Fossil Cetaceans Research Articles

Hearing abilities of a late-surviving archaeocete (Cetacea: Kekenodontidae), and implications for the evolution of sound in Neoceti.

Kekenodontids 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.

Mammal-bearing Pleistocene deposits, Vranić, southwestern Pannonian Basin System

Vranić site is a sand quarry that is located on the southern foothills of Papuk Mountain. From bottom to top of the succession, three sedimentary units have been recognized as: Unit 1 containing massive sand with scattered gravel-sized clasts, marl cobbles and boulders, and abundant marine mammal and fish fossils; Unit 2 consisting of sand intercalated with silt, clay and gravel, which may be horizontally bedded; and Unit 3, which is an erosionally-based lenticular matrix to clast-supported structureless gravel. The basal part of Unit 1 shows numerous reworked skeletal remains of Miocene marine mammals. Cosmogenic radionuclides constrain the age of burial of Unit 1 to 895 ± 211 ka, while the source area of Unit 1 had a quick denudation.The massive sands deposited on the slopes of Papuk Mountain were vulnerable to erosion due to the absence of clay. Heavy rainfall or water from snow melting created flash floods that infiltrated the sands, thereby causing slope destabilization and deformation. This process led to slumps that were transformed into a sandy debris flow. This sediment was probably deposited during the interglacial marine isotope age (MIS) 21 period when the scarce vegetation and a warmer climate favored the melting of permafrost ice and consequently triggered slope movements during MIS 22. The reworked skeletal material sampled at the Vranić site comprises fossilized fish along with mammal bones and teeth. Thus, the Vranić site represents an important site for cetacean fossil remains and serves as an important data source for marine life in the Central Paratethys.

Strontium isotopes reveal a globally unique assemblage of Early Miocene baleen whales

ABSTRACT The earliest Miocene (Aquitanian, 23–20 Ma) remains a critically under-sampled ‘dark age’ in cetacean evolution. This is especially true of baleen whales (mysticetes), Aquitanian specimens of which remain almost entirely unknown. Across the globe, the nature of the cetacean fossil record radically shifts at the Oligocene-Miocene boundary, with mysticetes and some archaic odontocete lineages suddenly disappearing despite the availability of cetacean-bearing rock units. New Zealand is the only place worldwide where this change is not readily apparent, with baleen whales apparently persisting into the earliest Miocene. Whether this is a genuine pattern has so far remained obscured by a lack of biostratigraphic resolution associated with the Oligo-Miocene boundary. Here, we report 23 new strontium (87Sr/86Sr) dates from Lentipecten shells associated with 16 mysticete and seven odontocete specimens, respectively. Of these, eight fall within the Early Miocene and seven – including five mysticetes – specifically within the Aquitanian. Our findings confirm the unique nature and global importance of the cetacean fossil record from New Zealand, and provide a foundation for investigations into the causes and effects of the Early Miocene cetacean ‘dark age’.

Chronology and Paleoenvironment of the Tunga Formation, a new lowermost Miocene sequence in the East Pisco Basin of southern Peru

The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32–19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206Pb/238U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.

Cetacean and hipparion fossils from the upper Miocene near General Marinovo Village, NW Bulgaria

The fossils of cetaceans are common in the Miocene marine deposits of North Bulgaria and along the Black Sea coast, however, they had received little attention until now. We report on abundant whale fossil material from the area near General Marinovo Village, NW Bulgaria. The finding of a hipparion tooth in the same area as the rest of the material implies a late Miocene age for the fossils. Taphonomical, XRD, and palaeohistological analyses reveal details about the pre-burial history and palaeobiology of part of the studied cetacean fossils.

A new fossil dolphin with tusk-like teeth from New Zealand and an analysis of procumbent teeth in fossil cetaceans

ABSTRACT Studies involving anatomical description and taxonomy of fossil odontocetes offer insights into their evolutionary history and diversity. This study analyses tusk-like teeth in odontocetes including the description of a new species, Nihoroa reimaea, from the Waitaki valley, North Otago, New Zealand. Dental features of Nihoroa reimaea, a gracile, longirostrine odontocete with procumbent tusk-like anterior teeth and slightly denticulate cheek teeth, are described in detail. A comparative analysis of tusk-like teeth from New Zealand specimens and from elsewhere in the world was performed allowing a classification of tusk-like teeth in odontocetes and highlighting the differences between true tusks and rooted procumbent teeth. Correlation analyses revealed significant associations between rostrum proportions and tooth crown morphology. This study contributes to the understanding of tusk-like teeth and illuminates their significance in odontocete evolution. Nihoroa reimaea expands our knowledge of fossil cetaceans and highlights the importance of New Zealand's exceptional fossil record of odontocetes with tusk-like teeth.

Structured-Light 3D Scanning as a Tool for Creating a Digital Collection of Modern and Fossil Cetacean Skeletons (Natural History Museum, University of Pisa)

The Natural History Museum of the University of Pisa hosts one of the most important osteological collections of cetaceans all over Europe, as well as a conspicuous paleontological collection, including several holotypes of Archaeoceti (archaic whales), Mysticeti (baleen whales), and Odontoceti (toothed whales). In order to valorize these collections, we used 3D technologies to digitize the most relevant specimens, create an online archive, and make the resulting models accessible and shareable with the broadest audience possible through social media profiles and internet browsers. Tens of specimens were surface-scanned using a structured-light scanner, and the resulting 3D models were processed for post-production through the 3D software Blender whenever necessary. All the 3D scans were then gathered in the online repository Sketchfab, which was chosen for its user-friendly interface and common usage among museum institutions. The result is a web page that hosts 35 surface scans of extant and extinct cetacean specimens. This Sketchfab account was linked to the social media (Facebook and Instagram) profiles of the MSNUP to increase the visibility of the museum and promote the dissemination of its outstanding collections of modern and fossil cetaceans. The preliminary results of such an effort are encouraging in terms of views and online interactions. Hopefully, this effort of digitization and online archiving will soon extend to other vertebrate collections.

New fossil Cetaceans from the Middle Miocene of Cuba

Remains of cetaceans, particularly odontocetes, are scarce in the Cuban fossil record. Here we describe the second odontocete (toothed whale) record from the Neogene of Cuba and extends the temporal distribution of this group in the Insular Caribbean into the Middle Miocene. This account is based on two isolated teeth found in limestones of the Güines Formation that crop out in a quarry near the town of Guanábana, Matanzas City, northwestern Cuba. The specimens are referred to the superfamily Physeteroidea incertae sedis. These findings, along with other fossils recovered from other Early and Middle Miocene localities in the region support the hypothesis of a complex, diverse marine vertebrate fauna on the formerly called “Habana-Matanzas channel” and circum-Cuban waters during the Neogene.

Bridging two oceans: small toothed cetaceans (Odontoceti) from the Late Miocene Chagres Formation, eastern Caribbean (Colon, Panama).

Fossil cetaceans are often found in Miocene marine outcrops across the globe. However, because this record is not homogeneous, the dissimilar increase in occurrences, along with the sampling bias has created regions with extensive records and others with great scarcity. Among these, the Caribbean has remained enigmatic due to the lack of well-preserved cetacean fossils. Here, we report new Caribbean fossil cetaceans from the Upper Miocene Chagres Formation exposed along Piña beach, Eastern Panama, including a scaphokogiine kogiid, an Acrophyseter-like physeteroid and the phocoenid Piscolithax. Along with previous records of the iniid Isthminia panamensis and the kogiine Nanokogia isthmia, the Chagres cetacean fauna shows some similarities with other Late Miocene cetacean communities such as the Californias in the North Pacific, although their closest affinities lie with the eastern South Pacific Pisco Formation, Peru. Such findings indicate that though deep and intermediate Caribbean-Pacific water interchange was reduced by the Middle Miocene due to the shallowing of the Central American Seaway, shallow waters marine connection that persisted until the Pliocene might have facilitated the dispersal of coastal species across both sides of the Isthmus.

Sedimentological and stratigraphically controlled preservation styles and distribution of fossil cetaceans from a new Early Miocene fossiliferous locality, Patagonia, Argentina

ABSTRACT Prospecting fieldwork in a new fossiliferous locality of the marine Early Miocene Gaiman Formation (Patagonia, Argentina) results in the discovery of abundant fossil cetaceans (n = 29). We analyse stratigraphic, sedimentologic, palaeontologic, and taphonomic data with the aim of understanding the factors that control the preservation and distribution of these specimens. The cetacean sample is dominated by small odontocetes exhibiting five different preservation categories. Based on sedimentological features, three distinct facies were recognised in the stratigraphic section. Stratigraphically condensed deposits of facies C, related to a ravinement surface and subsequent transgressive deposits, enclose 52% of the specimens, grading from isolated postcranial elements to articulated and associated postcranial and cranial elements. In contrast, facies A and B exhibit predominantly isolated postcranial elements. Facies C shows higher degrees of corrosion, encrustation and fragmentation than those specimens from facies A and B, reflecting differences in preservation quality among the facies. The higher abundance and evidence of long exposure times recorded for facies C seems to be resulted mostly from physico-chemical factors after stratigraphic condensation. Finally, intrinsic biological features and ecological preferences of the specimens could explain the dominance of small-sized odontocetes in a restricted inner shelf to lower shoreface environmental setting.

Evidence for a novel cranial thermoregulatory pathway in thalattosuchian crocodylomorphs.

Thalattosuchian crocodylomorphs were a diverse clade that lived from the Early Jurassic to the Early Cretaceous. The subclade Metriorhynchoidea underwent a remarkable transition, evolving from semi-aquatic ambush predators into fully aquatic forms living in the open oceans. Thalattosuchians share a peculiar palatal morphology with semi-aquatic and aquatic fossil cetaceans: paired anteroposteriorly aligned grooves along the palatal surface of the bony secondary palate. In extant cetaceans, these grooves are continuous with the greater palatine artery foramina, arteries that supply their oral thermoregulatory structures. Herein, we investigate the origins of thalattosuchian palatal grooves by examining CT scans of six thalattosuchian species (one teleosauroid, two early-diverging metriorhynchoids and three metriorhynchids), and CT scans of eleven extant crocodylian species. All thalattosuchians had paired osseous canals, enclosed by the palatines, that connect the nasal cavity to the oral cavity. These osseous canals open into the oral cavity via foramina at the posterior terminus of the palatal grooves. Extant crocodylians lack both the external grooves and the internal canals. We posit that in thalattosuchians these novel palatal canals transmitted hypertrophied medial nasal vessels (artery and vein), creating a novel heat exchange pathway connecting the palatal vascular plexus to the endocranial region. Given the general hypertrophy of thalattosuchian cephalic vasculature, and their increased blood flow and volume, thalattosuchians would have required a more extensive suite of thermoregulatory pathways to maintain stable temperatures for their neurosensory tissues.

New cetacean fossils from the late Cenozoic of South Africa

Marine sediments from the western coast of southern Africa record the origin of the Benguela Upwelling System, one of the most productive in the world. High productivity, in turn, is reflected in a diverse marine mammal fossil assemblage, comprising whales, dolphins and a phocid seal. Here, we describe new records of baleen whale (mysticete) fossils from the early Pliocene localities of Saldanha Steel, Milnerton and Langebaanweg, as well as several potentially younger specimens trawled from offshore sediments. The presence of the extinct rorquals Diunatans and Fragilicetus suggests biogeographical links with the eastern North Atlantic and, thus, potentially antitropical population structuring. The trawled specimens also include rorquals (e.g., the blue whale, Balaenoptera cf. musculus), as well as a right whale (Eubalaena) and a pygmy right whale (Caperea). The latter is the first fossil of this family every discovered in Africa, and only the seventh specimen to be reported worldwide.

Cetotheriidae (Cetacea: Mysticeti) from the Collections of the National Geological Museum, Bucharest (Romania)

Cetacean fossil remains attributed to Cetotheriidae are certainly not a novelty in the fossil record of the Carpathian Foreland or Foredeep, several sites being mentioned; however there remains much material in institutional collections that can still add to the number of fossiliferous localities where cetotheriids can be found. The aim of this paper is to bring to attention new material from fossiliferous localities from the western Dacian Basin (Gorj and Vâlcea Counties), from the collections of the National Geological Museum. The specimens are described, identified based on comparisons with similar specimens from published literature and a discussion about the species Cetotherium priscum is provided.

Oligocene-Miocene marine mammals from Belgrade Quarry, North Carolina

A diverse but fragmentary assemblage of fossil cetaceans is reported from the Oligocene-Miocene Belgrade Formation of North Carolina. This assemblage preserves many odontocetes including four xenorophids (Albertocetus, Echovenator sp., cf. Cotylocara, and Xenorophus sp.), a possible waipatiid (cf. Waipatiidae), a giant agorophiid-grade dolphin (Ankylorhiza), a shark-toothed dolphin (cf. Squalodon), longirostrine “swordfish” dolphins (Eurhinodelphinidae), a longirostrine eoplatanistid dolphin (cf. Eoplatanista), a longirostrine squalodelphinid dolphin, a possible early delphinidan (Kentriodontidae), as well as an eomysticetid baleen whale (Eomysticetus sp.) and sirenian fragments. Most of these taxa are characteristic of or unique to Oligocene deposits (Xenorophidae, cf. Waipatiidae, Ankylorhiza, Eomysticetus) whereas others are more typical of early or middle Miocene deposits (cf. Eoplatanista, Eurhinodelphinidae, cf. Squalodon, Squalodelphinidae, Kentriodontidae). The Belgrade Formation at Belgrade Quarry is dated to 25.95–21.12Ma, approximating the Oligocene-Miocene transition. The transitional composition of the Belgrade cetacean assemblage suggests gradual changes between Oligocene to Miocene cetacean faunas, to be verified by the discovery of more complete remains from the poorly sampled earliest Miocene (Aquitanian).

Pleistocene cetacean fossils from the coastal plain of Rio Grande do Sul in southern Brazil

Cetacean ear bones are useful for palaeontological studies because it is possible to identify most species based on their gross morphology, and thus glean information about past occurrences and distributions. This study describes cetacean tympanic bullae and periotics preserved in Middle–Late Pleistocene coastal barrier systems from Rio Grande do Sul in southern Brazil. The specimens were collected ex situ on the modern beach, and reveal the presence of the Franciscana dolphin, Pontoporia blainvillei, an indeterminate delphinid, the rorqual whale, Balaenoptera, and right whale, Eubalaena. Given the current diversity of dolphins and whales in the Atlantic Ocean, these fossils suggest that the reported diversity of Pleistocene cetaceans is probably underestimated. The barrier systems of Rio Grande do Sul are the only Brazilian deposits that have preserved Pleistocene cetacean remains to date. Thayara Silveira Carrasco* [thayaracarrasco@gmail.com], Laboratório de Estratigrafia e Paleontologia and Programa de Pós-graduação em Biodiversidade de Ambientes Costeiros, Instituto de Biociências, Campus do Litoral Paulista, Universidade Estadual Paulista, 11330-900 São Vicente, SP, Brazil; Francisco Sekiguchi Buchmann [paleonchico@yahoo.com.br], Laboratório de Estratigrafia e Paleontologia, Instituto de Biociências, Campus do Litoral Paulista, Universidade Estadual Paulista, 11330-900 São Vicente, SP, Brazil.

A basilosaurid archaeocete (Cetacea, Pelagiceti) from the Late Eocene of Oregon, USA.

BackgroundBasilosaurid 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.MethodsThese vertebrae were morphologically and morphometrically compared to other vertebrae of similar age from around the world.ResultsThe 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.

On Leonardo and a fossil whale: a reappraisal with implications for the early history of palaeontology

ABSTRACT A recent reappraisal of two passages in Leonardo da Vinci’s Codex Arundel, in which the then young Leonardo reports on visiting a cave and on some sort of ʽmarine monster’, has led to the proposition that Leonardo observed and wrote on fossil remains of a whale preserved in a cave. Whereas this hypothesis appears reasonable overall, some problems persist in accepting the purported location in which Leonardo would have observed the fossil. Here we provide a new analysis of the aforementioned passages by Leonardo which allows us to confirm that Leonardo saw a fossil whale and recognised it as such. However, his observation did not occur in a cave, but likely along the flank of a hill, as relatively common for Tuscan Pliocene fossil cetaceans. Leonardo seemingly made taphonomic observations on the fossil whale and inferred that a considerable amount of time must have passed from the death of the whale in the sea to allow for its eventual discovery on land – an observation that likely contributed to shaping Leonardo’s later thoughts on sedimentation and fossilisation. This might represent Leonardo’s earliest text devoted to a palaeontological theme. Moreover, it comprises the first known description of a cetacean fossil.

The First Finding of Basilosauridae (Mammalia: Cetacea) in the Upper Eocene of the Baltic States (Russia, Kaliningrad Region)

Remains of a fossil cetacean, belonging to the family Basilosauridae, are for the first time found in the territory of the Baltic States. This finding is represented by a large vertebra and comes from the Late Eocene amber-bearing “Blue Ground” bed of the Sambia Peninsula in the Kaliningrad Region. The described fossil expands our knowledge on paleogeography and stratigraphic occurrence of Basilosauridae.

Extensive Diversity and Disparity of the Early Miocene Platanistoids (Cetacea, Odontoceti) in the Southeastern Pacific (Chilcatay Formation, Peru).

Several aspects of the fascinating evolutionary history of toothed and baleen whales (Cetacea) are still to be clarified due to the fragmentation and discontinuity (in space and time) of the fossil record. Here we open a window on the past, describing a part of the extraordinary cetacean fossil assemblage deposited in a restricted interval of time (19–18 Ma) in the Chilcatay Formation (Peru). All the fossils here examined belong to the Platanistoidea clade as here redefined, a toothed whale group nowadays represented only by the Asian river dolphin Platanista gangetica. Two new genera and species, the hyper-longirostrine Ensidelphis riveroi and the squalodelphinid Furcacetus flexirostrum, are described together with new material referred to the squalodelphinid Notocetus vanbenedeni and fragmentary remains showing affinities with the platanistid Araeodelphis. Our cladistic analysis defines the new clade Platanidelphidi, sister-group to Allodelphinidae and including E. riveroi and the clade Squalodelphinidae + Platanistidae. The fossils here examined further confirm the high diversity and disparity of platanistoids during the early Miocene. Finally, morphofunctional considerations on the entire platanistoid assemblage of the Chilcatay Formation suggest a high trophic partitioning of this peculiar cetacean paleocommunity.

Large-sized cetacean fossils from the Tonohama Group in the Iwado area, Muroto City, Kochi Prefecture, Japan

Large-sized cetacean fossils from the Tonohama Group in the Iwado area, Muroto City, Kochi Prefecture, Japan