This year has seen a somewhat lower number of papers published on fossil marine mammals, myself included - though I'm quite pleased I finally got the paper on Valenictus sheperdi out. It's been a good year for fossil pinnipeds and cetaceans, especially from New Zealand - with the formal publication of the "Fossil Vertebrates of Southern Zealandia" edited volume. Additionally, a new edited volume on a single skeleton of the desmostylian Paleoparadoxia (or, at least a close relative) from Mizunami (Japan) also came out - though a formal taxonomic/morphological study was not included. As far as new taxa are concerned, there were two new genera of pinnipeds (both phocids) and four new species, six new genera and species of odontocetes, two new genera and species of mysticetes, and one new genus and species of archaeocete named this year.
[Abstract in Spanish] Los vertebrados fósiles de las líneas costeras marinas a lo largo de la costa atlántica de la provincia de Buenos Aires, en el este de Argentina, son bien conocidos desde el siglo XIX. A pesar de ser frecuentes a lo largo de la costa del área de Cabo San Antonio, la descripción de los vertebrados e invertebrados fósiles encontrados a lo largo de la costa permanece casi sin documentar y su descripción ha sido mayormente anecdótica. El objetivo de la presente contribución es el de describir una gran colección de fósiles encontrados a lo largo de la playa de varias localidades en el área del cabo de San Antonio. Los fósiles incluyen una mezcla de animales terrestres y marinos que probablemente pertenecen a la Formación Pozo 10 (aproximadamente 120.000 años antes del presente), correlacionable con el evento transgresivo marino conocido como "Belgranense". Varios fósiles sugieren aguas cálidas, reminiscentes de las que ocurren hoy en día en el norte de Brasil. Los fósiles aquí reportados son muy similares a los de los conjuntos de fósiles costeros encontrados en el sur de Brasil, Uruguay y el sur de la provincia de Buenos Aires, lo que sugiere algún tipo de continuidad faunística y ambiental a lo largo de las costas del sur durante el Pleistoceno medio.
Amane et al. Basilosauridae (Mammalia, Cetacea) from the Sahara Desert of southwestern Morocco.
The Sahara Desert in southwestern Morocco is today an important paleontological region for its richness of archaeocete whale remains from the middle and late Eocene. Remains of Basilosauridae have been reported from Gueran and El Breij of the Bartonian age and Ad-Dakhla of the Priabonian age. There are no complete skeletons, meaning it is rarely possible to associate the skull and the post-cranial bones directly. However, analysis of the size and shape of the recovered sequential vertebrae enables distinction and comparison of the species of basilosaurids. Lumbar vertebrae best distinguish the different species of Basilosauridae, and eight different species are present in the three localities combined. Reexamination of the characteristics of the vertebrae of the different species of basilosaurids allows a better expansion of knowledge concerning their taxonomy, stratigraphic distribution and paleogeography.
Bakker. Wrist and ankle bones of the walrus Odobenus rosmarus (Linnaeus, 1758).
This article discusses the characteristics of carpals and tarsals of the walrus Odobenus rosmarus (Linnaeus, 1758) and offers some notes on the fossil walrus Ontocetus emmonsi Leidy, 1859. The author investigated the bone characteristics on the basis of extant walrus bones and the extensive collection of fossil walrus material stored at the Natural History Museum Rotterdam. Identification sessions provided insights that may also be helpful to others. This article aims to contribute to better recognition and identification of the wrist and ankle bones of the walrus.
Several dolphin lineages have independently invaded freshwater systems. Among these, the evolution of the South Asian river dolphin Platanista and its relatives (Platanistidae) remains virtually unknown as fossils are scarce. Here, we describe Pebanista yacuruna gen. et sp. nov., a dolphin from the Miocene proto-Amazonia of Peru, recovered in phylogenies as the closest relative of Platanista. Morphological characters such as an elongated rostrum and large supraorbital crests, along with ecological interpretations, indicate that this odontocete was fully adapted to fresh waters. Pebanista constitutes the largest freshwater odontocete known, with an estimated body length of 3 meters, highlighting the ample resource availability and biotic diversity in the region, during the Early to Middle Miocene. The finding of Pebanista in proto-Amazonian layers attests that platanistids ventured into freshwater ecosystems not only in South Asia but also in South America, before the modern Amazon River dolphin, during a crucial moment for the Amazonian evolution.
Benites-Palomino et al. Trophic interacitons of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela.
Evidence of trophic interactions are not scarce in the fossil record, yet these are mostly represented by fragmentary fossils exhibiting marks of ambiguous significance. Differentiating between marks of active predation and scavenging events is therefore often challenging. Here, we report on a dugongine sea cow skeleton (partial skull and vertebrae) from the Lower to Middle Miocene Agua Clara Formation (Venezuela) with shark and crocodylian bite marks. The sirenian is identified as Culebratherium sp. and preserves crocodylian bite marks across the skeleton. The most conspicuous correspond to deep tooth impacts with dragging effect, concentrated in the rostrum of the specimen. We interpret these as the result of active predation because of the similarity with those produced when a crocodylian holds or rolls a prey. Additionally, shark bite marks can be observed throughout the skeleton, also evidenced by the finding of an isolated tiger shark (Galeocerdo aduncus) tooth associated with this skeleton. Because of the irregular distribution of the shark bite marks, these are interpreted as scavenging. Overall, these findings constitute one of the few records documenting multiple predators over a single prey, and as such provide a glimpse of the trophic networks during the Miocene in the region.
Bianucci et al. A new Late Miocene beaked whale (Cetacea, Odontoceti) from the Pisco Formation, and a revised age for the fossil Ziphiidae of Peru.
The previously scarce fossil record of Ziphiidae (beaked whales) has greatly increased recently thanks to the serendipitous discovery of high specimen concentrations along deep seafloors as well as to abundant inland finds from the Upper Miocene of the Pisco Formation (East Pisco Basin, Peru). In the latter unit, ziphiid remains are indeed among the most prevalent of the whole cetacean assemblage, being represented by four distinct genera and species plus at least two as-yet unnamed taxa. Here, we describe a fifth ziphiid genus and species from the Pisco strata, Mamaziphius reyesi n. gen. n. sp., based on a partial cranium from mid-Tortonian (lower Upper Miocene, 9.1-9.0 Ma) strata exposed at the locality of Cerros la Mama y la Hija. Though reminiscent of the extant genus Berardius, the holotype skull lacks two diagnostic characters of Berardiinae, namely, an isolated rounded protuberance formed by the interparietal or frontals on the posterior part of the vertex, and a posterior transverse narrowing of the nasals and frontals at the vertex. Our phylogenetic analysis reveals that Mamaziphius n. gen. is nested within the crown ziphiids, as sister group of the berardiines. In addition, we introduce two new clade names within Ziphiidae, namely, Messapicetiformes (for the so-called “Messapicetus clade”) and Vomeroziphii (for Ziphiinae + Hyperoodontinae and closely related forms). Another fragmentary specimen from the Pisco Formation is also briefly described herein. Furthermore, a comprehensive reappraisal of the geological age of the fossil beaked whales of Peru is provided based on new age calibrations, thus restricting the whole rich Peruvian record of this family (including the earliest-branching ziphiid, Ninoziphius platyrostris, which comes from Pisco-equivalent strata of the Sacaco area) to a Tortonian-Messinian interval younger than 9.10 Ma. No other inland unit worldwide preserves a record of fossil ziphiids as abundant, diverse and chronostratigraphically well-constrained as the Pisco Formation. In view of this, the absence of Vomeroziphii from the fossil content of the Pisco strata remains quite enigmatic.
A new fossil gray whale genus and species, Glaucobalaena inopinata, is established based on craniomandibular remains from the Pliocene Sabbie d’Asti Formation, Piedmont, northwestern Italy. The holotype (MGPT-PU 19512) consists of two cranial fragments corresponding to the posterolateral corners of the skull, including both partial periotics, and in the posterior portion of the right mandibular ramus preserving the condyle and angular process. The new taxon is characterized by gray whale (eschrichtiid) synapomorphies in the posterior portion of the mandible (dorsally raised mandibular condyle with articular surface faced dorsoposteriorly, well-developed and robust angular process of the mandible) and in the earbone (massive transverse elongation of the pars cochlearis, indistinct flange of the ventrolateral tuberosity, and triangular and short anterior process of the periotic). A CT scan of the cranial fragments allowed us to reconstruct tridimensional renderings of the periotic, revealing the dorsal morphology of this bone. A phylogenetic analysis confirmed the inclusion of Glaucobalaena inopinata within Eschrichtiidae (the family to whom gray whales are included) and showed that it is monophyletic with Gricetoides aurorae; our phylogenetic results show that Eschrichtioides gastaldii is the sister group of the genus Eschrichtius. Our work lends further support to the idea that Eschrichtiidae is a separate family of baleen whales, characterized by specialized ecomorphological characters evident in both skull and mandibular architecture.
Eomysticetidae are a clade of early diverging functionally toothless, longirostrine and likely baleen-bearing stem mysticete whales. Eomysticetid fossils are rare but known worldwide from Oligocene strata. The richest assemblage of eomysticetids has been uncovered in New Zealand from the Kokoamu Greensand and Otekaike Limestone (North Otago and South Canterbury regions, South Island). This includes some of the largest known eomysticetids, Tokarahia kauaeroa and Tokarahia lophocephalus, some older and more archaic forms such as Matapanui waihao, the fragmentary Tohoraata raekohao and Tohoraata waitakiensis, and the well-known Waharoa ruwhenua represented by several well-preserved skulls and mandibles of adults and juveniles. Studies of these New Zealand fossils strongly indicates monophyly of Eomysticetidae and suggest possible skim feeding behaviour, possession of non-functional teeth and baleen, extreme rostral lengthening during growth and peramorphic evolution, rostral kinesis, use of Zealandia as a calving ground, and probable extinction at or near the Oligo-Miocene boundary.
Remarks: A quick aside about this one. In spring 2023 I was drinking my morning coffee and had completely forgotten about the impending due date until I got an email from the editors informing me that the invited article was due in about three weeks. I had just gotten a flat tire, so I grabbed my laptop, pumped up the tire (hoping it wouldn't pop or leak too quickly), and drove down to Gerald's Tires. I had a two hour wait, and I cranked out ~90% of the text for this manuscript by the time the repairs were completed. Now, before you marvel at the speed at which I wrote it, bear in mind that it is a review article based mostly on my PhD thesis research - most PhDs can probably write a review of their own thesis material (hopefully from memory). Needless to say, we made the deadline!