Appearance
The unusual pear-like shape of the coffin ray distinguishes it from all other rays. Its body is flabby, with two large, kidney-shaped electric organs visible on both sides of the head. The pectoral fins form a greatly enlarged disc about as wide as long, that is thick at the center and thin at the margins. The leading margin of the disc is straight to gently concave. The eyes are minute and can be elevated on short stalks. Close behind the eyes and slightly larger are the spiracles, which are rimmed by small papillae in some individuals. The nostrils are located just ahead of the mouth, and are connected to it by a pair of broad grooves. Between the nostrils is a short curtain of skin that overlaps the mouth. The capacious mouth forms a very long, wide arch; the slender jaws can be distended dramatically, though are not particularly protrusible. Adults have over 60 rows of small teeth in either jaw; each tooth has three long cusps. The five pairs of gill slits are small and placed beneath the disc.The pelvic fins are relatively large and merged with the pectoral fin disc at the front to form a roughly circular secondary disc. The two dorsal fins are shaped like rounded lobes and are located very close to the caudal fin, which is of similar size with a nearly symmetrical, rounded margin. The tail is extremely short, such as that the caudal fin barely extends past the pelvic fin disc. The skin is entirely devoid of dermal denticles, and may be creased in areas. The dorsal colouration ranges from dark to reddish brown, to grayish, pinkish, or yellowish, and may be plain or sparsely patterned with irregular darker and lighter markings. The underside is pale, as are the spiracle papillae. This species grows to a length of 70 cm , or possibly even 92 cm , though most are only around 40 cm long.
Distribution
The coffin ray has a wide but disjunct distribution in tropical and warm-temperate Australian waters. The western part of its range extends from Gulf St Vincent in South Australia to Broome in Western Australia, and the eastern part from Eden in New South Wales to Heron Island in Queensland. It does not occur off Victoria or Tasmania. This common, bottom-dwelling species is typically found close to shore, no deeper than 80 m , though it has been recorded from as deep as 240 m . In 1910, the trawler ''Endeavour'' caught several coffin rays at depths ranging from 47 to 120 fathoms . The coffin ray favors habitats with sandy or muddy bottoms, including beaches, estuaries, and bays, and can also be found over seagrass as well as on and around rocky and coral reefs.Behavior
The coffin ray is a slow and weak swimmer that moves forward with a jerky, fluttery motion. It is nocturnal and spends most of the day buried in sediment with only its spiracles showing. When disturbed, it has been observed performing a possible defense behavior, wherein it erupts from the bottom and swims in a loop with its mouth agape. This species is sometimes stranded on land by the ebbing tide, but can survive out of water for hours. Like in other electric rays, the coffin ray's electric organs are derived from muscle tissue and consist of numerous vertical columns, each formed from a stack of jelly-filled "electric plates" that essentially acts as a battery. It is capable of generating up to 200 volts of electricity and delivering 50 shocks over span of ten minutes, with each successive shock weakening. The coffin ray employs electricity both to subdue prey and deter predators.The diet of the coffin ray consists mostly of benthic bony fishes, but also includes cephalopods and on occasion crustaceans and polychaete worms. Penguins and rats have also been recorded from the stomachs of this species. The coffin ray ambushes prey from the substrate, and swallows them whole head-first before re-burying. It often takes extremely large prey relative to its size; one observed individual 60 cm long had swallowed a flathead 70 cm long, and the tail of the prey fish was still protruding from its mouth. Dead specimens have been recovered that had apparently choked trying to swallow too-large prey. The coffin ray is aplacental viviparous, in which the developing embryos are nourished by yolk, later supplemented by histotroph secreted by the mother. Females give birth to litters of 4–8 pups in summer; the newborns measure approximately 8–11 cm long. Males and females both attain sexual maturity around 40–48 cm long. This species is known to be parasitized by the tapeworms ''Acanthobothrium angelae'' and ''Lacistorhynchus dollfusi'', and the nematode ''Echinocephalus overstreeti''.
They are preyed upon by tiger sharks. One large tiger shark caught at Port Stephens in the early 20th century had more than thirty of them in its stomach.
Habitat
The coffin ray has a wide but disjunct distribution in tropical and warm-temperate Australian waters. The western part of its range extends from Gulf St Vincent in South Australia to Broome in Western Australia, and the eastern part from Eden in New South Wales to Heron Island in Queensland. It does not occur off Victoria or Tasmania. This common, bottom-dwelling species is typically found close to shore, no deeper than 80 m , though it has been recorded from as deep as 240 m . In 1910, the trawler ''Endeavour'' caught several coffin rays at depths ranging from 47 to 120 fathoms . The coffin ray favors habitats with sandy or muddy bottoms, including beaches, estuaries, and bays, and can also be found over seagrass as well as on and around rocky and coral reefs.The coffin ray is a slow and weak swimmer that moves forward with a jerky, fluttery motion. It is nocturnal and spends most of the day buried in sediment with only its spiracles showing. When disturbed, it has been observed performing a possible defense behavior, wherein it erupts from the bottom and swims in a loop with its mouth agape. This species is sometimes stranded on land by the ebbing tide, but can survive out of water for hours. Like in other electric rays, the coffin ray's electric organs are derived from muscle tissue and consist of numerous vertical columns, each formed from a stack of jelly-filled "electric plates" that essentially acts as a battery. It is capable of generating up to 200 volts of electricity and delivering 50 shocks over span of ten minutes, with each successive shock weakening. The coffin ray employs electricity both to subdue prey and deter predators.
The diet of the coffin ray consists mostly of benthic bony fishes, but also includes cephalopods and on occasion crustaceans and polychaete worms. Penguins and rats have also been recorded from the stomachs of this species. The coffin ray ambushes prey from the substrate, and swallows them whole head-first before re-burying. It often takes extremely large prey relative to its size; one observed individual 60 cm long had swallowed a flathead 70 cm long, and the tail of the prey fish was still protruding from its mouth. Dead specimens have been recovered that had apparently choked trying to swallow too-large prey. The coffin ray is aplacental viviparous, in which the developing embryos are nourished by yolk, later supplemented by histotroph secreted by the mother. Females give birth to litters of 4–8 pups in summer; the newborns measure approximately 8–11 cm long. Males and females both attain sexual maturity around 40–48 cm long. This species is known to be parasitized by the tapeworms ''Acanthobothrium angelae'' and ''Lacistorhynchus dollfusi'', and the nematode ''Echinocephalus overstreeti''.
They are preyed upon by tiger sharks. One large tiger shark caught at Port Stephens in the early 20th century had more than thirty of them in its stomach.
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