EXPLORE PREHISTORY 240 prehistoric animal profiles · Scientific & movie-style image galleries
DinoGrove.
The collection/Xiphactinus

EXHIBIT 233

Xiphactinus

Xiphactinus audax

Prehistoric fish

A large toothed ray-finned fish, with a famous fossil preserving another fish inside it. [3]

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 Xiphactinus 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. [1]

Source-informed reconstruction. Appearance evidence [1]. 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

Xiphactinus audax 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]
DIETCarnivoreEvidence and uncertainty in the dossier
TOTAL LENGTHSee the dossierEstimate scope matters
FOSSILS FOUNDUnited States, Mexico[1]
CompareRead the dossierView the sources

MEET THE ANIMAL

Meet Xiphactinus

Xiphactinus was a ray-finned fish with large teeth, rather than a marine reptile or dinosaur. Mexican specimen MUZ3912 preserves enough head and fin anatomy for identification as X. audax. Other incomplete fossils can belong to the genus without allowing the same precise species identification. [D1]

One famous museum specimen contains a Gillicus fish inside it. This gives direct evidence that Xiphactinus swallowed fish. The fossil does not film the hunt or establish exactly why either animal died, so a dramatic account of a burst stomach should not be mistaken for a directly observed event. [D3]

A Venezuelan specimen comes from Cenomanian marine rocks of the La Luna Formation. Its authors identify only Xiphactinus, keeping the narrower species question open. This is an example of how an incomplete skull and vertebrae can still expand knowledge of a genus without answering every question about it. [D2]

Names also have histories. Museum records describe Portheus molossus as a historical name for X. audax, while older literature discusses a priority problem involving Polygonodon. Keeping those overlapping names together prevents the same animals being counted again as completely separate additions to a collection. [D3] [D5]

PREHISTORIC ANIMAL DOSSIER

A life in profile.

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

Teeth and fin rays help identify fragmentary fossils. A detailed comparison can support a name without supplying a complete body or an exact adult life stage. [D1]

Profile scope: Genus exhibit represented by X. audax; Mexican MUZ3912 is specifically identified, whereas Venezuelan MTG070 is referred only to the genus. [D1]

Time
Late Cretaceous
Fossil locations in this exhibit
United States, Mexico
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

Large genus references around6 m

The2012 paper summarizes large specimens. MUZ3912 is instead modeled at2.761–3.012 m standard length, with no secure maturity assessment. [D2] [D1]

Body mass

Not established

Not established here

The specimen account scales length from a partial head; it does not provide an adopted comparable adult mass estimate. [D1]

Diet

Source supported

Fish eating directly supported

The museum fossil preserves Gillicus inside Xiphactinus. It does not independently establish rupture, choking or the exact cause of death. [D3]

Habitat

Source supported

Cretaceous marine waters

MTG070 comes from Cenomanian La Luna marine rocks of Venezuela and is identified only to genus. [D2]

Locomotion

Inferred

Ray-finned fish swimmer inferred

Preserved pectoral rays and a streamlined fish body support swimming; precise speed is not established here. [D1]

Anatomy

Source supported

Irregularly sized conical teeth

Smooth, uncarinated teeth help identify Mexican MUZ3912 as X. audax; this is a specimen-based distinction. [D1]

Reproduction & life together

Reproduction

Not established

Not established here

The reviewed fossil atlas does not document eggs, embryos or a spawning site for X. audax. [D4]

Courtship

Not established

Not established here

The Venezuelan material preserves anatomy and locality rather than a mating display or breeding pair. [D2]

Social behavior

Not established

Not established here

A predator and swallowed prey are not evidence of a school, cooperative hunting or parental association. [D3]

Dossier research & sources

Sources and inspection notes for the claims in this profile.

  1. On the presence of Xiphactinus (Teleostei, Ichthyodectiformes) in the Coniacian-Campanian marine deposits of the Piedritas site, Coahuila, northern MexicoRevista Mexicana de Ciencias Geológicas / UNAM · Accessed 2026-10-06Original abstract, systematic description and comparisons inspected: MUZ3912 X. audax, smooth irregular conical teeth,2.761–3.012 m standard-length model and marine locality. · Inspected: page
  2. Primer registro de Xiphactinus (Teleostei, Ichthyodectiformes) en el Cretácico Superior de América del Sur (Formación La Luna, Venezuela)Revista Brasileira de Paleontologia · Accessed 2026-10-06Original introduction, specimen description and stratigraphy inspected: genus-only MTG070, Cenomanian marine locality and genus large-size references. · Inspected: page
  3. Fish Within Fish at Sternberg MuseumFort Hays State University / Sternberg Museum archives · Accessed 2026-10-06Institutional photo description: Gillicus within Xiphactinus; historical Portheus molossus noted as junior species synonym of X. audax. Exact fatal mechanism not established. · Inspected: page
  4. Xiphactinus audaxCretaceous Atlas of Ancient Life · Accessed 2026-10-06Institutional fossil atlas taxonomy and specimen images inspected: ray-finned ichthyodectiform classification, not a dinosaur/shark. · Inspected: page
  5. Chondrichthyan and Osteichthyan Paleofaunas from the Cretaceous (Late Maastrichtian) Fox Hills Formation of North Dakota, USA: Paleoecology, Paleogeography, and ExtinctionBulletins of American Paleontology / Paleontological Research Institution · Accessed 2026-10-06Original publisher PDF pp53–54 systematic Xiphactinus/Polygonodon discussion inspected: published priority overlap and retained Xiphactinus usage, not confirmation of a completed ICZN ruling. · Inspected: page

THE STORY IN THE FOSSILS

One fish inside another.

The Sternberg fossil contains Gillicus inside Xiphactinus, directly supporting fish feeding while leaving the fatal event unresolved. [3]

A Venezuelan skull-and-vertebra specimen extends the known occurrence of the genus into South America. Its authors identify Xiphactinus without forcing a species name onto incomplete evidence, demonstrating why genus and species records are different. [2]

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. On the presence of Xiphactinus (Teleostei, Ichthyodectiformes) in the Coniacian-Campanian marine deposits of the Piedritas site, Coahuila, northern MexicoRevista Mexicana de Ciencias Geológicas / UNAM · Accessed 2026-10-06Original abstract, systematic description and comparisons inspected: MUZ3912 X. audax, smooth irregular conical teeth,2.761–3.012 m standard-length model and marine locality. · Inspected: page
  2. Primer registro de Xiphactinus (Teleostei, Ichthyodectiformes) en el Cretácico Superior de América del Sur (Formación La Luna, Venezuela)Revista Brasileira de Paleontologia · Accessed 2026-10-06Original introduction, specimen description and stratigraphy inspected: genus-only MTG070, Cenomanian marine locality and genus large-size references. · Inspected: page
  3. Fish Within Fish at Sternberg MuseumFort Hays State University / Sternberg Museum archives · Accessed 2026-10-06Institutional photo description: Gillicus within Xiphactinus; historical Portheus molossus noted as junior species synonym of X. audax. Exact fatal mechanism not established. · Inspected: page
  4. Xiphactinus audaxCretaceous Atlas of Ancient Life · Accessed 2026-10-06Institutional fossil atlas taxonomy and specimen images inspected: ray-finned ichthyodectiform classification, not a dinosaur/shark. · Inspected: page
  5. Chondrichthyan and Osteichthyan Paleofaunas from the Cretaceous (Late Maastrichtian) Fox Hills Formation of North Dakota, USA: Paleoecology, Paleogeography, and ExtinctionBulletins of American Paleontology / Paleontological Research Institution · Accessed 2026-10-06Original publisher PDF pp53–54 systematic Xiphactinus/Polygonodon discussion inspected: published priority overlap and retained Xiphactinus usage, not confirmation of a completed ICZN ruling. · Inspected: page

FOLLOW YOUR CURIOSITY

Who will you meet next?

KEEP EXPLORING

More from the collection