Avaceratops lammersi

Avaceratops lammersi lived in central Montana during the Campanian. Its holotype is much smaller than most adult ceratopsids and preserves a partial skull plus a substantial disarticulated skeleton. Whether that individual was fully grown remains uncertain. A larger skull referred to Avaceratops suggests the genus may have reached a more typical ceratopsid size, but its assignment is not universally secure.

Its fossils occur between approximately 76.4 and 75.6 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

The holotype preserves much of a short, broad frill, jaws, vertebrae and limb bones. Its parietal lacks the large open windows typical of many adult ceratopsids, possibly because the openings were small or closed during growth. The exact nasal and brow-horn arrangement is uncertain: an older hornless restoration is used here, while the referred larger skull has been reconstructed with more developed brow horns. The colour-coded frill diagram shows how recent studies identify its marginal ossification positions.

• Short, broad parietal and squamosal forming the frill
• Frill openings absent or very small in the holotype
• Deep beak and dental batteries for processing plants
• Substantial but disarticulated postcranial skeleton
• Holotype much smaller than most adult ceratopsids
• Horn form uncertain because the key skull regions are incomplete

Commercial collector Eddie Cole found the scattered bones at Careless Creek Ranch near Shawmut, Montana, in 1981. Peter Dodson examined the collection that October, returned to the site in 1982 and helped recover more material. He named Avaceratops lammersi in 1986, honouring Cole’s wife Ava and the ranch-owning Lammers family. The holotype ANSP 15800 entered the Academy of Natural Sciences collection in Philadelphia.

Discovery credit: Eddie Cole, Peter Dodson and field team.

Naming authors: Peter Dodson.

The Judith River Formation records rivers, floodplains, ponds and coastal environments west of the Western Interior Seaway. The Careless Creek animal was scattered through an ancient stream deposit, probably after transport. Vegetation included conifers, flowering plants, ferns and low wetland plants, while hadrosaurs, armoured dinosaurs, other ceratopsians and theropod predators occupied the wider region.

Avaceratops used a beak to crop vegetation and dense cheek teeth to slice it. The frill may have supported species recognition or display, but its external soft tissue is unknown. One scattered skeleton and a referred skull cannot establish social group size. Claims about charging, parental care or herd behaviour therefore go beyond the available evidence.

• The genus name honours Ava Cole, wife of the collector who found the first bones.
• The species name honours the Lammers family, owners of Careless Creek Ranch.
• The holotype was the first new ceratopsid named since Pachyrhinosaurus in 1950.
• Its possible adult size depends heavily on whether a larger referred skull truly belongs to Avaceratops.

A research repository is not necessarily a public exhibit. Loan and display status can change, so check with the institution before visiting.

1. 01
   Avaceratops lammersi: a new ceratopsid from the Judith River Formation of Montana

   Peter Dodson · Proceedings of the Academy of Natural Sciences of Philadelphia 138(2), 305–317 · 1986

   Open source
2. 02
   The morphology and systematics of Avaceratops, a primitive horned dinosaur from the Judith River Formation (Late Campanian) of Montana, with the description of a second skull

   Paul Penkalski, Peter Dodson · Journal of Vertebrate Paleontology 19(4), 692–711 · 1999

   Open source
3. 03
   Academy of Natural Sciences collections

   Academy of Natural Sciences of Drexel University

   Open source