|
Saw Shark
A sawshark or saw shark is a member of a shark order (Pristiophoriformes ) bearing a unique long, saw-like rostrum (snout or bill) edged with sharp teeth, which they use to slash and disable their prey. There are eight species within the Pristiophoriformes, including the longnose or common sawshark (''Pristiophorus cirratus''), shortnose sawshark (''Pristiophorus nudipinnis''), Japanese sawshark (''Pristiophorus japonicas''), Bahamas sawshark (''Pristiophorus schroederi''), sixgill sawshark (''Pliotrema warreni''), African dwarf sawshark (''Pristiophorus nancyae''), Lana's sawshark (''Pristiophorus lanae'') and the tropical sawshark (''Pristiophorus delicatus''). Sawsharks are found in many areas around the world, most commonly in waters from the Indian Ocean to the southern Pacific Ocean. They are normally found at depths around 40–100 m, but can be found much lower in tropical regions. The Bahamas sawshark was discovered in deeper waters (640 m to 915 m) of the northwest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Santonian
The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya (million years ago) and 83.6 ± 0.7 mya. The Santonian is preceded by the Coniacian and is followed by the Campanian.Gradstein ''et al.'' (2004) Stratigraphic definition The Santonian Stage was established by French geologist Henri Coquand in 1857. It is named after the city of Saintes in the region of Saintonge, where the original type locality is located. The base of the Santonian Stage is defined by the appearance of the inoceramid bivalve '' Cladoceramus undulatoplicatus''. The GSSP (official reference profile) for the base of the Santonian Stage is located near Olazagutia, Spain; it was ratified by the Subcommission on Cretaceous Stratigraphy in 2012. The Santonian's top (the base of the Campanian Stage) is informally marked by the extinction of the crinoid '' Marsup ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caribbean
The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Sea and the North Atlantic Ocean) and the surrounding coasts. The region is southeast of the Gulf of Mexico and the North American mainland, east of Central America, and north of South America. Situated largely on the Caribbean Plate, the region has more than 700 islands, islets, reefs and cays (see the list of Caribbean islands). Island arcs delineate the eastern and northern edges of the Caribbean Sea: The Greater Antilles and the Lucayan Archipelago on the north and the Lesser Antilles and the on the south and east (which includes the Leeward Antilles). They form the West Indies with the nearby Lucayan Archipelago ( the Bahamas and Turks and Caicos Islands), which are considered to be part of the Caribbean despite not borde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliotrema Kajae
The sixgill sawshark, ''Pliotrema warreni'' is a sawshark of the family Pristiophoridae. Presence of 6 pairs of gill slits highlights this genus among sharks; outside Hexanchiformes order, ''Pliotrema'' is the only shark with more than 5 gill slits. Unlike other sawsharks, the barbs on this shark's rostrum continue onto the sides of the head. Its barbels are also closer to its mouth than in other species. At maximum, females can reach over 136 cm long, and males can reach over 112 cm long. Range and habitat The sixgill sawshark is found in the temperate and subtropical waters of the western Indian Ocean between latitudes 23° S and 37° S, at depths of between 37 and 500 m. This shark lives in the benthic and benthopelagic zones of the continental shelf. Adults are partially segregated from juveniles, as they naturally tend to aggregate at lower depths. Behavior Using their sensitive barbels and electric sense, sixgill sawsharks are able to find their p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sketchbook Of Fishes - 25
A sketchbook is a book or pad with blank pages for sketching and is frequently used by artists for drawing or painting as a part of their creative process. Some also use sketchbooks as a sort of blueprint for future art pieces. The exhibition of sketchbooks at the Fogg Art Museum at Harvard University in 2006 suggested that there were two broad categories for classifying sketches: *Observation: this focuses on the documentation of the external world and includes many such travel and nature studies and sketches recording an artist's travels. *Invention: this follows the artists' digressions and internal journeys as they develop compositional ideas. Types of sketchbooks Sketchbooks come in a wide variety of shapes and sizes, with varied covers, and differing numbers of pages. Sketchbooks began as a way to provide a readily available supply of drawing paper in the convenient form of a book. Finish of the work found in the sketchbook varies widely depending on the artist and their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pristiophorus Nudipinnis McCoy
''Pristiophorus'' is a genus of sawsharks found in the Pacific, Atlantic and Indian oceans. Members of this genus differ from the Sixgill Sawshark ''(Pliotrema warreni)'' in having five gill slits. Their rostral sawteeth lack prominent transverse ridges on the basal ledges, and the large teeth are not posteriorly serrated. Species There are currently seven recognized species in this genus: * ''Pristiophorus cirratus'' ( Latham, 1794) (Longnose sawshark) * ''Pristiophorus delicatus'' Yearsley, Last & W. T. White, 2008 (Tropical sawshark) * ''Pristiophorus japonicus'' Günther, 1870 (Japanese sawshark) * ''Pristiophorus lanae'' Ebert & Wilms, 2013 (Lana's sawshark)Ebert, D.A. & Wilms, H.A. (2013)''Pristiophorus lanae'' sp. nov., a new sawshark species from the Western North Pacific, with comments on the genus ''Pristiophorus'' Müller & Henle, 1837 (Chondrichthyes: Pristiophoridae).Pp. 86-100 in: de Carvalho, M.R., Ebert, D.A., Ho, H.-C. & White, W.T. (eds.) : Systematics and b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovoviviparous
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch. The young of some ovoviviparous amphibians, such as '' Limnonectes larvaepartus'', are born as larvae, and undergo further metamorphosis outside the body of the mother. Members of genera '' Nectophrynoides'' and '' Eleutherodactylus'' bear froglets, not only the hatching, but all the most conspicuous metamorphosis, being completed inside the body of the mother before birth. Among insects that depend on opportunistic exploitation of transient food sources, such as many Sarcophagidae and other carrion flies, and species such as many Calliphoridae, that rely on fresh dung, and parasitoids such as tachinid flies that depend on entering the host as soon as possible ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ampullae Of Lorenzini
Ampullae of Lorenzini (singular ''Ampulla'') are electroreceptors, sense organs able to detect electric fields. They form a network of mucus-filled pores in the skin of cartilaginous fish (sharks, rays, and chimaeras) and of basal actinopterygians (bony fishes) such as reedfish, sturgeon, and lungfish. They are associated with and evolved from the mechanosensory lateral line organs of early vertebrates. Most bony fishes and terrestrial vertebrates have lost their ampullae of Lorenzini. History Ampullae were initially described by Marcello Malpighi and later given an exact description by the Italian physician and ichthyologist Stefano Lorenzini in 1679, though their function was unknown. Electrophysiological experiments in the 20th century suggested a sensibility to temperature, mechanical pressure, and possibly salinity. In 1960 the ampullae were identified as specialized receptor organs for sensing electric fields. One of the first descriptions of calcium-activated po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. Some crustaceans ( Remipedia, Cephalocarida, Branchiopoda) are more closely related to insects and the other hexapods than they are to certain other crustaceans. The 67,000 described species range in size from '' Stygotantulus stocki'' at , to the Japanese spider crab with a leg span of up to and a mass of . Like other arthropods, crustaceans have an exoskeleton, which they moult to grow. They are distinguished from other groups of arthropods, such as insects, myriapods and chelicerates, by the possession of biramous (two-parted) l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin. Squid diverged from other cephalopods during the Jurassic and occupy a similar role to teleost fish as open water predators of similar size and behaviour. They play an important role in the open water food web. The two long tentacles are used to grab prey and the eight arms to hold and control it. The beak then cuts the food into suitable size chunks for swallowing. Squid are rapid swimmers, moving by jet propulsion, and largely locate their prey by sight. They are among the most intelligent o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 contrast, bony fishes have a single outer bony gill covering called an operculum. Most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head. The anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow. A modified slit, called a spiracle, lies just behind the eye, which assists the shark with taking in water during respiration and plays a major role in bottom–dwelling sharks. Spiracles are reduced or missing in active pelagic sharks. While the shark is moving, water passes through the mouth and over the gills in a process known as "ram ventilation". While at rest, most sharks pump water over their gills ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.jpg "Click for more on -> Squid")
