''Kogia pusilla'' is an extinct

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 ...

of sperm whale from the Middle Pliocene of Italy related to the modern day

dwarf sperm whale The dwarf sperm whale (''Kogia sima'') is a sperm whale that inhabits temperate and tropical oceans worldwide, in particular continental shelves and slopes. It was first described by biologist Richard Owen in 1866, based on illustrations by n ...

(''K. sima'') and

pygmy sperm whale The pygmy sperm whale (''Kogia breviceps'') is one of two extant species in the family Kogiidae in the sperm whale superfamily. They are not often sighted at sea, and most of what is known about them comes from the examination of stranded speci ...

(''K. breviceps''). It is known from a single skull discovered in 1877, and was considered a species of

beaked whale Beaked whales (systematic name Ziphiidae) are a family of cetaceans noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-k ...

until 1997. The skull shares many characteristics with other sperm whales, and is comparable in size to that of the dwarf sperm whale. Like the modern ''Kogia'', it probably hunted squid in the twilight zone, and frequented

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

s. The environment it inhabited was likely a calm, nearshore area with a combination sandy and hard-rock

seafloor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean The ocean (also the sea or the world ocean) is the body of salt water that covers approximately 70.8% of the surface of Earth an ...

. ''K. pusilla'' likely died out due to the

ice ages An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages and gree ...

at the end of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58holotype specimen A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, IGF1540V, comprises an incomplete skull lacking teeth,

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

s, and the right and bottom side of the braincase. It was found in La Rocca

locality Locality may refer to: * Locality (association), an association of community regeneration organizations in England * Locality (linguistics) * Locality (settlement) * Suburbs and localities (Australia), in which a locality is a geographic subdivis ...

near the city of

Volterra Volterra (; Latin: ''Volaterrae'') is a walled mountaintop town in the Tuscany region of Italy. Its history dates from before the 8th century BC and it has substantial structures from the Etruscan, Roman, and Medieval periods. History Volt ...

Tuscany it, Toscano (man) it, Toscana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Citizenship , demographics1_footnotes = , demographics1_title1 = Italian , demogra ...

, Italy, an area that is dated to the Middle Pliocene between 3 and 2.6

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago) ...

(mya). Teeth and periotic bones of the inner ear were also found in the area, possibly belonging to ''K. pusilla''. The skull was first donated to the Museo di Paleontologia of the

University of Florence The University of Florence (Italian: ''Università degli Studi di Firenze'', UniFI) is an Italian public research university located in Florence, Italy. It comprises 12 schools and has around 50,000 students enrolled. History The first universi ...

in 1877 by Italian

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

Roberto Lawley. In 1893, paleontologist

Giovanni Capellini Giovanni Capellini (23 August 1833 – 28 May 1922) was an Italian geologist and paleontologist. He was a Senator of the Kingdom of Italy in the seventeenth legislature. Birth and education Giovanni Capellini was born on 23 August 1833 in L ...

thought it was a

; on first look, he thought it represented the genus '' Choneziphius'', but then he concluded it represented the now-

dubious Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty ...

genus '' Placoziphius'' based on similarities with the snouts. In 1987, it was described as ''Hyperoodon pusillus'' as a species of

bottlenose whale ''Hyperoodon'' (or ''Hyperoödon'') is a genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes ...

–which is also a beaked whale–by Georg Pilleri. In 1997, it was finally described as ''K. pusilla'' by

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althoug ...

Giovanni Bianucci. The

species name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''pusilla'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

for "small". ''K. pusilla'' is the third fossil kogiid whale described, after '' Praekogia'' from 1973 and '' Scaphokogia'' from 1988, and the third member of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

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'', Italy, ...

'', with the modern day

(''K. sima'') and

(''K. breviceps''). The other two kogiids are '' Thalassocetus'' and '' Nanokogia''. The dwarf and pygmy sperm whales are more derived than ''K. pusilla''. The discovery of ''K. pusilla'' pushed up 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 t ...

point between the dwarf and pygmy sperm whales from the previous estimate of around 9.3 mya to after

Early Pliocene Early may refer to: History * The beginning or oldest part of a defined historical period, as opposed to middle or late periods, e.g.: ** Early Christianity ** Early modern Europe Places in the United States * Early, Iowa * Early, Texas * Early ...

5.3 mya.

Description

''K. pusilla'' is differentiated from the dwarf and pygmy sperm whales by its more elongated snout, smaller

lacrimal bone The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

, less pronounced cheekbones, less elevation of the back top side of the skull, and more asymmetry between the left and right sides of the skull. It is smaller than the pygmy sperm whale and has a narrower sagittal crest along the mid-line of the skull. The blowhole is displaced even farther to the left than in modern-day ''Kogia'' and the sagittal crest more to the right. However, the skull size is comparable to that of the dwarf sperm whale. The braincase of ''K. pusilla'' has a basin formed by the right

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

, which, in modern ''Kogia'', houses the spermaceti organ. The organ is unique to

sperm whales 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 '' Physeter'' and one of three extant species in the sperm whale fam ...

and aids in echolocation by focusing sound. Due to the less-pronounced cheekbones, the

anterior cranial fossa The anterior cranial fossa is a depression in the floor of the cranial base which houses the projecting frontal lobes of the brain. It is formed by the orbital plates of the frontal, the cribriform plate of the ethmoid, and the small wings and fr ...

–depressions on the skull–are smaller than in modern ''Kogia''. The lacrimal bone is hooked-shape like in Physeteridae in contrast to the triangular lacrimal bone of Kogiidae. Like other kogiids, it does not have nasal bones. Thinking it was a beaked whale and using the holotype of ''Placoziphius'' for scale, Capellini estimated the length at .

Paleoecology

''K. pusilla'', like the other ''Kogia'', had a blunt snout, likely an adaptation for

suction feeding Aquatic feeding mechanisms face a special difficulty as compared to feeding on land, because the density of water is about the same as that of the prey, so the prey tends to be pushed away when the mouth is closed. This problem was first identifi ...

. It, like the modern ''Kogia'', probably hunted squid in the sunlight and

twilight Twilight is light produced by sunlight scattering in the upper atmosphere, when the Sun is below the horizon, which illuminates the lower atmosphere and the Earth's surface. The word twilight can also refer to the periods of time when this i ...

zones between . Considering the squid-eating fossil

pilot whale Pilot whales are cetaceans belonging to the genus ''Globicephala''. The two extant species are the long-finned pilot whale (''G. melas'') and the short-finned pilot whale (''G. macrorhynchus''). The two are not readily distinguishable at sea, ...

'' Globicephala etruriae'' was discovered in the same area and occupied the same

niche Niche may refer to: Science *Developmental niche, a concept for understanding the cultural context of child development *Ecological niche, a term describing the relational position of an organism's species *Niche differentiation, in ecology, the ...

, squid were probably more abundant in the Mediterranean during the Pliocene than present-day.

Paleobiology

The Rocca locality in Volterra is representative of a

neritic The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminate ...

-to-

littoral The littoral zone or nearshore is the part of a sea, lake, or river that is close to the shore. In coastal ecology, the littoral zone includes the intertidal zone extending from the high water mark (which is rarely inundated), to coastal a ...

zone along a

. The dwarf and pygmy sperm whales also inhabit the continental slope. The area has yielded the extinct dolphins '' Etruridelphis'' and ''

Hemisyntrachelus ''Hemisyntrachelus'' is an extinct genus of cetacean.''Hemisyntrachelus''
at ...

'', ''G. etruriae'', the baleen whale '' Balaena paronai'', the sperm whale (''Physeter macrocephalus''), the ''Mesoplodon'' beaked whales '' M. lawleyi'' and '' M. danconae'', and the

manatee Manatees (family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living speci ...

'' Metaxytherium subapenninum''. The area has an unusually large and one of the most diverse decapod

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 ...

assemblages known from the Pliocene; this implies a sandy-muddy and at places hard-rock

with calm, well-oxygenated, nearshore water, which are conducive for decapod life. Further, areas could have been covered with

seagrass Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families (Posidoniaceae, Zosteraceae, Hydrocharitaceae and Cymodoceaceae), all in the or ...

, similar to the modern day Mediterranean neptune grass (''Posidonia oceanica''). Some invertebrates, including a possible squid

cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopods. In other cephalopod families it is calle ...

, were preserved. ''K. pusilla'' likely died out along with several fish and mollusk species in an extinction event in the Mediterranean in the

Late Pliocene Late may refer to: * LATE, an acronym which could stand for: ** Limbic-predominant age-related TDP-43 encephalopathy, a proposed form of dementia ** Local-authority trading enterprise, a New Zealand business law ** Local average treatment effect, ...

with the onset of the

References

{{Taxonbar, from=Q21359914 Sperm whales Fossil taxa described in 1987 Pliocene cetaceans