The Pondicherry shark (Carcharhinus hemiodon) is an extremely rare species of requiem shark, in the family
Carcharhinidae. A small and stocky gray shark, it grows not much longer
than 1 m (3.3 ft) and has a fairly long, pointed snout. This species
can be identified by the shape of its upper teeth, which are strongly
serrated near the base and smooth-edged near the tip, and by its first dorsal fin, which is large with a long free rear tip. Furthermore, this shark has prominent black tips on its pectoral fins, second dorsal fin, and caudal fin lower lobe.
The Pondicherry shark is critically endangered. It was once found throughout Indo-Pacific coastal waters from the Gulf of Oman to New Guinea, and is known to enter fresh water. Fewer than 20 specimens are available for study, and most aspects of its natural history are unknown. It probably feeds on bony fishes, cephalopods, and crustaceans, and gives birth to live young with the embryos forming a placental connection to their mother. While the International Union for Conservation of Nature (IUCN) has listed the Pondicherry shark as Critically endangered,
also thought to have been extinct since the 1970s, it continues to be
found in markets, most recently in 2019 at a local fishing village in
southern Sri Lanka after the continuous efforts made by the famous
biologist and conservationist Forrest Galante,
and his wife, zoologist Jessica Summerfield, in a special episode 'The
Lost Shark' of the Discovery channel program 'Extinct or Alive' Newsweek. The specimen found will be displayed in the museum of Sri Lanka[when?]
to raise awareness of the critically endangered species. It is probably
threatened by intense and escalating fishing pressure throughout its
range. The shark is among the 25 "most wanted lost" species that are the
focus of Global Wildlife Conservation's "Search for Lost Species"
initiative. The Pondicherry has been spotted in rivers in India in the late 2010s.
A Pondicherry shark was caught in the Menik Ganga (river) in SE Sri
Lanka in 2011. It was photographed and released alive. An illustration
of the shark appears on page 298 of 'Sri Lankan Freshwater Fishes'.
Taxonomy
The illustration that accompanied Müller and Henle's description.
The first scientific description of the Pondicherry shark was authored by German biologists Johannes Müller and Jakob Henle in their 1839 Systematische Beschreibung der Plagiostomen. Their account was based on a 47 cm (19 in) long immature male from Puducherry (formerly Pondicherry), India and three more paratypes from the same region. Müller and Henle attributed the name for the new species, Carcharias (Hypoprion) hemiodon, to French zoologist Achille Valenciennes. The specific epithet hemiodon is derived from the Greek hemi ("half") and odon ("tooth").
In 1862, Theodore Gill elevated Hypoprion to the rank of full genus and also placed the Pondicherry shark in its own genus, Hypoprionodon, based on the relative positions of the dorsal and pectoral fins. Subsequent authors generally accepted Gill's first revision but not his second, and thus this species became known as Hypoprion hemiodon. In 1985, Jack Garrick followed up on earlier taxonomic work by Leonard Compagno and synonymized Hypoprion with Carcharhinus. Another common name for the Pondicherry shark is long nosed shark.
Description
The Pondicherry shark has a robust build and a moderately long, pointed snout. The large and circular eyes are equipped with nictitating membranes.
Each nostril is broad with a small, narrow nipple-shaped lobe on the
anterior rim. The arched mouth lacks conspicuous furrows or enlarged
pores at the corners. The upper and lower jaws contain 14–15 and 12–14 tooth rows
on either side respectively; in addition, there are one or two rows of
small teeth at the upper and lower symphyses (jaw midpoints). The upper
teeth have a single narrow, smooth-edged central cusp,
flanked on both sides by very large serrations. The lower teeth are
narrower and more upright than the uppers, and may be smooth to finely
serrated. The five pairs of gill slits are fairly long.
Originating below the fourth pair of gill slits, the pectoral
fins are short, broad, and falcate (sickle-shaped) with pointed tips.
The first dorsal fin is tall and falcate with a distinctively long free
rear tip, and is positioned just behind the pectoral fin bases. The
second dorsal fin is large and tall without a notably elongated free
rear tip, and is positioned over or slightly behind the anal fin. Usually there is no midline ridge between the dorsal fins, and when present the ridge is slight. The caudal peduncle has a deep crescent-shaped notch at the upper caudal fin
origin. The asymmetrical caudal fin has a well-developed lower lobe and
a longer upper lobe with a notch in the trailing margin near the tip.
The skin is covered by overlapping dermal denticles;
each denticle has three horizontal ridges leading to three (rarely
five) marginal teeth. This species is gray above and white below, with
an obvious pale stripe on the flanks. The pectoral fins, second dorsal
fin, and lower caudal fin lobe are prominently tipped in black, while
the first dorsal fin and dorsal caudal fin lobe are narrowly edged in
black. The maximum size reached by the Pondicherry shark is uncertain
due to a lack of large specimens, but is probably not much greater than
1 m (3.3 ft).
