Fig 17 - uploaded by Robert W Boessenecker
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-Reconstruction of the skull of Balaenoptera bertae n. sp.; A, lateral view; B, ventral view; C, dorsal view. Scale bar: 20 cm.
Source publication
The newly discovered Upper Miocene to Upper Pliocene San Gregorio assemblage
of the Purisima Formation in Central California has yielded a diverse
collection of 34 marine vertebrate taxa, including eight sharks, two bony fish,
three marine birds (described in a previous study), and 21 marine mammals.
Pinnipeds include the walrus Dusignathus sp., cf...
Citations
... The lack of the median promontorial groove is typical of a group of extant and fossil balaenopterids including Balaenoptera, Megaptera, Marzanoptera tersillae (Bisconti, Pellegrino, & Carnevale, 2021), and Protororqualus wilfriedneesi . Given the scattered positions of these species in the phylogenies of mysticetes provided in different articles (Boessenecker, 2013;Marx & Kohno, 2016), it is possible that the loss of the median promontorial groove occurred in different balaenopterid lineages and became fixed in the modern Balaenoptera clade. ...
... Tympanoperiotic morphology supports the monophyly of Balaenoidea including Neobalaenidae or pygmy right whales (here represented by Caperea marginata) and Balaenidae or right and bowhead whales (here represented by species of Eubalaena and Balaena mysticetus). Such a result finds corroboration in several morphologybased studies like those of Bisconti et al. (2023Bisconti et al. ( , 2017; Bisconti, Damarco, Mao, et al. (2021), Boessenecker andEl Adli et al. (2014). However, this result, again, contrasts with molecular phylogenies in which Caperea is not related to Balaenidae (Dutoit et al., 2023;Wolf et al., 2023). ...
The tympanoperiotic complex of a blue whale Balaenoptera musculus is described and compared to the homologous structures in the other extant and fossil baleen whale species. The periotic and the tympanic bulla represent informative anatomical regions in both functional and phylogenetic studies and for this reason a micro-CT scan of the bones was performed in order to better characterize their external aspect and to reconstruct the inner structures. In particular, the cochlea, the semicircular canals and associated portions of the periotic are reconstructed so that these structures may be used in phylogenetic analyses. We observed that the blue whale periotic is characterized by the presence of a strong dorsal protrusion which is posteriorly bordered by a previously undescribed morphological character that we name the posterotransverse fossa. The peculiar shape of the anterior process and the en echelon organization of the posterior foramina of the pars cochlearis are also described and compared. From a phylogenetic perspective, the blue whale is confirmed to be closely related to the fin whale, Balaenoptera physalus, but it is suggested, based on ear bone characters only, that it diverged before the other balaenopterid species in the phylogeny of Balaenopteridae. This placement supports a series of morphological observations suggesting that the extant blue whale was an early-diverging member of Balaenoptera. Our results help to decipher the evolutionary origin of the blue whale, the largest living animal, by allowing new and more detailed morphological analyses of the balaenopterid fossil record.
... Multispecies otariid assemblages seem to have been in place by at least the Middle Pleistocene, perhaps following immigration from the western North Pacific (Poust & Boessenecker, 2017). The timing of arrival of phocids remains poorly constrained, but no later than Middle Pleistocene (Boessenecker, 2013a). Extant Pacific walrus rarely range south of the Aleutian Peninsula, though some fossils of Odobenus have been reported in Late Pleistocene deposits in British Columbia (Harington & Beard, 1992) and as far south as northern California (Harington, 1984), but these occurrences lack robust paleoclimatic context (e.g., glacial vs. interglacial, paleotemperature). ...
... The Purisima Formation of northern California ( Fig. 1) has produced several diverse and stratigraphically separated marine vertebrate fossil assemblages dating to the latest Miocene through Late Pliocene. While collections from the Purisima Formation are numerically modest compared with the expansive collections from Pliocene rocks of southern California (e.g., Capistrano, San Mateo, and San Diego formations), assemblages from this formation are emerging as the most thoroughly studied from the Pacific coast of North America (e.g., Boessenecker, 2013aBoessenecker, , 2017Boessenecker et al., 2015;Repenning & Tedford, 1977). The Purisima Formation preserves sharks, bony fishes, birds, a sea turtle, pinnipeds, dolphins, baleen whales, and a sea cow (e.g., Boessenecker et al., 2014: table 1). ...
... Osodobenus sp., Gomphotaria sp. nov., and Valenictus sp.; Kellogg, 1927;Repenning & Tedford, 1977;Boessenecker, 2013aBoessenecker, , 2017. This pinniped assemblage is an aggregate one, and most published specimens are known from the base of the formation (e.g., Thalassoleon sp., cf. ...
Currently limited to cold climates near the Arctic circle, living walruses are the sole survivors of a previously much more diverse clade that occupied coastal waters throughout the northern hemisphere during the Mio–Pliocene. Though pinniped faunas have the highest diversity of walruses in the Miocene, the Purisima Formation of California records a moderately diverse assemblage of four walrus species. We report new specimens of tusked walruses (Odobeninae) including the oldest known members of Odobeninae, and Odobenini, and fossils of the specialized toothless odobenine walrus Valenictus Mitchell, 1961. Among these is the new species Valenictus sheperdi sp. nov., represented by a complete skull and referred post-crania from lower Pliocene strata within the Purisima Formation (5.33–4.89 Ma). Additionally, we report a geochronologically younger skull of Valenictus chulavistensis Deméré, 1994 from further up section (4.89–3.59 Ma). Expanded phylogenetic analysis recovers Odobeninae including Ontocetus Leidy, 1859 as the earliest diverging lineage in the Odobenini, and places a monophyletic Valenictus as the sister taxon to Pliopedia, Kellogg, 1921 which is included in a phylogeny for the first time; Odobenus is sister to the Valenictus + Pliopedia clade. Discovery of an isolated metacarpal near the base of the formation provides the oldest known well-dated evidence of odobenines. A diverse assemblage of molluskivores characterized the Neogene eastern North Pacific and their extinction around the Pliocene– Pleistocene boundary coincided with tectonically driven paleogeographic changes on the Pacific coast. The loss of temperate walruses may have provided opportunities for both new molluskivores and the otariid and phocid pinnipeds that make up present North Pacific pinniped communities.
... physeteroids, ziphiids, phocoenids and inioids), along with early representatives of modern taxa, including modern balaenopterids and oceanic dolphins. These transitional faunas have been recorded in fossiliferous localities across the world [1][2][3][4][5]. Despite the seemingly abundant cetacean fossil record, some regions such as the Caribbean remain poorly known due to the scarcity of fossiliferous outcrops and therefore, well-preserved fossils. ...
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.
... The same observation is made for the time interval between 9 and 2 Ma when the TL reduction in the Cetotheriidae occurred with the TL increase occurring in the Balaenopteridae. The last cetotheriids (Herpetocetus sp.; Boessenecker, 2013) had the smallest size of all Cetotheriidae and were living side to side with large balaenopterids (Fig. S2). ...
... The same observation is made for the time interval between 9 and 2 Ma when the TL reduction in the Cetotheriidae occurred with the TL increase occurring in the Balaenopteridae. The last cetotheriids (Herpetocetus sp.; Boessenecker, 2013) had the smallest size of all Cetotheriidae and were living side to side with large balaenopterids (Fig. S2). ...
... These records seem to indicate that monk seals were widespread around Australasia during the Pliocene, only to go extinct during the marine megafauna extinction (3.8-2.4 Ma;Boessenecker, 2013;Pimiento et al., 2017). This extinction coincided with the late Pliocene pinniped turnover events (Avery and Klein, 2011;Valenzuela-Toro et al., 2013;Rule et al., 2020d;Benites-Palomino et al., 2022), which saw the disappearance of most archaic phocids in the Southern Hemisphere. ...
The fossil record of true seals (Family Phocidae) is notoriously poorly preserved, most notably in the Southern Hemisphere. This fossil record bias has made it difficult to assess whether populations of phocid species in the Southern Hemisphere remained resident in particular regions throughout deep time, with only the eastern South Pacific preserving a near-continuous fossil record. Here we report two new seal fossil remains from the late Miocene-early Pliocene of southeastern Australia, discovered from a new site, Black Rock. This is the fourth phocid fossil site in Australia, and the seventh in Australasia. The two fossils are referrable to the clades Pinnipedia and Monachinae. Combined with other recent fossil phocid finds in Australasia, this suggests that true seals were continuously present in the region at least throughout the Pliocene. This lends further support for the importance of Australasia in the global evolution of true seals.
... In light of the host specificity of extant whale barnacles, other (sub)fossil finds of Cetopirus have been regarded as marking the passage of ancient populations of Eubalaena (Álvarez-Fernández et al. 2014;Collareta 2016;Collareta et al. 2016Collareta et al. , 2017Bosselaers et al. 2017 (Boessenecker 2013b). ...
A small lot of fossil whale barnacles from the Upper Pleistocene of California and the Middle Pleistocene (Chibanian) of Oregon (United States West Coast), described in a 1972 unpublished MA thesis, are formally described and illustrated herein. In that thesis, a new genus and species name were proposed; however, according to the International Code of Zoological Nomenclature, they have no taxonomic standing and are thus unavailable. Based on our reappraisal, two specimens in this lot belong to a new, extinct species that can be assigned to the purportedly extant genus Cetopirus. Cetopirus polysyrinx sp. nov. differs from congeners in that its secondary T-shaped flanges are multitubiferous internally, that is, they are perforated by a high number of irregularly-sized and irregularly-spaced tubules that result in a spongy aspect in transverse section. Whether or not this peculiar condition had any adaptive significance is difficult to determine. Considering that Cetopirus is currently known as an obligate epibiont of right whales (including the North Pacific form Eubalaena japonica (Lacépède 1818)), the host of C. polysyrinx sp. nov. was E. japonica or some other species of Eubalaena. The Plio-Pleistocene deposits of the Pacific coast of North America have yielded a rather idiosyncratic fossil whale barnacle fauna, inclusive of the genera Cetolepas, Cryptolepas and now Cetopirus, which seemingly contrasts with all other coeval assemblages worldwide, the latter being in turn dominated by Coronula spp.
... Instead, beaked whales (Ziphiidae), marine relatives of the presentday 'river dolphins' (Inioidea) and porpoises (Phocoenidae) were common in coastal environments, along with smallsized balaenopterids and even smaller cetotheriids like Piscobalaena nana. This pattern of predominantly small coastal cetaceans was extended across the eastern Pacific, as evidenced by fossils from the Mio-Pliocene of California [59,60]. By the end of the Miocene, a minor local turnover event occurred, coinciding with the appearance and first radiation of true dolphins [37]. ...
Shark–cetacean trophic interactions, preserved as bite marks in the fossil record, mostly correspond to isolated or fragmentary findings that bear limited information about major trophic patterns or roles. Here, we provide evidence of focalized foraging by sharks in the form of tooth bite marks over physeteroids fossil bones from the late Miocene of Peru. These findings indicate that sharks were targeting the forehead of coeval physeteroids to actively feed on their lipid-rich nasal complexes. Miocene physeteroids displayed a broad diversity, including giant predatorial forms, small benthic foragers and suction feeders. Like their extant relatives, these animals exhibited enlarged fatty forehead organs responsible for their sound production capabilities, thus evolving taxon-specific cranial architecture. Bite marks are found on the cranial bones where these structures were attached, indicating that sharks actively targeted this region; but also, in areas that would only be accessible following the consumption of the surrounding soft tissues. The shape of the bite marks and their distribution suggests a series of consecutive scavenging events by individuals of different shark species. Similar bite patterns can be recognized on other Miocene physeteroids fossils from across the globe, suggesting that sharks actively exploited physeteroid carcasses as fat sources.
... By contrast, fur seals and sea lions only crossed into the Southern Hemisphere following Pliocene cooling and an attendant increase in productivity along the equator (Churchill et al. 2014). The same cooling event produced sea-level fluctuations that impacted coastal habitats (with lowered sea levels eliminating shallow coastal waters) and likely disrupted the global distribution of phocids by driving their replacement with otariids at southern temperate latitudes (Boessenecker 2013;Valenzuela-Toro et al. 2013;Govender 2015;Pimiento et al. 2017;Rule et al. 2019). This idea is again consistent with our results, which suggest that-contrary to earlier suggestions (Ray 1976)-changing climates likely did not exceed the temperature tolerances of phocids as such. ...
True seals (phocids) have achieved a global distribution by crossing the equator multiple times in their evolutionary history. This is remarkable, as warm tropical waters are regarded as a barrier to marine mammal dispersal and – following Bergmann's rule – may have limited crossings to small‐bodied species only. Here, we show that ancestral phocids were medium‐sized and did not obviously follow Bergmann's rule. Instead, they ranged across a broad spectrum of environmental temperatures, without undergoing shifts in temperature‐ or size‐related evolutionary rates following dispersals across the equator. We conclude that the tropics have not constrained phocid biogeography. This article is protected by copyright. All rights reserved
... Similar faunal shifts have occurred in several other vertebrate and invertebrate groups of the eastern South Pacific during the Pliocene (Cione et al. 2007;Villafaña and Rivadeneira 2014;Rivadeneira and Nielsen 2017). Evidence across the globe indicates that this faunal shift was a worldwide event, as demonstrated by fossils from Australia, South Africa, and the Northern Hemisphere (Olson 1983;Boessenecker 2013a;Peredo and Uhen 2016;Rule et al. 2020c). This faunal shift coincides with strong sea-level oscillations in the late Pliocene. ...
The fossil record of marine mammals from the upper Pliocene of the western coast of South America is poorly known, hindering our knowledge about how and when marine mammal faunas attained their modern distribution in the area. Here, we describe a new marine mammal assemblage from the Horcón Formation (upper Pliocene), located in the Valparaíso Region of central Chile. The material reported comprises postcranial remains of an indeterminate seal (Phocidae), Delphinoidea vertebrae, and mysticete elements (still in the field). The Phocidae remains constitute the youngest pre-Pleistocene record of this family in South America, providing new information regarding the timing for the establishment of the modern diversity and distribution of pinnipeds in the Southern Hemisphere. Furthermore, the pinniped and cetacean remains reported indicate that the marine mammal assemblage from the upper Pliocene along central Chile was composed of a mixture of modern and extinct taxa.
