''Gaviacetus'' (from Latin ''Gavia'', "
loon
Loons (North American English) or divers (British / Irish English) are a group of aquatic birds found in much of North America and northern Eurasia. All living species of loons are members of the genus ''Gavia'', family Gaviidae and order Gavi ...
" and ''cetus'', "whale")
is an extinct
archaeocete
Archaeoceti ("ancient whales"), or Zeuglodontes in older literature, is a paraphyletic group of primitive cetaceans that lived from the Early Eocene to the late Oligocene (). Representing the earliest cetacean Evolutionary radiation, radiation, t ...
whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...
that lived approximately . ''Gaviacetus'' was named for its characteristic narrow
rostrum
Rostrum may refer to:
* Any kind of a platform for a speaker:
**dais
**pulpit
* Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects
* Rostrum (ship), a form of bow on naval ships
* Ros ...
and the fast
pursuit predation
Pursuit predation is a form of predation in which predators actively give chase to their prey, either solitarily or as a group. It is an alternate predation strategy to ambush predation — pursuit predators rely on superior speed, endurance an ...
suggested by its unfused
sacral
Sacral may refer to:
*Sacred
Sacred describes something that is dedicated or set apart for the service or worship of a deity; is considered worthy of spiritual respect or devotion; or inspires awe or reverence among believers. The property ...
vertebrae.
Location
The only known ''Gaviacetus razai'' specimen was found in
Punjab
Punjab (; Punjabi: پنجاب ; ਪੰਜਾਬ ; ; also romanised as ''Panjāb'' or ''Panj-Āb'') is a geopolitical, cultural, and historical region in South Asia, specifically in the northern part of the Indian subcontinent, comprising ...
,
Pakistan
Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
. (, paleocoordinates )
Description
The skull of ''Gaviacetus'' is characteristic of protocetids, but the rostrum is extremely narrow anterior to P
3, suggesting some kind of
trophic
Trophic, from Ancient Greek τροφικός (''trophikos'') "pertaining to food or nourishment", may refer to:
* Trophic cascade
* Trophic coherence
* Trophic egg
* Trophic function
* Trophic hormone
* Trophic level index
* Trophic level
* Trop ...
specialization.
The well-preserved
auditory bulla
The tympanic part of the temporal bone is a curved plate of bone lying below the squamous part of the temporal bone, in front of the mastoid process, and surrounding the external part of the ear canal.
It originates as a separate bone (tympanic ...
in 's specimen is dense like in other archaeocetes, is equipped with a prominent sigmoid process, but has 3-5 contacts with the rest of the cranium.
Preserved
alveoli Alveolus (; pl. alveoli, adj. alveolar) is a general anatomical term for a concave cavity or pit.
Uses in anatomy and zoology
* Pulmonary alveolus, an air sac in the lungs
** Alveolar cell or pneumocyte
** Alveolar duct
** Alveolar macrophage
* ...
(tooth sockets) show that ''Gaviacetus'' had double- and triple-rooted cheek teeth,
but some controversy remains regarding the number of molars. Based on other cranial characters, concluded that ''Gaviacetus'' is a protocetid (more primitive archeocetes with a third upper molar) and therefore assumed the presence of M
3 though no traces thereof are preserved in their specimen. In opposition to this, , whose specimen is also lacking the essential maxillar part, thought the cranium above the very small M
2 to be to narrow for the presence of M
3, hence indicating ''Gaviacetus'' is a
basilosaurid
Basilosauridae is a family of extinct cetaceans. They lived during the middle to the early late Eocene and are known from all continents, including Antarctica. They were probably the first fully aquatic cetaceans.Buono M, Fordyce R.E., Marx F.G. ...
(a more derived archaeocetes lacking a third upper molar).
argued against this assignment until more solid evidence has been found.
The preserved sacral vertebra was not fused with its posterior neighbour, indicating that ''Gaviacetus'' was a tail-powered swimmer like ''
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 ...
'', better adapted to pursuit predation than ''
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 ...
''. The preserved transverse process of the sacral vertebra is distally expanded, suggesting a
synchondrosal joint between the vertebral column and pelvis.
Although often represented as having small hind limbs, this is an inference from the general progression of other fossil species towards limb loss; the only postcranial remains found for ''Gaviacetus'' are a rib and several vertebrae. At least three popular science books misspell this genus as ''Gaviocetus''.
[Donald Prothero (2007). ''Evolution: What the Fossils Say and Why it Matters''][Richard Dawkins (2009). '' The Greatest Show on Earth'']
Taxonomic history
The
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''Gaviacetus'' was established in 1995 with the description of ''G. razai''. A second species,'' G. sahnii'', was described in 1998, but'' ''transferred to its own genus,''
Kharodacetus
''Kharodacetus'' is a genus of protocetid cetacean from the middle Eocene (late Lutetian, 42 mya) of Kutch, Gujarat, southwestern India.
Description
''Kharodacetus'' is a large-sized protocetid with large premolars and a flat supraorbital shiel ...
'' in 2014 based on newly discovered remains.
Notes
References
*
*
*
{{Taxonbar, from=Q5528061
Extinct mammals of Asia
Protocetidae
Fossil taxa described in 1995
Prehistoric cetacean genera