Sphyrna alleni, Gonzalez & Postaire & Driggers & Caballero & Chapman, 2024

Gonzalez, Cindy, Postaire, Bautisse, Driggers, William, Caballero, Susana & Chapman, Demian, 2024, Sphyrna alleni sp. nov., a new hammerhead shark (Carcharhiniformes, Sphyrnidae) from the Caribbean and the Southwest Atlantic., Zootaxa 5512 (4), pp. 491-511 : 501-506

Sphyrna alleni sp. nov.

Family: Sphyrnidae , Carcharhiniformes ; Genus Sphyrna, Gilbert 1967 .

Sphyrna tiburo Bigelow & Schroeder, 1948 ; Gilbert, 1967; Compagno, 1973, 1979, 1988.

Sphyrna cf. tiburo Naylor, 2012 ; Fields, 2016; Gonzalez, 2019; Gonzalez, 2021.

Sphyrna aff. tiburo Gonzalez, 2021 ; Aroca, 2022.

Proposed common name. Shovelbill Shark (EN), Requin-marteau pelle (FR), Tiburón Cabeza de Pala (SP) ( Figure 8 ).

Materials examined. Sphyrna alleni sp. nov. specimens were collected at Robinson Point and Riversdale Village , Belize, and were provided by local fishermen in 2016 and 2019. S. tiburo specimens were collected in Panama City, Terra Ceia Bay , and Sarasota Bay , FL between 2015–2021 and provided by Dr. J. Carlson from NOAA and Dr. J Gardiner from New College of Florida. Type specimens were placed in the collection of the Florida Museum of Natural History (see Table 1 for details).

Holotype. UF 245705 , female, 103 cm TL. Riversdale , Riversdale, Belize; Collected: February 2019 by C. Gonzalez ( Figure 9 ).

Paratypes. All from Riversdale, Riversdale, Belize., and collected by C. Gonzalez in February 2019. UF 245723 , male, TL 60.5 cm ; UF 245724 , female, 83 cm ; UF245725 , female, TL 71.5 cm ; UF245726 , male, TL 63 cm , UF245727 , male, 64.5 cm .

Non-Types. Six S. alleni sp. nov., sharks collected by D. Chapman and local fishermen in 2016 at Robinson Point, Riversdale, Belize, decayed after fixing them with 10% formalin, probably because the meat was decomposed after shipping delays. After taking the measurements and correspondent genetic samples, the vertebrae and the jaws were kept frozen at the Mote Marine Laboratory & Aquarium, Sarasota, FL.

Diagnosis. Small hammerhead shark (<150 cm at maturity) with a flat, shovel shaped head that lacks indentations on its anterior edge. Cephalofoil anterior margin is pointed (like a tringle) in both sexes and the posterior margins are lobule shaped. The anterior margin of males exhibits a pronounced bulge. Enlarged, molariform posterior teeth, first dorsal rear tip in front of pelvic origins, and shallowly concave posterior anal margin. It is distinct from S. tiburo because in this species the anterior margin of the head is more rounded and the lobules on the posterior margin are not present. Precaudal vertebral counts for S. alleni sp. nov., are between 80-83 (~10 more vertebrae than S. tiburo ).

Description. Proportional measurements expressed as a percentage of the total length (TL) are given for the specimens analyzed ( Table 6 ).

Body slender; expanded and narrow pre-branchial head that is shovel-shaped, no indentation on the anterior margin, tip of the head with a triangular contour shape ( Figure 8 ). Head dorsoventrally flattened and narrow but longitudinally elongated, measuring from 19 to 22% of total length (TL) in the specimens analyzed. Distance from tip of snout to mouth about a 34-36% of the head length; posterior margins of head short, forming a lobule shape with a pronounced angular termination; pre-narial grooves not present; mucous pores on the ventral side and on the top of the head distributed in a diffuse pattern, pores highly concentrated in the tip of snout, and surrounding the eyes. There is sexual dimorphism in the individuals, so males have a more pronounced triangular termination of the head than females that have a slightly more rounded head ( Figure 3 ). Eyes oval, small, located at the lateral sides of the head with a diameter of about 1.2 cm (1.2- 1.5% of TL). Nostrils small, apertures transversely oval to tear shaped; internarial space about 66% of the total head width (11% of TL). Prominent rostral cartilage on the top of the head. Mouth about a 40% of the head width, broadly arched; symphysis of mouth; 25 teeth in average in the upper and lower rows of functional teeth; anterior teeth not serrated with short, smooth-edged cusps; posterior molar teeth with a broader basis, flattened, cusp-less, keeled, expanded, and rounded; lower teeth shorter than uppers. Labial furrow around corner of mouth on the lower jaw, but none on the upper jaw ( Figure 3 ).

First dorsal moderately hooked or curved like a sickle on its anterior margin, its origin over the end of the inner margins of pectoral fins, vertical height of the dorsal fin about 60% and base about a 40% of the length of head; posterior margin slightly curved with very small serrations on the end, its free rear tip usually somewhat anterior to pelvic origins. Interdorsal space about 25% of the total length. Second dorsal fin small, moderately high, height is about 35% of the dorsal fin height, one centimeter less than anal fin, concave posterior margin like an “L” shape; inner margin moderately long, longer than fin height. Five gill openings extended after the posterior head lobules, evenly spaced; each slit increases a little bit after the first one, each slit is about 2.2-2.5 cm in length. Pectoral fins originate just after the gill openings, about 74% of the head length and proportional to 14% of the total length. Pelvic fins slightly curved at the corners, with posterior margins almost straight to slightly curved. Anal fins larger and longer than second dorsal fin; base of anal fin is 6.8 to 7.8% of the total length, its origin well in front of second dorsal origin; posterior margin shallowly concave. Caudal fin long about 25%–28% of the total length; well defined precaudal pit; lower lobule of the fork about 1/3 (36–40%) of the upper lobule; upper margin and subterminal caudal margin straight, fork width about ¼ (26%) of total caudal fin length. Precaudal vertebrae counts between 80 to 83, ten or nine vertebrae more than S. tiburo (72-74).

Teeth counts of the functional rows for the upper and lower jaw were 25 in average for each row. When compared to S. tiburo no significant differences in shape or structure of the jaws were found. The S. alleni sp. nov., sharks have anterior teeth that are pointier, narrower, and more sharpened than S. tiburo , that have wider teeth. Also, S. alleni sp. nov., the anterior and posterior teeth seem to be bigger than S. tiburo . Lower jaw: S. alleni sp. nov., have fewer posterior teeth without cusps with a flatter crown foot, fewer rows of teeth exposed (3-2 rows), and are more spaced than S. tiburo . Contrary, the arrangement of posterior teeth in S. tiburo is a clumped pattern and more rows of teeth are exposed (5-3 rows). Upper jaw: S. alleni sp. nov., have only one column of posterior teeth without cusps and flattened crown foots. The second column of teeth have a small cusp developed, that starts to get more prominent until the anterior teeth with well-defined cusp ends. In comparison, the upper jaws of S. tiburo have 3 columns of posterior teeth that are cusp-less and flattened. Only in the 4 th column of posterior teeth the cusps start to develop, but they are not as pointed and sharp as the new species. Dermal denticles with 5 ridges imbricated or loosely spaced in the body ( Figure 8 ).

Coloration. Color after preservation varies from light brown to dark gray; the ventral side tends to become “yellower” with formalin and keeps its original color if preserved in ethanol ( Figure 9 ). In life color varies between gray or gray-brown on the dorsal side; white, or light beige on the ventral side, often with small dark spots on lateral sides of the body ( Figure 10 ).

Distribution range. S. alleni sp. nov. is distributed in coastal waters, estuaries, coral reefs, seagrass beds, and sand bottoms from Belize to Brazil. Presence has been confirmed in the Caribbean in Belize, Panama, Colombia, Trinidad and Tobago, and in the southwestern Atlantic in Brazil. S. tiburo is distributed from North Carolina, U.S to Belize where a potential contact zone for the two species could occur between Mexico and Belize (Yucatan Peninsula).

Etymology. S. alleni sp. nov., is named after Paul G. Allen (1953-2018) who was an investor, co-founder of Microsoft, and philanthropist who, through the Paul G. Allen Family Foundation , has generously supported shark research and conservation.

Comparative material. Eleven S. tiburo specimens from Sarasota Bay, FL, U.S were used. From those, six specimens were fixed and kept at the Florida Museum of Natural History. UF 247324 (n=3): female, TL 86; female, TL 74.5; female, TL 82, Collected 07/20/20; UF 247325 (n=2): male, TL 80.5; male, TL 73.5, Collected 10/13/20; UF 247326 (n=1): male ( Figure 10 ), TL 59.5 Collected 08/18/20, all specimens collected by J. Gardiner. The other five specimens were measured, genetic samples were taken, and the vertebrae and teeth were cleaned and counted by hand. The vertebrae and jaws were kept frozen at the Predator Ecology and Conservation Lab at Florida International University. They correspond to the following individuals: FLO-017, male, TL 82.3 cm; FLO-023, female, TL 71.6; FLO-004, male TL 83.3; FLO- 008, female TL 82cm; FLO-006, male, TL 76 cm, collected by J. Carlson from NOAA in 2015 in Panama City, FL.

Figures

FIGURE 3. Cephalofoil comparison (dorsal and ventral views of each specimen are provided). Bar scale: 5cm. TL: Total length of specimen. A) S. alleni sp. nov.; B) S. tiburo; C) and S. vespertina. Photos: Cindy Gonzalez.

FIGURE 8. Sphyrna alleni sp. nov. A) Horizontal view of the shark; B) dermal denticles; C) upper and D) lower teeth; Dorsal and ventral representation of the head shape of E) Female and F) Male. Illustrations: Gina Clementi.

FIGURE 9. Holotype of Sphyrna alleni sp. nov. collected in Riversdale, Belize. UF 245705, Female, 103 cm TL. Photo: Zachary Randall, Digital Imaging Division, Florida Museum.

FIGURE 10. Paratype. External morphology and coloration of a fresh specimen of Sphyrna alleni sp. nov., collected in Riversdale, Belize. UF: 247326, Male, 64.5 cm TL. Photos: Cindy Gonzalez.