Gremlin: the small ceratopsian known from a single frontal

Gremlin slobodorum was a small ceratopsian from the Campanian Oldman Formation of Alberta, Canada. It was formally described in 2023 from one right frontal bone, part of the roof of the skull. That bone carries a distinctive transverse ridge, but nearly every other part of the animal must be inferred from better-known leptoceratopsids.

The unusual name can make the dinosaur sound more completely known than it is. No jaw, teeth, vertebrae or limb bones have been assigned securely to Gremlin. Its value is more specific: the frontal expands the known diversity and timing of small hornless ceratopsians in Alberta. It is included in the dinosaur catalogue with its fragmentary basis made clear.

Quick facts

Evidence note

The name is based on one incomplete frontal bone, whose ridge and surface anatomy distinguish it from known relatives. Body size, diet details, display function and the complete skull remain comparative or unknown.

Wendy Sloboda’s discovery

Wendy Sloboda found the fossil in 2011 during the Southern Alberta Dinosaur Project. The Royal Tyrrell Museum of Palaeontology catalogued it as TMP 2011.053.0027. The right frontal is incomplete: erosion removed its front outer edge, but enough of the bone’s surface remains to compare its shape with other leptoceratopsids.

Michael Ryan, Logan Micucci, Hanika Rizo, Corwin Sullivan, Yong Nam Lee and David Evans described the genus in 2023 in a volume on the evolution of ancient reptiles and synapsids. The species name slobodorum honours Wendy Sloboda and her father, Ed, both of whom supported palaeontological work in southern Alberta.

The bone had appeared earlier in conference material under a preliminary referral to Cerasinops. A later comparison found a distinctive combination of frontal features and named it as a separate genus and species. A formal name records a testable identification; it does not mean the animal is represented by a complete skeleton.

What the frontal bone shows

In life, the paired frontal bones lay between the nasal region and the eyes and formed part of the skull roof. In TMP 2011.053.0027, a transverse ridge begins near the midline and extends outward towards the upper margin of the eye socket. Its sculpturing and direction differ from the frontal anatomy described in other leptoceratopsids.

A diagnostic bone is not a full portrait. Gremlin has no known jaws or teeth with which to estimate bite mechanics, no vertebrae from which to assess posture, and no limb bones from which to measure body size or locomotion. The single frontal also cannot show how its surface changed with age. The descriptive authors therefore compared the preserved skull roof with homologous bones in related genera rather than treating its outline as a complete skull.

The ridge’s function is unresolved. It may have affected the shape of the skull roof, but there is no direct evidence that it supported a horn, display structure or specialised muscle. Its present use is anatomical: it helps distinguish the fossil. A behavioural story would require evidence not preserved in this specimen.

A small leptoceratopsid

The authors assigned Gremlin to Leptoceratopsidae, a branch of relatively small ceratopsians that lacked the enormous brow horns and broad bony frills of many later ceratopsids. The better-known Leptoceratops provides a useful comparison because more of its skeleton is known. It suggests a compact body, a strong beak and a relatively short frill as a reasonable family-level outline, but none of those details has been found in Gremlin.

The phylogenetic analysis placed it among non-ceratopsid ceratopsians near leptoceratopsids. Relationships within that part of the tree were poorly resolved: several genera formed a polytomy, meaning the analysis could not determine their branching order. Naming one genus as its closest relative would therefore overstate the result.

Gremlin was not a miniature Pachyrhinosaurus. They belong to different ceratopsian branches, and the latter lived later and had a much more massive skull. Their catalogue neighbours illustrate the range of ceratopsian anatomy, not a close relationship.

Age, landscape and regional sequence

The fossil comes from the Oldman Formation in southern Alberta. The describing authors place it in the Campanian Stage of the Late Cretaceous at approximately 78 million years old. This is an estimate for the fossil-bearing level, not a precise date for the individual.

The region was a low river plain in western North America. Channels carried sand and mud across floodplains that alternated between wetter and drier ground. The formation contains hadrosaurids, predators and other horned dinosaurs, but a formation accumulated over many places and a long interval. Shared formation names do not prove that every listed species met in one locality at the same moment.

Within the Alberta succession, Gremlin helps fill a time interval between the older Gryphoceratops and the higher Unescoceratops. One frontal cannot reveal population size or abundance, but it documents the presence of a distinct leptoceratopsid lineage during that interval.

How much can be reconstructed?

A cautious illustration can use the broad proportions of known leptoceratopsids: a four-legged stance, a beaked mouth, a moderately long tail and a small frill. These are comparisons, not features preserved in the type specimen. Colour, skin covering, cheek outline and exact proportions are artistic choices. No limb bone exists to provide a reliable scale for the animal’s total length.

Herding, courtship displays and defensive behaviour are likewise unknown. The transverse ridge belongs to the skull roof, but its function has not been established. The fossil is valuable precisely because its known limits can be stated: one named ceratopsian, distinguished by one informative but incomplete skull bone.