Journal articles: 'Basilosauridae'

1

Gol'din, Pavel, and Evgenij Zvonok. "Basilotritus uheni, a new cetacean (Cetacea, Basilosauridae) from the late middle Eocene of eastern Europe." Journal of Paleontology 87, no. 2 (2013): 254–68. http://dx.doi.org/10.1666/12-080r.1.

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A new basal basilosaurid cetacean, Basilotritus uheni n. gen. n. sp., comes from the late middle Eocene (Bartonian) of Ukraine. It is the earliest dated record of a cetacean from Eastern Europe. The tympanic bulla of Basilotritus uheni shares basilosaurid synapomorphies but possesses unusual traits inherited from protocetids. Cetaceans related to Basilotritus uheni and referred to as Eocetus or “Eocetus” have been recorded from Africa, Europe, North America and South America. “Eocetus” wardii from North America is recombined as Basilotritus wardii. Platyosphys paulsonii and Platyosphys einori from Ukraine are considered as nomina dubia; specimens prior referred to as Platyosphys sp. are similar or related to Basilotritus. Other records of the Eocene cetaceans from Ukraine and south Russia are identified as Basilotritus or related genera. Early basilosaurids are demonstrated to be a paraphyletic, morphologically and geographically diverse group of the genera that colonized the world ocean as late as in Bartonian age and were probably the ancestors of Neoceti, as well as of more derived basilosaurids.

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Тарасенко, К. К. "ПЕРВАЯ НАХОДКА BASILOSAURIDAE (MAMMALIA, CETACEA) В ЭОЦЕНЕ КРАСНОДАРСКОГО КРАЯ (АПШЕРОНСКИЙ РАЙОН, ГОРНЫЙ ЛУЧ)". Доклады Российской академии наук. Науки о жизни 502, № 1 (2022): 66–69. http://dx.doi.org/10.31857/s268673892201019x.

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Davydenko, Svitozar, Manuel J. Laime, and Pavel Gol'din. "The earliest record of a marine mammal (Cetacea: Basilosauridae) from the Eocene of Amazonia." Journal of Vertebrate Paleontology 38, no. 6 (2018): e1549060. http://dx.doi.org/10.1080/02724634.2018.1549060.

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Uhen, Mark D., and David Taylor. "A basilosaurid archaeocete (Cetacea, Pelagiceti) from the Late Eocene of Oregon, USA." PeerJ 8 (October 2, 2020): e9809. http://dx.doi.org/10.7717/peerj.9809.

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Background Basilosaurid archaeocetes are known from the Late Eocene of virtually all coastlines bearing coeval marine rocks except the North Pacific Basin, until now. Here we report on three consecutive posterior thoracic vertebrae of a large, basilosaurid archaeocete from a Late Eocene horizon in the Keasey Formation in Oregon. Methods These vertebrae were morphologically and morphometrically compared to other vertebrae of similar age from around the world. Results The specimens were determined to be different from all currently named species of fossil cetacean, but most similar to those found in the Gulf Coast region of North America. These vertebrae represent the first confirmed specimen of a Late Eocene basilosaurid from the North Pacific. These and other basilosaurids known only from vertebrae are reviewed here in the context of Late Eocene paleoceanography and cetacean evolution.

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Kalmykov, N. P. "New finding of the ancient whale Basilosaurus (Cetacea, Archaeoceti: Basilosauridae) in the Lower Don area." Doklady Earth Sciences 442, no. 2 (2012): 178–80. http://dx.doi.org/10.1134/s1028334x12020055.

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Tarasenko, K. K. "First Record of Basilosauridae (Mammalia, Cetacea) in the Eocene of the Krasnodar Territory (Apsheron District, Gorny Luch)." Doklady Biological Sciences 502, no. 1 (2022): 11–14. http://dx.doi.org/10.1134/s0012496622010094.

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Martínez-Cáceres, Manuel, Olivier Lambert, and Christian de Muizon. "The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru." Geodiversitas 39, no. 1 (2017): 7–163. https://doi.org/10.5252/g2017n1a1.

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Martínez-Cáceres, Manuel, Lambert, Olivier, Muizon, Christian de (2017): The anatomy and phylogenetic affinities of Cynthiacetus peruvianus, a large Dorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru. Geodiversitas 39 (1): 7-163, DOI: 10.5252/g2017n1a1, URL: http://dx.doi.org/10.5252/g2017n1a1

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Mychko, E. V., and K. K. Tarasenko. "The First Finding of Basilosauridae (Mammalia: Cetacea) in the Upper Eocene of the Baltic States (Russia, Kaliningrad Region)." Paleontological Journal 54, no. 3 (2020): 311–18. http://dx.doi.org/10.1134/s0031030120030119.

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Gingerich, Philip D., Ayoub Amane, and Samir Zouhri. "Skull and partial skeleton of a new pachycetine genus (Cetacea, Basilosauridae) from the Aridal Formation, Bartonian middle Eocene, of southwestern Morocco." PLOS ONE 17, no. 10 (2022): e0276110. http://dx.doi.org/10.1371/journal.pone.0276110.

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Pachycetus paulsonii, Pachycetus wardii, and Antaecetus aithai are middle Eocene archaeocete whales found in Europe, North America, and Africa, respectively. The three are placed in the new basilosaurid subfamily Pachycetinae. Antaecetus is a new genus known from Egypt and Morocco, and the only pachycetine known from a substantial postcranial skeleton. The skull of A. aithai described here resembles that of Saghacetus osiris in size, but lacks the narrowly constricted rostrum of Saghacetus. Antaecetus is smaller than Pachycetus and its teeth are more gracile. Upper premolars differ in having two rather than three accessory cusps flanking the principal cusp. Pachycetines differ from dorudontines in having elongated posterior thoracic and lumbar vertebrae like those of Basilosaurus, but differ from basilosaurines and from dorudontines in having conspicuously pachyosteosclerotic vertebrae with dense and thickly laminated cortical bone surrounding a cancellous core. Pachycetinae are also distinctive in having transverse processes on lumbar vertebrae nearly as long anteroposteriorly as the corresponding centrum. We infer from their pachyosteosclerotic vertebrae that pachycetines were probably sirenian-like slow swimmers living in shallow coastal seas and feeding on passing fish and mobile invertebrates.

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Bianucci, Giovanni, Olivier Lambert, Mario Urbina, et al. "A heavyweight early whale pushes the boundaries of vertebrate morphology." Nature 620 (June 28, 2023): 824–29. https://doi.org/10.1038/s41586-023-06381-1.

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Bianucci, Giovanni, Lambert, Olivier, Urbina, Mario, Merella, Marco, Collareta, Alberto, Bennion, Rebecca, Salas-Gismondi, Rodolfo, Benites-Palomino, Aldo, Post, Klaas, Muizon, Christian de, Bosio, Giulia, Celma, Claudio Di, Malinverno, Elisa, Pierantoni, Pietro Paolo, Villa1, Igor Maria, Amson1, Eli (2023): A heavyweight early whale pushes the boundaries of vertebrate morphology. Nature 620: 824-829, DOI: 10.1038/s41586-023-06381-1

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Corrie, Joshua E., and R. Ewan Fordyce. "A redescription and re-evaluation of Kekenodon onamata (Mammalia: Cetacea), a late-surviving archaeocete from the Late Oligocene of New Zealand." Zoological Journal of the Linnean Society 196, no. 4 (2022): 1637–70. https://doi.org/10.1093/zoolinnean/zlac019.

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Corrie, Joshua E, Fordyce, R Ewan (2022): A redescription and re-evaluation of Kekenodon onamata (Mammalia: Cetacea), a late-surviving archaeocete from the Late Oligocene of New Zealand. Zoological Journal of the Linnean Society 196 (4): 1637-1670, DOI: 10.1093/zoolinnean/zlac019, URL: https://academic.oup.com/zoolinnean/article/196/4/1637/6598844

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BENAMMI, MOULOUD, SYLVAIN ADNET, LAURENT MARIVAUX, et al. "Geology, biostratigraphy and carbon isotope chemostratigraphy of the Palaeogene fossil-bearing Dakhla sections, southwestern Moroccan Sahara." Geological Magazine 156, no. 1 (2017): 117–32. http://dx.doi.org/10.1017/s0016756817000851.

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AbstractNew Palaeogene vertebrate localities were recently reported in the southern Dakhla area (southwestern Morocco). The Eocene sediment strata crops out on cliffs along the Atlantic Ocean coast. Vertebrate remains come from five conglomeratic sandstone beds and are principally represented by isolated teeth belonging to micromammals, selachians and bony fishes, a proboscidean assigned to ?Numidotheriumsp. and many remains of archaeocete whales (Basilosauridae). From fieldwork five lithostratigraphic sections were described, essentially based on the lithological characteristic of sediments. Despite the lateral variations of facies, correlations between these five sections were possible on the basis of fossil-bearing beds (A1, B1, B2, C1 and C2) and five lithological units were identified. The lower part of the section consists of rhythmically bedded, chert-rich marine siltstones and marls with thin black phosphorite with organic matter at the base. The overlying units include coarse-grained to microconglomeratic sandstones interbedded with silts, indicating deposition in a shallow-marine environment with fluvial influence. The natural remanence magnetization of a total of 50 samples was measured; the intensity of most of the samples is too weak however, before or after the first step of demagnetization. The palaeomagnetic data from the samples are very unstable, except for eight from three similar sandstone levels which show a normal polarity. Matched with biostratigraphic data on rodents, primates, the selachian, sirenian and cetacean faunas, the new carbon isotope chemostratigraphy on organics (1) refines the age of the uppermost C2 fossil-bearing bed to earliest Oligocene time and (2) confirms the Priabonian age of the B1 to C1 levels.

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van Vliet, Henk Jan, Mark E. J. Bosselaers, Dirk K. Munsterman, Marcel L. Dijkshoorn, Jeffrey Joël de Groen, and Klaas Post. "A vertebra of a small species of Pachycetus from the North Sea and its inner structure and vascularity compared with other basilosaurid vertebrae from the same site." PeerJ 12 (January 25, 2024): e16541. http://dx.doi.org/10.7717/peerj.16541.

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In the Western Scheldt Estuary near the Belgian-Dutch border, middle to late Eocene strata crop out at the current seafloor. Most vertebrae of large Eocene basilosaurid taxa from this area were previously described in several papers. They represent three morphotypes: elongated vertebrae of a large species of Pachycetus (Morphotype 1b), a not-elongated vertebra of a large ‘dorudontid’ basilosaurid (Morphotype 2) and ‘shortened’ vertebrae of a new, unnamed taxon (Morphotype 3). This article deals with a still undescribed, smaller vertebra, NMR-16642, from this site. Our first aim was to date it by dinoflagellate cysts in adhering sediments. Yielding an age of about 38 Ma, it is one of the very few remains of basilosaurids from Europe, of which the age could be assessed with reasonable certainty. The vertebra, Morphotype 1a, is assigned to a small species of Pachycetus. High-quality CT scans are used to differentiate between NMR-16642, Morphotype 1a, and the large species of Pachycetus, Morphotype 1b. Another aim of this paper is to investigate the inner structure and vascularity of the study vertebra and that of the other morphotypes (1b, 2, 3) from this area by using high-quality CT scans. Notwithstanding differences in size, shape and compactness, the vertebral inner structure with a multi-layered cortex of periosteal bone, surrounding two cones of endosteal bone appears to be basically similar in all morphotypes. Apparently, this inner structure reflects the ontogenetic vertebral growth. An attempt to reconstruct the vascularity of the vertebrae reveals a remarkable pattern of interconnected vascular systems. From the dorsal and, if present, ventral foramina, vascular canals are running to a central vascular node. From this node a system of vascular canals goes to the epiphyseal ends, giving rise to separate systems for cortex and cones. It is the first time that the vascularity of vertebrae of archaeocetes is investigated.

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ADNET, SYLVAIN, HENRI CAPPETTA, and RODOLPHE TABUCE. "A Middle–Late Eocene vertebrate fauna (marine fish and mammals) from southwestern Morocco; preliminary report: age and palaeobiogeographical implications." Geological Magazine 147, no. 6 (2010): 860–70. http://dx.doi.org/10.1017/s0016756810000348.

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AbstractRecent field work in the southern Moroccan Sahara (‘Western Sahara’), south of the city of ad-Dakhla, has led to the discovery of several new fossiliferous sites with fossil vertebrates in sedimentary deposits previously reported for the Mio-Pliocene. The sedimentology and geological setting of the studied area are briefly reported here, and at least three units have been identified in successive stratigraphical sequences according to their fossil content. The first preliminary list of vertebrate associations is reported and consists mainly of isolated teeth belonging to selachian and bony fishes, a proboscidean tooth currently assigned to ?Numidotherium sp. and many remains of archaeocete whales (Basilosauridae). At least 48 species of selachians are presently identified; many of them are new and others are recorded in the late Middle Eocene (Bartonian) and Late Eocene (Priabonian) of Wadi Al-Hitan (Egypt) or Wadi Esh-Shallala Formation (Jordan) as in other African localities (e.g. Otodus cf. sokolowi, ‘Cretolamna’ twiggsensis, Xiphodolamia serrata, Misrichthys stromeri, Hemipristis curvatus, Galeocerdo cf. eaglesomi, Propristis schweinfurthi), probably indicating a Late Eocene age for unit 2 of the bedrock successions. The evolutionary trend noticeable on the proboscidean tooth is in agreement with such an assumption, by comparison with the close relative species known from the Eocene of Egypt, Libya and Algeria. Indeed, the faunal associations from the Dakhla area clearly demonstrate the erroneous age of these deposits, previously thought to be Mio-Pliocene. It suggests a correlation in age (late Middle Eocene–Late Eocene) and a similar environment with the famous marine deposits from Egypt and Jordan. It opens new opportunities to understand the biogeography and the surprising similarity of landscape between West and Northeast Africa during the Bartonian–Priabonian period.

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Zalmout, Iyad S., Hakam A. Mustafa, Ahmad A. Smadi, Jammal A. Nazzal, and Philip D. Gingerich. "Marine mammals (Cetacea and Sirenia) from the middle and late Eocene of Jordan." Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 298, no. 2 (2020): 121–36. http://dx.doi.org/10.1127/njgpa/2020/0938.

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Marine mammals including archaeocete Cetacea and dugongid Sirenia are reported from two Eocene localities in Jordan. The first locality, Jebal eth Thuleithuwat, is Lutetian or Bartonian middle Eocene in age. Jebal eth Thuleithuwat has yielded the astragalus and other skeletal elements of a protocetid archaeocete, possible fragments of basilosaurid teeth, and the virtually complete rib of a dugongid (all gen. et sp. indet.). The second locality, Qa' Faydat ad Dahikiya is Priabonian late Eocene in age. Qa' Faydat ad Dahikiya has yielded teeth or postcranial remains of four basilosaurid archaeocetes (Stromerius nidensis, Dorudon atrox, Masracetus markgrafi, and Basilosaurus isis) and postcranial remains of a dugongid (Eotheroides sp).

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Buono, Mónica R., Marta S. Fernández, Marcelo A. Reguero, Sergio A. Marenssi, Sergio N. Santillana, and Thomas Mörs. "Eocene Basilosaurid Whales from the La Meseta Formation, Marambio (Seymour) Island, Antarctica." Ameghiniana 53, no. 3 (2016): 296. http://dx.doi.org/10.5710/amgh.02.02.2016.2922.

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Gingerich, Philip D. "Identification of basilosaurid archaeocetes (Mammalia, Cetacea) collected in Egypt by Richard Markgraf (1901–1916)." Paläontologische Zeitschrift 88, no. 3 (2013): 361–65. http://dx.doi.org/10.1007/s12542-013-0204-2.

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Martínez-Cáceres, Manuel, and Christian de Muizon. "A new basilosaurid (Cetacea, Pelagiceti) from the Late Eocene to Early Oligocene Otuma Formation of Peru." Comptes Rendus Palevol 10, no. 7 (2011): 517–26. http://dx.doi.org/10.1016/j.crpv.2011.03.006.

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Hulbert, Richard C., Richard M. Petkewich, Gale A. Bishop, David Bukry, and David P. Aleshire. "A new middle Eocene protocetid whale (Mammalia: Cetacea: Archaeoceti) and associated biota from Georgia." Journal of Paleontology 72, no. 5 (1998): 907–27. http://dx.doi.org/10.1017/s0022336000027232.

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A shallow-marine fossil biota was recovered from the Blue Bluff unit (formerly part of the McBean Formation) in the Upper Coastal Plain of eastern Georgia. Biochronologically significant mollusks (e.g., Turritella nasuta, Cubitostrea sellaeformis, Pteropsella lapidosa) and calcareous nannoplankton (e.g., Chiasmolithus solitus, Reticulofenestra umbilica, Cribocentrum reticulatum) indicate a latest Lutetian-earliest Bartonian age, or about 40 to 41 Ma. Georgiacetus vogtlensis new genus and species is described from a well-preserved, partial skeleton. Georgiacetus is the oldest known whale with a true pterygoid sinus fossa in its basicranium and a pelvis that did not articulate directly with the sacral vertebrae, two features whose acquisitions were important steps toward adaptation to a fully marine existence. The posterior four cheek teeth of G. vogtlensis form a series of carnassial-like shearing blades. These teeth also bear small, blunt accessory cusps, which are regarded as being homologous with the larger, sharper accessory cusps of basilosaurid cheek teeth.

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Gol’din, Pavel, Evgenij Zvonok, Leonid Rekovets, Aleksandr Kovalchuk, and Tatiana Krakhmalnaya. "Basilotritus (Cetacea: Pelagiceti) from the Eocene of Nagornoye (Ukraine): New data on anatomy, ontogeny and feeding of early basilosaurids." Comptes Rendus Palevol 13, no. 4 (2014): 267–76. http://dx.doi.org/10.1016/j.crpv.2013.11.002.

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Martínez-Cáceres, Manuel, Olivier Lambert, and Christian de Muizon. "The anatomy and phylogenetic affinities ofCynthiacetus peruvianus, a largeDorudon-like basilosaurid (Cetacea, Mammalia) from the late Eocene of Peru." Geodiversitas 39, no. 1 (2017): 7–163. http://dx.doi.org/10.5252/g2017n1a1.

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Park, Travis, Alistair R. Evans, Stephen J. Gallagher, and Erich M. G. Fitzgerald. "Low-frequency hearing preceded the evolution of giant body size and filter feeding in baleen whales." Proceedings of the Royal Society B: Biological Sciences 284, no. 1848 (2017): 20162528. http://dx.doi.org/10.1098/rspb.2016.2528.

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Living baleen whales (mysticetes) produce and hear the lowest-frequency (infrasonic) sounds among mammals. There is currently debate over whether the ancestor of crown cetaceans (Neoceti) was able to detect low frequencies. However, the lack of information on the most archaic fossil mysticetes has prevented us from determining the earliest evolution of their extreme acoustic biology. Here, we report the first anatomical analyses and frequency range estimation of the inner ear in Oligocene (34–23 Ma) fossils of archaic toothed mysticetes from Australia and the USA. The cochlear anatomy of these small fossil mysticetes resembles basilosaurid archaeocetes, but is also similar to that of today's baleen whales, indicating that even the earliest mysticetes detected low-frequency sounds, and lacked ultrasonic hearing and echolocation. This suggests that, in contrast to recent research, the plesiomorphic hearing condition for Neoceti was low frequency, which was retained by toothed mysticetes, and the high-frequency hearing of odontocetes is derived. Therefore, the low-frequency hearing of baleen whales has remained relatively unchanged over the last approximately 34 Myr, being present before the evolution of other signature mysticete traits, including filter feeding, baleen and giant body size.

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Uhen, M. D. "New species of protocetid archaeocete whale,Eocetus wardii(Mammalia: Cetacea) from the middle Eocene of North Carolina." Journal of Paleontology 73, no. 3 (1999): 512–28. http://dx.doi.org/10.1017/s002233600002802x.

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A new species of protocetid archaeocete,Eocetus wardiin. sp., is named based on material from the late Lutetian (middle Eocene, 43-44 Ma) Comfort Member of the Castle Hayne Formation, North Carolina. This material includes portions of the skull, thoracic, lumbar and caudal vertebrae, ribs, and the right innominate. The innominate (pelvis exclusive of the sacral vertebrae) has some characters in common with the innominata of other protocetids, including sufficient size to support a weight-bearing hind limb. This suggests thatEocetus wardiiwas capable of both terrestrial and aquatic locomotion. The innominate also includes some features in common with basilosaurid archaeocetes including a shift in the relative positions of the pubis and obturator foramen. In addition, the bone histology ofEocetusis found to be very different from that of other archaeocetes and sirenians (sea cows and dugongs). The ribs and vertebrae are composed of a central area of trabecular bone enveloped by layers of dense cortical bone.Eocetushas previously only been known from a few specimens from Gebel Mokattam near Cairo, Egypt. This identification makesEocetusthe only protocetid archaeocete genus known from both sides of the Atlantic Ocean.

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Motani, Ryosuke, and Nicholas D. Pyenson. "Downsizing a heavyweight: factors and methods that revise weight estimates of the giant fossil whale Perucetus colossus." PeerJ 12 (February 29, 2024): e16978. http://dx.doi.org/10.7717/peerj.16978.

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Extremes in organismal size have broad interest in ecology and evolution because organismal size dictates many traits of an organism’s biology. There is particular fascination with identifying upper size extremes in the largest vertebrates, given the challenges and difficulties of measuring extant and extinct candidates for the largest animal of all time, such as whales, terrestrial non-avian dinosaurs, and extinct marine reptiles. The discovery of Perucetus colossus, a giant basilosaurid whale from the Eocene of Peru, challenged many assumptions about organismal extremes based on reconstructions of its body weight that exceeded reported values for blue whales (Balaenoptera musculus). Here we present an examination of a series of factors and methodological approaches to assess reconstructing body weight in Perucetus, including: data sources from large extant cetaceans; fitting published body mass estimates to body outlines; testing the assumption of isometry between skeletal and body masses, even with extrapolation; examining the role of pachyostosis in body mass reconstructions; addressing method-dependent error rates; and comparing Perucetus with known physiological and ecological limits for living whales, and Eocene oceanic productivity. We conclude that Perucetus did not exceed the body mass of today’s blue whales. Depending on assumptions and methods, we estimate that Perucetus weighed 60–70 tons assuming a length 17 m. We calculated larger estimates potentially as much as 98–114 tons at 20 m in length, which is far less than the direct records of blue whale weights, or the 270 ton estimates that we calculated for body weights of the largest blue whales measured by length.

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Waugh, David A., and J. G. M. Thewissen. "The pattern of brain-size change in the early evolution of cetaceans." PLOS ONE 16, no. 9 (2021): e0257803. http://dx.doi.org/10.1371/journal.pone.0257803.

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Most authors have identified two rapid increases in relative brain size (encephalization quotient, EQ) in cetacean evolution: first at the origin of the modern suborders (odontocetes and mysticetes) around the Eocene-Oligocene transition, and a second at the origin of the delphinoid odontocetes during the middle Miocene. We explore how methods used to estimate brain and body mass alter this perceived timing and rate of cetacean EQ evolution. We provide new data on modern mammals (mysticetes, odontocetes, and terrestrial artiodactyls) and show that brain mass and endocranial volume scale allometrically, and that endocranial volume is not a direct proxy for brain mass. We demonstrate that inconsistencies in the methods used to estimate body size across the Eocene-Oligocene boundary have caused a spurious pattern in earlier relative brain size studies. Instead, we employ a single method, using occipital condyle width as a skeletal proxy for body mass using a new dataset of extant cetaceans, to clarify this pattern. We suggest that cetacean relative brain size is most accurately portrayed using EQs based on the scaling coefficients as observed in the closely related terrestrial artiodactyls. Finally, we include additional data for an Eocene whale, raising the sample size of Eocene archaeocetes to seven. Our analysis of fossil cetacean EQ is different from previous works which had shown that a sudden increase in EQ coincided with the origin of odontocetes at the Eocene-Oligocene boundary. Instead, our data show that brain size increased at the origin of basilosaurids, 5 million years before the Eocene-Oligocene transition, and we do not observe a significant increase in relative brain size at the origin of odontocetes.

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Velez-Juarbe, Jorge. "New heterodont odontocetes from the Oligocene Pysht Formation in Washington State, U.S.A., and a reevaluation of Simocetidae (Cetacea, Odontoceti)." PeerJ 11 (June 23, 2023): e15576. http://dx.doi.org/10.7717/peerj.15576.

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Odontocetes first appeared in the fossil record by the early Oligocene, and their early evolutionary history can provide clues as to how some of their unique adaptations, such as echolocation, evolved. Here, three new specimens from the early to late Oligocene Pysht Formation are described further increasing our understanding of the richness and diversity of early odontocetes, particularly for the North Pacific. Phylogenetic analysis shows that the new specimens are part of a more inclusive, redefined Simocetidae, which now includes Simocetus rayi, Olympicetus sp. 1, Olympicetus avitus, O. thalassodon sp. nov., and a large unnamed taxon (Simocetidae gen. et sp. A), all part of a North Pacific clade that represents one of the earliest diverging groups of odontocetes. Amongst these, Olympicetus thalassodon sp. nov. represents one of the best known simocetids, offering new information on the cranial and dental morphology of early odontocetes. Furthermore, the inclusion of CCNHM 1000, here considered to represent a neonate of Olympicetus sp., as part of the Simocetidae, suggests that members of this group may not have had the capability of ultrasonic hearing, at least during their early ontogenetic stages. Based on the new specimens, the dentition of simocetids is interpreted as being plesiomorphic, with a tooth count more akin to that of basilosaurids and early toothed mysticetes, while other features of the skull and hyoid suggest various forms of prey acquisition, including raptorial or combined feeding in Olympicetus spp., and suction feeding in Simocetus. Finally, body size estimates show that small to moderately large taxa are present in Simocetidae, with the largest taxon represented by Simocetidae gen. et sp. A with an estimated body length of 3 m, which places it as the largest known simocetid, and amongst the largest Oligocene odontocetes. The new specimens described here add to a growing list of Oligocene marine tetrapods from the North Pacific, further promoting faunistic comparisons across other contemporaneous and younger assemblages, that will allow for an improved understanding of the evolution of marine faunas in the region.

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Malkani, Muhammad Sadiq. "Recently Discovered Basilosaurid, Baluchithere Rhinoceros, Horses, Sea Cow, Proboscidean, Eucrocodile, Pterosaurs, Plesiosaur, Fishes, Invertebrates and Wood Fossils, Tracks and Trackways of Dinosaurs from Pakistan; Comparison of Recognized Four Titanosaur Taxa of Indo-Pakistan with Madagascar." Open Journal of Geology 09, no. 12 (2019): 919–55. http://dx.doi.org/10.4236/ojg.2019.912098.

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Boessenecker, Robert W., and Jonathan H. Geisler. "New Skeletons of the Ancient Dolphin Xenorophus sloanii and Xenorophus simplicidens sp. nov. (Mammalia, Cetacea) from the Oligocene of South Carolina and the Ontogeny, Functional Anatomy, Asymmetry, Pathology, and Evolution of the Earliest Odontoceti." Diversity 15, no. 11 (2023): 1154. http://dx.doi.org/10.3390/d15111154.

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The early diverging, dolphin-sized, cetacean clade Xenorophidae are a short-lived radiation of toothed whales (Odontoceti) that independently evolved two features long thought to be odontocete synapomorphies: the craniofacial and cochlear morphology underlying echolocation and retrograde cranial telescoping (i.e., posterior migration of the viscerocranium). This family was based on Xenorophus sloanii, which, for the past century, has been known only by a partial skull lacking a braincase and tympanoperiotics, collected around 1900 from the Ashley Formation (28–29 Ma, Rupelian) near Ladson, South Carolina. A large collection of new skulls and skeletons (ChM PV 5022, 7677; CCNHM 104, 168, 1077, 5995) from the Ashley Formation considerably expands the hypodigm for this species, now the best known of any stem odontocete and permitting evaluation of intraspecific variation and ontogenetic changes. This collection reveals that the holotype (USNM 11049) is a juvenile. Xenorophus sloanii is a relatively large odontocete (70–74 cm CBL; BZW = 29–31 cm; estimated body length 2.6–3 m) with a moderately long rostrum (RPI = 2.5), marked heterodonty, limited polydonty (13–14 teeth), prominent sagittal crest and intertemporal constriction, and drastically larger brain size than basilosaurid archaeocetes (EQ = 2.9). Dental morphology, thickened cementum, a dorsoventrally robust rostrum, and thick rugose enamel suggest raptorial feeding; oral pathology indicates traumatic tooth loss associated with mechanically risky predation attempts. Ontogenetic changes include increased palatal vomer exposure; fusion of the nasofrontal, occipito-parietal, and median frontal sutures; anterior lengthening of the nasals; elaboration of the nuchal crests; and blunting and thickening of the antorbital process. The consistent deviation of the rostrum 2–5° to the left and asymmetry of the palate, dentition, neurocranium, mandibles, and vertebrae in multiple specimens of Xenorophus sloanii suggest novel adaptations for directional hearing driven by the asymmetrically oriented pan bones of the mandibles. A second collection consisting of a skeleton and several skulls from the overlying Chandler Bridge Formation (24–23 Ma, Chattian) represents a new species, Xenorophus simplicidens n. sp., differing from Xenorophus sloanii in possessing shorter nasals, anteroposteriorly shorter supraorbital processes of the frontal, and teeth with fewer accessory cusps and less rugose enamel. Phylogenetic analysis supports monophyly of Xenorophus, with specimens of Xenorophus simplicidens nested within paraphyletic X. sloanii; in concert with stratigraphic data, these results support the interpretation of these species as part of an anagenetic lineage. New clade names are provided for the sister taxon to Xenorophidae (Ambyloccipita), and the odontocete clade excluding Xenorophidae, Ashleycetus, Mirocetus, and Simocetidae (Stegoceti). Analyses of tooth size, body size, temporal fossa length, orbit morphology, and the rostral proportion index, prompted by well-preserved remains of Xenorophus, provide insight into the early evolution of Odontoceti.

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Antar, Mohammed S., Abdullah S. Gohar, Heba El-Desouky, et al. "A diminutive new basilosaurid whale reveals the trajectory of the cetacean life histories during the Eocene." Communications Biology 6, no. 1 (2023). http://dx.doi.org/10.1038/s42003-023-04986-w.

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AbstractSoon after whales originated from small terrestrial artiodactyl ancestors, basal stem forms (archaeocetes) came to inhabit more specialized aquatic ecologies and underwent a tremendous adaptive radiation that culminated in the adoption of a fully aquatic lifestyle. This adaptive strategy is first documented by the geographically widespread extinct family Basilosauridae. Here we report a new basilosaurid genus and species, Tutcetus rayanensis, from the middle Eocene of Fayum, Egypt. This new whale is not only the smallest known basilosaurid, but it is also one of the oldest records of this family from Africa. Tutcetus allows us to further test hypotheses regarding basilosaurids’ early success in the aquatic ecosystem, which lasted into the latest Eocene, and their ability to outcompete amphibious stem whales and opportunistically adapt to new niches after they completely severed their ties to the land. Tutcetus also significantly expands the size range of the basilosaurids and reveals new details about their life histories, phylogeny, and paleobiogeography.

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Davydenko, Svitozar, Roman Tretiakov, and Pavel Gol’din. "Diverse bone microanatomy in cetaceans from the Eocene of Ukraine further documents early adaptations to fully aquatic lifestyle." Frontiers in Earth Science 11 (May 9, 2023). http://dx.doi.org/10.3389/feart.2023.1168681.

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Basilosauridae, fully aquatic archaeocetes from the Eocene, had osteosclerotic or pachyosteosclerotic structure of ribs and, sometimes, other bones. Such a structure is far different from osteoporotic-like bones of modern cetaceans. A microanatomical and histological study was conducted on axial and limb skeleton of several basilosaurid specimens assigned to the genus Basilotritus, from Bartonian (late middle Eocene) deposits of Ukraine, remarkable for its pachyostotic bones. The postcranial skeleton of these specimens is a complex mosaic of diverse types of bone structure, which include pachyosteosclerotic, osteosclerotic and cancellous elements. The vertebrae have a pachyostotic layered cortex reaching its greatest thickness in the lumbar region. This cortex was strongly vascularized, and its layered structure is due to concentric circles mostly made by longitudinal vascular canals, in addition to cyclical growth lines. Heavy bones are concentrated in the dorsal and ventral areas. Swollen distal ends of thoracic ribs are interpreted as serving as ballast in the ventral area, as also previously proposed for Basilosaurus cetoides. Cortical bone tissue in vertebrae and ribs showed signs of intensive resorption and remodeling. This indicates the use of the axial skeleton not only for buoyancy control but also possibly for calcium and phosphorus recycling.

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Davydenko, Svitozar, Thomas Mörs, and Pavel Gol'din. "A small whale reveals diversity of the Eocene cetacean fauna of Antarctica." Antarctic Science, October 16, 2020, 1–8. http://dx.doi.org/10.1017/s0954102020000516.

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Abstract Cetacean fossils have been recorded from middle and late Eocene deposits on Seymour Island since the beginning of the twentieth century and include fully aquatic Basilosauridae and stem Neoceti. Here, we report a small cetacean vertebra tentatively referred to as Neoceti from the late Eocene of Seymour Island. It shows a mosaic of traits, some of which are characteristic of early Neoceti (anteroposteriorly long transverse processes; a ventral keel on the ventral side of the centrum; thin pedicles of the neural arch), whereas others are shared with Basilosauridae (low-placed bases of the transverse processes). However, some traits are unique and may be autapomorphic: presence of separate prezygapophyses on the vertebra at the thoracic/lumbar boundary and a proportionally short centrum. Both traits imply a fast swimming style, which is characteristic of modern dolphins rather than Eocene cetaceans. Thus, this specimen can be identified as Neoceti indet., with some hypothetical odontocete affinities. Along with a few other Eocene whale taxa, it seems to be among the earliest known members of Neoceti on Earth. The finding of small and fast-swimming Neoceti in Antarctica also demonstrates early diversification of cetaceans and ecological niche partitioning by them dating back as early as the late Eocene.

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Fahlke, JM. "Bite marks revisited – evidence for middle-to-late Eocene Basilosaurus isis predation on Dorudon atrox (both Cetacea, Basilosauridae)." Palaeontologia Electronica, 2012. http://dx.doi.org/10.26879/341.

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Corrie, Joshua, and Travis Park. "Hearing abilities of a late‐surviving archaeocete (Cetacea: Kekenodontidae), and implications for the evolution of sound in Neoceti." Journal of Anatomy, September 30, 2024. http://dx.doi.org/10.1111/joa.14137.

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AbstractKekenodontids are the only known archaeocetes (stem cetaceans) from the late Oligocene. They possess a unique combination of morphological features seen in both more primitive Eocene basilosaurid archaeocetes and more derived Neoceti (mysticetes and odontocetes). However, much remains unknown about the clade, including its acoustic biology. Based on its phylogenetic position crownward to basilosaurids as the latest‐diverging archaeocete, we hypothesize that kekenodontids would be specialized for hearing low‐frequency sounds. Here, we provide the first report on the cochlear anatomy of a kekenodontid using the holotype of Kekenodon onamata from New Zealand. We compare the cochlear morphology of K. onamata to a sample of extinct and extant cetaceans and quantify shape differences using three‐dimensional geometric morphometrics. The analyses show that K. onamata was indeed adapted to hear low frequencies and suggests low‐frequency hearing may be a characteristic of raptorial macrophagous fossil cetaceans in contrast to infrasonic bulk filter‐feeding mysticetes and ultrasonic echolocating odontocetes.

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Ibrahim, Esraa S., Magdy M. El Hedeny, Ahmed M. El-Sabbagh, et al. "Shallow-water whale-fall communities: Evidence from the middle-late Eocene basilosaurid whale bones, Wadi El-Hitan, Fayum, Egypt." Palaeoworld, July 2024. http://dx.doi.org/10.1016/j.palwor.2024.06.006.

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Bennion, Rebecca F., Jamie A. MacLaren, Ellen J. Coombs, Felix G. Marx, Olivier Lambert, and Valentin Fischer. "Convergence and constraint in the cranial evolution of mosasaurid reptiles and early cetaceans." Paleobiology, August 22, 2022, 1–17. http://dx.doi.org/10.1017/pab.2022.27.

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Abstract The repeated return of tetrapods to aquatic life provides some of the best-known examples of convergent evolution. One comparison that has received relatively little focus is that of mosasaurids (a group of Late Cretaceous squamates) and archaic cetaceans (the ancestors of modern whales and dolphins), both of which show high levels of craniodental disparity, similar initial trends in locomotory evolution, and global distributions. Here we investigate convergence in skull ecomorphology during the initial aquatic radiations of these groups. A series of functionally informative ratios were calculated from 38 species, with ordination techniques used to reconstruct patterns of functional ecomorphospace occupation. The earliest fully aquatic members of each clade occupied different regions of ecomorphospace, with basilosaurids and early russellosaurines exhibiting marked differences in cranial functional morphology. Subsequent ecomorphological trajectories notably diverge: mosasaurids radiated across ecomorphospace with no clear pattern and numerous reversals, whereas cetaceans notably evolved toward shallower, more elongated snouts, perhaps as an adaptation for capturing smaller prey. Incomplete convergence between the two groups is present among megapredatory and longirostrine forms, suggesting stronger selection on cranial function in these two ecomorphologies. Our study highlights both the similarities and divergences in craniodental evolutionary trajectories between archaic cetaceans and mosasaurids, with convergences transcending their deeply divergent phylogenetic affinities.

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Young, Mark T., Julia A. Schwab, David Dufeau, et al. "Skull sinuses precluded extinct crocodile relatives from cetacean-style deep diving as they transitioned from land to sea." Royal Society Open Science 11, no. 10 (2024). http://dx.doi.org/10.1098/rsos.241272.

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During major evolutionary transitions, groups develop radically new body plans and radiate into new habitats. A classic example is cetaceans which evolved from terrestrial ancestors to become pelagic swimmers. In doing so, they altered their air-filled sinuses, transitioning some of these spaces to allow for fluctuations in air capacity and storage via soft tissue borders. Other tetrapods independently underwent land-to-sea transitions, but it is unclear if they similarly changed their sinuses. We use computed tomography to study sinus changes in thalattosuchian crocodylomorphs that transformed from land-bound ancestors to become the only known aquatic swimming archosaurs. We find that thalattosuchian braincase sinuses reduced over their transition, similar to cetaceans, but their snout sinuses counterintuitively expanded, distinct from cetaceans, and that both trends were underpinned by high evolutionary rates. We hypothesize that aquatic thalattosuchians were ill suited to deep diving by their snout sinuses, which seem to have remained large to help drain their unusual salt glands. Thus, although convergent in general terms, thalattosuchians and cetaceans were subject to different constraints that shaped their transitions to water. Thalattosuchians attained a stage similar to less pelagic transitional forms in the cetacean lineage (late protocetid-basilosaurid) but did not become further specialized for ocean life.

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Jamison-Todd, Sarah, Philip D. Mannion, and Paul Upchurch. "The earliest fossil cetacean with Osedax borings: narrowing the spatiotemporal gap between Cretaceous marine reptiles and late Cenozoic whales." Royal Society Open Science 12, no. 6 (2025). https://doi.org/10.1098/rsos.250446.

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Borings of the extant bone-eating worm Osedax have previously been found in Cenozoic cetaceans and Cretaceous marine reptiles. The stratigraphically youngest Cretaceous example is from the Maastrichtian, and, until now, the oldest Cenozoic example was from the Oligocene. This leaves a substantial temporal and taxonomic gap between examples from both Osedax- hosting tetrapod groups. Here, we report nine fossil cetacean specimens with Osspecus ( Osedax bioerosion), identified via CT scans. These include a late Eocene occurrence of the basilosaurid Zyghorhiza kochii from the eastern USA, which represents the earliest known Cenozoic occurrence of Osedax borings, narrowing the temporal gap between occurrences of Osspecus in Cretaceous marine reptiles and Cenozoic whales. These specimens also include the first Osspecus- bearing fossil cetaceans from the northwestern Atlantic, expanding the Cenozoic biogeography of Osedax . Six ichnospecies of Osspecus are found in these cetacean fossils, including one newly described ichnospecies. The high morphological diversity of Osspecus in these Cenozoic specimens is broadly consistent with that of the Late Cretaceous, with several ichnospecies now known from both time intervals. Surviving lineages of other large marine vertebrates, such as turtles, crocodyliforms and fish, likely acted as suitable resources for Osedax across the Cretaceous–Paleogene boundary, bridging both the temporal and taxonomic gap.

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Journal articles on the topic 'Basilosauridae'

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