Travis Park

Ultrasonic hearing and echolocation in the earliest toothed whales.

The evolution of biosonar (production of high-frequency sound and reception of its echo) was a key innovation of toothed whales and dolphins (Odontoceti) that facilitated phylogenetic diversification and rise to ecological predominance. Yet exactly when high-frequency hearing first evolved in odontocete history remains a fundamental question in cetacean biology. Here, we show that archaic odontocetes had a cochlea specialized for sensing high-frequency sound, as exemplified by an Oligocene xenorophid, one of the earliest diverging stem groups. This specialization is not as extreme as that seen in the crown clade. Paired with anatomical correlates for high-frequency signal production in Xenorophidae, this is strong evidence that the most archaic toothed whales possessed a functional biosonar system, and that this signature adaptation of odontocetes was acquired at or soon after their origin.

A behavioural framework for the evolution of feeding in predatory aquatic mammals

Extant aquatic mammals are a key component of aquatic ecosystems. Their morphology, ecological role and behaviour are, to a large extent, shaped by their feeding ecology. Nevertheless, the nature of this crucial aspect of their biology is often oversimplified and, consequently, misinterpreted. Here, we introduce a new framework that categorizes the feeding cycle of predatory aquatic mammals into four distinct functional stages (prey capture, manipulation and processing, water removal and swallowing), and details the feeding behaviours that can be employed at each stage. Based on this comprehensive scheme, we propose that the feeding strategies of living aquatic mammals form an evolutionary sequence that recalls the land-to-water transition of their ancestors. Our new conception helps to explain and predict the origin of particular feeding styles, such as baleen-assisted filter feeding in whales and raptorial ‘pierce’ feeding in pinnipeds, and informs the structure of present and past ecosystems.

First giant bony-toothed bird (Pelagornithidae) from Australia

First giant bony-toothed bird (Pelagornithidae) from Australia Erich M. G. Fitzgerald a , Travis Park a b & Trevor H. Worthy c a Geosciences, Museum Victoria, GPO Box 666, Melbourne, Victoria, 3001, Australia b School of Life and Environmental Sciences, Deakin University, Victoria, 3125, Australia c School of Biological, Earth and Environmental Sciences, University of New South Wales, New South Wales, 2052, Australia

Low-frequency hearing preceded the evolution of giant body size and filter feeding in baleen whales

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

Reply to comment by Kienle et al. 2017

Kienle et al . [1] suggest amendments to our framework for feeding in predatory aquatic mammals [2]. Below we reply to their suggestions and demonstrate that they are fundamentally flawed from both a mechanical (feeding cycle, strategies) and an evolutionary perspective. They do, however, inspire an important addition to the range and structuring of capture behaviours encoded in our framework. Feeding cycle . Our framework groups feeding behaviours with similar functions, such as capture and processing, and thus clarifies how different species perform similar tasks during feeding. Kienle et al . [1] suggest that these groupings should be broken up, with capture, ‘external’ processing and manipulation behaviours instead being clustered into a single ‘ingestion’ stage. We question the biological justification for lumping behaviours as disparate as chasing, killing and dismembering. Capturing prey is unrelated to, and need not be followed by, processing. By contrast, ‘external’ and intraoral processing behaviours are functionally akin, with both aiming to dismember prey to start the digestive process. Lumping capture and processing furthermore deviates from the most recent conceptualization of the tetrapod feeding cycle by Schwenk & Rubega [3], which, contra [1], both explicitly includes a separate capture/subjugation stage (p. 12) and specifically associates ‘external’ with intraoral processing (p. 21). Besides the inclusion of water removal, our model differs from [3] only in not recognizing a separate ‘ingestion’ stage. This is because we view ingestion as a moment in time—namely, when food enters the mouth [4]—that can occur during multiple stages, and be achieved and reversed several times during feeding. By contrast, capture, manipulation and processing reflect periods of time over which specific behaviours are performed. Feeding strategies . Kienle et al. [1] criticize our use of a semi-aquatic …

The cochlea of the enigmatic pygmy right whale Caperea marginata informs mysticete phylogeny

The pygmy right whale, Caperea marginata, is the least understood extant baleen whale (Cetacea, Mysticeti). Knowledge on its basic anatomy, ecology, and fossil record is limited, even though its singular position outside both balaenids (right whales) and balaenopteroids (rorquals + grey whales) gives Caperea a pivotal role in mysticete evolution. Recent investigations of the cetacean cochlea have provided new insights into sensory capabilities and phylogeny. Here, we extend this advance to Caperea by describing, for the first time, the inner ear of this enigmatic species. The cochlea is large and appears to be sensitive to low‐frequency sounds, but its hearing limit is relatively high. The presence of a well‐developed tympanal recess links Caperea with cetotheriids and balaenopteroids, rather than balaenids, contrary to the traditional morphological view of a close Caperea‐balaenid relationship. Nevertheless, a broader sample of the cetotheriid Herpetocetus demonstrates that the presence of a tympanal recess can be variable at the specific and possibly even the intraspecific level.

Redescription of the Miocene penguin Pseudaptenodytes macraei Simpson (Aves: Sphenisciformes) and redefinition of the taxonomic status of ?Pseudaptenodytes minor Simpson

Pseudaptenodytes macraei is redescribed in detail using current avian anatomical terminology. The age of the species is constrained to the late Miocene, and two humeral autapomorphies are identified for the species: a flattened elliptical ventral portion of the fossa tricipitalis and a curved margo cranialis lacking a preaxial angle. Pseudaptenodytes macraei is a distinct taxon based on a diagnostic-type specimen, but it is recommended that the nominal congener Pseudaptenodytes minor be designated a nomen dubium pending the discovery of more complete material.

A late Miocene–early Pliocene Mihirung bird (Aves: Dromornithidae) from Victoria, southeast Australia

Park, T. & Fitzgerald, E.M.G. September 2012. A late Miocene–early Pliocene Mihirung bird (Aves: Dromornithidae) from Victoria, southeast Australia. Alcheringa 36, 427–430. ISSN 0311-5518. An incomplete tarsometatarsus identified as an indeterminate species of Dromornithidae is described from the upper Miocene–lower Pliocene shallow marine Black Rock Sandstone at Beaumaris, Victoria, Australia. This isolated specimen represents one of the few pre-Pleistocene dromornithids with a well-constrained geologic age. Additionally, it is one of the few pre-Quaternary dromornithid fossils recorded from southeast Australia. Comparisons with known dromornithid taxa suggest that the Beaumaris dromornithid is distinct from previously established species. This hitherto unknown species of dromornithid in the late Neogene of southeastern Australia cautions against deriving evolutionary patterns solely on the basis of fossils from northern Australia.

A Miocene pygmy right whale fossil from Australia

Neobalaenines are an enigmatic group of baleen whales represented today by a single living species: the pygmy right whale, Caperea marginata, found only in the Southern Hemisphere. Molecular divergence estimates date the origin of pygmy right whales to 22–26 Ma, yet so far there are only three confirmed fossil occurrences. Here, we describe an isolated periotic from the latest Miocene of Victoria (Australia). The new fossil shows all the hallmarks of Caperea, making it the second-oldest described neobalaenine, and the oldest record of the genus. Overall, the new specimen resembles C. marginata in its external morphology and details of the cochlea, but is more archaic in it having a hypertrophied suprameatal area and a greater number of cochlear turns. The presence of Caperea in Australian waters during the Late Miocene matches the distribution of the living species, and supports a southern origin for pygmy right whales.

How Mammals Conquered the Oceans

The field of marine mammal palaeontology is currently thriving, with more researchers than ever attempting to address questions about the transition of multiple mammalian lineages (at least seven of them) to aquatic life and their eventual domination of the world’s oceans and rivers. Whilst basic anatomical description remains the Bbread and butter^ variety of research, these core techniques are being increasingly supplemented with more modern approaches such as molecular genetics, biomechanics, and various 3D scanning techniques. Increased numbers of researchers have led to increased discoveries all around the planet—marine mammal evolution truly is a global story. It is in this context that Annalisa Berta is extremely well suited to be the author of this book. The Rise of Marine Mammals: 50 Million Years of Evolution aims to provide an overview of the diversity of marine mammals and their evolution. Berta is one of the giants of the field, with a research career stretching back four decades that has touched on most, if not all, of the marine mammal lineages mentioned in her book. Additionally, under her supervision, several of her students have become the next generation of leaders in the field, featuring heavily in the pages of this volume. This hardback is extremely well produced, with high quality text and figures. The illustrations, in particular, stand out for their aesthetic beauty as much as their scientific rigor. These are produced by some of the preeminent marine mammal illustrators such as Carl Buell, Robert Boessenecker, and Ray Troll. The book is mostly logically structured, with an opening chapter giving the reader the basics of taxonomy, cladistics, fossil collection, and preparation. Chapters two, three, and five cover cetaceans (whales and dolphins) and sirenians (manatees and dugongs). Stem group cetaceans and sirenians are lumped together in chapter two with crown cetaceans and sirenians getting their own chapters. Given that the material on stem sirenians only covers three pages (with multiple figures), it may have been better to put all the sirenian material in a single chapter (as was done with the aquatic carnivorans) rather than have the reader going back and forth. The final chapter, with its focus on climate change, feels a little bit tacked on, but does provide interesting information on trophic interactions and whale falls. In terms of content, the book takes each marine mammal lineage and proceeds to detail species diversity, distribution in space and in time, and give notable features about the major groups within each lineage. In this sense, this volume is very much a textbook rather than something someone would want to sit down and read. The content itself is interesting, but at times does feel a bit dry in the way it is presented. For those readers who purchase The Rise of Marine Mammals as a reference volume instead, this will not be an issue; indeed, it will prove to be a remarkably useful reference for interested laypeople and researchers in the field alike. Additional sections within each chapter briefly delve into some aspects of paleobiology. Similar to the taxonomic sections these are brief overviews of the research history of these areas, but again also provide an adequate amount of information and references for people to dig deeper if they so choose. Given the amount of research covered in this volume, it is remarkably error free and up to date. The current fast pace of the field however means that in some aspects the book is already out of date; e.g., the descriptions of Inermorostrum, Coronodon, and Mystacodon (Boessenecker et al. 2017; * Travis Park t.park@nhm.ac.uk