A fossil tooth from near the sanctuary of Covadonga in Asturias expands the known distribution of early large cartilaginous fishes. The new study assigns the approximately 331-million-year-old piece to the extinct genus Carcharopsis. At 43 millimeters in height, it is the largest tooth of this genus documented so far.
The fossil comes from a slab of red Griotte limestone, which is known in the region as Roja Covadonga. Members of the organization GeĆ³logos del Mundo found the piece, broken into two parts, near the basilica and the sanctuary. The research team assembled the fragments and examined the tooth without further damaging it.
Micro-CT makes the internal structure visible
Using micro-computed tomography, the researchers reconstructed the vascular canals in the tooth root and the shape of the crown in three dimensions. The broad, longitudinally curved tip has double-saw edges. Its small serrations, formed from the enamel, are functionally similar to those of modern tiger sharks and indicate a diet in which meat and hard prey were cut. This does not imply a close relationship with the modern tiger shark: similar cutting edges can arise independently.
Five to six meters remain a model estimate
From the proportions of the tooth, the study derives a possible body length of about five to six meters. For this, relationships between tooth and body size of modern sharks were used as a comparison. Therefore, the figure is not a measurement of a complete skeleton, but a model-dependent range. So far, only this tooth of the animal is known, and an assignment to a single species within Carcharopsis is not possible.
The first evidence in the northern Gondwana
So far, well-documented finds of Carcharopsis have come almost exclusively from areas of the former Laurussia, particularly from parts of present-day North America and Europe. Covadonga was located in the Mississippian at the northern edge of Gondwana. The tooth thus significantly expands the known range and supports the assumption that these large predators were able to use both coastal habitats and more open seas.
A top predator after a major extinction crisis
The find falls into a phase in which marine ecosystems reorganized after the Hangenberg crisis at the end of the Devonian. A several-meter-long apex predator could only exist if a complex food web was already present beneath it. The single tooth does not prove how common the animals were, but it provides an additional temporal and geographical clue for the recovery of these ecosystems.
A communication from the involved UNED emphasizes the exceptional preservation and the value of non-destructive analysis. The find complements other fossil evidence that allows us to understand how sharks and their early relatives explored new habitats. At the same time, it shows the limits of such reconstructions: size, diet, and lifestyle remain hypotheses derived from a rare single specimen.