Heterodontus is a small genus of sharks inside the household Heterodontidae of the order Heterodontiformes.
First found in Australia within the 18th century within the type of the Port Jackson shark, it now contains 10 scientifically acknowledged species.
All Heterodontus species are comparatively small, with the most important species reaching 1.65 m (5.5 ft) in size.
They’re generally often known as bullhead sharks or horn sharks.
They first appeared within the fossil document within the Early Jurassic epoch, effectively earlier than any of different Galeomorphii, a bunch that features all fashionable sharks besides the dogfish and its relations.
They happen in warm-temperate and tropical continental waters of the western Indian Ocean, western and japanese Pacific, however are absent from the Atlantic and from oceanic insular waters.
These are sluggish, uncommon to unusual night-active sharks, slowly swimming and crawling on rocky, kelp-covered and sandy backside. Some species no less than favor rocky crevices and caves, the place they spend the day resting.
These sharks are oviparous, producing eggs in distinctive, massive, spiral-flanged egg circumstances. Not less than two species lay eggs in particular ‘nesting’ websites. Eggs might take over 5 months to hatch, and younger hatch at a big dimension, over 14 cm (5.5 inches).
They primarily feed on benthic invertebrates. Sea urchins are a favourite meals, however crabs, shrimp and different crustaceans, abalone, high shells and different marine gastropods, oysters, polychaetes, sipunculid worms and extra hardly ever small fish are additionally eaten.
Some Heterodontus sharks are encountered by divers, who’ve generally harassed them.
Though considered innocent, these sharks can and do snap when provoked and sometimes pursue and chew their tormentors.
“The Heterodontiformes is a singular shark order comprising a single household and single extant genus,” stated lead creator Dr. William White from CSIRO Australian Nationwide Fish Assortment and colleagues.
“They’re additionally one of many earliest recognized fashionable elasmobranch lineages with distinctly recognizable remoted enamel recorded from the Early Jurassic, roughly 175 million years in the past.”
“These horn or bullhead sharks are characterised by their massive, blunt heads with outstanding crests above the orbits and a small mouth.”
“Additionally they have a big backbone in entrance of each dorsal fins and an anal fin.”
“Australia is house to 2 endemic Heterodontus species, i.e., Heterodontus galeatus and Heterodontus portusjacksoni, which happen in temperate waters,” they added.
“A 3rd species, Heterodontus zebra, is discovered within the Western Central Pacific from tropical northern Australia extending additional north to Japan.”
The newly-identified species, named Heterodontus marshallae, was beforehand thought of to be conspecific with Heterodontus zebra from the Western Pacific.
Regardless of the coloration being related between the 2 species, i.e., pale background with 22 darkish brown bands and saddles, they differ persistently in two key elements.
“Firstly, the snout of Heterodontus marshallae has a darkish semicircular bar, normally bifurcated for many of its size vs. a pointed, triangular formed darkish marking in Heterodontus zebra,” the scientists stated.
“Secondly, Heterodontus zebra has a darkish bar originating under the posterior gill slits and lengthening onto anterior pectoral fin, which is absent in Heterodontus marshallae.”
Heterodontus marshallae is as much as 60 cm (2 ft) in size, has a reasonably sturdy physique and a barely humped nape.
The species happens in northern Australia from west of Exmouth Peninsula east to no less than off Bathurst Island within the Northern Territory.
“Heterodontus zebra is a primarily shallow water species occurring from shut inshore to depths of no less than 143 m (469 ft),” the authors stated.
“In distinction, Heterodontus marshallae has solely been recorded between 125 and 229 m (410-751 ft) off northwestern Australia.”
The invention is described in a paper revealed within the journal Range.
Quotation:
William T. White et al. 2023. Species in Disguise: A New Species of Hornshark from Northern Australia (Heterodontiformes: Heterodontidae). Range 15 (7): 849; doi: 10.3390/d15070849
This text by Natali Anderson was first revealed by Sci-Information on 31 July 2023. Lead Picture: Heterodontus marshallae. Picture credit score: Sci.Information / White et al., doi: 10.3390/d15070849.
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