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EXHIBIT 227

Tylosaurus

Tylosaurus proriger

Marine reptile

A marine lizard with an elongated adult snout tip, whose fossil identities are still being revised. [2]

Evidence profile

TWO WAYS TO PICTURE THE PAST

Compare the evidence with the familiar movie image. The illustrations are not to a shared scale.

01 / SOURCE-INFORMED RECONSTRUCTION

A life reconstruction from the evidence

Illustrative life reconstruction of Tylosaurus in a period-appropriate environment; coloration and missing anatomy are interpretations.

An illustrative reconstruction. Compare its anatomy with the evidence and limitations in the dossier. [2]

Source-informed reconstruction. Appearance evidence [2]. Original illustration; missing anatomy, coloration and scenery include interpretation.

Fossils constrain this life reconstruction. Missing anatomy, coloration and the environmental scene include interpretation; the dossier explains the evidence limits.

02 / MOVIE-STYLE INTERPRETATION

A cinematic imagination

Tylosaurus proriger restored in a period-appropriate marine setting; colors and missing soft tissues are interpretive.

An illustrative reconstruction. Compare its anatomy with the evidence and limitations in the dossier. Lighting, coloration and scenery are artistic choices. This image does not document a fossil locality or behavior.

Original artwork · artistic interpretation.

Scientific view: source-informed reconstruction, credited paleoart or specimen-based imagery. Movie-style view: Original artistic interpretation. Reconstructions involve uncertainty.

PERIODLate Cretaceous[1]
DIETCarnivore (inferred)Evidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDUnited States[1]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Tylosaurus

Tylosaurus was a mosasaur: a marine lizard, rather than a dinosaur or a fish. The T. proriger type specimen includes parts of a toothed skull and jaw. Scientists use that specimen as a reference when deciding whether another fossil belongs to the same species. [D1]

Its toothless adult snout tip is an important feature, but growth changes matter. A much smaller specimen, FHSM VP14845, has a short, rounded snout. It was interpreted as newborn-sized and identified only as Tylosaurus, so it cannot tell us the appearance of every T. proriger baby. [D3]

Names can change even for well-known museum fossils. In2026, researchers placed Bunker and Sophie in a newly named species, Tylosaurus rex. This means their size claims should stay with those particular fossils and their revised identification, rather than being silently transferred to the species shown here. [D4]

Research on growing skulls can separate age differences from species differences. One analysis did not recover skeletal differences attributable to sex. That does not reveal a courtship dance, a mating season or the colors of living animals; those details remain beyond the reviewed evidence. [D2]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

The animal, the evidence, and the questions still open.

Historical museum material remains valuable. A rediscovered type specimen supplies a reference for testing names attached to other fossils. [D6]

Profile scope: Genus exhibit represented by T. proriger from the Niobrara Formation; the holotype MCZ VPRA4374 anchors species identification. [D1]

Time
Late Cretaceous
Fossil locations in this exhibit
United States
How to read the evidence

Source supported identifies a description documented by the cited source. Inferred marks a reconstruction or functional estimate. Debated marks competing interpretations. Not established means the sources reviewed for this dossier do not support a firm conclusion; it does not mean a behavior never occurred.

A size reference is an estimate, not a population range. Nesting evidence does not by itself establish courtship, mate choice, or lifelong pairing.

Length

Inferred

8.24 m holotype estimate

Corrected Table 2 estimates MCZ VPRA4374 from jaw proportions. This individual model is not an adult species range or direct whole-skeleton measurement. [D1]

Body mass

Not established

Not established here

The inspected holotype study models length, not a comparable body-mass estimate; no kilogram value is adopted. [D1]

Diet

Inferred

Animal feeding inferred

Large teeth and predatory anatomy support animal feeding; a specific hunting sequence is not directly observed. [D6]

Habitat

Source supported

Niobrara marine waters

T. proriger type material is attributed to western Kansas Niobrara deposits; its exact original collecting site is uncertain. [D1]

Locomotion

Inferred

Aquatic swimmer

Flippers and a propulsive tail characterize restored Tylosaurus; swimming speed and stroke details are not measured here. [D6]

Anatomy

Source supported

Elongated adult snout tip

The adult skull has a toothless premaxillary extension; newborn proportions differ and should not be copied from adults. [D2]

Reproduction & life together

Reproduction

Inferred

Live birth inferred comparatively

Clidastes neonates support broader mosasaur viviparity; they are not Tylosaurus embryos or a measured T. proriger litter. [D7]

Courtship

Not established

Not established here

The growth analysis found no recovered skeletal sexual dimorphism. That result establishes neither mating displays nor their absence. [D2]

Social behavior

Not established

Not established here

Injury and swallowed prey do not establish stable groups, solitary routines or fighting specifically over mates. [D6]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. Redescription of the holotypes of Tylosaurus proriger and Tylosaurus nepaeolicus (Squamata: Mosasauridae)Deinsea / Natural History Museum Rotterdam · Accessed 2026-10-06Original paper and July6 erratum inspected: type provenance, diagnosis, jaw-based length estimation and corrected Table 2. · Inspected: page
  2. Craniofacial ontogeny in TylosaurinaePeerJ / NCBI PMC · Accessed 2026-10-06Growth series, specimen identifications and sexual-dimorphism discussion; historical referrals require comparison with 2026 revisions. · Inspected: page
  3. The smallest-known neonate individual of Tylosaurus (Mosasauridae, Tylosaurinae) sheds new light on the tylosaurine rostrum and heterochronyJournal of Vertebrate Paleontology · Accessed 2026-10-06Original abstract inspected: fragmentary FHSM VP14845,30cm estimated skull and newborn-size inference; not identified to species. · Inspected: abstract
  4. Giant Mosasaur Species from Texas Named T. rexAmerican Museum of Natural History · Accessed 2026-10-06May2026 institutional account of T. rex and reassignment of Bunker/Sophie. It does not establish T. proriger size or mating behavior. · Inspected: page
  5. A New Hypothesis of the Phylogenetic Relationships of the Tylosaurinae (Squamata: Mosasauroidea)Frontiers in Earth Science · Accessed 2026-10-06Systematic Tylosaurus diagnosis and 2019 Hainosaurus synonymy; compared with 2026 paper that again uses Hainosaurus. · Inspected: page
  6. How a giant predator of prehistoric seas was discovered — twiceHarvard Faculty of Arts and Sciences · Accessed 2026-10-06Institutional account of MCZ4374 provenance and predatory anatomy. Interview interpretations of solitary life/mate fighting are not treated as direct behavioral evidence. · Inspected: page
  7. Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous mosasaursPalaeontology / Wiley · Accessed 2026-10-06Systematic description of cf. Clidastes neonates and discussion of broader mosasaur viviparity; comparative evidence, not pregnancy in this exhibit genus. · Inspected: page

THE STORY IN THE FOSSILS

A name anchored by an old jaw.

The type specimen MCZ VPRA4374 was never actually lost from its museum. Re-examination reconnects the species name with bones that can be checked, instead of relying on assumptions about other famous skeletons. [6]

Bunker and Sophie were reassigned to Tylosaurus rex in 2026. Their measurements and injuries therefore cannot automatically describe T. proriger. A familiar museum label can change when scientists compare the underlying anatomy. [4]

A note on scale and time

The dossier identifies the scope of each reference estimate. A mount, an individual fossil and a species-wide adult range are different measurements. Comparison metrics remain unavailable where adult scope has not been established. Unknown does not mean zero.

Sources & editorial notes

Sources support the stated claims and scopes. Refer to the evidence notes for uncertainty.

  1. Redescription of the holotypes of Tylosaurus proriger and Tylosaurus nepaeolicus (Squamata: Mosasauridae)Deinsea / Natural History Museum Rotterdam · Accessed 2026-10-06Original paper and July6 erratum inspected: type provenance, diagnosis, jaw-based length estimation and corrected Table 2. · Inspected: page
  2. Craniofacial ontogeny in TylosaurinaePeerJ / NCBI PMC · Accessed 2026-10-06Growth series, specimen identifications and sexual-dimorphism discussion; historical referrals require comparison with 2026 revisions. · Inspected: page
  3. The smallest-known neonate individual of Tylosaurus (Mosasauridae, Tylosaurinae) sheds new light on the tylosaurine rostrum and heterochronyJournal of Vertebrate Paleontology · Accessed 2026-10-06Original abstract inspected: fragmentary FHSM VP14845,30cm estimated skull and newborn-size inference; not identified to species. · Inspected: abstract
  4. Giant Mosasaur Species from Texas Named T. rexAmerican Museum of Natural History · Accessed 2026-10-06May2026 institutional account of T. rex and reassignment of Bunker/Sophie. It does not establish T. proriger size or mating behavior. · Inspected: page
  5. A New Hypothesis of the Phylogenetic Relationships of the Tylosaurinae (Squamata: Mosasauroidea)Frontiers in Earth Science · Accessed 2026-10-06Systematic Tylosaurus diagnosis and 2019 Hainosaurus synonymy; compared with 2026 paper that again uses Hainosaurus. · Inspected: page
  6. How a giant predator of prehistoric seas was discovered — twiceHarvard Faculty of Arts and Sciences · Accessed 2026-10-06Institutional account of MCZ4374 provenance and predatory anatomy. Interview interpretations of solitary life/mate fighting are not treated as direct behavioral evidence. · Inspected: page
  7. Pelagic neonatal fossils support viviparity and precocial life history of Cretaceous mosasaursPalaeontology / Wiley · Accessed 2026-10-06Systematic description of cf. Clidastes neonates and discussion of broader mosasaur viviparity; comparative evidence, not pregnancy in this exhibit genus. · Inspected: page

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