Archaeoceti Explained
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 .[1] Representing the earliest cetacean radiation, they include the initial amphibious stages in cetacean evolution, thus are the ancestors of both modern cetacean suborders, Mysticeti and Odontoceti. This initial diversification occurred in the shallow waters that separated India and Asia, resulting in some 30 species adapted to a fully oceanic life. Echolocation and filter-feeding evolved during a second radiation .
All archaeocetes from the Ypresian (56–47.8 mya) and most from the Lutetian (47.8–41.3 mya) are known exclusively from Indo-Pakistan, but Bartonian (41.3–38.0 mya) and Priabonian (38.0–33.9 mya) genera are known from across Earth, including North America, Egypt, New Zealand, and Europe. Although no consensus exists regarding the mode of locomotion of which cetaceans were capable during the late Lutetian, they were very unlikely to be nearly as well-adapted to the open ocean as living cetaceans. They probably reached as far as North America along coastal waters, either around Africa and over to South America, or more likely, over the Tethys Sea (between Eurasia and Africa) and along the coasts of Europe, Greenland, and North America.
The archaeocetes are paraphyletic in relation to their extant modern descendants, the Neoceti (neocetes). Neocetes consist of two subgroups, the toothed whales (odontocetes) and the baleen whales (mysticetes).
Description
Pakicetidae
First identified as cetaceans by, the pakicetids, the most archaic of whales, had long, slender legs and a long, narrow tail, and could reach the size of a modern wolf. They have only been found in sediments from freshwater streams in northwestern India and northern Pakistan, and were probably waders rather than swimmers.
Dozens of fossils are known, but only of skulls, teeth, and jaw fragments; no complete skeletons have been found. The dentition varied; the smallest species had teeth like modern fish eaters, and the largest were more like modern hyenas. The pakicetids may have been predators or carrion feeders. Neither the skull nor the dentition of pakicetids resembles those of modern whales, but the sigmoid process, involucrum, pachyostotic (compact) and rotated ossicles of their ears still reveal their cetacean nature.
Ambulocetidae
The next diverging family of whales, the Ambulocetidae, were large, already fully aquatic,[2] and crocodile-like with large feet and a strong tail. Sediments indicate that they lived in coastal areas and their compact bones suggest that they were ambush rather than fast-pursuit predators. Also known exclusively from Pakistan and India, the ambulocetids include the oldest known whale, Himalayacetus, which is believed to be, some 4 million years older than the rest of its family.
Of the less than 10 fossils that have been described, one, Ambulocetus natans, is nearly complete and the main source of information concerning early cetacean evolution. The size of a male sea lion, it had a large head with a long snout and robust, strongly worn teeth. The lower jaw shows that Ambulocetus had an unusual soft tissue connecting the back of the jaw to the middle ear — a small equivalent to the large sound-receiving fat pad in modern odontocetes. Its eyes were placed dorsally on the head, but were facing laterally. The musculature of the head, neck, and back was strong and the fluke-less tail was long. The hind limbs were short, but equipped with long feet. The fore limbs were also short and equipped with five short hooves. Ambulocetus probably swam with its hind feet like a modern otter, and was incapable of supporting its own weight on land. It probably was an ambush hunter like modern crocodiles.
Remingtonocetidae
The Remingtonocetidae had short limbs, and a strong and powerful tail with flattened vertebrae. Their long snout, tiny eyes, and ear morphology suggest their vision was poor and that hearing was their dominant sense. They, too, have only been found in Pakistan and India, and sediments suggest that they lived in turbid waters in coastal areas. Though they were probably able to live on land, they apparently used their tails to swim.
Dozens of fossils have been described, but most are only skulls and lower jaws with few dental and postcranial remains. Remingtonocetids probably varied in size with the smallest species matching Pakicetus and the largest Ambulocetus. Remingtonocetids had longer snouts than other archaeocetes, except that the cranial morphology also varied considerably, probably reflecting different diets. The eyes were small, but the ears were large and set far apart — probably reflecting an increased emphasis on underwater hearing. The fragmentary remains of remingtonocetid postcrania suggest that they had a long neck and large hind limbs that were probably able to support the body weight on land.
The remaining families and later crown cetaceans form a clade united by six synapomorphies: The anterior margin of external nares is located above or behind the third upper incisor, the rostrum is wide, the supraorbital processes are present but short, the anterior edge of the orbit is located above the second or third upper molar, the postorbital process forms a 90° angle with the sagittal crest, and the cervical vertebrae are short.
Protocetidae
The Protocetidae, known from both Africa and America, were a diversified family with hind limbs and a strong tail, indicating that they were strong swimmers that colonized shallow and warm oceans, such as reefs. They greatly affected cetacean evolution, because they spread across Earth's oceans. They had long snouts, large eyes, and a nasal opening located farther up the head than in earlier archaeocetes — suggesting they could breathe with the head held horizontally, similar to modern cetaceans — a first step towards a blowhole. Their dentition varied, but started to evolve towards the nonmasticating teeth of modern cetaceans, and they were probably active hunters. Their ability to move on land seems to have been variable: in Rodhocetus and Peregocetus possess a sacroiliac joint, indicating they could move on land.[3] In other genera (Georgiacetus and Aegicetus), the pelvis was not connected to the vertebral column, suggesting the hind limbs could not have supported the body weight. Some genera (Rodhocetus) had large hind feet forming large paddles, while Aegicetus seems to have relied more on its tail to propel itself through the water.[4]
Basilosauridae
Basilosaurids, which had tiny hind limbs and flipper-shaped fore limbs, were obligatorily aquatic and came to dominate the oceans. They still lacked the echolocation and baleen of modern odontocetes and mysticeti. Basilosaurids and dorudontids are the oldest obligate aquatic cetaceans for which the entire skeleton is known. They display a number of aquatic adaptations not present in earlier archaeocetes: In the vertebral column, the neck vertebrae are short, the thoracic and lumbar vertebrae are of similar length, the sacral vertebrae are unfused, the sacroiliac joints are absent, and the short tail has a ball vertebra (indicating the presence of a fluke). The scapulae are broad and fan-shaped with anterior acromions and small supraspinous fossae. The ulnae are large and have transversely flat olecranons, the wrists and distal forearms are flattened in the plane of the hands, and the hind limbs are tiny.
Taxonomy
The Archaeoceti include five well-established families: The status of the Kekenodontidae is still disputed, and the family is placed in either the Archaeoceti, Mysticeti, or even Delphinoidea.
Cetartiodactyla
Archaeoceti
Pakicetidae
Pakicetus
Nalacetus
Ichthyolestes
Ambulocetidae
Ambulocetus
Gandakasia
Himalayacetus
Remingtonocetidae
Andrewsiphius
Attockicetus
Dalanistes
Kutchicetus
Remingtonocetus
Rayanistes (Bebej et al., 2016)
Protocetidae
Georgiacetinae
Aegicetus (Gingerich et.al. 2019)
Babiacetus
Carolinacetus
Crenatocetus
Georgiacetus
Natchitochia
Pappocetus
Pontobasileus
Makaracetinae
Makaracetus
Protocetinae
Aegyptocetus
Artiocetus
Dhedacetus
Gaviacetus
Indocetus
Maiacetus
Peregocetus
Protocetus
Qaisracetus
Rodhocetus
Takracetus
Togocetus
Basilosauridae
Basilosaurinae
Basilosaurus
Basiloterus
Eocetus
Dorudontinae
Ancalecetus
Basilotritus
Chrysocetus
Cynthiacetus
Dorudon
Masracetus
Ocucajea
Pontogeneus
Saghacetus
Stromerius
Supayacetus
Tutcetus (Antar et al. 2023)
Zygorhiza
Pachycetinae
Antaecetus
Pachycetus
Perucetus
Kekenodontidae
Kekenodon
References
- Andrews . C. W. . A description of new species of zeuglodont and of leathery turtle from the Eocene of Southern Nigeria . Proceedings of the Zoological Society of London . 1919 . 18 . 3–4 . 309–19 . 1 April 2013 . 228169273 . 10.1111/j.1096-3642.1919.tb02124.x . 4 January 2015 . https://web.archive.org/web/20150104210528/http://biostor.org/cache/pdf/b4/7c/2f/b47c2fdc30a96c11d84e3edaf28d6090.pdf . dead .
- Bajpai . Sunil . Gingerich . Philip D . A new Eocene archaeocete (Mammalia, Cetacea) from India and the time of origin of whales . December 1998 . PNAS . 95 . 26 . 15464–68 . 10.1073/pnas.95.26.15464 . 678707438 . 1998PNAS...9515464B . 9860991 . 28065 . free .
- Bajpai . Sunil . Hans Thewissen . Thewissen. J. G. M. . A new, diminutive Eocene whale from Kachchh (Gujarat, India) and its implications for locomotor evolution . 2000 . Current Science . 79 . 10 . 1478–82 . 1 July 2013 .
- Bajpai . S . Hans Thewissen . Thewissen. JG . Sahni . A . The origin and early evolution of whales: macroevolution documented on the Indian subcontinent . 2009 . J Biosci . 34 . 5 . 673–86 . 1 February 2013 . 10.1007/s12038-009-0060-0 . 20009264 . 28232300 . 565869881 .
- Bianucci . Giovanni . Gingerich . Philip D. . Aegyptocetus tarfa, n. gen. et sp. (Mammalia, Cetacea), from the middle Eocene of Egypt: clinorhynchy, olfaction, and hearing in a protocetid whale . 2011 . Journal of Vertebrate Paleontology . 31 . 6 . 1173–88 . 10.1080/02724634.2011.607985 . 85995809 .
- Clementz . Mark T. . Fordyce . R. Ewan . Peek . Stephanie L. . Fox . David L. . Ancient marine isoscapes and isotopic evidence of bulk-feeding by Oligocene cetaceans . 2014 . Palaeogeography, Palaeoclimatology, Palaeoecology . 10.1016/j.palaeo.2012.09.009 . 400 . 28–40. 2014PPP...400...28C .
- Book: Dehm . Richard . Oettingen-Spielberg . Therese zu . Paläontologische und geologische Untersuchungen im Tertiär von Pakistan. 2. Die mitteleocänen Säugetiere von Ganda Kas bei Basal in Nordwest-Pakistan . 1958 . Munich . Beck . Abhandlungen / Neue Folge, 91 . 163296508 .
- Flower . William Henry . William Henry Flower . On the Arrangement of the Orders and Families of Existing Mammalia . 1883 . Proceedings of the Zoological Society of London . 178–86 . 83091701 .
- Book: Fordyce, Ewan
. Cetacean Evolution . 214–25 . Encyclopedia of Marine Mammals . Perrin . William R . Wiirsig . Bernd . Thewissen. J G M . 2002 . Academic Press . 978-0-12-551340-1 .
- Book: Fordyce . R. E. . Neoceti . 758–763 . Perrin . W. F. . Wursig . B. . Thewissen. J. G. M. . Encyclopedia of Marine Mammals . 2 . 2008 . Academic Press . 978-0-12-373553-9 .
- Fraas . Eberhard . Eberhard Fraas . Neue Zeuglodonten aus dem unteren Mitteleocän vom Mokattam bei Cairo . 1904 . Geologische und Paläontologische Abhandlungen . 6 . 3 . 199–220 . 1 July 2013 .
- Geisler . Jonathan H . Sanders . Albert E . Luo . Zhe-Xi . A new protocetid whale (Cetacea, Archaeoceti) from the late middle Eocene of South Carolina . July 2005 . American Museum Novitates . 3480 . 1–68 . 10.1206/0003-0082(2005)480[0001:ANPWCA]2.0.CO;2 . 4630500767 . 2246/5671 . 54060094 .
- Gervais . Paul . Paul Gervais . Remarques au sujet du genre Phocodon d'Agasiz . 1876 . Journal de Zoologie . 5 . 64–70 . 1 July 2013 .
- Gibbes . Robert Wilson . Description of the teeth of a new fossil animal found in the Green Sand of South Carolina . 1845 . Proceedings of the Academy of Natural Sciences of Philadelphia . 2 . 9 . 254–256 . 1 July 2013 .
- Gingerich . P. D. . Philip D. Gingerich . Marine Mammals (Cetacean and Sirenia) from the Eocene of Gebel Mokattam and Fayum, Egypt: Stratigraphy, Age, and Paleoenvironments . 1992 . University of Michigan Papers on Paleontology . 30 . 1–84 . 26941847 . 2027.42/48630 .
- Book: Gingerich, Philip D.
. Cetacea . 234–252 . Rose . K. D. . Archibald . J. D. . Placental mammals: origin, timing, and relationships of the major extant clades . 2005 . Johns Hopkins University Press . Baltimore . http://www-personal.umich.edu/~gingeric/PDFfiles/PDG432_RoseArch_cetacea.pdf . 1 December 2013 .
- Gingerich . Philip D . Stromerius nidensis, new archaeocete (Mammalia, Cetacea) from the Upper Eocene Qasr El-Sagha Formation, Fayum, Egypt . 2007 . Contributions from the Museum of Paleontology . 31 . 13 . 363–78 . 214233870 .
- Gingerich . Philip D. . Arif . M. . Bhatti . M. Akram . Anwar . M. . Sanders. William J. . Basilosaurus drazindai and Basiloterus hussaini, New Archaeoceti (Mammalia, Cetacea) from the Middle Eocene Drazinda Formation, with a Revised Interpretation of Ages of Whale-Bearing Strata in the Kirthar Group of the Sulaiman Range, Punjab (Pakistan) . 1997 . Contributions from the Museum of Paleontology, University of Michigan . 30 . 2 . 55–81 . 742731913 . 2027.42/48652 .
- Gingerich . Philip D. . Arif . Muhammad . Clyde . William C. . New Archaeocetes (Mammalia, Cetacea) from the middle Eocene Domanda Formation of the Sulaiman Range, Punjab (Pakistan) . 1995 . Contributions from Museum of Paleontology, the University of Michigan . 29 . 11 . 291–330 . 34123868 . 2027.42/48650 .
- Gingerich . Philip D. . Cappetta . Henri . A New Archaeocete and Other Marine Mammals (Cetacea and Sirenia) from Lower Middle Eocene Phosphate Deposits of Togo . 2014 . Journal of Paleontology . 88 . 1 . 109–129 . 10.1666/13-040 . 85915213 .
- Gingerich . Philip D. . Raza . S. M. . Arif . M. . Anwar . M. . Zhou. X. . New whale from the Eocene of Pakistan and the origin of cetacean swimming . 1994 . Nature . 368 . 844–47 . 10.1038/368844a0 . 742745707 . 1994Natur.368..844G . 6474. 2027.42/62571 . 4315623 . free.
- Gingerich . Philip D. . Russell . Donald E. . Pakicetus inachus, A New Archaeocete (Mammalia, Cetacea) from the Early-Middle Eocene Kuldana Formation of Kohat (Pakistan) . 1981 . Contributions from the Museum of Paleontology, the Museum of Michigan . 25 . 11 . 20 September 2018 . 742729300 .
- Gingerich . Philip D. . Uhen . Mark D. . Ancalecetus simonsi, a new dorudontine archaeocete (Mammalia, Cetacea) from the early late Eocene of Wadi Hitan, Egypt . 1996 . Contributions from the Museum of Paleontology, University of Michigan . 29 . 13 . 359–401 . 1 July 2013 . 742731018 .
- Gingerich . Philip D . Ul-Haq . Munir . Khan . Intizar Hussain . Zalmout . Iyad S. . Eocene stratigraphy and archaeocete whales (Mammalia, Cetacea) of Drug Lahar in the eastern Sulaiman range, Balochistan (Pakistan) . 2001 . Contributions from the Museum of Paleontology, University of Michigan . 30 . 11 . 269–319 . 50061585 . 2027.42/48661 .
- Gingerich . Philip D. . ul-Haq . Munir . von Koenigswald . Wighart . Sanders . William J. . Smith . B. Holly . Zalmout . Iyad S. . New Protocetid Whale from the Middle Eocene of Pakistan: Birth on Land, Precocial Development, and Sexual Dimorphism . 2009 . PLOS ONE . 4 . 2 . e4366 . 10.1371/journal.pone.0004366 . 678622523 . 2629576 . 2009PLoSO...4.4366G . 19194487. free .
- Gingerich . Philip D. . Ul-Haq . Munir . Zalmout . Iyad S. . Khan . Intizar Hussain . Malkani . S. . Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan . September 2001 . Science . 293 . 5538 . 2239–2242 . 0036-8075. 11567134 . 10.1126/science.1063902 . 2001Sci...293.2239G . 21441797 . free .
- Gingerich . Philip D. . Zalmout . Iyad S. . Ul-Haq . Munir . Bhatti . M. Akram . Makaracetus bidens, a new protocetid archaeocete (Mammalia, Cetacea) from the early middle Eocene of Balochistan (Pakistan) . 2005 . Contributions from the Museum of Paleontology . 31 . 9 . 197–210 . 1 March 2013 . 742723177 .
- Goldin . Pavel . Zvonok . Evgenij . Basilotritus uheni, a New Cetacean (Cetacea, Basilosauridae) from the Late Middle Eocene of Eastern Europe . 2013 . Journal of Paleontology . 87 . 2 . 254–68 . 10.1666/12-080R.1 . 83864139 . 4960242901 .
- Harlan . R. . Richard Harlan . Notice of fossil bones found in the Tertiary formation of the State of Louisiana . 1834 . Transactions of the American Philosophical Society . 4 . 397–403 . 63356837 . 1004838 . 10.2307/1004838.
- Hector . J. . Notes on New Zealand Cetacea, recent and fossil . 1881 . Transactions and Proceedings of the New Zealand Institute . 13 . 434–37 . 1 July 2013 . 31837919 .
- Hulbert . Richard C. Jr. . Petkewich . Richard M. . Bishop . Gale A. . Bukry . David . Aleshire . David P. . A New Middle Eocene Protocetid Whale (Mammalia: Cetacea: Archaeoceti) and Associated Biota from Georgia . September 1998 . Journal of Paleontology . 72 . 5 . 907–927 . 4908698029 . 1306667 . 10.1017/S0022336000027232 . 131420545 .
- Kumar . K. . Sahni . A. . Remingtonocetus harudiensis, new combination, a middle Eocene archaeocete (Mammalia, Cetacea) from western Kutch, India . 1986 . Journal of Vertebrate Paleontology . 6 . 4 . 326–349 . 10.1080/02724634.1986.10011629 . 4649653943 .
- Book: McLeod . S. A. . Barnes . L. G. . A new genus and species of Eocene protocetid archaeocete whale (Mammalia, Cetacea) from the Atlantic Coastal plain . Geology and Vertebrate Paleontology of Western and Southern North America . Wang . Xiaoming . Barnes . Lawrence G. . 2008 . Science Series, Natural History Museum of Los Angeles County . 41 . 73–98 . http://www.nhm.org/site/sites/default/files/pdf/contrib_science/SS-41.pdf . 1 February 2013 .
- Book: Rose, Kenneth David
. The Beginning of the Age of Mammals . 2006 . JHU Press . 978-0-8018-8472-6 .
- Sahni . Ashok . Mishra . Vijay Prakash . Lower Tertiary vertebrates from western India . 1975 . Monograph of the Paleontological Society of India . 3 . 1–48 . 3566369 . B0007AL8UE .
- Steeman . M. E. . Hebsgaard . M. B. . Fordyce . R. Ewan . Ho . S. Y. W. . Rabosky . D. L. . Nielsen . R. . Rahbek . C. . Glenner . H. . Sørensen . M. V. . Willerslev. E. . Radiation of Extant Cetaceans Driven by Restructuring of the Oceans . 2009 . Systematic Biology . 58 . 6 . 573–585 . 10.1093/sysbio/syp060 . 20525610 . 2777972.
- Book: Stromer, Ernst . Ernst Stromer von Reichenbach . Die Archaeoceti des ägyptischen Eozäns: Beiträge zur paläontologie und geologie Österreich-Ungarns und des Orients . 1908 . W. Braumüller . 1 July 2013 . 21174007 .
- Book: Thewissen
, J. G. M.
. Hans Thewissen . Archaeocetes, Archaic . 36–9 . Encyclopedia of Marine Mammals . Perrin . William R . Wiirsig . Bernd . Thewissen. J. G. M. . 2002 . Academic Press . 978-0-12-551340-1 .
- Thewissen. J. G. M. . Hussain . S.T. . Attockicetus praecursor, a new remingtonocetid cetacean from marine Eocene sediments of Pakistan . 2000 . Journal of Mammalian Evolution . 7 . 3 . 133–46 . 10.1023/A:1009458618729 . 5700031 . 362777268 . Hans Thewissen .
- Thewissen. J. G. M. . Hussain . S. T. . Systematic review of the Pakicetidae, Early and middle Eocene Cetacea (Mammalia) from Pakistan and India . 1998 . Bulletin of the Carnegie Museum . 34 . 220–38 . Hans Thewissen .
- Book: Thewissen. J. G. M. . Madar . S. I. . Hussain . S. T. . Ambulocetus natans, an Eocene cetacean (Mammalia) from Pakistan . Courier Forschungsinstitut Senckenberg . 191 . 1–86 . 1996 . 978-3-929907-32-2 . 36463214 . Hans Thewissen .
- Thewissen. J. G. M. . Williams . E. M. . Roe . L. J. . Hussain . S. T. . Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls . 2001 . Nature . 413 . 6853 . 277–81 . 1 February 2013 . 10.1038/35095005 . 118116179 . 11565023. 2001Natur.413..277T . 4416684 . Hans Thewissen .
- Trivedy . A. N. . Satsangi . P. P. . A new archaeocete (whale) from the Eocene of India . 1984 . Abstracts of 27th International Geological Congress, Moscow . 1 . 322–23 .
- True . F.W. . Frederick W. True . The fossil cetacean, Dorudon serratus Gibbes . 1908 . Bulletin of the Museum of Comparative Zoology . 52 . 4 . 5–78 . 1 July 2013 . 355813868 . 19219818M .
- Uhen . Mark D . New protocetid (Mammalia, Cetacea) from the late middle Eocene Cook Mountain Formation of Louisiana . 1998 . Journal of Vertebrate Paleontology . 18 . 3 . 664–8 . 10.1080/02724634.1998.10011093 . 204612030 . 4523937 .
- Uhen . Mark D. . A new genus and species of archaeocete whale from Mississippi . 2005 . Southeastern Geology . 43 . 3 . 157–72 .
- Uhen . M. D. . New protocetid whales from Alabama and Mississippi, and a new cetacean clade, Pelagiceti . 2008 . Journal of Vertebrate Paleontology . 28 . 3 . 589–593 . 10.1671/0272-4634(2008)28[589:NPWFAA]2.0.CO;2 . 86326007 .
- Uhen . Mark D . Gingerich . Philip D . New genus of dorudontine archaeocete (Cetacea) from the middle-to-late Eocene of South Carolina . January 2001 . Marine Mammal Science . 17 . 1 . 1–34 . 10.1111/j.1748-7692.2001.tb00979.x . 204061291 . 2027.42/73005 . free .
- Uhen . Mark D. . Pyenson . Nicholas D. . Nicholas Pyenson . Devries . Thomas J. . Urbina . Mario . Renne . Paul R. . New Middle Eocene Whales from the Pisco Basin of Peru . 2011 . Journal of Paleontology . 85 . 5 . 955–69 . 10.1666/10-162.1 . 802202947 . 10088/17509 . 115130412 .
- West . Robert M . Middle Eocene large mammal assemblage with Tethyan affinities, Ganda Kas region, Pakistan . 1980 . Journal of Paleontology . 54 . 3 . 508–533 . 4899161959 . 1304193 .
Notes and References
- Web site: Archaeoceti . Paleobiology Database . 20 September 2018.
- 10.1111/joa.12518 . 229 . Farewell to life on land - thoracic strength as a new indicator to determine paleoecology in secondary aquatic mammals . 2016 . Journal of Anatomy . 768–777 . Ando . Konami . 6 . 27396988 . 5108153.
- Olivier L, Bianucci G, Salas-Gismondi R, Di Celma C, Steurbaut E, Urbina M & de Muizon C (2019). "An amphibious whale from the Middle Eocene of Peru reveals early South Pacific dispersal of quadrupedal cetaceans". Current Biology 29(8): p. 1352–1359.e3.
- Gingerich P.D., Antar M.S.M. & Zalmout I.S. (2019). "Aegicetus gehennae, a new late Eocene protocetid (Cetacea, Archaeoceti) from Wadi Al Hitan, Egypt, and the transition to tail-powered swimming in whales". PLOS ONE 15(3): e0230596