Hey sailors! Welcome to our first species lesson and an exciting new shark discovery. Introducing Sphyrna alleni, the shovebill shark, a newly identified species of hammerhead. Finding a new shark species is always a reminder of how much is still unknown about our oceans.

Working with three young hammerheads at the aquarium was one of my favorite experiences. They were super sweet and full of energy, always fascinating to watch as they used their cephalofoil* to navigate and sense their surroundings. Seeing firsthand how hammerheads interact with their environment makes this discovery even more exciting. I can’t wait to dive into what makes the shovebill shark unique. Let’s set sail.

Summary:

Sphyrna alleni sp. nov., a new species of hammerhead shark from the Caribbean and Southwest Atlantic. This species, previously considered part of a bonnethead complex, was distinguished based on morphometric, meristic, and genetic differences from Sphyrna tiburo. Key differences include a shovel-shaped cephalofoil and higher vertebral counts (80-83). Genetic analysis confirmed the separation between S. alleni and S. tiburo using mitochondrial and nuclear markers. The study combines traditional taxonomic methods with genetics to support species identification, emphasizing the importance of resolving bonnethead shark taxonomy for conservation.

https://doi.org/10.11646/zootaxa.5512.4.2

Full Story:

The newly identified hammerhead shark species, Sphyrna alleni, has a distinctive shovel-shaped cephalofoil, setting it apart from other members of its genus. Named in honor of the biologist who contributed significantly to shark research, this species features unique characteristics that distinguish it from other hammerheads, including differences in the shape of its head (cephalofoil) and its geographic distribution. This unique head shape could play a role in its sensory capabilities and hunting strategy, aiding in the detection of prey on the ocean floor.

Twelve mature bonnethead sharks were provided by fishermen from Robinson Point and Riversdale Village, Belize, while another eleven mature bonnethead sharks were collected in Panama City and Sarasota, Florida. Fin, muscle, and liver samples were taken and preserved, and the whole sharks were kept in an ice bath to prevent decay before being preserved in ethanol for three months. A total of 61 morphometric measurements were performed on each shark.

A recent study comparing bonnethead shark specimens from the Western Atlantic (WA) and Eastern Pacific (EP) supports the classification of Sphyrna vespertina as a distinct species. This conclusion is based on diagnostic differences in cephalofoil shape, electroreceptor densities, and mitochondrial genetic markers that distinguish it from all WA bonnethead sharks (Aroca et al., 2022).

Like other hammerhead sharks, Sphyrna alleni likely plays an important role in marine ecosystems as both predator and scavenger, helping maintain healthy fish populations. Discoveries like this highlight the incredible diversity of marine life and the need for ongoing research and conservation to protect vulnerable shark species and their habitats.

Hammerhead sharks are among the most threatened shark families due to overfishing, bycatch, and the high demand for their fins. Their distinctive cephalofoil, while providing sensory advantages, also makes them more vulnerable to being caught in fishing nets. Many species within this family, including the newly identified Sphyrna alleni, face significant population declines, emphasizing the urgent need for conservation efforts to protect their habitats and reduce fishing pressures.

The significance of the findings lies in the identification and description of Sphyrna alleni as a distinct hammerhead shark species, previously thought to be part of a bonnethead complex. This discovery contributes to a better understanding of the biodiversity within the hammerhead shark family and helps clarify the species' taxonomy. By distinguishing S. alleni from Sphyrna tiburo, the study highlights the presence of cryptic diversity* within the species, which is important for the accurate assessment of population sizes, distribution, and conservation status.

Understanding these distinctions is crucial for conservation efforts, as hammerhead sharks are among the most threatened shark families due to overexploitation and habitat loss. Proper species identification allows for more targeted and effective conservation measures, ensuring that each species receives appropriate protection. Additionally, these findings emphasize the need for further genetic and meristic examination of other bonnethead populations, particularly in the Eastern Pacific, to better understand and preserve shark diversity.

*Definitions:

Cephalofoil - A clear structure of the head forming a lateral expansion providing an increased maneuverability.

Cryptic diversity - Where two species are impossible to identify consistently and accurately from morphology (study of structure) alone.

Semi-Cryptic - Where two species can be identified consistently and accurately from morphology when geographical location is known.

Citations:

Gonzalez, C., et al. (2024). Sphyrna alleni sp. nov., a new hammerhead shark (Carcharhiniformes, Sphyrnidae) from the Caribbean and the Southwest Atlantic. Zootaxa, 5512(4), 491-511. https://doi.org/10.11646/zootaxa.5512.4.2

Gaylord, M. K., Blades, E. L., & Parsons, G. R. (2020). A hydrodynamics assessment of the hammerhead shark cephalofoil. Scientific Reports, 10, 14495. https://doi.org/10.1038/s41598-020-71472-2

Mann, D. G., & Evans, K. M. (2008). The species concept and cryptic diversity. In Proceedings of the 12th International Conference on Harmful Algae (pp. 262-268). International Society for the Study of Harmful Algae and Intergovernmental Oceanographic Commission of UNESCO.