The sand devil or Atlantic angel shark (''Squatina dumeril'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

angelshark The angelsharks are a group of sharks in the genus ''Squatina'' of the family Squatinidae. They commonly inhabit sandy seabeds close to in depth. Many species are now classified as critically endangered by the International Union for Conservat ...

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Squatinidae, native to the northwestern

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

. It occurs off the eastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, in the northern

Gulf of Mexico The Gulf of Mexico ( es, Golfo de México) is an oceanic basin, ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of ...

, and possibly in parts of the

Caribbean Sea The Caribbean Sea ( es, Mar Caribe; french: Mer des Caraïbes; ht, Lanmè Karayib; jam, Kiaribiyan Sii; nl, Caraïbische Zee; pap, Laman Karibe) is a sea of the Atlantic Ocean in the tropics of the Western Hemisphere. It is bounded by Mexico ...

. This bottom-dwelling shark is found in shallow

inshore A shore or a shoreline is the fringe of land at the edge of a large body of water, such as an ocean, sea, or lake. In physical oceanography, a shore is the wider fringe that is geologically modified by the action of the body of water past a ...

waters in summer and fall, and deep offshore waters in winter and spring. The sand devil's flattened body and enlarged

pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectoralis ...

and

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s give it a ray-like appearance. There is a band of enlarged thorns running along the middle of its back. It is gray or brown in color, with scattered small dark spots. This species reaches in length. The diet of the sand devil consists mainly of small

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...

fishes and

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

, which are captured via ambush attack. This species is

viviparous Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the m ...

, with the unborn young nourished by their

yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is far ...

s. Females have a multi-year reproductive cycle and give birth to 4–25 pups in spring or early summer, following a 12-month

gestation period In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it ...

. The sand devil is not aggressive, but may attempt to bite if harassed or captured. Though not valued economically, it is caught incidentally by

commercial Commercial may refer to: * a dose of advertising conveyed through media (such as - for example - radio or television) ** Radio advertisement ** Television advertisement * (adjective for:) commerce, a system of voluntary exchange of products and s ...

bottom trawl Bottom trawling is trawling (towing a trawl, which is a fishing net) along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing ...

fisheries Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

Taxonomy and phylogeny

French naturalist

Charles Alexandre Lesueur Charles Alexandre Lesueur (1 January 1778 in Le Havre – 12 December 1846 in Le Havre) was a French Natural history, naturalist, artist, and explorer. He was a prolific natural-history collector, gathering many type specimens in Australia, ...

described the sand devil in an 1818 volume of ''Journal of the Academy of Natural Sciences of Philadelphia''. Previously, it had been regarded as the same species as the European ''

Squatina squatina ''Squatina squatina'', the angelshark or monkfish, is a species of shark in the family Squatinidae (known generally also as angel sharks), that were once widespread in the coastal waters of the northeastern Atlantic Ocean. Well-adapted for ca ...

''. Lesueur based his account on an adult male long caught off the eastern United States, and named the species in honor of

André Marie Constant Duméril André Marie Constant Duméril (1 January 1774 – 14 August 1860) was a French zoologist. He was professor of anatomy at the Muséum national d'histoire naturelle from 1801 to 1812, when he became professor of herpetology and ichthyology. His ...

Phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

analysis, based on

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

, has concluded that the sand devil and the Pacific angel shark (''S. californica'') are

sister species In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

. The two of them in turn form a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

with other angel sharks found in the

Americas The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. Along with th ...

Molecular clock The molecular clock is a figurative term for a technique that uses the mutation rate of biomolecules to deduce the time in prehistory when two or more life forms diverged. The biomolecular data used for such calculations are usually nucleoti ...

estimation has timed the

divergence In vector calculus, divergence is a vector operator that operates on a vector field, producing a scalar field giving the quantity of the vector field's source at each point. More technically, the divergence represents the volume density of the ...

of ''S. dumeril'' and ''S. californica'' at ''c.'' 6.1 Ma, around the time that the

Isthmus of Panama The Isthmus of Panama ( es, Istmo de Panamá), also historically known as the Isthmus of Darien (), is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North and South America. It contains the country ...

formed. The rise of the Isthmus likely split the ancestral angel shark population, leading to their becoming separate species.

Description

The sand devil has a flattened, moderately narrow body with greatly enlarged

and

s. The skin folds along the sides of the head have smooth margins, without lobes. The large eyes are placed on top of the head and have prominent

spiracle Spiracle or spiraculum may refer to: * Spiracle (arthropods), opening in the exoskeletons of some arthropods * Spiracle (vertebrates), openings on the surface of some vertebrates * Spiraculum, a genus of land snails in family Cyclophoridae Cycl ...

s behind. The nostrils bear thin, pointed

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some ...

with smooth or slightly fringed margins. The wide mouth is positioned terminally on the head. The jaws contain 10 upper and 9 lower tooth rows on each side, with toothless gaps at the middle. Each tooth has a broad base and a single pointed cusp with smooth edges. There are five pairs of

gill slit Gill slits are individual openings to gills, i.e., multiple gill arches, which lack a single outer cover. Such gills are characteristic of cartilaginous fish such as sharks and rays, as well as deep-branching vertebrates such as lampreys. In con ...

s located on the sides of the head. The pectoral fins are broad and angular with narrow rear tips; the front of the pectoral fin is separate from the head, forming a triangular lobe. The two

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

s are similar in size and shape, and are positioned far back on the body. The

anal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is absent. The lower lobe of the

caudal fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

is larger than the upper. The

dermal denticle A fish scale is a small rigid plate that grows out of the skin of a fish. The skin of most jawed fishes is covered with these protective scales, which can also provide effective camouflage through the use of reflection and colouration, as we ...

s have rounded bases and three horizontal ridges. There is a distinctive band of larger thorns running along the midline of the back, from the nape to the

caudal peduncle Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. The dorsal coloration varies from greenish or bluish gray to reddish brown, with a scattering of small, darker spots and sometimes irregular splotches; the underside is uniformly pale. This species reaches in length and at least in weight. Squatina dumeril SI.jpg, The sand devil is a ray-like shark with a color pattern of many small dark spots on a gray-brown background. Squatina dumeril SI2.jpg, Underside Squatina dumeril jaws.jpg, Jaws Squatina dumeril jaws2.jpg, Jaws Squatina dumeril central teeth2.jpg, Central teeth Squatina dumeril lower teeth.jpg, Lower teeth

Distribution and habitat

The sand devil is found in the northwestern

from

Massachusetts Massachusetts (Massachusett language, Massachusett: ''Muhsachuweesut assachusett writing systems, məhswatʃəwiːsət'' English: , ), officially the Commonwealth of Massachusetts, is the most populous U.S. state, state in the New England ...

to the

Florida Keys The Florida Keys are a coral cay archipelago located off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about south of Miami, and e ...

, where it is fairly common. It also occurs in the northern

, and there are additional unconfirmed records from

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...

Jamaica Jamaica (; ) is an island country situated in the Caribbean Sea. Spanning in area, it is the third-largest island of the Greater Antilles and the Caribbean (after Cuba and Hispaniola). Jamaica lies about south of Cuba, and west of His ...

Nicaragua Nicaragua (; ), officially the Republic of Nicaragua (), is the largest country in Central America, bordered by Honduras to the north, the Caribbean to the east, Costa Rica to the south, and the Pacific Ocean to the west. Managua is the cou ...

, and

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

. The southern extent of its range is uncertain due to confusion with the disparate angelshark (''S. heteroptera'') and Mexican angelshark (''S. mexicana''). Because they inhabit deep-waters and because of their low commercial value the effort put into data collection is low, as with many species under these circumstances. Although their appearances are fragmented they still are classified under large broader spaces due to the lack of research done. As a result, ranges of deep-water shark species are often considered continuous across broad expanses de-spite records of occurrence, in many cases, being spatially fragmented. This bottom-dwelling shark is found over sandy or muddy bottoms on the

continental shelf A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

and

slope In mathematics, the slope or gradient of a line is a number that describes both the ''direction'' and the ''steepness'' of the line. Slope is often denoted by the letter ''m''; there is no clear answer to the question why the letter ''m'' is use ...

. Off the eastern

, the sand devil has been documented to migrate seasonally. In the summer, it moves towards the shore to depths of less than , and many can be found in water only meters deep. During fall it can be found

, down to a depth of . In winter and spring, it is found around the outer continental shelf at depths greater than ; individuals have been recorded as far as from land and deep.

Biology and ecology

The sand devil is an

ambush predator Ambush predators or sit-and-wait predators are carnivorous animals that capture or trap prey via stealth, luring or by (typically instinctive) strategies utilizing an element of surprise. Unlike pursuit predators, who chase to capture prey us ...

that spends much time buried in the bottom

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...

. Its diet consists mainly of

demersal The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

fishes such as

croakers Sciaenidae are a family of fish in the order Acanthuriformes. They are commonly called drums or croakers in reference to the repetitive throbbing or drumming sounds they make. The family consists of about 286 to 298 species in about 66 to 70 gene ...

goatfish The goatfishes are perciform fish of the family Mullidae. The family is also sometimes referred to as the red mullets, which also refers more narrowly to the genus ''Mullus''. The family name and the English common name mullet derived from Lati ...

es, and butterfishes. However, some types of demersal fishes such as jacks are rarely eaten, perhaps because they are more active and thus likely to escape attacks.

Squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

are a major secondary food source, particularly for smaller sharks.

Crab Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...

shrimp Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...

mantis shrimp Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in lengt ...

, skates, and

bivalve Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bival ...

s are infrequently eaten. This species feeds both during the day and at night. It tends to select prey approximately 50–60% as long as its mouth is wide; this size is consistent with what is predicted from

optimal foraging theory Optimal foraging theory (OFT) is a behavioral ecology model that helps predict how an animal behaves when searching for food. Although obtaining food provides the animal with energy, searching for and capturing the food require both energy and t ...

to yield the most efficient rate of

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of heat a ...

return. The variety of prey taken is greatest in fall and least in winter, and smaller sharks have a more varied diet than larger ones. In the northern Gulf of Mexico, the most important prey species are

Atlantic croaker The Atlantic croaker (''Micropogonias undulatus'') is a species of marine ray-finned fish belonging to the family Sciaenidae and is closely related to the black drum (''Pogonias cromis''), the silver perch (''Bairdiella chrysoura''), the spot cro ...

(''Micropogonias undulatus''), longspine porgy (''Stenotomus caprinus''),

spot croaker The spot (''Leiostomus xanthurus''), also known Common name, commonly as the Norfolk spot and the Virginia spot, is a species of small short-lived saltwater fish in the Family (biology), family Sciaenidae. The species inhabits estuary and coas ...

(''Leiostomus xanthurus''),

Gulf butterfish The Gulf butterfish (''Peprilus burti'') is a fish species of the family Stromateidae found in the Gulf of Mexico and off the coast of the Eastern United States.Page, L.M., Espinosa-Perez, L.T. Findley, C.R. Gilbert, R.N. Lea, N.E. Mandrak, R.L. M ...

(''Peprilus burti''), red goatfish (''Mullus auratus''), dwarf goatfish (''Upeneus parvus''), and

longfin inshore squid The longfin inshore squid (''Doryteuthis pealeii'') is a species of squid of the family Loliginidae. Description This species of squid is often seen with a reddish hue, but like many types of squid can manipulate its color, varying from a deep ...

(''Doryteuthis pealeii''). The relative importance of each differs across seasons (for example, squid are more important in winter), perhaps due to seasonal variation in their availability. A known

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...

of the sand devil is the

copepod Copepods (; meaning "oar-feet") are a group of small crustaceans found in nearly every freshwater and saltwater habitat (ecology), habitat. Some species are planktonic (inhabiting sea waters), some are benthos, benthic (living on the ocean floor) ...

'' Eudactylina spinula''. Like other angel sharks, the sand devil is

with the developing

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s sustained by

yolk Among animals which produce eggs, the yolk (; also known as the vitellus) is the nutrient-bearing portion of the egg whose primary function is to supply food for the development of the embryo. Some types of egg contain no yolk, for example bec ...

. Mature females have one functional

ovary The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. ...

, on the left, and two functional

uterus The uterus (from Latin ''uterus'', plural ''uteri'') or womb () is the organ in the reproductive system of most female mammals, including humans that accommodates the embryonic and fetal development of one or more embryos until birth. The uter ...

es.

Mating In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproduc ...

occurs in the spring; adult males have spines on the outer margins of their pectoral fins, which may help in gripping the female during

copulation Sexual intercourse (or coitus or copulation) is a sexual activity typically involving the insertion and thrusting of the penis into the vagina for sexual pleasure or reproduction.Sexual intercourse most commonly means penile–vaginal penetrat ...

. Females reproduce no more than once every two years, perhaps longer. Litter size varies from four to 25 pups, and does not appear related to the size of the female. The

lasts roughly 12 months, and birthing occurs between February and June at depths of . The newborns measure in length. Males and females

sexually mature Sexual maturity is the capability of an organism to reproduce. In humans it might be considered synonymous with adulthood, but here puberty is the name for the process of biological sexual maturation, while adulthood is based on cultural definitio ...

at around long respectively; the fact that females mature at a smaller size than males is unusual among sharks.

Human interactions

Though not normally aggressive towards humans, the sand devil can inflict serious wounds if provoked. Its

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often contrast ...

refers to its habit of snapping vigorously at

fishery Fishery can mean either the enterprise of raising or harvesting fish and other aquatic life; or more commonly, the site where such enterprise takes place ( a.k.a. fishing ground). Commercial fisheries include wild fisheries and fish farms, both ...

workers when caught, and even out of the water it is capable of lunging upwards to bite. This shark is caught incidentally in

s operated by

commercial fisheries Commercial fishing is the activity of catching fish and other seafood for commercial profit, mostly from wild fisheries. It provides a large quantity of food to many countries around the world, but those who practice it as an industry must often ...

targeting other species. It is edible but seldom brought to market. The

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

(IUCN) presently rates this species as

least concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

References

External links

''Squatina dumeril'', Sand devil
a
FishBase''Squatina dumeril'' (Atlantic Angel Shark, Sand Devil)
a
IUCN Red List
a
Florida Museum of Natural History Ichthyology Department
{{Taxonbar, from=Q756873 sand devil Fauna of the Southeastern United States Fish of the Caribbean Fish of the Dominican Republic sand devil