Aegyptocetus
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''Aegyptocetus'' is an
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of protocetid archaeocete
whale Whales are a widely distributed and diverse group of fully Aquatic animal, aquatic placental mammal, placental marine mammals. As an informal and Colloquialism, colloquial grouping, they correspond to large members of the infraorder Cetacea ...
known from
Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
.


Taxonomy

''Aegyptocetus'' is known from the articulated
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
MSNTUP I-15459, an almost complete
cranium The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
,
lower jaw In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...
s (with teeth) and a partial
postcrania The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...
l
skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...
(cervical and thoracic
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 and
rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...
s). The specimen was recovered when
marble Marble is a metamorphic rock consisting of carbonate minerals (most commonly calcite (CaCO3) or Dolomite (mineral), dolomite (CaMg(CO3)2) that have recrystallized under the influence of heat and pressure. It has a crystalline texture, and is ty ...
ized limestone was imported commercially to Italy. It was collected in the Khashm el-Raqaba limestone quarry (, paleocoordinates ) from the Gebel Hof Formation on the northern flank of Wadi Tarfa in the
Eastern Desert The Eastern Desert (known archaically as Arabia or the Arabian Desert) is the part of the Sahara Desert that is located east of the Nile River. It spans of northeastern Africa and is bordered by the Gulf of Suez and the Red Sea to the east, a ...
of
Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
, dating to the late
Mokattam The Mokattam (  , also spelled Muqattam), also known as the Mukattam Mountain or Hills, is the name of an Eastern Desert plateau as well as the district built over it in the Southern Area of Cairo, Egypt. Etymology The Arabic name ''Moka ...
ian age of the middle
Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...
, about . Its cause of death may have been an attack by a large
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 ...
as pattern of shark tooth marks preserved on the ribs. ''Aegyptocetus'' was first named by Giovanni Bianucci and Philip D. Gingerich in
2011 The year marked the start of a Arab Spring, series of protests and revolutions throughout the Arab world advocating for democracy, reform, and economic recovery, later leading to the depositions of world leaders in Tunisia, Egypt, and Yemen ...
and the
type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...
is ''Aegyptocetus tarfa''. The generic name is derived from ''Aegyptus'',
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 ...
for Egypt, and ''cetus'', Latin for whale. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
refers to Wadi Tarfa, the desert valley where the holotype was found.


Description

''Aegyptocetus'' had features in its cranium and dentaries adapted for hearing in water. Its thoracic vertebrae (T1–T8), however, had long
neural spine 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 spinal ...
s which is a characteristic of the weight-bearing system of land-living mammals retained in protocetids, such as ''
Rodhocetus ''Rodhocetus'' (from ''Rodho'', the geological anticline at the type locality, and ''cetus'', Latin for whale) is an extinct genus of protocetid early whale known from the Lutetian of Pakistan. The best-known protocetid, ''Rodhocetus'' is known ...
'' and ''
Qaisracetus ''Qaisracetus'' is an extinct protocetid early whale known from the Eocene (Lutetian, ) of Baluchistan, Pakistan (, paleocoordinates ). Etymology The genus is named after the Qaisrani Baloch tribe which assisted Gingerich and his team during ...
'', but absent in the more derived basilosaurids, such as ''
Dorudon ''Dorudon'' ("spear-tooth") is a genus of extinct basilosaurid ancient whales that lived alongside ''Basilosaurus'' 41.03 to 33.9 million years ago in the Eocene. It was a small whale, with ''D. atrox'' measuring long and weighing . ''Dorudon'' ...
''. This suggests that ''Aegyptocetus'', like other protocetids, was able to support its body on land and probably was semi-aquatic.


Skull

The endocranial reconstruction of ''Aegyptocetus'' revealed well-defined
olfactory bulbs The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...
situated at the end of elongated olfactory tracts, resembling the configuration seen in ''
Protocetus ''Protocetus atavus'' ("first whale") is an extinct species of primitive cetacean from Egypt. It lived during the middle Eocene period 45 million years ago. The first discovered protocetid, ''Protocetus atavus'' was described by based on a cran ...
''. These features suggest that ''Aegyptocetus'' retained a functional
olfactory system The olfactory system, is the sensory nervous system, sensory system used for the sense of smell (olfaction). Olfaction is one of the special senses directly associated with specific organs. Most mammals and reptiles have a main olfactory system ...
during its semi-aquatic stage. The
skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...
also preserves a full complement of turbinals, including intricately folded ethmoturbinals and maxilloturbinals—key components of the
mammalian A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
olfactory apparatus. These structures are critical for increasing the surface area available for
olfactory epithelium The olfactory epithelium is a specialized epithelium, epithelial tissue inside the nasal cavity that is involved in olfaction, smell. In humans, it measures and lies on the roof of the nasal cavity about above and behind the nostrils. The olfact ...
and enhancing the ability to detect
odorants An aroma compound, also known as an odorant, aroma, fragrance, flavoring or flavor, is a chemical compound that has a smell or odor. For an individual chemical or class of chemical compounds to impart a smell or fragrance, it must be sufficien ...
.The presence of anatomical features such as the dorsal nasal meatus and the olfactory recess further supports the hypothesis that ''Aegyptocetus'' retained airborne olfaction, despite its aquatic adaptations. These traits suggest that olfactory capabilities in this species were likely comparable to those of
terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...
artiodactyls Artiodactyls are placental mammals belonging to the order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof). The other thre ...
, its closest
extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...
relatives.Berger, E., Amson, E., Peri, E., Gohar, A.S., Sallam, H.M., Ferreira, G.S., Chowdhury, R.R., & Martinez, Q. (2025). 3D models related to the publication: The endocranial anatomy of protocetids and its implications for early whale evolution. ''MorphoMuseuM'' e264. https://doi.org/10.18563/journal.m3.264


References


Notes


Sources

* {{Taxonbar, from1=Q28605495, from2=Q3605934 Protocetidae Eocene mammals of Africa Fossil taxa described in 2011 Monotypic prehistoric cetacean genera