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The name “Cetartiodactyla” was proposed in 1997 to reflect the molecular data that suggested that Cetacea is closely related to Artiodactyla. Since then, that taxon has spread in popularity, even outside the scientific literature. However, the implications of the name are confusing, because Cetacea and Artiodactyla are not sister-taxa. Instead, the evidence clearly shows that cetaceans are a group embedded within Artiodactyla, not a sister-taxon of equal rank. It has long been accepted practice that systematists do not modify the names of higher groups when new subgroups are added to them. For example, Owen’s original concept of Artiodactyla did not change its name when more and more disparate taxa were added to it. Dinosauria did not become “Avedinosauria” when it became clear that birds are a subgroup of dinosaurs, nor did Reptilia become “Avereptilia”. In the interests of taxonomic priority and stability, and especially because the name is inherently misleading, we recommend that the name “Cetartiodactyla” be abandoned. If one wishes to make a reference to the fact that whales are now considered to be a subgroup of artiodactyls, they could be referred to informally as “whales and other artiodactyls” or “whales and terrestrial artiodactyls” without using a formal taxonomic name that is confusing and misleading.

The Egyptian word seshen (“water lily,” a cognate of the Hebrew name Susanna, written with hieroglyphs depicting a door bolt, a garden pool, and water), may have inspired the setting of the Theodotion form of Daniel 13:1–27. This may constitute a novel type of “bilingual visual paronomasia,” and point to an Egyptian source of the details of Susanna’s bath, absent in the earliest (Old Greek) form of the biblical text of Daniel.

The oblique extraocular muscles (EOMs) were dissected in 19 cetacean species and 10 non-cetacean mammalian species. Both superior oblique (SO) and inferior oblique (IO) muscles in cetaceans are well developed in comparison to out-groups and have unique anatomical features likely related to cetacean orbital configurations, swimming mechanics, and visual behaviors. Cetacean oblique muscles originate at skeletal locations typical for mammals: SO, from a common tendinous cone surrounding the optic nerve and from the medially adjacent bone surface at the orbital apex; IO, from the maxilla adjacent to lacrimal and frontal bones. However, because of the unusual orbital geometry in cetaceans, the paths and relations of SO and IO running toward their insertions onto the temporal ocular sclera are more elaborate than in humans and most other mammals. The proximal part of the SO extends from its origin at the apex along the dorsomedial aspect of the orbital contents to a strong fascial connection proximal to the preorbital process of the frontal bone, likely the cetacean homolog of the typical mammalian trochlea. However, the SO does not turn at this connection but continues onward, still a fleshy cylinder, until turning sharply as it passes through the external circular muscle (ECM) and parts of the palpebral belly of the superior rectus muscle. Upon departing this "functional trochlea" the SO forms a primary scleral insertion and multiple accessory insertions (AIs) onto adjacent EOM tendons and fascial structures. The primary SO scleral insertions are broad and muscular in most cetacean species examined, while in the mysticete minke whale (Balaenoptera acutorostrata) and fin whale (Balaenoptera physalus) the muscular SO bellies transition into broad fibrous tendons of insertion. The IO in cetaceans originates from an elongated fleshy attachment oriented laterally on the maxilla and continues laterally as a tubular belly before turning caudally at a sharp bend where it is constrained by the ECM and parts of the inferior rectus which form a functional trochlea as with the SO. The IO continues to a fleshy primary insertion on the temporal sclera but, as with SO, also has multiple AIs onto adjacent rectus tendons and connective tissue. The multiple IO insertions were particularly well developed in pygmy sperm whale (Kogia breviceps), minke whale and fin whale. AIs of both SO and IO muscles onto multiple structures as seen in cetaceans have been described in humans and domesticated mammals. The AIs of oblique EOMs seen in all these groups, as well as the unique "functional trochleae" of cetacean SO and IO seem likely to function in constraining the lines of action at the primary scleral insertions of the oblique muscles. The gimble-like sling formed by SO and IO in cetaceans suggest that the "primary" actions of the cetacean oblique EOMs are not only to produce ocular counter-rotations during up-down pitch movements of the head during swimming but also to rotate the plane containing the functional origins of the rectus muscles during other gaze changes.

Each rectus extraocular muscle in cetaceans divides into two portions: a massive palpebral belly that inserts into the deep surface of the eyelids and a smaller scleral belly that inserts onto the eyeball. While the cetacean palpebral insertions have long been recognized, their homologies and functions remain unclear. To compare cetacean rectus EOM insertions with the global and orbital rectus EOM insertions of other mammals we dissected orbital contents of 20 odontocete species, 2 mysticete species and 18 non-cetacean species, both aquatic and terrestrial. Four cetacean species were also examined with magnetic resonance imaging (MRI). All four rectus muscles in cetaceans had well-developed palpebral bellies and insertions. Adjacent palpebral bellies showed varying degrees of fusion, from near independence to near complete fusion. Fusion was most complete towards palpebral insertions and less towards origins. A medial moiety of the superior rectus palpebral belly is likely the levator palpebrae superioris. Smaller but still robust scleral insertions were present on all recti, with the medial rectus (MR) being significantly more muscular than the others. All non-cetacean species examined had recti with distinct global and orbital insertions, the latter generally onto Tenon's capsule. Orbital insertions in pygmy hippopotamus and Florida manatee extended into the deep surfaces of the eyelids, hence qualifying as palpebral insertions. Our results suggest that rectus EOMs of mammals generally have both global and orbital insertions, and that palpebral bellies of cetaceans and other species are modified homologs of the orbital insertions. The presence of palpebral insertions in pygmy hippopotamus and absence in other cetartiodactyls suggests an intermediate condition between terrestrial cetartiodactyls and cetaceans. Palpebral insertions in Florida manatee and reports of their presence in some pinnipeds suggest parallel evolution in multiple aquatic lineages. Various functions of cetacean palpebral recti have been proposed, including eyelid dilators, protection during diving and thermogenesis for warming eye and brain. For further insight into their possible functions, we observed eye movements of captive bottlenose dolphins (Tursiops truncatus) at the U.S. National Aquarium. Our observations showed that in addition to rotation of the eyeball the entire surrounding palpebral region also moves during gaze changes. For example during upward gaze the globe not only rotates in supraduction but translates dorsally as well. It appears the rectus palpebral bellies are responsible for flexing the palpebral structures and thus also translating the globe, while the scleral insertions act directly for ocular rotation. Along with frequent non-conjugate eye movements, the oculomotor mechanics and repertoire of cetaceans are thus quite distinctive. Summarily, axial displacement within the orbit is a major 'eye movement' in cetaceans, with protrusion and retraction mediated by well-developed circular muscles and retractor bulbi respectively. Torsional eye movements driven by elaborate oblique EOMs are likewise significant. The roles of rectus EOMs for ocular rotation via their scleral insertions, especially the highly muscular MR, are for typical supra/infraductions and nasal/temporal ductions. The palpebral bellies accentuate these ductions by translating the globe and surrounding structures in the same direction.

The manatee family encompasses three extant congeneric species: Trichechus senegalensis (African manatee), T. inunguis (Amazonian manatee), and T. manatus (West Indian manatee). The fossil record for manatees is scant, and few phylogenetic studies have focused on their evolutionary history. We use full mitogenomes of all extant manatee species to infer the divergence dates and biogeographical histories of these species and the effect of natural selection on their mitogenomes. The complete mitochondrial genomes of T. inunguis (16,851 bp), T. senegalensis (16,882 bp), and T. manatus (16,882 bp), comprise 13 protein-coding genes, 2 ribosomal RNA genes (rRNA - 12S and 16S), and 22 transfer RNA genes (tRNA), and (D-loop/CR). Our analyses show that the first split within Trichechus occurred during the Late Miocene (posterior mean 6.56 Ma and 95% HPD 3.81–10.66 Ma), followed by a diversification event in the Plio-Pleistocene (posterior mean 1.34 Ma, 95% HPD 0.1–4.23) in the clade composed by T. inunguis and T. manatus; T. senegalensis is the sister group of this clade with higher support values (pp > 0.90). The branch-site test identified positive selection on T. inunguis in the 181st position of the ND4 amino acid gene (LRT = 6.06, p = 0.0069, BEB posterior probability = 0.96). The ND4 gene encodes one subunit of the NADH dehydrogenase complex, part of the oxidative phosphorylation machinery. In conclusion, our results provide novel insight into the evolutionary history of the Trichechidae during the Late Miocene, which was influenced by geological events, such as Amazon Basin formation.

The last comprehensive review of the fossil vertebrates from the Miocene of Calvert Cliffs was published more than 100 years ago. This volume is a collection of papers that updates some of the geological features of Calvert Cliffs and provides reviews of the fossil biota that include representatives from the following taxonomic groups: chondrichthyans (chimaeras, shark, skates, and rays), actinopterygians (ray-finned fishes), crocodilians (crocodiles), and sirenians (sea cows). Peter Vogt, Ralph E. Eshelman, and Stephen J. Godfrey document how the 20–40 m [65–130 ft] high Calvert Cliffs along the western shore of the Chesapeake Bay continue to yield insights into 18–8 mya (Miocene) geology, marine and terrestrial vertebrate fauna, and the origin and evolution of Chesapeake Bay and Calvert Cliffs up to the present. These exposures rank high among the best-known fossiliferous deposits of any age. Bretton W. Kent describes the cartilaginous fish (the chondrichthyan) fauna, consisting of 54 species—3 chimaeras (ratfishes), 39 sharks, and 12 skates and rays—a fauna rich in large macrophagous sharks and large neritic rays. In an addendum to Kent’s chapter, he and David J. Ward describe a new species of giant thresher shark with serrated teeth. Giorgio Carnevale and Stephen J. Godfrey present an account of the 38 actinopterygian taxa known from osteological remains and a diverse otolith assemblage of at least 55 taxa. These actinopterygians show an affinity for well-oxygenated muddy and sandy substrates dominated primarily by shallow-water species characteristic of the inner shelf and secondarily by epipelagic taxa. Robert E. Weems details the crocodilians referable to the tomistomine Thecachampsa. The closest living relative is Tomistoma schlegelii, the false gharial of Southeast Asia. Two species are present: Thecachampsa sericodon and T. antiquus. These tomistomines are found in shallow marine coastal deposits, indicating that they inhabited coastal waters. Daryl P. Domning reports that fossils of the Miocene marine fauna include rare sirenians of the family Dugongidae. Three taxa are known: the halitheriine dugongid Metaxytherium crataegense, the dugongine dugongid Nanosiren sp., and another dugongine, aff. Corystosiren. The St. Marys Formation contains remains that may be referable to Metaxytherium floridanum, but confirmation awaits the discovery of more complete specimens.

We describe a new genus and species of early Oligocene halitheriine dugongid from the Western Atlantic region. Priscosiren atlantica, gen. et sp. nov., differs from all other halitheriine dugongids by displaying the following unique combination of characters: supraorbital processes dorsoventrally thin (≤1 cm) with well-developed prominent posterolateral corner; supraoccipitals wider in the dorsal half than the ventral half; exoccipitals meeting dorsal to the foramen magnum; posttympanic process with a prominent anteroventral process for attachment of m. sternomastoideus; nasals separated in midline; ventral extremity of jugal located ventral to orbit; ventral border of mandible strongly concave; absence of accessory mental foramina; dorsoventrally broad horizontal ramus of mandible; loss of all permanent premolars; and concave anteroventral surface of jugal (a possible autapomorphy). Differs further from the similar species Caribosiren turneri in having lesser rostral deflection (of about 44°); p...

We describe a new species of the halitheriine dugongid genus Metaxytherium from the late Oligocene of Florida and South Carolina. The new species is represented by cranial and postcranial material, including parts of the axial and appendicular skeleton. Metaxytherium albifontanum, sp. nov., differs from other species of Metaxytherium by the following unique combination of plesiomorphic and derived characters: posterior end of nasal process of premaxilla broad and flat relative to what is observed in most other members of the genus (somewhat resembling M. subapenninum); ventral extremity of jugal under posterior edge of orbit (character 85[1]) (shared with M. krahuletzi); exoccipitals separated in dorsal midline (character 66[1]) (shared with all other species in the genus, except some M. krahuletzi); and innominate with acetabulum (nearly lost or lost in M. crataegense, M. floridanum, M. serresii). This new species was sympatric with two dugongines, Crenatosiren olseni and Dioplotherium manigault...

Stegosiren macei, a new genus and species of halitheriine dugongid from the mid-Oligocene of South Carolina, U.S.A. (Ashley and Chandler Bridge formations, late Rupelian–late Chattian), rep...

Among the four subfamilies of Phocidae (Phocinae, Monachinae, Cystophorinae, and Devinophocinae), fossil remains of monachine seals from the late and especially from the early to middle Miocene (ca...

Appeltans, Ward ... et al., Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are ∿226,000 eukaryotic marine species described. More species were described in the past decade (∿20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are ∿170,000 synonyms, that 58,000-72,000 species are collected but not yet described, and that 482,000-741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7-1.0 million marine species. Past rates of description of new species indicate there may be 0.5 ± 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century. © 2012 Elsevier Ltd., WoRMS has benefited from funding as part of several EU projects: Network of Excellence in Marine Biodiversity and Ecosystem Functioning (MarBEF), Pan-European Species directories Infrastructure (PESI), Distributed Dynamic Diversity Databases for Life (4D4Life), the Global Biodiversity Information Facility (GBIF), and the Census of Marine Life (CoML). It originated in the European Register of Marine Species (ERMS) that was funded by the EU Marine Science and Technology (MAST) research program

The clade Paenungulata, which is part of the mammalian superorder Afrotheria, comprises three morphologically diverse extant orders: the Sirenia (manatees and dugongs), the Proboscidea (elephants),...

The near lack of vertebrate fossils from the Cenozoic of Madagascar has left many of the details regarding the origin and evolution of the island's extant faunas unknown. However, recent fossil discoveries from Madagascar's nearshore marine deposits have begun to elucidate this mystery. These finds include sharks, bony fish, turtles, crocodylians, a middle Eocene sirenian (Eotheroides lambondrano), and the island's first fossil dolphin. We report here at least three (possibly four) different early (or possibly later) Miocene dugongid sirenians recovered from the island of Nosy Makamby, Mahajanga Basin, northwestern Madagascar. These include (1) a fragmentary braincase originally attributed to the genus Halitherium but here reidentified as a previously named species known only from Libya (Rytiodus heali; Dugonginae); (2) a newly named genus and species (Norosiren zazavavindrano) interpreted as a primitive relative of Xenosiren (Dugonginae); (3) a probable dugongine not yet identified with any known species; and (4) a taxon reported here as Metaxytherium cf. krahuletzi (Halitheriinae), the first Neogene halitheriine credibly reported from the Indian Ocean basin. This pattern of shallow marine environments harboring multispecies sirenian paleofaunas is seen elsewhere in the world, and these three or four contemporaneous sirenians represent the first glimpse into Madagascar's sea cow diversity during the Miocene. This specific time period is a poorly known and critical interval for interpreting Madagascar's past, and these specimens are potentially highly significant for reconstructing sirenian evolutionary and biogeographic history. Surprisingly, this sirenian fauna, so far, shares no genera with the roughly contemporaneous and relatively nearby one from Kutch, western India.

Kutchisiren cylindrica, n. gen. n. sp., is a dugongine sirenian represented by a single skull with mandible from the Lower Miocene (Aquitanian or Burdigalian) Khari Nadi Formation in the district of Kutch (= Kachchh), Gujarat State, western India. It is characterized by a braincase of nearly cylindrical form, a strong rostral deflection of about 78°, and a large upper incisor tusk with a lozenge-shaped cross section. It evidently coexisted with at least two other dugongine taxa: Bharatisiren kachchhensis and Domningia sodhae. These three forms differed in rostral deflection, body size, and other details of skull and tusk morphology that apparently enabled them to partition the available marine seagrass resources. Their exact phylogenetic relationships, however, remain unresolved for now.

Estimates of fossil sirenian body size are important for understanding niche partitioning among possibly sympatric species. Because of the paucity of complete fossil skeletons, we explored the utility of three morphometric predictors of body size: (condylobasal skull length [BSL]; occipital condyle width [OCW]; and foramen magnum width [FMW]) in extant sirenians—Florida manatees (Trichechus manatus latirostris) and dugongs (Dugong dugon)—and then applied these to obtain estimates of body size in extinct sirenian taxa. Condylobasal length of the skull is a more accurate predictor of body size in extant Florida manatees and dugongs than are width of the occipital condyles or width of the foramen magnum. Body length (BL) is predicted more accurately than is body weight (BW) for all three morphometric predictors. For our sample of fossil sirenians, BSL, OCW, and FMW were used to generate predicted BLs and BWs. Preliminary assessments of fossil sirenian faunas from Florida and India suggest that body mass could have been one of several possible important morphological parameters accounting for feeding niche separation.

Osteosclerosis, or inner bone compaction, and pachyostosis, or outer hyperplasy of bone cortices (swollen bones), are typical features of tetrapods secondarily adapted to life in water. These peculiarities are spectacularly exemplified by the ribs of extant and extinct Sirenia. Sea cows are thus the best model for studying this kind of bone structural specializations. In order to document how these features differentiated during sirenian evolution, the ribs of 15 species, from the most basal form (Pezosiren portelli) up to extant taxa, were studied, and compared to those of other mammalian species from both morphometric and histological points of view. Pachyostosis was the first of these two specializations to occur, by the middle of the Eocene, and is a basal feature of the Sirenia. However, it subsequently regressed in some taxa that do not exhibit hyperplasic rib cortices. Osteosclerosis was only incipient in P. portelli. Its full development occurred later, by the end of the Eocene. These two structural specializations of bone are variably pronounced in extinct and extant sirenians, and relatively independent from each other, although frequently associated. They are possibly due to similar heterochronic mechanisms bearing on the timing of osteoblast activity. These results are discussed with respect to the functional constraints of locomotion in water.

Ashokia antiqua is a new genus and species of protosirenid sirenian based on a subadult skull from the early middle Eocene (Lutetian) Harudi Formation of Kutch district, Gujarat State, western India. While more derived than prorastomids, and more primitive than trichechids or dugongids, in comparison with other protosirenids it displays a mosaic of primitive and derived character states that places it at the evolutionary grade of a relatively primitive protosirenid. Cladistically, its sister group may be an unnamed genus and species of protosirenid from the Lutetian of Libya, which shares with it several synapomorphies of the zygomatic arch and ear region. This relationship with the unpublished Libyan form reinforces a pattern in Eocene paleobiogeography previously noted by SAGNE (2001): generically-distinct and endemic sirenian faunas on the north and south shores, respectively, of the former Tethys Seaway. The Kutch sirenian fauna, with Eotheroides, Eosiren, Protosiren, and now a relative of the Libyan protosirenid, resembles the fauna from North Africa, while the European genera Halitherium, Prototherium, and Sirenavus are absent - as predicted by SAGNE's (2001) hypothesis.

Sirenians (sea cows: manatees and dugongs) have been primary consumers in tropical and subtropical shallow-water marine ecosystems for more than 50 m.y. Though fossils of the earliest sirenians have been recovered from the Caribbean, sirenians are thought to have originated in the Tethys-Mediterranean region, which underwent significant climate change over the course of the Cenozoic. Application of stable isotope analysis can provide new insight into how diet and habitat preferences were affected by climate change and how these ecological changes correlate with diversity patterns for this region. Tooth enamel was sampled from 57 specimens of sirenians from the Tethys-Mediterranean and adjacent seas spanning the Eocene to Pliocene. Enamel δ13C values across this time interval were consistently high and indicative of diets composed mostly of marine seagrasses. In contrast, enamel δ18O values showed significant change over time and across the region. Sirenians from southern sites (i.e., Egypt, Libya) had significantly higher mean δ18O values than specimens from most European locations, suggesting variation in salinity within the Tethys-Mediterranean. The range in enamel δ18O values increased from the Paleogene through the Neogene, but enamel δ13C values remained steady, indicating that changes in environmental conditions did not necessarily coincide with major changes in dietary preferences. Declines in sirenian taxonomic diversity in the late Miocene were likely due to the rapid climate and oceanographic changes during the latter half of the Cenozoic and their impacts on available dietary resources. Elevated δ13C and δ18O values in Mediterranean sirenians during the Messinian salinity crisis corroborate the hypothesis of ecophenotypic dwarfing in these animals.

(2008). “Snagging” teeth and premolar homologies in Paleoparadoxiidae (Mammalia: Desmostylia) Journal of Vertebrate Paleontology: Vol. 28, No. 3, pp. 923-927.

The new dugongine dugongid Nanosiren garciae is the third species of fossil sirenian to be described from the Bone Valley phosphate deposits of Florida. It is found in the Upper Bone Valley Formation and is of latest Hemphillian (early Pliocene) age. Nanosiren sanchezi is described from the late Miocene upper member of the Urumaco Formation, Falcon State, Venezuela. It appears to be directly ancestral to N. garciae, and was preceded in the West Atlantic, Caribbean, and East Pacific region by other, undescribed members of the same generic lineage dating back at least to the early Miocene. The Nanosiren lineage is the most basal clade of the Subfamily Dugonginae after Crenatosiren olseni, and is the sister group to all remaining dugongines. It comprises the smallest known post-Eocene sirenians, with adult body lengths and weights probably around 2 m and 150 kg. Newborn animals may have had body masses little greater than the theoretical limit of 6.8 kg for a viable aquatic endotherm. In addition to...

According to Stejneger [[1][1]], it is most likely that the last of the great northern sea cows went extinct around 1768. Many Steller's sea cow ( Hydrodamalis gigas ) bones have been located on the Commander and Aleutian Islands to date [[2][2],[3][3]]. However, no verified H. gigas bones have ever

Although subject to debate, it has been shown that there is a phylogenetic signal in the microstructural and histological characters of bones (Legendre et al., 2013, and references therein). More s...

A new survey has permitted us to ascertain that at least 27 skeletons, 62 additional skulls, and more than 550 bones of Hydrodamalis gigas from the Commander Islands are currently stored in 51 museums in 42 localities. It is possible that only two to four skeletons originate from a single individual. The other skeletons are assemblages of bones from two to 16 animals. After 27 years of heavy persecution, the Steller’s sea cow was exterminated in about 1768. For decades after extinction, no osteological evidence indicated the existence of H. gigas. The first bones were likely retrieved shortly before 1840, the first partial skull was collected in 1844, and the first skeleton was unearthed in 1855. Most of the skeletal remains were found under the supervision of N. A. Grebnitskiy, A. E. Nordenskiold, B. Dybowski, and L. H. Stejneger. One skeleton and several bones have also been collected in recent decades.

All known Pleistocene fossils of manatees from North America are conspecific with the living West Indian manatee, Trichechus manatus. However, those of late Pleistocene (late Rancholabrean) age differ from all modern manatees, and are here assigned to a new subspecies, T. m. bakerorum. In contrast, early Pleistocene manatees from the late early Irvingtonian Leisey Shell Pit Local Fauna, Florida, do not clearly differ from modern West Indian manatees and are here referred to T. manatus, subspecies indeterminate. I hypothesize that warm intervals during the Quaternary allowed manatees from the Caribbean (represented today by the Antillean subspecies, T. m. manatus) to disperse northward into the United States. Ecological barriers (cool winters on the northern Gulf of Mexico coast, deep water and strong currents in the Straits of Florida) then impeded genetic contact with Caribbean populations and permitted evolution of endemic North American forms (T. m. bakerorum and the living Florida manatee, T....

It is commonly recognized that paleontological and other biological data have numerous qualitative dimensions as well as some quantitative ones; but the fact that the latter include up to 24 or more distinct spatiotemporal dimensions has not been pointed out. Paleontologists can hold these in mind simultaneously, without effort or confusion, by virtue of these dimensions' hierarchical logical arrangement. This observation may point to a useful way of conceptualizing multiple spatiotemporal dimensions in the physical sciences.

The recently extinct (ca. 1768) Steller's sea cow (Hydrodamalis gigas) was a large, edentulous North Pacific sirenian. The phylogenetic affinities of this taxon to other members of this clade, living and extinct, are uncertain based on previous morphological and molecular studies. We employed hybridization capture methods and second generation sequencing technology to obtain >30 kb of exon sequences from 26 nuclear genes for both H. gigas and Dugong dugon. We also obtained complete coding sequences for the tooth-related enamelin (ENAM) gene. Hybridization probes designed using dugong and manatee sequences were both highly effective in retrieving sequences from H. gigas (mean = 98.8% coverage), as were more divergent probes for regions of ENAM (99.0% coverage) that were designed exclusively from a proboscidean (African elephant) and a hyracoid (Cape hyrax). New sequences were combined with available sequences for representatives of all other afrotherian orders. We also expanded a previously published morphological matrix for living and fossil Sirenia by adding both new taxa and nine new postcranial characters. Maximum likelihood and parsimony analyses of the molecular data provide robust support for an association of H. gigas and D. dugon to the exclusion of living trichechids (manatees). Parsimony analyses of the morphological data also support the inclusion of H. gigas in Dugongidae with D. dugon and fossil dugongids. Timetree analyses based on calibration density approaches with hard- and soft-bounded constraints suggest that H. gigas and D. dugon diverged in the Oligocene and that crown sirenians last shared a common ancestor in the Eocene. The coding sequence for the ENAM gene in H. gigas does not contain frameshift mutations or stop codons, but there is a transversion mutation (AG to CG) in the acceptor splice site of intron 2. This disruption in the edentulous Steller's sea cow is consistent with previous studies that have documented inactivating mutations in tooth-specific loci of a variety of edentulous and enamelless vertebrates including birds, turtles, aardvarks, pangolins, xenarthrans, and baleen whales. Further, branch-site dN/dS analyses provide evidence for positive selection in ENAM on the stem dugongid branch where extensive tooth reduction occurred, followed by neutral evolution on the Hydrodamalis branch. Finally, we present a synthetic evolutionary tree for living and fossil sirenians showing several key innovations in the history of this clade including character state changes that parallel those that occurred in the evolutionary history of cetaceans. (C) 2015 Elsevier Inc. All rights reserved.

The Pliocene Beds of the Pisco Formation on the southern coast of Peru have yielded three new skulls of the walrus-like odontocete, Odobenocetops (Delphinoidea, Cetacea). Two of the skulls are from a slightly younger horizon than the holotype of O. peruvianus and belong to a different species, O. leptodon. The holotype of O. leptodon bears a 135 cm long needle-like right tusk and a small 25 cm long left tusk, the apex of which was erupted. The third skull, referred to a female of O. peruvianus, bears two small tusks similar in size to the small left tusk of the holotype. The new specimens include periotic, tympanic and ear ossicles, which confirm referral to the Order Cetacea and the morphology of the humerus reinforces affinities of odobenocetopsids to monodontids. Because the anterodorsal edge of its orbit is slightly concave O. leptodon had reduced anterodorsal binocular vision, a condition compensated for by the probable presence of a small melon (and inferred echolocation). The head was bent ventrally when swimming in such a way that the long tusk was approximately parallel to the axis of the body. The extremely salient occipital condyles of Odobenocetops are indicative of great mobility of the neck, probably related to bottom-feeding. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 134, 423–452.

Fossil sirenian specimens collected in 1964 by the late R. J. G. Savage's expeditions in north-central Libya are described. They come from early middle Eocene (lower Lutetian, 47.8–43.6 Ma) deposits at the locality of Bu el Haderait and represent a new genus and species, Libysiren sickenbergi. This animal is the largest known protosirenid, and the largest Eocene sirenian known to date (condylobasal length >420 mm). Its dental formula was apparently 3.1.5.3, with five premolar loci as in all other Eocene sirenians, but the teeth are mostly not preserved. Its postcranial skeleton is unknown except for the atlas, a thoracic vertebra, and rib fragments. Stable isotopes indicate a mostly seagrass diet and a habitat of fully marine salinity. The Protosirenidae presently comprise the genera Protosiren, Ashokia, and Libysiren, with their interrelationships unresolved. Together, they are most parsimoniously regarded as a paraphyletic group basal to both Trichechidae and Dugongidae. However, as more of thei...

The Kommandorskiye Islands population of Steller's sea cow ( Hydrodamalis gigas ) was extirpated ca 1768 CE. Until now, Steller's sea cow was thought to be restricted in historic times to Bering and Copper Islands, Russia, with other records in the last millennium from the western Aleutian Islands. However, Steller's sea cow bone has been obtained by the authors from St Lawrence Island, Alaska, which is significantly further north. Bone identity was verified using analysis of mitochondrial DNA. The nitrogen-15 (δ 15 N)/carbon-13 (δ 13 C) values for bone samples from St Lawrence Island were significantly ( p ≤ 0.05) different from Bering Island samples, indicating a second population. Bone samples were dated to between 1030 and 1150 BP (approx. 800–920 CE). The samples date from close to the beginning of the mediaeval warm period, which could indicate that the population at St Lawrence Island was driven to extinction by climate change. A warming of the climate in the area may have changed the availability of kelp; alternatively or in addition, the animals may have been driven to extinction by the expansion of the Inuit from the Bering Strait region, possibly due to opening waterways, maybe following bowhead whales ( Balaena mysticetus ), or searching for iron and copper. This study provides evidence for a previously unknown population of sea cows in the North Pacific within the past 1000 years and a second Steller's sea cow extirpation event in recent history.

The Western Atlantic–Caribbean region preserves the longest (some 50 million years) and most diverse fossil record of the mammalian order Sirenia in the world. Sirenians are aquatic herbivores; in marine waters, they eat mainly seagrasses (Hydrocharitaceae and Potamogetonaceae). Though the fossil record of seagrasses and other marine macrophytes is meager, we can use it together with that of sirenians to frame interesting hypotheses about marine plant evolution, and speculate about the nature and dynamics of the Caribbean seagrass ecosystem during the ages when (unlike today) it was dominated by diverse large mammalian herbivores. In this synthesis, I define the aquatic megaherbivore adaptive zone, and identify those of its ecological dimensions that are likely to have been most critical in feeding-niche partitioning among fossil sirenians. Possible morphological indicators of such partitioning are specified for each of these dimensions, using data on functional anatomy and ecology of living sirenians. Faunal lists of Caribbean sirenians (including unpublished taxonomic and morphological data) show what suites of species have occurred sympatrically at different times during the Cenozoic. Based on cranial morphology, I suggest how these herbivores most probably partitioned their resources. This makes it possible to follow the history of individual feeding niches within the sirenian guild through geological time, and, in turn, to speculatively reconstruct gross aspects of Caribbean seagrass communities and their changes through time. Eocene Caribbean sirenian faunas included prorastomids, protosirenids, and early dugongids. These were diverse in both locomotor and feeding adaptations, ranging from amphibious to fully aquatic forms and from selective browsers to incipiently indiscriminate grazers. Eocene Caribbean seagrass communities were already essentially modern in aspect, but included a greater diversity of species with mid-sized to large rhizomes. Oligocene faunas comprised as many as six apparently sympatric species. These included only dugongids, but were differentiated into halitheriines (generalized feeders on seagrass leaves and smaller rhizomes, or specialists on leaves) and dugongines (specialists on larger rhizomes). Miocene faunas of marine sirenians continued the Oligocene pattern. In freshwater habitats of South America, trichechids appeared in the record and adapted to an increase in abundance of fibrous, abrasive aquatic grasses (Gramineae). Pliocene marine sirenian faunas in the Caribbean consist only of dugongine dugongids, plus a trichechid species which evidently extended its range to North America. The dugongines most specialized for eating large rhizomes apparently died out during this epoch. Pleistocene and Recent faunas comprise only trichechids (manatees). Large-tusked dugongines probably acted as “keystone species”, disrupting climax seagrass communities and thereby increasing their productivity and diversity (including sirenian diversity). Under these conditions (which prevailed up to about 2–3 Ma), most primary productivity was presumably consumed by herbivores, in contrast to the detritus-based seagrass ecosystems of today, which include few if any large herbivores. Pliocene oceanographic changes following closure of the Central American Seaway probably led to the collapse of this diverse system, causing extinction of several large, “climax” seagrass species and producing the florally and faunally depauperate seagrass communities of the present-day Caribbean. The resulting “vacuum” in marine sirenian niches may have enabled manatees to spread from South America into the Caribbean and North America, as well as West Africa.

Eocene sirenians and cetaceans simultaneously and independently evolved similar morphological adaptations to aquatic life. These included increased flexibility in the sacral region, reduction and loss of hind limbs, shortening of the neck, increased skeletal mass, and other modifications. Loss of hind limbs was probably driven by selection for the maintenance of horizontal trim. The advantage of a shorter neck lay in the more anterior position and consequently the greater turning moments of forelimb control surfaces that it made possible.

Three new specimens of the walrus-like dolphin Odobenocetops from the Pliocene of Peru, shed new light on the anatomy and adaptive strategies of this unique Cetacean. Odobenocetops leptodon nov. sp. is represented by a skull, which bears a 1 35-cm-long needle-like right tusk and a small 25-cm-long left tusk the apex of which was erupted. The long tusk was probably held almost parallel to the axis of the body when swimming. In contrast to O. peruvianus, O. leptodon probably had a small melon and, therefore, echolocation ability, but had reduced (or no) binocular vision. A skull of O. peruvianus with two small tusks similar in size is referred to a female.