against them (rated medium): authority (PBDB); parent group (PBDB); order (NHM).

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

Where sources disagree

2 open

Formations

  • NonePBDB
  • Greensand FormationNHM

One source names a formation the other does not. An editor hasn't ruled yet, so this is rated low until they do.

Formations

  • NonePBDB
  • West Melbury Marly Chalk FormationNHM

One source names a formation the other does not. An editor hasn't ruled yet, so this is rated low until they do.

Did it meet…?

?

No. Hylaeosaurus had gone at least 26.5 million years before Tyrannosaurus appears in the fossil record.

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

Lived alongside

Genera found in the same rock formations, from rocks of the same age.

IguanodonHypselospinusMegalosaurusIguanodontipusBariliumValdosaurusMetatetrapousPolacanthusBaryonyxCetiosaurusMantellisaurusPelorosaurus

Same family

Other genera in Nodosauridae with a full profile.

AcantholipanAnimantarxAnoplosaurusBorealopeltaEdmontoniaGastoniaGlyptodontopeltaHoplitosaurusHungarosaurusNiobrarasaurusNodosaurusPanoplosaurusPolacanthusSauropeltaSilvisaurusStruthiosaurusand 1 more

Credits

Where this page comes from

  • Paleobiology DatabaseCC BY 4.0 · fossil records, ages, classification
  • Natural History Museum Data PortalCC0 1.0 · catalogued specimens
  • WikidataCC0 1.0 · names and identifiers
  • 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

Pictures linked from this page are credited beside each one, with their own licences; the full list is in the JSON download.