No Flippant Matter: The Re-Invention of the Flipper and Why Ceatacean Flippers Are Unique

Cetaceans are not closely related to other aquatic vertebrates and represent a unique lineage derived from hoofed land mammals that returned to an aquatic lifestyle about 50 million years ago (Thewissen, 1998). The transition from land to water, i.e. the development from weight-bearing forelimb with five hoofed toes to tissue-encased flipper not capable to support locomotion on land, is well documented by fossils (Thewissen et al., 2001, 2009) and very different from other aquatic vertebrates. Consequently many morphological characteristics that cannot be detected in fossils have remained little documented or speculative. Freed from the constraints of gravity and the developmental links to the hind legs, there is also a persistent anatomical plasticity in the flipper of modern cetaceans, showing substantial skeletal disparities sometimes even within the same population or pod (Cooper et al., 2007). Although there are a small number of morphological studies investigating the flipper in extant cetaceans, the understanding of functional morphology in this group has so far remained largely unresolved.

There are less than two dozend studies that include odontocete (toothed whales and dophins) forelimb myology (soft tissue studies). About half are classical works (Howell, 1927, 1930; Murie, 1870, 1873; Schulte and Smith, 1918; Stannius, 1849; Struthers, 1873), most of them available at BHL, and a few are more modern (Benke, 1993; Klima et al., 1980; Pilleri, 1976; Pilleri et al., 1976; Smith et al., 1976; Sokalov and Rodionov, 1974; Strickler, 1978).

Among mysticetes (balaeen whales) the lack of data is particularly apparent. The few accounts that include soft tissue are limited to rorquals (Benke, 1993; Carte and Macalister, 1868; Kükenthal, 1921; Perrin, 1870; Schulte, 1916; Struthers, 1888, 1889) and right whales (Kükenthal, 1922; Struthers, 1878) – except Benke all are nearly or over a century old.

The question of how cetaceans transitioned from a weight-bearing leg to a flipper is one of considerable interest to Moyna K. Müller, a PhD student at the Geology Department, University of Otago, New Zealand.

Müller has been studying cetaceans for the past four years, with particular interest not only in the transition of the weight bearing leg to flipper (evo-devo), but also comparative muscoskeletal arrangement of the shoulder and forelimb and functional analysis of the flipper. Her research requires access to historic literature that forms the basis of her comparative analysis and provides access to data from morphological studies done in the past. Gaining access to this literature used to present a challenge for Müller, until she discovered the Biodiversity Heritage Library.

“[I discovered BHL] at the beginning of my studies when I couldn’t get an article and in desperation told a fellow student in our group, who then put me onto your website. Since then I felt like a kid in a lolly shop,” praises Müller. “[There are] way too many things to look at distracting me from my studies.”

Recently those studies have included work on the pygmy right whale, Caperea marginata, the least known and most elusive of all baleen whales. This species is only known from isolated remains, infrequent solitary strandings, and few sightings, thus sharply contrast with all other baleen whales that are known from a multitude of live observations, captures and strandings (Baker, 1985). The earliest descriptions of this cryptic whale were based on beach-cast fragments associated with a convoluted taxonomy and nomenclature only applied correctly as Caperea marginata from 1930s onwards (Beddard, 1901; Gray, 1873; Rice, 1998). The divergent external appearance and skeletal disparity of the pygmy right whale warrant hereby separation from the true right whales (Balanidae) into a discrete family (Neobalaenidae Gray 1873), separating C. marginata from all other living mysticete families (Balaenidae, Eschrichtiidae and Balaenopteridae). However, only recently has C. marginata also been associated with an otherwise extinct fossil family (Cetotheriidae) (Fordyce and Marx, 2013). It is with this family that the pygmy right whale also shares some of the most striking fatures of the postcranial skeleton, namely the shoulde blade and the ribs (Bouetel and de Muizon, 2006; Gol’din et al., 2013).

Müller confides that, to support her work, she uses BHL “too often to count,” downloading PDFs of papers, whole articles, and high resolution images from our collection. The material is invaluable to her research.

“A lot of older literature I cannot get anywhere else, and without it I would sometimes have no basis for comparative analysis or I would not be able to confirm the validity of citations by other authors,” explains Müller. “This was particularly the case when working on the pygmy right whale (Caperea marginata). Apart from the pygmy right whale’s convoluted taxonomy, there are only three detailed descriptions of the shoulder musculature of any baleen whale – two of them (also the most detailed ones) are about a hundred years old (Carte and Macalister 1868 and Schulte 1916).”

When asked to describe her favorite BHL feature, Müller could not narrow it down to a single service (something we love to hear!). She not only finds it easy to locate the journals she needs but also, once she has found a title of interest, quickly determines what volumes are available. She also likes the visually-attractive images displayed throughout the website (even the “stunning fish” displayed on our “item not found” page), as well as the ‘news’, ‘today’s picks’ and ‘featured collections’ components. Finally, she was particularly complimentary of our feedback service (shout-out to Jackie Chapman, our BHL Collections Librarian who triages all of our feedback), describing it as “fast, friendly and very competent.”

Likewise, Müller could not name a single-favorite item in BHL. As she describes:

“The problem in my field is that there is no complete work I could use as the fundament for my own work, but rather a host of different articles that cover some aspects, e.g. osteology (van Beneden, 1880, Ostéographie des Cétacés vivant et fossils), or myology (Carte, A. and A. Macalister, 1868, On the anatomy of Balaenoptera acutorostrata or Schulte, H. v. W., 1916, Anatomy of a foetus of Balaenoptera borealis), and equally important the description of little described whales and dolphins (many articles by e.g. W. H. Flower, F. J. Knox, J. Hector, J. E. Gray in various volumes of Transactions and Proceedings of the New Zealand Institute or The Annals and Magazine of Natural History).”

Thus, the ability to retrieve all of these works and more is critical to Müller’s research success. BHL makes that possible.

Finally, Müller did offer a wonderful suggestion for a way to improve BHL, particularly in relation to the many foreign works available.

“You have quite a bit of foreign literature. [It’s] no problem for me to translate e.g. German or French, but it might be worth considering creating an option to upload translations, or a summary created by researchers in that field who do speak that particular language and are familiar with the terminology in their field, since a crude translation or summary is still better than none for somebody who doesn’t speak that language at all.”

As we continue to explore more and more crowdsourcing opportunities within our BHL community, and investigate ways to allow our users to help us improve our collections and services, the ability to add translations, transcriptions, and annotations are just some of the features we’re considering for our next interation of BHL. You can stay up to date with all of our website and service changes and improvements by following us on this blog, Twitter, and Facebook or subscribing to our newsletter. If you have suggestions for ways to improve our website or collections, please send us feedback!

Thank you, Moyna, for taking the time to explain how BHL is useful to you in your daily work! Do you use BHL to support your work? Want to tell us about it? Send us a message at

Click here to see cetacean sources cited, used, or otherwise useful, outlined by Moyna K. Müller

With Contributions From:
Grace Costantino
Outreach and Communication Manager, Biodiversity Heritage Library

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Moyna K. Müller is a PhD student at the Geology Department of Otago University, New Zealand.