Obscure controversies in Cenozoic marine vertebrate paleontology 1: taxonomic feuding over the basilosaurid whales Zygorhiza, Pontogeneus, and Cynthiacetus

    Some of the most lively, and on occasion low-stakes and totally boring arguments in paleontology are over matters of taxonomy: what name do you use for a particular set of fossils? Taxonomic slapfights are common, because different researchers often represent different schools of thought and there are different philosophies behind what is needed to define a species or genus, what a type specimen should look like, what a type specimen means, how speciose genera should be, what families are (if anything), etc. Some of these questions may sound ridiculous given that genera and families are probably not biologically real – yet they are units that are counted through geological time by diversity measurements, so some meaning is ascribed to them for better or for worse. Some taxonomic disputes can rapidly get into the weeds, so to speak, and quickly lose the attention of even other seasoned researchers. But others highlight vastly different philosophical approaches – is “Torosaurus” the adult form (and therefore synonym of Triceratops? [narrator: it is] Is “Nanotyrannus” the juvenile form of Tyrannosaurus? [narrator: also yes]. These arguments are fascinating to me owing to nature of the dispute itself: do animals change shape as they grow? Many paleo aficionados are familiar with these examples, so I wanted to highlight three surprising examples most of you have not heard of within the field of paleocetology. Each of these three, again, highlights interesting contrasts in approaches to paleontology.

    One last point before this: many paleontologists and most science communicators are completely wrong about what the "validity" of a taxon is. Under the ICZN a name is valid if it is available and associated with an anatomical description or figure of a specimen in the literature. A valid name can have a horribly incomplete type specimen. What most have in mind when they think of validity is actually diagnoseability: is the fossil diagnostic?

The case of the crappy type specimen of Zygorhiza

    Type specimens are an established utilitarian concept in the life sciences. During the first century or so of biology, type specimens were generally not designated – meaning that species names were not tied to an individual specimen in a collection somewhere. Taxonomy in the late 18^th and early 19^th century was the wild west, and some conventions were honored on occasion, but naturalists frequently just re-named species all the time, so that for any taxon named before 1880 there’s likely going to be at least 10 or more synonymous names. Sometimes this was likely due to simple ignorance (someone had not read a paper published earlier) or due to the fact that frequently, few illustrations were ever published (wading through E.D. Cope’s paleocetological papers from the late 19^th century is a bit of a nightmare), or sometimes research was conducted on the same taxon in parallel and published nearly at the same time, the consequences of which only to be noticed decades later. Type specimens were meant to solidify the concept of a taxon by tying it to a particular individual specimen with a catalog number – so that anyone wanting to know what Zygorhiza kochii looks like, they can go to that collection and look at it. But, some type specimens are better than others. The type specimen of Basilosaurus cetoides, for example, is diagnoseable but not fantastic: a single partial (but very elongate) lumbar vertebra. The type specimen of the Cynthiacetus peruvianus is perhaps the best of any basilosaurid: a nearly complete skeleton with a complete skull and mandibles. Frequently in paleontology, the first known fossil of a new species is usually pretty shitty. I don’t know what to call this phenomenon, but it’s very real.

Kellogg's skeleton of Basilosaurus cetoides, excavated in the 1890s, on display in the Sant Ocean Hall in the Smithsonian NMNH.

    So what is the type specimen of Zygorhiza? It has a pretty ridiculous history, to be honest – and I’ll spare the more boring elements and summarize it as briefly as possible. The first basilosaurid whales discovered in the southeastern USA were found on plantations in Alabama – discovered by slaves ploughing the fields, who took all the bones near the surface and made a big pile of them. There’s a whole bizarre story with Albert Koch, who purchased these non-associated basilosaurid specimens and strung them together to make the chimaeric and fantastical skeleton of Hydrarchos – which, like an early P.T. Barnum, paraded around the USA as a traveling exhibition. Koch originally named it Hydrarchos sillimani, after Dr. Benjamin Silliman, who was not involved, and quickly requested the species to be renamed. Koch did this, and re-named it Hydrarchos harlani (you can’t really do that in taxonomy, but as I said before, it was the ‘wild west’). This composite “skeleton” was eventually purchased by King Friedrich Wilhelm IV of Prussia, who put it on display in the Royal Anatomical Museum, but much of it eventually perished during World War II when the Museum fur Naturkunde in Berlin was bombed in 1945 (note: a separate bombing than what destroyed Stromer’s fantastic Egyptian fossil collection, including Spinosaurus and many archaeocetes, at Palaontologisches Museum Munchen in April 1944). More on Koch later…

The famous illustration of Albert Koch's archaeocete chimaera, Hydrarchos.

    Many contemporaries considered Hydrarchos to be a junior synonym of Basilosaurus cetoides, famously misinterpreted as a marine reptile by Harlan in 1835 (and ironically the namesake of the replacement species name Hydrarchos harlani, despite being a junior synonym). Harlan would later be corrected by Sir Richard Owen, who decided to re-name it Zeuglodon (it REALLY was the wild west!) and identified it as a whale after all. After being sold to the king of Prussia and quickly reidentified as Basilosaurus cetoides by various German paleontologists, Reichenbach (1847) noticed that one of the parts of the skeleton, a partial braincase, was much smaller and represented a different species. He  named this Basilosaurus kochii. A few years later, Muller (1851) named a different species, Zeuglodon brachyspondylus, based on a collection of non associated vertebrae with short bodies, differing from the lengthened vertebrae of Basilosaurus cetoides. Muller unfortunately also named the subspecies (we don’t really use these in vertebrate paleontology) Zeuglodon brachyspondylus minor for a small collection of cranial material including the holotype skull fragment of Basilosaurus kochii, named four years prior (again, you can’t do that). Frederick True (1908) thought that this “species” did not belong to Zeuglodon (ironically, not because the name was technically invalid owing to synonymy with Basilosaurus), and named it Zygorhiza. Despite being applied to a different species (Z. brachyspondylus minor), the earliest named species name available is kochii, and so the taxonomy stabilized around Zygorhiza kochii (with Z. brachyspondylus minor as a junior synonym) as the preferred binomial for the smaller basilosaurid whale from the Eocene Pachuta Marl of Alabama. For much more in depth reviews of this, I refer the reader to Kellogg (1936) and Uhen (2013A, 2013B).

Stitched panorama of the mounted skeleton of Zygorhiza kochii (reference specimen USNM 11962) in the old marine paleontology display hall at the Smithsonian NMNH in Washington D.C. before they decommissioned the gallery, photographed just before Hurricane Sandy in 2012.

    Since Kellogg (1936) published his monograph A Review of the Archaeoceti, the de facto reference specimen for Zygorhiza kochii has been USNM 11962, a beautiful partial skeleton including a very well-preserved skull with mandibles. Paleocetologists have more or less treated this specimen as the honorary holotype. However, as pointed out by Uhen (2013A), the holotype is that crappy braincase first discussed by Reichenbach (1847). That specimen (Mb Ma 43248) is pretty terrible – a small braincase missing the vertex and with broken earbones. Uhen (2013A) notes that because the earbones are damaged, the teeth missing, and the vertex broken away, the holotype is non-diagnostic. This might mean that Zygorhiza kochii is at the mercy of opportunistic taxonomists who might move to declare it a nomen dubium – despite nearly a century of work being done with a clear idea of what Zygorhiza kochii “means” in terms of its anatomy. This situation, while not necessarily an issue in paleocetology, has plagued the horribly overcrowded field of dinosaur paleontology recently – with competing researchers finding ways to declare old taxa as nomina dubia and substituting new specimens (often only marginally better) as type specimens. This often comes across as a transparently desperate ploy to get to name something – and has generated no shortage of controversy in recent years. In some cases, estranged paleontologists desperate to make their mark have even gone trawling through cabinets in established collections looking for any fossils that might just barely push the envelope of anatomical differences into the “new species” zone – or opportunistically given a species a new genus name (e.g. if it was not already the type species of a particular genus) and screwed colleagues out of the opportunity to do it themselves.

The holotype (left) and reference specimen (USNM 11962 - and proposed neotype, right) - of Zygorhiza kochii. Photo on the right taken during my first visit to the Smithsonian in fall 2012; image on left from Uhen, 2013A.

    Fear of a nomenclatural coup d’etat led Mark Uhen (2013B) to formally petition the International Commission on Zoological Nomenclature to designate a neotype for Zygorhiza kochii. What’s a neotype? A neotype is a “new type”, an action permitted by the ICZN if the holotype specimen is ever lost or destroyed. In this case, the holotype very much still exists – but it is so bad, Uhen (2013B) argued that a neotype specimen was needed in order to preserve the taxonomic stability of the species. He further argued that the distinction between the Zygorhiza holotype and other southeastern basilosaurids, like Dorudon serratus and Chrysocetus healyorum from the upper Eocene of South Carolina – is not obvious. Therefore, a neotype was needed – and he proposed to use USNM 11962, Kellogg’s beautiful skeleton at the Smithsonian, to be the neotype. While you can’t really designate a neotype if it’s not missing, the ICZN can make exceptions – hence the petition.

    Two years later, a rebuttal was written by preeminent archaeocete paleontologist Philip Gingerich – who was Uhen’s Ph.D. adviser, to make things a bit strange. Gingerich is famous for discovering Pakicetus, Rodhocetus, Artiocetus, Maiacetus, and a Basilosaurus isis specimen with hindlegs, among other incredible archaeocete discoveries from Egypt and Pakistan – and has become ever more combative over the past 15 years. At my second SVP meeting I watched him deliver a particularly scathing talk critiquing recent papers on remingtonocetids by JGM Thewissen and colleagues – ironically, Gingerich’s other prominent Ph.D. student. I find it interesting that he’s been, at least publicly, lashing out at his former graduate students – it is, at minimum, bizarre behavior. There’s a lot more to the story, but I’ve been sworn to secrecy. Gingerich’s (2015A) rebuttal requests, quite frankly, that the ICZN not designate a neotype specimen for Zygorhiza and ignore Uhen’s (2013B) proposal. Gingerich reiterates the convoluted taxonomic history of Zygorhiza kochii, and uses a number of arguments.

1)      Dorudon serratus and Chrysocetus healyorum are not easily mistaken for Zygorhiza, since they are both slightly older (early late Eocene rather than latest Eocene), and the former is larger than Zygorhiza and the latter is smaller than Zygorhiza.

2)      The proposed neotype is from a different locality, 50 km away. [This is more of a technicality and means nothing scientifically since they’re from the same unit, but ICZN is pretty specific about specimens originating from the same locality in order to be part of the type series.]

3)      The type specimen and USNM 11962 are the same species based on size: there are probably three basilosaurids from the Jackson Group [the plot thickens immensely – see below!] and the smallest is Zygorhiza.

4)      Gingerich argues that since the type specimen and USNM 11962 both clearly represent the same species, and since the known sample of Zygorhiza kochii “should be thought of as a population of individual[s]…replacement of the existing holotype by a neotype will not solve any pressing problem.”

This last point is the most critical: at its core, Gingerich’s interpretation of the diagnostic value of the type specimen of Zygorhiza kochii is based entirely on its size. There’s some problems here: the first and most obvious is the fallout that would occur should somebody identify the holotype as a juvenile, in which case it could easily represent one of the other two basilosaurids. There is also the possibility that another smaller species could be discovered – but Gingerich (2015B) discounts this in a subsequent paper, saying he’s not holding his breath given that it hasn’t happened after nearly two centuries of collecting in the southeast. The last, and most serious problem, is that type specimens should be diagnostic, and ‘small size’ by itself is not a great start. However, to paraphrase my Ph.D. adviser R.E. Fordyce, “we shouldn’t judge the quality of historical type specimens and the judgement of researchers in the past based entirely on modern conventions” since conventions and attitudes change and are ultimately subjective. He advocates taxonomic conservatism: conserve existing names when possible, and quarantine them when conservation is not (e.g. designate nomina dubia).

Exceptions can be made for taxa that are already taxonomically stable: neotype or no, USNM 11962 serves as the ‘touchstone’ specimen for Zygorhiza – the de facto reference specimen. More extreme examples abound: Zarhachis flagellator was originally named based on a caudal vertebra by Cope – but Kellogg stabilized it in the 1920s based upon what he considered to be referable specimens. Is a caudal vertebra diagnostic today? Of course not! But Kellogg stabilized it and everyone has followed it through ‘taxonomic inertia’. So, I do sort of agree with Gingerich – a neotype is not needed – though I find virtually all of his reasoning problematic, and I think the last century of cetacean paleontology speaks for itself: Zygorhiza is stabilized. There is actually an argument here: names that have been in use for a long time and would cause quite a bit of confusion if fundamentally changed can be conserved  - though I forget if this is in the code or simply tradition.

Ultimately, my opinion on the matter is moot: in 2017, the ICZN declined to designate USNM 11962 as a neotype for Zygorhiza kochii.

The spectacular remains of Pontogeneus brachyspondylus, selected from the chimaeric assemblage of Hydrarchos. From Kellogg, 1936.

Pontogeneus or Cynthiacetus?

A third basilosaurid from the Eocene Yazoo Clay, Cynthiacetus maxwelli, was named in 2005 by Mark Uhen based on a well-preserved skull and mandibles with postcrania from the collections of the Mississipi Museum of Nature and Science. We actually had it on loan here for several years, and our museum’s benefactor Mace Brown spent quite a bit of time preparing off the hard limestone concretion that still encased it. It pretty clearly did not belong to Zygorhiza or Basilosaurus, and was pretty clearly separable: a bit smaller than Basilosaurus cetoides, and a LOT larger than Zygorhiza kochii. It differs chiefly from Basilosaurus in having normally proportioned lumbar vertebrae, like Zygorhiza – rather than the elongate, coke-can shaped vertebrae of Basilosaurus. The skull of Cynthiacetus maxwelli was not figured well by Uhen (2005), likely owing to its incomplete state of preservation. The teeth are nearly the same size as Basilosaurus, and I am not quite sure how the teeth differ between these species. The teeth are nearly double the size of their counterparts in Zygorhiza. One issue with basilosaurids is that the skulls all seem to be similar in most features – slight differences in proportions, a suture pushed over here or there, but basilosaurids *seem* to lack the more extreme anatomical diversity (disparity) of the skulls of early mysticetes and odontocetes.

The holotype (MNMNS 445) mandible and palate of Cynthiacetus maxwelli. This is a big, horribly heavy, slightly crushed, but reasonably well preserved specimen. The upper teeth are folded inwards. Photographed in 2019 at CCNHM just before it was returned to MMNS.

As it turns out, there is a different archaeocete taxon named from the same stratigraphic unit, also initially "discovered" amongst the chimaeric remains of "Hydrarchos" and named Zeuglodon brachyspondylus (later Pontogeneus brachyspondylus) by Muller (1851). Leidy (1852) shortly thereafter named Pontogeneus priscus, based off of an isolated cervical vertebra. Kellogg (1936) provided a figure and a description of the vertebra, classified it as Archaeoceti incertae sedis (uncertain position), remarked on its similarity to Basilosaurus, and even went so far as to refer some additional specimens to the taxon - but did not comment on its diagnoseability. Starting in the 1970s, paleocetologists moved away from naming all sorts of taxa based off of isolated vertebrae or even headless skeletons – with the exception of archaeocete paleontologists. Archaeocete paleontologists have been obsessed with finding archaeocete postcrania – and quite rightly so: for about 20 years it was a ‘cash cow’ so to speak in terms of scientific publishing: find any skeletons telling us about the land to sea transition in whales, and you’ve earned yourself a paper in Science or Nature. For fifteen years paleocetologists were searching for the first ancestral whale with ankles – and when that discovery was made, suspiciously in parallel, both Gingerich and Thewissen made the cover of Science and Nature (respectively) on the same day. Owing to this, there’s been a focus by archaeocete paleontologists on postcrania, and many descriptions of archaeocetes in recent years have skimped on the details of the skull (see my recent post on Ankylorhiza for more on this). Despite the more widespread use of postcranial features in diagnosing archaeocetes, defining and diagnosing a species based on an isolated vertebra is poor practice.

The beautifully preserved skeleton of Cynthiacetus peruvianus - a bit smaller than Cynthiacetus maxwelli, from the upper Eocene of Peru. From Martinez-Caceres et al., 2017.

    In a recent report on a partial skeleton of Zygorhiza kochii, Gingerich (2015B) reevaluated the taxonomy of Cynthiacetus and Pontogeneus. He pointed out that Muller (1851) indicated that “Z. brachyspondylus” differed from B. cetoides (which he referred to as Z. macrospondylus at the time) in vertebral shape and length. In 1852, Joseph Leidy described Pontogeneus priscus based on an isolated cervical vertebra from the Jackson Group in Louisiana – a little bit smaller than cervicals of Basilosaurus cetoides. Later, Leidy (1869) admitted that cervical vertebrae of “Z. brachyspondylus” were very similar and likely the same taxon. Kellogg synonymized these, and applied Leidy’s genus name to Muller’s species, recombining it as Pontogeneus brachyspondylus. Gingerich (2015B) made sure to mention that in a 1997 conference abstract, Uhen initially referred to MMNS 445 as Pontogeneus brachyspondylus – the specimen which he would later designate as the holotype of Cynthiacetus maxwelli in 2005. This meant that at some point, Uhen recognized that the Cynthiacetus maxwelli holotype had *something* to do with Pontogeneus.

    Uhen (2005) declared “Z. brachyspondylus” and Pontogeneus priscus as nomina nuda, or naked names: taxa lacking a proper publication. As correctly pointed out by Gingerich (2015B), this doesn’t really apply to 19^th century publications, and at the minimum, associating a name with an illustration is all that’s needed for a name to be valid. Uhen (2005) further argued that the holotype cervical vertebra of Pontogeneus priscus was so incomplete and similar to Basilosaurus, that it was not sufficiently diagnoseable – albeit incorrectly referring to it as a nomen nudum, rather a nomen dubium. Gingerich (2015B) further went on to indicate that, since there were only three apparent basilosaurids in the Jackson Group of Alabama, Mississippi, and Louisiana – a small species (Zygorhiza kochii), a large species (Basilosaurus cetoides), and a third medium sized species – the oldest available name for this taxon should be used. Therefore, Gingerich declared Cynthiacetus maxwelli to be a junior synonym of Pontogeneus brachyspondylus. Gingerich (2015B) further indicated that the P. brachyspondylus holotype had larger vertebrarterial foramina than Basilosaurus, and therefore is not easily confused with.

Comparison figure of the cervical vertebrae of Basilosaurus isis, Cynthiacetus maxwelli, and Pontogeneus brachyspondylus (this one happens to be Leidy's P. "priscus" holotype). From Gingerich (2015B). 

    There are of course, problem with this. The first and most important is that isolated vertebrae are not diagnostic. Within Neoceti, headless skeletons are not really diagnostic, and the few species erected on postcrania alone in the past few decades attract serious grumbling and eye rolling in private from other paleocetologists. Second, is that the ontogenetic status of the Pontogeneus priscus type specimen is uncertain, though it may have fused epiphyses. Third, it’s just a vertebral centrum and even for a vertebra is woefully incomplete; the argument that the vertebrarterial foramina are larger than in Basilosaurus is not defensible either. Fourth, unlike Zygorhiza and Zarhachis, Pontogeneus has not generally been in use, though Kellogg (1936) helpfully clarified the taxonomy and suggested it may be a third basilosaurid from the Jackson Group. Therefore, it does not deserve to be “grandfathered in” like Zarhachis flagellator. Lastly, and perhaps most critical, is that synonymy of Pontogeneus and Cynthiacetus relies on the interpretation that there are only three basilosaurids in the fauna. Gingerich admits this, and that the hypothesis can be tested by finding a second medium-sized basilosaurid – in that case, vertebrae of two similarly sized basilosaurids would not be distinguishable, and Cynthiacetus maxwelli would be clearly diagnoseable. By this line of reasoning, Gingerich (2015B) tacitly admitted that the holotype of Pontogeneus brachyspondylus is not diagnostic. It’s also a bit problematic to diagnose a taxon based on a fauna interpretation rather than morphology. In my opinion, there’s not much difference between naming a nomen dubium now, or resurrecting one that has not really been in use for nearly a century. Regardless, it’s not completely clear-cut, but I’ll be using Cynthiacetus maxwelli for the time being. How to fix it? Find more basilosaurids in the Eocene of the southeastern USA, expand the sample – maybe conduct a statistical analysis of cervical vertebra dimensions.

The holotype bulla (left) and a thoracic vertebra (right) of Basilotritus uheni from the Eocene of Ukraine. From Gol'din and Zvonok (2013).

Basilotritus or Platyosphys?

    Another study by Uhen on a large protocetid skeleton from the middle Eocene of North Carolina named Eocetus wardii, based on some really unusual vertebrae with a partial rostrum. At the time owing to its incompleteness, Uhen (1999) identified it as a protocetid closely related to Eocetus schweinfurthi from the middle Eocene of Egypt. Later, the discovery of a more complete skeleton from the late Eocene of Ukraine with basilosaurid teeth and identical vertebrae led to the naming of Basilotritus uheni by my friend Pavel Gol’din and colleagues, in honor of Mark Uhen’s earlier research on E. wardii; they referred this species to their new genus, recombining it as Basilotritus wardii. Their phylogenetic analysis pulled the taxon into the Basilosauridae. The vertebrae of Basilotritus are quite strange: the vertebrae are generally similar to other basilosaurids in shape but extremely thick with compact layering exposed in fractures – this is called pachyostosis. The bones are also osteosclerotic, meaning that there is minimal development of porous cancellous bone internally. The external layering is quite distinctive – and in the future, histological examination of theses bones is an absolute must (the external dense layering is reminiscent of an “EFS” – external fundamental system, the smoking gun histological determination of maximum size and cessation of growth). The thickening is also present in the neural arches and spines, and most unusually, the transverse processes of the lumbar vertebrae are nearly as long as the centra themselves – quite different from Basilosaurus, Dorudon, and Zygorhiza.

The spectacular original fossils of Platyosphys paulsonii, illustrated by Brandt (1873). The whereabouts of the specimens are unknown, and this image is all we have. 

    As it turns out, there were two eastern European taxa (named by famed cetologist J.F. Brandt in 1873) with similar vertebrae which Uhen (1999) made no mention of – Platyosphys paulsonii, based on three isolated vertebrae from the middle-late  Eocene Kharkov Formation of Ukraine, and Platysophys einori, from unnamed phosphate beds of the same age elsewhere in Ukraine. Given the location of the new partial skeleton of Basilotritus uheni and Pavel’s familiarity with obscure cetaceans of eastern Europe and the Caucasus, Gol’din and Zvonok (2013) fully discussed Platyosphys in the context of their new find. They indicated that the holotype vertebrae of Platyosphys paulsonii are lost – they apparently disappeared some time between the 1920s and World War II – and note that these vertebrae are generally similar, with some differences, and that they are also in general similar to Eocetus. Given that the specimen is lost, and comparisons are no longer possible, they declared Platosphys paulsonii a nomen dubium (Gol’din and Zvonok, 2013). Platyosphys einori, on the other hand, was not lost, and these authors figure the specimen and indicate that while it is generally similar to Eocetus and Basilotritus, it is not diagnostic owing to its incompleteness and lack of clearly observed internal structure, and also declare it a nomen dubium.

The spectacular holotype specimen of Platyosphys aithai from the late middle Eocene of Gueran, Morocco. From Gingerich and Zouhri (2015).

    Gingerich and Zouhri (2015) reported a new and unusual assemblage of archaeocete whales from the late middle Eocene (Bartonian stage) of Morocco (Aridal Formation, near Gueran), including three protocetids (one of which being Pappocetus), the new species of small basilosaurid Chrysocetus foudassii, new material of Eocetus schweinfurthi, and resurrected Platyosphys and named within it their new species Platyosphys aithai. Gingerich and Zouhri (2015) fundamentally disagreed with the nomen dubium decisions by Gol’din and Zvonok (2013), indicating that the survival of a type specimen to the present has no bearing on whether the name is valid or if the taxon is diagnoseable, which is technically correct under ICZN rules, which are (to be fair) extremely lax. Gingerich and Zouhri (2015) indicate that the illustrations from Brandt (1873) are sufficient to diagnose Platyosphys, the main characteristic being the elongated shelf-like transverse processes as well as the internal structure. This is fundamentally true – after all, the holotype specimen of Agorophius pygmaeus is missing (aside from a single tooth) and Fordyce (1980) redescribed it from the plates, and a new specimen was referred to it by Godfrey et al. (2016).

    Gingerich and Zouhri (2015) then reassigned Basilotritus uheni and B. wardii to Platyosphys, recombining them as Platyosphys uheni and Platyosphys wardii – though to be honest, I am surprised that they did not go further and declare Basilotritus uheni a junior synyonym of P. paulsonii (e.g. the sinking of Cynthiacetus, above). A few years ago, Gingerich presented an SVP talk about a new skeleton of Platyosphys aithai from Gueran, which included a well-preserved skull and articulated vertebral column and ribcage. I remember the ribs were extremely thick, like sea cow ribs – actually about what I would have predicted given the state of the vertebrae. The paper has not yet come out, and I am very much looking forward to it when it does. There’s been no followup by Pavel Gol’din and colleagues – and I know from correspondence that the annexation of Crimea by Russia in 2014 (following the Ukrainian revolution earlier that year) forced Pavel to leave his job at the Taurida National University in Sebastopol; he spent some time in Tel Aviv and Moldova before being hired again at the National Academy of Sciences in Kiev, where he’s continued much of his research on Paratethyan baleen whales. Needless to say, Pavel’s had a host of unfortunate career interruptions since describing Basilotritus.

Concluding remarks

    These three taxonomic controversies for Basilosauridae highlight several different questions. What standards should holotypes have? Are 150 year old drawings of isolated vertebrae really sufficient to diagnose a taxon? At what lengths should we go to preserve obscure old names? Which are worth preserving? I am still of the opinion that isolated vertebrae are not diagnostic, and you can make the same argument that I did above for Pontogeneus – since Platyosphys has not been in continuous use or widely recognized since the late 19^th century, it doesn’t really pass the same test as Zarhachis, for example – and in the time being, the new taxon Basilotritus was erected on clearly better material. Raising the spectre of lost specimens, preserved only as drawings in a tome from the 1870s, seems like a major “gotcha!” to me. I have no skin in the game, but have some sympathy for Uhen and Gol'din: they were motivated to move the field forward and nominate diagnoseable specimens as holotypes, not by taxonomic piracy. One issue is that isolated vertebrae cannot be diagnostic at the species level. If a specimen is not diagnostic at the species level, it cannot really be diagnosed as a species. The vertebrae of Platyosphys are perhaps diagnostic at the genus level. In my opinion, much of these recent taxonomic opinions issued by Gingerich seem to be examples of taking the ICZN at face value and defining taxa at the very limits of what is permitted – what we *can* do versus what we *should* do. We *can* name taxa based on non-diagnostic remains, but we *should* use diagnostic remains instead. These arguments are far removed from ‘best practices’ and perhaps unfair to paleontologists wanting to move the field of cetacean paleontology forward. At the same time - if an old holotype is diagnoseable, we shouldn't circumvent it - for that is the path to nomenclatural anarchy (not that I'm saying that's taken place).

Further Reading

Gingerich, 2015A: https://www.biotaxa.org/bzn/article/view/13742

Gingerich, 2015B: https://deepblue.lib.umich.edu/handle/2027.42/113064

Gingerich and Zouhri, 2015: https://www.sciencedirect.com/science/article/pii/S1464343X1530039X

Gol'din and Zvonok, 2013: https://www.cambridge.org/core/journals/journal-of-paleontology/article/basilotritus-uheni-a-new-cetacean-cetacea-basilosauridae-from-the-late-middle-eocene-of-eastern-europe/291BF670BF4B3D57664D25C9CBDC8E79

Godfrey et al. 2016: https://bioone.org/journals/journal-of-paleontology/volume-90/issue-1/jpa.2016.4/A-new-specimen-of-Agorophius-pygmaeus-Agorophiidae-Odontoceti-Cetacea-from/10.1017/jpa.2016.4.short

Kellogg, 1936: http://publicationsonline.carnegiescience.edu/publications_online/archaeoceti.pdf.

Martinez-Caceres et al., 2017: https://bioone.org/journals/Geodiversitas/volume-39/issue-1/g2017n1a1/The-anatomy-and-phylogenetic-affinities-of-Cynthiacetus-peruvianus-a-large/10.5252/g2017n1a1.short

Uhen, 1999: https://www.cambridge.org/core/journals/journal-of-paleontology/article/new-species-of-protocetid-archaeocete-whale-eocetus-wardii-mammalia-cetacea-from-the-middle-eocene-of-north-carolina/7F100C92C1A92CC11FCE5B04E4B46949

Uhen, 2005: A new genus and species of archaeocete whale from Mississippi. Southeastern Geology, 43:3:157-172.

Uhen, 2013A: A review of North American Basilosauridae. Bulletin of the Alabama Museum of Natural History, 31:2:1-45.

Uhen, 2013B: https://bioone.org/journals/The-Bulletin-of-Zoological-Nomenclature/volume-70/issue-2/bzn.v70i2.a14/Case-3611Basilosaurus-kochii-Reichenbach-1847-currently-Zygorhiza-kochii-Mammalia-Cetacea/10.21805/bzn.v70i2.a14.short

Note: I've left out many of the 19th century references here, since very few of you will read them, and I need to wrap this up and go to work. The most thorough account of the 19th century nomenclatural history of archaeocetes can be found in Kellogg (1936), so if you're really so desperate that you want *more*, I refer you to Kellogg.