Quick facts
| Scientific name | Asagaolacerta tricuspidens |
|---|---|
| Named by | Susan Evans and Ryoko Matsumoto, 2015 |
| Age | Early Cretaceous, probably Barremian–Aptian |
| Locality | Kaseki-kabe, Hakusan, Japan |
| Formation | Kuwajima Formation, Tetori Group |
| Holotype | SBEI 1566, associated cranial and postcranial bones |
| Estimated size | About 90 mm snout to vent by comparison |
| Possible position | Lacertoidea, perhaps Borioteiioidea; uncertain |
What can the fossils tell us?
They are interpreted as one individual, possibly concentrated in a predator pellet.
This diagnoses the animal but does not identify one exact diet.
The 90 mm body and especially 290 mm total length are model-based estimates.
A borioteiioid result is plausible but sensitive to missing anatomy.
Asagaolacerta tricuspidens was a small Early Cretaceous lizard from the Kuwajima Formation of Japan. Its holotype combines pieces of the skull and jaws with vertebrae, pelvis and hind limbs from one individual. The clearest diagnostic feature lies in the tooth row: the rear crowns bear three sharp cusps of nearly equal development.
Name and fossil association
Asagao is the Japanese name for morning glory, a flower associated with the city of Hakusan, while lacerta means lizard. The species name tricuspidens refers to the three-cusped teeth.
Holotype SBEI 1566 lies in a small block with overlapping bones. Their consistent size and the absence of duplicated paired elements support interpretation as one individual. The original authors considered that the tangled association could be a predator pellet, but no animal can be identified as its producer.
What is preserved
The cranial material includes the left maxilla, both dentaries, portions of the rear lower jaw, both jugals, a frontal fragment, a palatine and a quadrate. The postcranial sample contains several vertebrae, part of the left pelvis, both femora and separate phalanges.
No shoulder girdle or forelimb was recognised. CT examination did not reveal these bones inside the dense cluster, although very small pieces could remain hidden. Associated osteoderms are absent.
Three cusps on one crown
Rear teeth carry a tall central cusp with smaller cusps in front and behind. The crown does not widen into a bulbous base and is about as broad as the shaft. This combination distinguishes Asagaolacerta from other Kuwajima lizards.
Tricuspid teeth evolved in unrelated herbivorous and omnivorous squamates. They can cut or crush food, but they do not name a menu. The specimen preserves no plant fragments, insects or intestinal contents, so a mixed or plant-rich diet remains a possibility rather than a fact.
Hind limbs and estimated size
The left femur was approximately 11.5 to 12 millimetres long. Pelvis and thigh resemble those of an unspecialised quadrupedal lizard. Comparison of jaw, pelvic and limb dimensions with the living whiptail Aspidoscelis tigris produced an estimate near 90 millimetres from snout to vent and about 290 millimetres including the tail.
Neither figure is a direct measurement of a complete fossil. The trunk and tail are missing, and total length is especially dependent on the chosen modern proportions. Additional partial skeletons have similar dimensions but cannot be assigned confidently to the genus.
Position among squamates
Only 94 of 622 morphological characters could be scored. Analyses often placed the animal near Borioteiioidea within Lacertoidea, consistent with heterodont dentition, tricuspid teeth, paired smooth frontals and a long jugal process.
Other fossil lizards also developed three-cusped teeth but differ in crown and jaw proportions. Similar dentition is evidence to compare, not proof of direct ancestry.
Kuwajima environment and reconstruction
The formation records peat-forming wetland, a shallow lake and vegetated terrestrial ground that flooded periodically. Most land vertebrates came from the last setting. Asagaolacerta shared this varied fauna with other small lizards using different teeth.
The hind limbs, part of the pelvis, several vertebrae and incomplete head are direct evidence. An ordinary four-legged body is likely, while exact tail length, scales and colour are artistic unknowns. The associated fossil block preserves the strongest evidence for the animal body proportions.
Evidence, inference and reconstruction
| Direct | Associated jaws, skull bones, vertebrae, pelvis, femora and tricuspid teeth |
| Inference | Quadrupedal movement and processing of varied food |
| Uncertain | Exact diet, body length, pellet origin and phylogenetic position |
| Reconstruction | Complete body, tail, scales, colour and behaviour |
Frequently asked questions
What does Asagaolacerta tricuspidens mean?
The genus refers to Hakusan's morning-glory symbol, while the species name points to three cusps on each diagnostic rear tooth.
How large was Asagaolacerta?
Comparison with a living lizard suggests about 90 mm from snout to vent. The estimated total length near 290 mm is more uncertain because the tail is missing.
What belongs to the holotype?
SBEI 1566 includes jaw and skull parts, several vertebrae, part of the pelvis, both femora and phalanges from one small individual.
What did Asagaolacerta eat?
Tricuspid teeth permit plant-rich or mixed food processing, but no direct dietary remains survive.