Thornback guitarfish

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Thornback guitarfish
Platyrhinoidis triseriata.jpg
Scientific classification

Garman, 1881
P. triseriata
Binomial name
Platyrhinoidis triseriata
Platyrhinoidis triseriata rangemap.png
Range of the thornback guitarfish [1]

Platyrhina triseriataD. S. Jordan & Gilbert, 1880

The thornback guitarfish (Platyrhinoidis triseriata) is a species of ray in the family Platyrhinidae, and the only member of its genus. Despite its name and appearance, it is more closely related to electric rays than to true guitarfishes of the family Rhinobatidae. [2] This species ranges from Tomales Bay to the Gulf of California, generally in inshore waters no deeper than 6 m (20 ft). It can be found on or buried in sand or mud, or in and near kelp beds. Reaching 91 cm (36 in) in length, the thornback guitarfish has a heart-shaped pectoral fin disc and a long, robust tail bearing two posteriorly positioned dorsal fins and a well-developed caudal fin. The most distinctive traits of this plain-colored ray are the three parallel rows of large, hooked thorns that start from the middle of the back and run onto the tail.


Encountered singly or in groups, the thornback guitarfish feeds on small, benthic invertebrates and bony fishes. It is aplacental viviparous, with the developing young drawing sustenance from a yolk sac. Females give birth to 1–15 pups annually in late summer, following a roughly year-long gestation period. The International Union for Conservation of Nature (IUCN) has listed the thornback guitarfish under Least Concern because the majority of its range lies within United States waters, where it is common since it has no commercial value and is not heavily fished commercially or recreationally. The status of this species in Mexican waters is inadequately known but may be more precarious.

Taxonomy and phylogeny

The thornback guitarfish was scientifically described by American ichthyologists David Starr Jordan and Charles Henry Gilbert in an 1880 issue of the scientific journal Proceedings of the United States National Museum. They assigned it to the genus Platyrhina , and named it triseriata from the Latin tres ("three") and series ("row"), in reference to the three rows of thorns on its back. [3] [4] One year later in the same journal, Samuel Garman placed this species in a newly created genus, Platyrhinoidis. [5] The type specimen is an adult male caught off Santa Barbara on February 8, 1880. [3] Other common names for this species include banjo shark (not to be confused with the Australian banjo sharks, Trygonorrhina ), California thornback, guitarfish, round skate, shovelnose, thornback, and thornback ray. [1]

Based on morphology, John McEachran and Neil Aschliman concluded in a 2004 phylogenetic study that Platyrhinoidis and Platyrhina together form the most basal clade of the order Myliobatiformes, and are thus the sister group to all other members of the order (encompassing stingrays and their relatives), rather than being closely related to the true guitarfishes of the family Rhinobatidae, a possibility that had long been considered by taxonomists. [6] Molecular phylogenetics, by contrast, consistently recovers Platyrhinidae as being a close relative of neither guitarfish nor stringrays, but rather as the sister-group to Torpediniformes, the electric rays. [2]


The three rows of large dorsal thorns are a characteristic feature of the thornback guitarfish. Platyrhinoidis triseriata pismo.jpg
The three rows of large dorsal thorns are a characteristic feature of the thornback guitarfish.

The pectoral fin disc of the thornback guitarfish is heart-shaped, slightly longer than it is wide, and thick towards the front. The snout is short and broad, with a blunt tip protruding slightly from the disc. The eyes are small and widely spaced; the spiracles are larger than the eyes and lie closely behind. The wide nostrils are preceded by moderately large, broad flaps of skin. The mouth is wide and gently arched; there are a pair of creases running from the mouth corners to the nostrils, enclosing a roughly trapezoidal area. The lower lip is inscribed by a deep furrow that wraps around the mouth corners. The small teeth have low crowns that may be sharp to blunt, and are arranged in 68–82 rows in the upper jaw and 64–78 rows in the lower jaw. The five pairs of gill slits are small and located beneath the disc. [3] [4] [5]

The pelvic fins have curved outer margins and angular rear tips; males have long claspers. The tail is robust and much longer than the disc, with lateral skin folds running along either side. The two dorsal fins are similar in size and shape, being longer than tall with rounded posterior margins. The first dorsal fin lies closer to the caudal fin than the pelvic fins. The caudal fin is well-developed and almost elliptical, without a distinct lower lobe. The skin is entirely covered by tiny dermal denticles; additionally there are large recurved thorns in two or three rows along the leading margin of the disc, in small groups on the snout tip, around the eyes, and on the "shoulders", and most distinctively in three rows running from the middle of the back to the second dorsal fin. This species is plain olive to grayish brown above and off-white below. The snout and disc margins are barely translucent. It grows up to 91 cm (36 in) long. [3] [4] [5]

Distribution and habitat

Endemic to the northeastern Pacific Ocean, the thornback guitarfish is found from Tomales Bay to Magdalena Bay, with additional isolated populations in the Gulf of California. It is reportedly very abundant in some coastal waters off California and Baja California, such as in Elkhorn Slough, and uncommon north of Monterey and in the Gulf of California. [1] [4] Bottom-dwelling in nature, this species is typically found close to shore in less than 6 m (20 ft) of water, though it has been recorded from as deep as 137 m (449 ft). It inhabits coastal habitats with muddy or sandy bottoms, including bays, sloughs, beaches, and lagoons, and can also be found in kelp beds and adjacent areas. [1]

Biology and ecology

The thornback guitarfish can often be found lying on sand. Platyrhinoidis triseriata 1.jpg
The thornback guitarfish can often be found lying on sand.

During the day, the thornback guitarfish spends much time partially buried in sediment. It may be encountered singly, in small groups, or in large aggregations that form seasonally in particular bays and sloughs. The diet of this ray consists of polychaete worms, crustaceans (including crabs, shrimps, and isopods), squids, and small bony fishes (including anchovies, sardines, gobies, sculpins, and surfperches). [1] [7] It can detect prey with its electroreceptive ampullae of Lorenzini, which are most sensitive to electric fields with a frequency of 5–15 Hz. [8] In turn, the thornback guitarfish is preyed upon by sharks and the northern elephant seal (Mirounga angustirostris). [4] Known parasites of this species include the tapeworm Echinobothrium californiense [9] and the nematode Proleptus acutus . [10] Thornback guitarfish mate in late summer, and females give birth the following year at around the same time, peaking in August. It is aplacental viviparous, with developing embryos sustained until birth by yolk. Females bear litters of 1–15 pups every year; the newborn rays measure about 11 cm (4.3 in) long. Males and females reach sexual maturity at 37 and 48 cm (15 and 19 in) long respectively. [1]

Human interactions

Harmless and docile, the thornback guitarfish can be readily approached underwater, and fares well in public aquariums. [4] [7] Off the United States, this ray is common and faces no substantial threats: it is only occasionally caught incidentally by commercial and recreational fishers, and has no economic value. As most of its range lies within US waters, the species has been assessed as Least Concern overall by the International Union for Conservation of Nature (IUCN). However, in Mexican waters the thornback guitarfish population is small and fragmented, and the degree to which it is affected by fishing is uncertain. There, the IUCN has listed it locally under Data Deficient while noting its susceptibility to inshore lagoon fisheries and shrimp trawlers, and the urgent need for additional information to ensure its long-term regional survival. [1]

Related Research Articles

Guitarfish family of fishes

The guitarfish are a family, Rhinobatidae, of rays. The guitarfish are known for an elongated body with a flattened head and trunk and small, ray-like wings. The combined range of the various species is tropical, subtropical, and warm temperate waters worldwide.

Rajiformes order of fishes

Rajiformes is one of the four orders in the superorder Batoidea, flattened cartilaginous fishes related to sharks. Rajiforms are distinguished by the presence of greatly enlarged pectoral fins, which reach as far forward as the sides of the head, with a generally flattened body. The undulatory pectoral fin motion diagnostic to this taxon is known as rajiform locomotion. The eyes and spiracles are located on the upper surface of the head and the gill slits are on the underside of the body. Most species give birth to live young, although some lay eggs with a horny capsule.

Urolophidae family of fishes

The Urolophidae are a family of rays in the order Myliobatiformes, commonly known as stingarees or round stingrays. This family formerly included the genera Urobatis and Urotrygon of the Americas, which are presently recognized as forming their own family Urotrygonidae. Stingarees are found in the Indo-Pacific region, with the greatest diversity off Australia. They are sluggish, bottom-dwelling fish that have been recorded from shallow waters close to shore to deep waters over the upper continental slope. Measuring between 15 and 80 cm long, these rays have oval to diamond-shaped pectoral fin discs and relatively short tails that terminate in leaf-shaped caudal fins, and may also have small dorsal fins and lateral skin folds. Most are smooth-skinned, and some have ornate dorsal color patterns.

Sixgill stingray species of stingray (Hexatrygon bickelli)

The sixgill stingray is a species of stingray and the only extant member of the family Hexatrygonidae. Although several species of sixgill stingrays have been described historically, they may represent variations in a single, widespread species. This flabby, heavy-bodied fish, described only in 1980, is unique among rays in having six pairs of gill slits rather than five. Growing up to 1.7 m (5.6 ft) long, it has a rounded pectoral fin disc and a long, triangular, and flexible snout filled with a gelatinous substance. It is brownish above and white below, and lacks dermal denticles.

Deepwater stingray species of stingray (Plesiobatis daviesi)

The deepwater stingray or giant stingaree is a species of stingray and the sole member of the family Plesiobatidae. It is widely distributed in the Indo-Pacific, typically over fine sediments on the upper continental slope at depths of 275–680 m (900–2,230 ft). This species reaches 2.7 m (8.9 ft) in length and 1.5 m (4.9 ft) in width. It has an oval pectoral fin disc with a long, flexible, broad-angled snout. Most of the entire latter half of its tail supports a distinctively long, slender, leaf-shaped caudal fin. Its coloration is dark above and white below, and its skin is almost completely covered by tiny dermal denticles.

Borneo shark species of fish

The Borneo shark is a species of requiem shark, and part of the family Carcharhinidae. Extremely rare, it is known only from inshore waters around Mukah in northwestern Borneo, though it may once have been more widely distributed. A small, gray shark reaching 65 cm (26 in) in length, this species is the only member of its genus with a row of enlarged pores above the corners of its mouth. It has a slender body with a long, pointed snout and a low second dorsal fin placed posterior to the anal fin origin.

Fiddler ray genus of fishes

Trygonorrhina, also known as the fiddler rays or banjo rays, is a genus of guitarfish, family Rhinobatidae. The two species are found along the eastern and southern coasts of Australia. They are benthic in nature, favoring shallow, sandy bays, rocky reefs, and seagrass beds. The eastern fiddler is found to a depth of 120 m and the southern fiddler to a depth of 180 m.

<i>Rhina ancylostoma</i> species of fish

Rhina ancylostoma, the bowmouth guitarfish, shark ray or mud skate, is a species of ray and a member of the family Rhinidae. Its evolutionary affinities are not fully resolved, though it may be related to true guitarfishes and skates. This rare species occurs widely in the tropical coastal waters of the western Indo-Pacific, at depths of up to 90 m (300 ft). Highly distinctive in appearance, Rhina ancylostoma has a wide and thick body with a rounded snout and large shark-like dorsal and tail fins. Its mouth forms a W-shaped undulating line, and there are multiple thorny ridges over its head and back. It has a dorsal color pattern of many white spots over a bluish gray to brown background, with a pair of prominent black markings over the pectoral fins. This large species can reach a length of 2.7 m (8.9 ft) and weight of 135 kg (298 lb).

<i>Rhinobatos</i> genus of fishes

Rhinobatos is a genus of fish in the Rhinobatidae family. Although previously used to encompass all guitarfishes, it was found to be polyphyletic, and recent authorities have transferred many species included in the genus to Acroteriobatus, Glaucostegus, and Pseudobatos.

The masked stingaree is a common species of stingray in the family Urolophidae, endemic to southwestern Australia. It prefers moderately deep areas of sand or seagrass some distance from shore, though it can be found in very shallow water or to a depth of 115 m (377 ft). The masked stingaree can be identified by the two large, dark blotches on the upper surface of its rounded pectoral fin disc, one of which encompasses its eyes like a mask. The outer rims of its nostrils are expanded into prominent lobes, while between the nostrils is a skirt-like curtain of skin with a deeply fringed trailing margin. Its tail bears a small dorsal fin just before the stinging spine, and end in a leaf-like caudal fin. This species grows up to 31 cm (12 in) across.

The circular stingaree is an uncommon, little-known species of stingray in the family Urolophidae. Endemic to the coastal waters of southwestern Australia, it prefers a rocky and/or vegetated habitat. Reaching 60 cm (24 in) in length, this species is characterized by an oval pectoral fin disc bearing a striking dorsal pattern of lighter spots and rings, and a central circle of white-margined black spots, on a bluish gray background. Between its nostrils is a skirt-shaped curtain of skin, with the posterior corners drawn out into lobes. Its tail bears a rather large dorsal fin in front of the stinging spine, and ends in a deep, lance-like caudal fin. Negligibly affected by human activity, the circular stingaree has been listed under Least Concern by the International Union for Conservation of Nature (IUCN).

The patchwork stingaree is a little-known species of stingray in the family Urolophidae, with a disjunct distribution off northwestern and northeastern Australia. It usually inhabits the outer continental shelf, at a depth of 60–320 m (200–1,050 ft). This species has a diamond-shaped pectoral fin disc much wider than long, and a short, flattened tail with a prominent dorsal fin and leaf-like caudal fin. There is a skirt-shaped curtain of skin between its nostrils. Its dorsal color pattern resembles a mosaic of dark brown rings with light-colored centers, separated by fine reticulated lines. The International Union for Conservation of Nature (IUCN) has listed the patchwork stingaree under Least Concern, as it is subject to minimal fishing pressure.

The lobed stingaree is a common species of stingray in the family Urolophidae, endemic to southern Western Australia in shallow, inshore sand and seagrass habitats. This species is plain sandy in color above and has a broad, rounded pectoral fin disc. It is characterized by an enlarged, semicircular skin lobe of unknown function on the inner rim of each nostril. Its tail is slender, with lateral skin folds and a lance-like caudal fin but no dorsal fin. The maximum recorded width is 27 cm (11 in).

The butterfly stingaree is a little-known species of stingray in the family Urolophidae, endemic to the continental slope off the Chesterfield Islands. This species is characterized by a diamond-shaped pectoral fin disc much wider than long, and a rather short tail terminating in a leaf-shaped caudal fin, as well as bearing a dorsal fin and sometimes indistinct lateral skin folds. There is a skirt-shaped flap of skin between its nostrils. It is plain yellowish to brownish above, and reaches a length of at least 40 cm (16 in). The International Union for Conservation of Nature (IUCN) has listed this ray as of Least Concern, since no commercial trawl fishing occurs within its range.

The Coral Sea stingaree is a little-known species of stingray in the family Urolophidae, found at a depth of 171–310 m (561–1,017 ft) around the edge of the continental shelf off northern Queensland. Growing to a length of 48 cm (19 in), this species has a diamond-shaped pectoral fin disc with a protruding snout and a skirt-shaped flap of skin between the nostrils. Its tail bears a low dorsal fin before the stinging spine and terminates in a short leaf-shaped caudal fin. Its upper surface is grayish or brownish, sometimes with tiny dark spots. The Coral Sea stingaree may represent two closely similar species, one large and one small. There is very little fishing activity within its range, and thus it has been listed under Least Concern by the International Union for Conservation of Nature (IUCN).

Finless sleeper ray species of fish

The finless sleeper ray is a species of electric ray in the family Narkidae, and the sole member of its genus. It is found over the continental shelf of Southeast Asia from the eastern Andaman Sea to Vietnam and Borneo. Typically growing no more than 15 cm (5.9 in) long, it may be the smallest cartilaginous fish. The finless sleeper ray is the only electric ray that lacks dorsal fins. It has an oval pectoral fin disc that varies from longer than wide to wider than long, depending on age, and a short, robust tail that terminates in a short, deep caudal fin. The trailing margins of its pelvic fins are sexually dimorphic, being more concave in males.

<i>Platyrhina</i> genus of fishes

Platyrhina is a genus of rays in the family Platyrhinidae, containing three species. They are native to the warm-temperate to tropical marine waters in the western Pacific Ocean. They are little-known bottom-dwellers that feed on small invertebrates such as crustaceans, molluscs, and worms. The fanray is found inshore to a depth of 60 m on rocky or rock sandy bottoms.

Platyrhinidae family of fishes

The Platyrhinidae are a family of rays, commonly known as thornbacks due to their dorsal rows of large thorns. They resemble guitarfishes in shape. Though traditionally classified with stingrays, molecular evidence suggests they are more closely related to electric rays in the order Torpediniformes.

Indonesian angelshark species of fish

The Indonesian angelshark is a rare species of angelshark, family Squatinidae, known only from a few specimens collected from fish landing sites in southern Indonesia. It is thought to inhabit the deep waters of the continental slope. Reaching at least 1.34 m (4.4 ft) long, this species has a flattened, ray-like shape and a well-developed tail and caudal fin. It is characterized by the absences of fringes on its nasal barbels and thorns down the midline of its back, as well as by its relatively plain grayish-brown dorsal coloration with dark saddles beneath the dorsal fin bases and a black leading margin on the underside of the pectoral fins. The International Union for Conservation of Nature (IUCN) presently lacks sufficient information to assess the conservation status of this species.

Rhinopristiformes order of flat-bodied cartilaginous marine fishes

Rhinopristiformes is an order of rays, cartilaginous fishes related to sharks, containing shovelnose rays and allied groups.


  1. 1 2 3 4 5 6 7 8 Carlisle, A.B.; Garayzar, C.V. (2006). "Platyrhinoidis triseriata". IUCN Red List of Threatened Species . IUCN. 2006. Retrieved October 27, 2011.
  2. 1 2 Aschliman, Neil C.; Nishida, Mutsumi; Miya, Masaki; Inoue, Jun G.; Rosana, Kerri M.; Naylor, Gavin J.P. (2012). "Body plan convergence in the evolution of skates and rays (Chondrichthyes: Batoidea)". Molecular Phylogenetics and Evolution. Elsevier BV. 63 (1): 28–42. doi:10.1016/j.ympev.2011.12.012. ISSN   1055-7903.
  3. 1 2 3 4 Jordan, D.S.; Gilbert , C.H. (May 18, 1880). "Description of a new ray (Platyrhina triseriata), from the coast of California". Proceedings of the United States National Museum. 3 (108): 36–38. doi:10.5479/si.00963801.3-108.36.
  4. 1 2 3 4 5 6 Ebert, D.A. (2003). Sharks, Rays, and Chimaeras of California. University of California Press. pp. 188–189. ISBN   978-0-520-22265-6.
  5. 1 2 3 Garman, S. (February 23, 1881). "Synopsis and descriptions of the American Rhinobatidae". Proceedings of the United States National Museum. 3 (180): 516–523. doi:10.5479/si.00963801.180.516.
  6. McEachran, J.D.; Aschliman, N. (2004). "Phylogeny of Batoidea". In Carrier, L.C.; Musick, J.A.; Heithaus, M.R. (eds.). Biology of Sharks and Their Relatives. CRC Press. pp. 79–113. ISBN   978-0-8493-1514-5.
  7. 1 2 Michael, S.W. (1993). Reef Sharks & Rays of the World. Sea Challengers. p. 75. ISBN   978-0-930118-18-1.
  8. Froese, Rainer and Pauly, Daniel, eds. (2011). "Platyrhinoidis triseriata" in FishBase. April 2011 version.
  9. Ivanov, V.A.; Campbell, R.A. (May 1998). "Echinobothrium californiense n. sp. (Cestoda: Diphyllidea) from the thornback ray Platyrhinoidis triseriata (Chondrichthyes: Rajoidei) and a key to the species in the genus". Systematic Parasitology. 40 (1): 49–54. doi:10.1023/a:1005907607272.
  10. Specian, R.D.; Ubelaker, J.E.; Dailey, M.D. (1975). "Neoleptus gen. n. and a revision of the genus Proleptus Dujardin, 1845" (PDF). Proceedings of the Helminthological Society of Washington. 42 (1): 14–21.