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''Zygophyseter varolai'' is an extinct
sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...
that lived during the
Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...
age of the
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...
11.2 to 7.6 million
year A year is a unit of time based on how long it takes the Earth to orbit the Sun. In scientific use, the tropical year (approximately 365 Synodic day, solar days, 5 hours, 48 minutes, 45 seconds) and the sidereal year (about 20 minutes longer) ...
s ago. It is known from a single specimen from the
Pietra Leccese Formation Pietra means "stone" in Italian language. It is also rarely used as a given name (feminine of Pietro, ''Peter''), corresponding at almost to Petra. It may refer to: People * Pietra Brettkelly (born 1965), New Zealand film director * Pietra Mon ...
in Italy. It was a member of a
stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
of fossil
macroraptorial sperm whale Macroraptorial sperm whales were highly predatory whales of the sperm whale superfamily (Physeteroidea) of the Miocene epoch (geology), epoch that hunted large marine mammals, including other whales, using their large teeth. They consist of six ge ...
s (often shortened to "raptorial") also including ''
Brygmophyseter ''Brygmophyseter'', known as the biting sperm whale, is an extinct genus of toothed whale in the Physeteroidea, sperm whale family with one species, ''B. shigensis''. When it was first described in 1994, the species was placed in the genus ''Sc ...
'', '' Acrophyseter'', and ''
Livyatan ''Livyatan'' is an extinct genus of macroraptorial Physeteroidea, sperm whale containing one known species: ''L. melvillei''. The genus name was inspired by the Bible, biblical sea monster Leviathan, and the species name by Herman Melville, th ...
''. It probably grew to be around in length and shared some characteristics with other raptorials, such as large teeth with
tooth enamel Tooth enamel is one of the four major Tissue (biology), tissues that make up the tooth in humans and many animals, including some species of fish. It makes up the normally visible part of the tooth, covering the Crown (tooth), crown. The other ...
that were functional in both the upper and lower jaws which the modern
sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...
(''Physeter macrocephalus'') lacks. It also had a
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for pecking, grasping, and holding (in probing for food, eating, manipulating and ...
, the ability to echolocate prey, and could have probably swum faster than the modern-day sperm whale which can reach . These were probably used in the capture of large prey, such as large fish, seals, and whales. In fact, its common name, the killer sperm whale, refers to its feeding habits that would have had a resemblance to the modern-day
killer whale The orca (''Orcinus orca''), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus '' Orcinus'', it is recognizable by its black-and-white-patterned body. A cosmopolit ...
(''Orcinus orca'').


Discovery and naming

The
type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * ...
and only specimen, labelled
MAUL A maul may refer to any number of large hammers, including: * War hammer, a medieval weapon * Post maul, a type of sledgehammer * Spike maul, railroad hand tool * Splitting maul, heavy wood-splitting tool resembling both axe and hammer People * A ...
229/1, is of an almost complete skeleton discovered in southern Italy by
geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...
Angelo Varola in the marine lime mudstone of the
Pietra Leccese Formation Pietra means "stone" in Italian language. It is also rarely used as a given name (feminine of Pietro, ''Peter''), corresponding at almost to Petra. It may refer to: People * Pietra Brettkelly (born 1965), New Zealand film director * Pietra Mon ...
near the city of
Lecce Lecce (; ) is a city in southern Italy and capital of the province of Lecce. It is on the Salentine Peninsula, at the heel of the Italian Peninsula, and is over two thousand years old. Because of its rich Baroque architecture, Lecce is n ...
. It was described in 2006 by geologists Giovanni Bianucci and Walter Landini from the
University of Pisa The University of Pisa (, UniPi) is a public university, public research university in Pisa, Italy. Founded in 1343, it is one of the oldest universities in Europe. Together with Scuola Normale Superiore di Pisa and Sant'Anna School of Advanced S ...
. The
genus name Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial spec ...
''Zygophyseter'' comes from the
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
word ''zygomaticus'', which emphasizes the elongation of the
zygomatic process The zygomatic processes (aka. malar) are three processes (protrusions) from other bones of the skull which each articulate with the zygomatic bone. The three processes are: * Zygomatic process of frontal bone from the frontal bone * Zygomatic ...
of the only known species ''Z. varolai'', and the term ''physeter'' refers to the modern-day
sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...
(''Physeter macrocephalus'') of the family
Physeteridae Physeteroidea is a superfamily that includes three extant species of whales: the sperm whale, in the genus '' Physeter'', and the pygmy sperm whale and dwarf sperm whale, in the genus ''Kogia''. In the past, these genera have sometimes been unit ...
. The
species name In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...
honors the discoverer.


Description


Skull

A characteristic of related raptorials, ''Zygophyseter'' had
buccal exostoses A buccal exostosis is an exostosis (bone prominence) on the buccal surface (cheek side) of the alveolar ridge of the maxilla or mandible. More commonly seen in the maxilla than the mandible, buccal exostoses are considered to be site specific. Exi ...
, bony outgrowths in the
alveolar ridge The alveolar process () is the portion of bone containing the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The alveolar process is covered by gums within the mouth, terminating roughly along the line of the mandib ...
in the mouth, which are thought to have increased their
bite force Bite force quotient (BFQ) is a numerical value commonly used to represent the bite force of an animal adjusted for its body mass, while also taking factors like the allometry effects. The BFQ is calculated as the regression of the quotient of an ...
. Like other raptorials, it had large
temporal fossa The temporal fossa is a fossa (shallow depression) on the side of the skull bounded by the temporal lines above, and the zygomatic arch below. Its floor is formed by the outer surfaces of four bones of the skull. The fossa is filled by the te ...
e, probably for supporting strong temporal and
masseter In anatomy, the masseter is one of the muscles of mastication. Found only in mammals, it is particularly powerful in herbivores to facilitate chewing of plant matter. The most obvious muscle of mastication is the masseter muscle, since it is the ...
muscles, the strongest muscles between the skull and the jaw, meaning this adaptation allowed it to shut its jaws harder. The
zygomatic bone In the human skull, the zygomatic bone (from ), also called cheekbone or malar bone, is a paired irregular bone, situated at the upper and lateral part of the face and forming part of the lateral wall and floor of the orbit, of the temporal fos ...
(cheekbone) projects outward (anteriorly), indicating it had a
beak The beak, bill, or rostrum is an external anatomical structure found mostly in birds, but also in turtles, non-avian dinosaurs and a few mammals. A beak is used for pecking, grasping, and holding (in probing for food, eating, manipulating and ...
, which featured an abrupt narrowing; this may have allowed it to clamp down on prey more effectively. The head probably took up 21–23% of the total body size, compared to that of the modern sperm whale which takes up around one fourth to one third of the total body size. Like in other sperm whales, the blowhole was slanted towards the left side of the animal, and it may have lacked a right nasal passage. The falciform process on the
squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral ...
was large and ventrally facing; as opposed to the ones in the
Kogiidae Kogiidae is a family comprising at least two extant species of Cetacea, the pygmy (''Kogia breviceps)'' and dwarf (''K. sima)'' sperm whales. As their common names suggest, they somewhat resemble sperm whales, with squared heads and small lower ...
(''
Kogia ''Kogia'' is a genus of toothed whales within the superfamily Physeteroidea comprising two extant and two extinct species from the Neogene: *Pygmy sperm whale, ''Kogia breviceps'' *Dwarf sperm whale, ''Kogia sima'' *†'' Kogia pusilla'', Ital ...
'' and ''
Praekogia ''Praekogia'' is an extinct genus of cetacean in the family Kogiidae Kogiidae is a family comprising at least two extant species of Cetacea, the pygmy (''Kogia breviceps)'' and dwarf (''K. sima)'' sperm whales. As their common names suggest, ...
'') which are either reduced or absent. These may have been reduced in kogiids due to adaptations to deep-sea diving. Like in modern sperm whales, ''Zygophyseter'' had a very large basin above the braincase, known as the supracranial basin, which probably housed the
spermaceti organ The spermaceti organ is an organ present in the heads of toothed whales of the superfamily Physeteroidea, in particular the sperm whale. The organ contains a waxy liquid called spermaceti and is thought to be involved in the generation of sound ...
and the
melon A melon is any of various plants of the family Cucurbitaceae with sweet, edible, and fleshy fruit. It can also specifically refer to ''Cucumis melo'', commonly known as the "true melon" or simply "melon". The term "melon" can apply to both the p ...
. These are used in the generation and focusing of sound for
biosonar Echolocation, also called bio sonar, is a biological active sonar used by several animal groups, both in the air and underwater. Echolocating animals emit calls and listen to the echoes of those calls that return from various objects near them ...
in the modern sperm whale, indicating ''Zygophyseter'' had some mechanisms for biosonar; that is to say this animal could have used echolocation. The zygomatic processes of the temporal bone on the cheeks were elongated probably because they supported the spermaceti organ. The skull features a pronounced slope into the supracranial basin. It probably had an echolocation system similar to that of the modern sperm whale, and ''Zygophyseter'' may have, in comparison to the echolocative abilities of other modern toothed whales, produced smaller bandwidths and lower center frequencies. This would have made it inept at detecting anything that did not have a diameter of at least .


Teeth

''Zygophyseter'' had 28 teeth in the lower jaws and 26 in the upper jaws. The curvature of the teeth increased
medially Medial may refer to: Mathematics * Medial magma, a mathematical identity in algebra Geometry * Medial axis, in geometry the set of all points having more than one closest point on an object's boundary * Medial graph, another graph that repr ...
, that is, the teeth in the front of the mouth were straighter than the teeth in the back of the mouth. The back teeth featured more wear than the front teeth. Like ''Brygmophyseter'', it had a relatively small
crown A crown is a traditional form of head adornment, or hat, worn by monarchs as a symbol of their power and dignity. A crown is often, by extension, a symbol of the monarch's government or items endorsed by it. The word itself is used, parti ...
, making up only 18% of the tooth.
Killer whale The orca (''Orcinus orca''), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus '' Orcinus'', it is recognizable by its black-and-white-patterned body. A cosmopolit ...
s (''Orcinus orca''), in comparison, have crowns that make up 20–25% of the tooth. Other characteristics include the presence of the
gumline The gums or gingiva (: gingivae) consist of the mucosal tissue that lies over the mandible and maxilla inside the mouth. Gum health and disease can have an effect on general health. Structure The gums are part of the soft tissue lining of the m ...
below the crown-root boundary (meaning that part of the root was exposed), and longitudinal grooves on the root. In the
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
, the teeth ranged in height from with an average height of , and ranged in diameter from with an average of . Like in other raptorials, and unlike in the modern sperm whale, ''Zygophyseter'' had tooth enamel. Like in ''Acrophyseter'', the
mandibular foramen The mandibular foramen is an opening on the internal surface of the ramus of the mandible. It allows for divisions of the mandibular nerve and blood vessels to pass through. Structure The mandibular foramen is an opening on the internal surfac ...
takes up about 40% of the lower jawbone. The teeth of the upper jaw form an angle of nearly 120 degrees between the crown and the root, which is possibly a characteristic shared by all raptorials.


Vertebrae

''Zygophyseter'' could reach an estimated length of , compared to the modern sperm whale. It is thought that this whale had twelve
thoracic vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...
and at least ten
lumbar vertebra The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the ...
e. The type specimen had only 8 thoracic vertebrae preserved, and only the
atlas An atlas is a collection of maps; it is typically a bundle of world map, maps of Earth or of a continent or region of Earth. Advances in astronomy have also resulted in atlases of the celestial sphere or of other planets. Atlases have traditio ...
of the neck vertebrae. Like in the modern sperm whales, the neck
vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...
e may have been fused. The centrum of the thoracic vertebrae formed a large and almost pear-shaped
central canal The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it r ...
which transports nutrients to the
spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...
. The width between the transverse processes (the diagonal projections from a vertebral centrum) of the thoracic vertebrae were ; and the neural spine, the part of the spine that projects away from the centrum, is missing in the type specimen, but it was probably short and thin. The lumbar vertebrae were elongated and may have supported large
multifidus The multifidus (multifidus spinae; : ''multifidi'') muscle consists of a number of fleshy and tendinous fasciculi, which fill up the groove on either side of the spinous processes of the vertebrae, from the sacrum to the axis. While very thin, t ...
and
longissimus The longissimus () is the muscle lateral to the semispinalis muscles. It is the longest subdivision of the erector spinae muscles that extends forward into the transverse processes of the posterior cervical vertebrae. Structure Longissimus th ...
muscles in the back, likely larger than the modern sperm whale, and so it probably swam faster than the modern sperm whale; the modern sperm whale typically travels horizontally at , comparable to other large open-ocean animals. The type specimen had eight
caudal vertebrae Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...
in the tail. The animal probably had 12 ribs. The length of the ribs increased from the first to the fifth, then decreased from the fifth to the twelfth; and the width of the ribs decreased from the first to the twelfth, similar to other
cetacea Cetacea (; , ) is an infraorder of aquatic mammals belonging to the order Artiodactyla that includes whales, dolphins and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively c ...
ns.


Classification

''Zygophyseter'' is part of a fossil
stem group In phylogenetics, the crown group or crown assemblage is a collection of species composed of the living representatives of the collection, the most recent common ancestor of the collection, and all descendants of the most recent common ancestor. ...
of hyper-predatory
macroraptorial sperm whale Macroraptorial sperm whales were highly predatory whales of the sperm whale superfamily (Physeteroidea) of the Miocene epoch (geology), epoch that hunted large marine mammals, including other whales, using their large teeth. They consist of six ge ...
s (often shortened to "raptorial") which also includes ''
Brygmophyseter ''Brygmophyseter'', known as the biting sperm whale, is an extinct genus of toothed whale in the Physeteroidea, sperm whale family with one species, ''B. shigensis''. When it was first described in 1994, the species was placed in the genus ''Sc ...
'', '' Acrophyseter'', and ''
Livyatan ''Livyatan'' is an extinct genus of macroraptorial Physeteroidea, sperm whale containing one known species: ''L. melvillei''. The genus name was inspired by the Bible, biblical sea monster Leviathan, and the species name by Herman Melville, th ...
''. This group is characterized by having large, functional teeth on both the upper and lower jaw with an enamel coating; whereas the modern sperm whale lacks enamel, teeth in the upper jaws, and functionality in the teeth for catching prey. ''Zygophyseter'' is more closely related to ''Brygmophyseter'' and ''Acrophyseter'' than to ''Livyatan'', and the enlarged teeth of this group are thought to have evolved either from a common
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., F ...
-like ancestor, or independently once or twice within the group. Some fossil remains, mostly teeth, of the genus ''
Scaldicetus ''Scaldicetus'' is an extinct genus of highly predatory macroraptorial sperm whale. Although widely used for a number of extinct physeterids with primitive dental morphology consisting of enameled teeth, ''Scaldicetus'' as generally recognized ...
'' were reassigned to these raptorials, including ''Z. varolai''. ''Scaldicetus'' is now considered to be a grade taxon with reported specimens probably united only by similar physical characteristics rather than a shared ancestry as a
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
. It has been proposed that these raptorials be placed into the extinct, possibly
paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...
(which would make it invalid)
subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...
Hoplocetinae, alongside ''Scaldicetus'', ''
Diaphorocetus ''Diaphorocetus'' is an extinct genus of odontocete cetacean belonging to Physeteroidea. Its remains were found in the Monte León Formation of Argentina, dating to the Early Miocene.Idiorophus ''Idiorophus'' is a genus of extinct toothed whales in the family Physeteridae. Fossils have been found in the Colhuehuapian Gaiman Formation of Argentina and the Libano Sandstone in Italy. The teeth of ''Idiorophus'' were similar in size to ...
'', and ''
Hoplocetus ''Hoplocetus'' is an extinct genus of raptorial cetacean of the sperm whale superfamily (biology), superfamily, Physeteroidea. Its remains have been found in the Miocene of Belgium, France, Germany and Malta, the Pliocene of Belgium and France, a ...
''.
Phylogenetical In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...
analysis shows that ''Zygophyseter'' is most closely related to ''Brygmophyseter''. The
cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
below show the relationship of ''Zygophyseter'' with other sperm whales, the raptorials in bold:


Paleobiology


Feeding and bite force

Since the teeth of ''Zygophyseter'' are large, exhibit wearing not unlike the teeth of modern-day killer whales, and had functionality in both the upper and lower jaws, it was likely a macropredator. The position of the
condyloid process The condyloid process or condylar process is the process on the human and other mammalian species' mandibles that ends in a condyle, the mandibular condyle. It is thicker than the coronoid process of the mandible and consists of two portions: the ...
es between the jaw and the skull, like in the modern sperm whale, allowed it to open its jaw wider in order to grab large prey. Its apparent similarity to the feeding habits of the killer whale gave it its nickname "killer sperm whale." A 2021 multi-author study led by Emanuele Peri reconstructed the bite force of ''Zygophyseter'' using
finite element analysis Finite element method (FEM) is a popular method for numerically solving differential equations arising in engineering and mathematical models, mathematical modeling. Typical problem areas of interest include the traditional fields of structural ...
of the skull. The model calculated an anterior bite force (the bite force at the front end of the jaws) of and posterior bite force (at the back end of the jaws) of from a bite simulated at a 35-degree jaw gape. This is roughly the same bite force that could be exerted by an adult
great white shark The great white shark (''Carcharodon carcharias''), also known as the white shark, white pointer, or simply great white, is a species of large Lamniformes, mackerel shark which can be found in the coastal surface waters of all the major ocea ...
that is long and is stronger than that in other strong-biting animals like
lion The lion (''Panthera leo'') is a large Felidae, cat of the genus ''Panthera'', native to Sub-Saharan Africa and India. It has a muscular, broad-chested body (biology), body; a short, rounded head; round ears; and a dark, hairy tuft at the ...
s, though not as strong as in
saltwater crocodile The saltwater crocodile (''Crocodylus porosus'') is a crocodilian native to saltwater habitats, brackish wetlands and freshwater rivers from India's east coast across Southeast Asia and the Sundaland to northern Australia and Micronesia. It ha ...
s and '' Basilosaurus isis''. Nevertheless, the posterior bite force of ''Zygophyseter'' was strong enough to crush bone. The significant disparity between the anterior and posterior bite forces and the pattern of stress distribution in the finite element analysis model suggests that ''Zygophyseter'' employed a "grip-and-shear" feeding strategy, in which the animal would grasp prey with its front teeth and cut them using its back teeth. This strategy is somewhat unique, being absent in modern marine macropredators such as sharks and orcas, which instead use a "grip-and-tear" method that dismembers prey by holding and shaking them, and was only previously present in some basilosaurids. However, it is likely that the feeding strategy evolved independently in ''Zygophyseter'' and related macroraptorial sperm whales, as it was absent in more ancestral genera like '' Eudelphis''. Given the similar bite force between ''Zygophyseter'' and a fully grown great white shark, it was hypothesized that the cetacean occupied a similar ecological niche that primarily fed on local large fish such as
marlin Marlins are fish from the family Istiophoridae, which includes between 9 and 11 species, depending on the taxonomic authority. Name The family's common name is thought to derive from their resemblance to a sailor's marlinspike. Taxonomy T ...
and
wahoo The wahoo (''Acanthocybium solandri'') is a scombrid fish found worldwide in tropical and subtropical seas. In Hawaii, the wahoo is known as ono. The species is sometimes called hoo in the United States. It is best known to sports fishermen, a ...
s and small to medium-sized marine mammals such as seals,
dugong The dugong (; ''Dugong dugon'') is a marine mammal. It is one of four living species of the order Sirenia, which also includes three species of manatees. It is the only living representative of the once-diverse family Dugongidae; its closest ...
s, and small cetaceans. However, neither stomach contents nor cut marks on the bones of prey species have been discovered, and thus its diet is speculative.


Paleoecology

The ''Z. varolai'' specimen from the Pietra Leccese Formation dates back to the
Tortonian The Tortonian is in the geologic time scale an age or stage of the late Miocene that spans the time between 11.608 ± 0.005 Ma and 7.246 ± 0.005 Ma (million years ago). It follows the Serravallian and is followed by the Messinian. The Tort ...
age of the
Late Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million ye ...
epoch, around 11.6 to 7.2
million years ago Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds. Usage Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
(mya), and most likely inhabited the
Paratethys The Paratethys sea, Paratethys ocean, Paratethys realm or just Paratethys (meaning "beside Tethys"), was a large shallow inland sea that covered much of mainland Europe and parts of western Asia during the middle to late Cenozoic, from the lat ...
sea. This formation has also unearthed the remains of several other large vertebrate species. Ancient
sirenia The Sirenia (), commonly referred to as sea cows or sirenians, are an order of fully aquatic, herbivorous mammals that inhabit swamps, rivers, estuaries, marine wetlands, and coastal marine waters. The extant Sirenia comprise two distinct famili ...
ns of the genus ''
Metaxytherium ''Metaxytherium'' is an extinct genus of dugong that lived from the Oligocene until the end of the Pliocene. Fossil remains have been found in Africa, Europe, North America and South America. Generally marine seagrass specialists, they inhabited ...
'' were apparently common throughout the ancient
Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
. Many fish remains of
teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...
fish,
rays Ray or RAY may refer to: Fish * Ray (fish), any cartilaginous fish of the superorder Batoidea * Ray (fish fin anatomy), the bony or horny spine on ray-finned fish Science and mathematics * Half-line (geometry) or ray, half of a line split at an ...
, and at least twenty species of
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 ...
s have been discovered, such as the
tiger shark The tiger shark (''Galeocerdo cuvier'') is a species of ground shark, and the only extant member of the genus '' Galeocerdo'' and family Galeocerdonidae. It is a large apex predator, with females capable of attaining a length of over . Popula ...
(''Galeocerdo cuvier'') and the extinct ''Otodus
megalodon ''Otodus megalodon'' ( ; meaning "big tooth"), Common name, commonly known as megalodon, is an extinction, extinct species of giant mackerel shark that lived approximately 23 to 3.6 million years ago (Mya), from the Early Miocene to the Earl ...
''. Three species of
turtle Turtles are reptiles of the order (biology), order Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Crypt ...
s have been identified: '' Trachyaspis lardyi'', '' Procolpochelys melii'', which are both ancient
marine turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...
s, and ''
Psephophorus ''Psephophorus'' is an extinct genus of sea turtle that lived from the Oligocene to the Pliocene. Its remains have been found in Europe, Africa, North America, and New Zealand. It was first named by Hermann von Meyer in 1847, and contains seven s ...
polygonus'', an ancient leatherback sea turtle. Aside from ''Zygophyseter'', two other cetacean species have been described from this formation: the oldest-known
gray whale The gray whale (''Eschrichtius robustus''), also known as the grey whale,Britannica Micro.: v. IV, p. 693. is a baleen whale that migrates between feeding and breeding grounds yearly. It reaches a length of , a weight of up to and lives between ...
'' Archaeschrichtius ruggieroi'', and a species of
beaked whale Beaked whales (systematic name Ziphiidae) are a Family (biology), family of cetaceans noted as being one of the least-known groups of mammals because of their deep-sea habitat, reclusive behavior and apparent low abundance. Only three or four of ...
'' Messapicetus longirostris''.


See also

*''
Aulophyseter ''Aulophyseter'' is an extinct genus of sperm whales from the Miocene formations of the west and east coasts of North America. ''Aulophyseter'' reached a length of approximately with an estimated body weight of .R. Nieuwenhuys (1998) ''The cent ...
'' *''
Orycterocetus ''Orycteocetus'' is an extinct genus of sperm whale from the Miocene of the northern Atlantic Ocean. Classification ''Orycterocetus'' is a member of Physeteroidea closely related to crown-group sperm whales. The type species, ''O. quadratidens'' ...
''


References


External links

* {{Taxonbar, from=Q20672357, from2=Q2357420 Prehistoric toothed whales Miocene mammals of Europe Miocene cetaceans Monotypic prehistoric cetacean genera Physeteroidea Fossil taxa described in 2006