|
Pachycetus
''Pachycetus'' (meaning "thick whale") is an extinct genus of Pachycetinae, pachycetine basilosaurid from Middle Eocene of the eastern United States (North Carolina & Virginia) and Europe (chiefly Germany and Ukraine). The best known remains generally suggest that ''Pachycetus'' lived during the Bartonian, however, fossil finds have also been recovered from sediments of less certain age that could suggest that it may have also lived during the Late Lutetian and Early Priabonian. ''Pachycetus'' is primarily known from vertebrae and ribs and is characterized by its highly osteosclerotic and pachyostotic skeleton. This means the bones not only featured thickened rings of cortical bone surrounding the internal cancellous bone, but the cortical bone was furthermore much denser than in other basilosaurids. Two species of ''Pachycetus'' are recognized: ''Pachycetus paulsonii'' from Europe and ''Pachycetus wardii'' from the United States. A third species might be represented by ''"Zeuglo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pachycetinae
Pachycetinae is an extinct subfamily of Basilosauridae, basilosaurid cetaceans that lived during the middle Eocene. The best-dated remains stem from Bartonian strata, but some finds suggest that they could have first appeared during the Lutetian and may have survived until the Priabonian. Fossils of pachycetines are chiefly known from the southern United States, Ukraine, Morocco and Germany, among others. They differ from other basilosaurids in having pachyostotic and osteosclerotic vertebrae and ribs, making them denser and heavier by comparison. Based on this it has been suggested that these whales lived in shallow waters and that these thickened bones act as a buoyancy control as seen in sirenians. Analysis of the teeth suggests that pachycetines had a varying diet, with the robust teeth of the larger ''Pachycetus'' indicating that it possibly fed on sharks, whereas the more gracile teeth of ''Antaecetus'' suggest a diet of smaller prey items. The clade currently only includes t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antaecetus
''Antaecetus'' is an extinct genus of pachycetine basilosaurid from the middle Eocene Aridal Formation of Morocco as well as the Fayum, Egypt. ''Antaecetus'', although known from fewer remains in total, is markedly more complete than the closely related ''Pachycetus'', with one specimen preserving large parts of the vertebral column up to the lumbar vertebrae and a well preserved skull. Based on these remains ''Antaecetus'' appears to have been smaller than ''Pachycetus'', with a proportionally smaller head and much more gracile teeth. Both genera however share a highly osteosclerotic and pachyostotic skeleton, greatly increasing their weight and possibly serving as additional ballast. In turn the elongation and thickening of the vertebrae severely impacts the animals movement, most likely causing it to have been much slower and far less mobile than other archaeocetes. It has been proposed that ''Antaecetus'' was a slow moving inhabitant of shallow coastal waters, where it would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basilosaurus
''Basilosaurus'' (meaning "king lizard") is a genus of large, predatory, prehistoric archaeocete whale from the late Eocene, approximately 41.3 to 33.9 million years ago (mya). First described in 1834, it was the first archaeocete and prehistoric whale known to science. Fossils attributed to the type species ''B. cetoides'' were discovered in the southeastern United States. They were originally thought to be of a giant reptile, hence the suffix "-saurus", Ancient Greek for "lizard". The animal was later found to be an early marine mammal, prompting attempts at renaming the creature, which failed as the rules of zoological nomenclature dictate using the original name given. The second species named in 1904, ''B. isis'', lived in the region currently known as the Mediterranean Sea, with fossils found in North Africa and Jordan. ''Basilosaurus'' is thought to have been one of the largest animals of the Paleogene, with the type species ''B. cetoides'' measuring around long and we ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basilosaurid
Basilosauridae is a family of extinct cetaceans that lived during the middle to late Eocene. Basilosaurids are known from all continents including Antarctica, and are probably the first fully aquatic cetaceans.Buono M, Fordyce R.E., Marx F.G., Fernández M.S. & Reguero M. (2019). "Eocene Antarctica: a window into the earliest history of modern whales". ''Advances in Polar Science'' 30(3): p. 293-302. doi:10.13679/j.advps.2019.0005 The group is noted to be a paraphyletic assemblage of stem group whales from which the monophyletic Neoceti are derived. Characteristics Basilosaurids ranged in size from and were fairly similar to modern cetaceans in overall body form and function. Some genera tend to show signs of convergent evolution with mosasaurs by having long serpentine body shape, which suggests that this body plan seems to have been rather successful. Basilosaurid forelimbs have broad and fan-shaped scapulae attached to a humerus, radius, and ulna which are flattened in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bartonian
The Bartonian is, in the International Commission on Stratigraphy's (ICS) geologic time scale, a stage or age in the middle of the Eocene Epoch or Series. The Bartonian Age spans the time between . It is preceded by the Lutetian and is followed by the Priabonian Age. Stratigraphic definition The Bartonian Stage was introduced by Swiss stratigrapher Karl Mayer-Eymar in 1857. The name derives from the Barton Group, a lithostratigraphic unit from the south English Hampshire Basin, which in turn derived its name from the local coastal village Barton-on-Sea (part of New Milton) in southern England. The distinction between group and stage was made in the second part of the 20th century, when stratigraphers saw the need to distinguish between litho- and chronostratigraphy. The base of the Bartonian is at the first appearance of the calcareous nanoplankton species ''Reticulofenestra reticulata''. In 2009, an official reference profile (GSSP) for the base of the Bartonian had not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Botanist
Botany, also called plant science, is the branch of natural science and biology studying plants, especially Plant anatomy, their anatomy, Plant taxonomy, taxonomy, and Plant ecology, ecology. A botanist or plant scientist is a scientist who specialises in this field. "Plant" and "botany" may be defined more narrowly to include only land plants and their study, which is also known as phytology. Phytologists or botanists (in the strict sense) study approximately 410,000 species of Embryophyte, land plants, including some 391,000 species of vascular plants (of which approximately 369,000 are flowering plants) and approximately 20,000 bryophytes. Botany originated as history of herbalism#Prehistory, prehistoric herbalism to identify and later cultivate plants that were edible, poisonous, and medicinal, making it one of the first endeavours of human investigation. Medieval physic gardens, often attached to Monastery, monasteries, contained plants possibly having medicinal benefit. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placoid Scales
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 scale (zoology), scales, which can also provide effective Underwater camouflage, camouflage through the use of animal reflectors, reflection and animal coloration, colouration, as well as possible hydrodynamic advantages. The term ''scale'' derives from the Old French , meaning a shell pod or husk. Scales vary enormously in size, shape, structure, and extent, ranging from strong and rigid armour plates in fishes such as shrimpfishes and boxfishes, to microscopic or absent in fishes such as eels and anglerfishes. The morphology (biology), morphology of a scale can be used to identify the species of fish it came from. Scales originated within the jawless ostracoderms, ancestors to all jawed fishes today. Most Osteichthyes, bony fishes are covered with the cycloid scales of salmon and carp, or the ctenoid scales of perch, or the ganoid scales of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Batoidea
Batomorphi is a Division (taxonomy), division of Chondrichthyes, cartilaginous fishes, commonly known as rays, this taxon is also known as the Order (biology), superorder Batoidea, but the 5th edition of ''Fishes of the World'' classifies it as the division Batomorphi. They and their close relatives, the sharks, compose the subclass Elasmobranchii. Rays are the largest group of cartilaginous fishes, with well over 600 species in 26 families. Rays are distinguished by their flattened bodies, enlarged pectoral fins that are fused to the head, and gill slits that are placed on their ventral surfaces. Anatomy Batomorphs are flat-bodied, and, like sharks, are cartilaginous fish, meaning they have a boneless skeleton made of a tough, elastic cartilage. Most batomorphs have five ventral slot-like body openings called gill slits that lead from the gills, but the Hexatrygonidae have six. Batomorph gill slits lie under the pectoral fins on the underside, whereas a shark's are on the sides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shark
Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the Division (taxonomy), division Selachii and are the sister group to the Batoidea, Batomorphi (Batoidea, rays and skate (fish), skates). Some sources extend the term "shark" as an informal category including Extinction, extinct members of Chondrichthyes (cartilaginous fish) with a shark-like morphology, such as hybodonts. Shark-like chondrichthyans such as ''Cladoselache'' and ''Doliodus'' first appeared in the Devonian Period (419–359 million years), though some fossilized chondrichthyan-like scales are as old as the Ordovician, Late Ordovician (458–444 million years ago). The earliest confirmed modern sharks (Selachii) are known from the Early Jurassic around , with the oldest known member being ''Agaleus'', though records of true shar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrichthyans
Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeletons primarily composed of bone tissue. Chondrichthyes are aquatic vertebrates with paired fins, paired nares, placoid scales, conus arteriosus in the heart, and a lack of opercula and swim bladders. Within the infraphylum Gnathostomata, cartilaginous fishes are distinct from all other jawed vertebrates. The class is divided into two subclasses: Elasmobranchii (sharks, rays, skates and sawfish) and Holocephali ( chimaeras, sometimes called ghost sharks, which are sometimes separated into their own class). Extant chondrichthyans range in size from the finless sleeper ray to the over whale shark. Anatomy Skeleton The skeleton is cartilaginous. The notochord is gradually replaced by a vertebral column during development, excep ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Animal Migration
Animal migration is the relatively long-distance movement of individual animals, usually on a seasonal basis. It is the most common form of migration in ecology. It is found in all major animal groups, including birds, mammals, fish, reptiles, amphibians, insects, and crustaceans. The cause of migration may be local climate, local availability of food, the season of the year or for mating. To be counted as a true migration, and not just a local dispersal or irruption, the movement of the animals should be an annual or seasonal occurrence, or a major habitat change as part of their life. An annual event could include Northern Hemisphere birds migrating south for the winter, or wildebeest migrating annually for seasonal grazing. A major habitat change could include young Atlantic salmon or sea lamprey leaving the river of their birth when they have reached a few inches in size. Some traditional forms of human migration fit this pattern. Migrations can be studied using tradition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
